Quantitative localized proton-promoted dissolution kinetics of calcite using scanning electrochemical microscopy (SECM)

Scanning electrochemical microscopy (SECM) has been used to determine quantitatively the kinetics of proton-promoted dissolution of the calcite (101̅4) cleavage surface (from natural “Iceland Spar”) at the microscopic scale. By working under conditions where the probe size is much less than the characteristic dislocation spacing (as revealed from etching), it has been possible to measure kinetics mainly in regions of the surface which are free from dislocations, for the first time. To clearly reveal the locations of measurements, studies focused on cleaved “mirror” surfaces, where one of the two faces produced by cleavage was etched freely to reveal defects intersecting the surface, while the other (mirror) face was etched locally (and quantitatively) using SECM to generate high proton fluxes with a 25 μm diameter Pt disk ultramicroelectrode (UME) positioned at a defined (known) distance from a crystal surface. The etch pits formed at various etch times were measured using white light interferometry to ascertain pit dimensions. To determine quantitative dissolution kinetics, a moving boundary finite element model was formulated in which experimental time-dependent pit expansion data formed the input for simulations, from which solution and interfacial concentrations of key chemical species, and interfacial fluxes, could then be determined and visualized. This novel analysis allowed the rate constant for proton attack on calcite, and the order of the reaction with respect to the interfacial proton concentration, to be determined unambiguously. The process was found to be first order in terms of interfacial proton concentration with a rate constant k = 6.3 (± 1.3) × 10–4 m s–1. Significantly, this value is similar to previous macroscopic rate measurements of calcite dissolution which averaged over large areas and many dislocation sites, and where such sites provided a continuous source of steps for dissolution. Since the local measurements reported herein are mainly made in regions without dislocations, this study demonstrates that dislocations and steps that arise from such sites are not needed for fast proton-promoted calcite dissolution. Other sites, such as point defects, which are naturally abundant in calcite, are likely to be key reaction sites

National survey of feasibility of NIV trials for management of children with bronchiolitis.

Background: Bronchiolitis is a major cause of admission to hospital in children. Non-invasive ventilation (NIV) support with continuous positive airway pressure (CPAP) or high-flow nasal cannula (HFNC) oxygen is routinely used for infants in the UK with bronchiolitis. Objective: To establish UK paediatric practice regarding management of bronchiolitis, and to explore issues pertinent to the design of a potential future randomised controlled trial of NIV. Design: Screening logs were completed in hospitals in England capturing information on paediatric bronchiolitis admissions. An online national survey of clinical practice was disseminated to healthcare professionals (HCPs) across the UK to ascertain current management strategies. Results: Screening logs captured data on 393 infants from 8 hospitals. Reasons for admission were most commonly respiratory distress and/or poor fluid intake. Oxygen was administered for 54% of admissions. Respiratory (CPAP and HFNC) and non-respiratory support administered varied considerably. The national survey was completed by 111 HCPs from 76 hospitals. Data were obtained on criteria used to commence and wean NIV, responsibilities for altering NIV settings, minimum training requirements for staff managing a child on NIV, and numbers of trained staff. Most centres were interested in and capable of running a trial of NIV, even out of normal office hours. Conclusions: Respiratory and non-respiratory management of bronchiolitis in UK centres varies widely. A trial of HFNC oxygen therapy in this group of patients is feasible and HCPs would be willing to randomise patients into such a trial. Future work should focus on defining trial eligibility criteria

Efficacy and Safety of Umeclidinium/Vilanterol in Current and Former Smokers with COPD: A Prespecified Analysis of The EMAX Trial.

INTRODUCTION: Smoking may reduce the efficacy of inhaled corticosteroids (ICS) in patients with chronic obstructive pulmonary disease (COPD), but its impact on bronchodilator efficacy is unclear. This analysis of the EMAX trial explored efficacy and safety of dual- versus mono-bronchodilator therapy in current or former smokers with COPD. METHODS: The 24-week EMAX trial evaluated lung function, symptoms, health status, exacerbations, clinically important deterioration, and safety with umeclidinium/vilanterol, umeclidinium, and salmeterol in symptomatic patients at low exacerbation risk who were not receiving ICS. Current and former smoker subgroups were defined by smoking status at screening. RESULTS: The analysis included 1203 (50%) current smokers and 1221 (50%) former smokers. Both subgroups demonstrated greater improvements from baseline in trough FEV1 at week 24 (primary endpoint) with umeclidinium/vilanterol versus umeclidinium (least squares [LS] mean difference, mL [95% CI]; current: 84 [50, 117]; former: 49 [18, 80]) and salmeterol (current: 165 [132, 198]; former: 117 [86, 148]) and larger reductions in rescue medication inhalations/day over 24 weeks versus umeclidinium (LS mean difference [95% CI]; current: - 0.42 [- 0.63, - 0.20]; former: - 0.25 - 0.44, - 0.05]) and salmeterol (current: - 0.28 [- 0.49, - 0.06]; former: - 0.29 [- 0.49, - 0.09]). Umeclidinium/vilanterol increased the odds (odds ratio [95% CI]) of clinically significant improvement at week 24 in Transition Dyspnea Index versus umeclidinium (current: 1.54 [1.16, 2.06]; former: 1.32 [0.99, 1.75]) and salmeterol (current: 1.37 (1.03, 1.82]; former: 1.60 [1.20, 2.13]) and Evaluating Respiratory Symptoms-COPD versus umeclidinium (current: 1.54 [1.13, 2.09]; former: 1.50 [1.11, 2.04]) and salmeterol (current: 1.53 [1.13, 2.08]; former: 1.53 [1.12, 2.08]). All treatments were well tolerated in both subgroups. CONCLUSIONS: In current and former smokers, umeclidinium/vilanterol provided greater improvements in lung function and symptoms versus umeclidinium and salmeterol, supporting consideration of dual-bronchodilator therapy in symptomatic patients with COPD regardless of their smoking status

Minimax Current Density Coil Design

'Coil design' is an inverse problem in which arrangements of wire are designed to generate a prescribed magnetic field when energized with electric current. The design of gradient and shim coils for magnetic resonance imaging (MRI) are important examples of coil design. The magnetic fields that these coils generate are usually required to be both strong and accurate. Other electromagnetic properties of the coils, such as inductance, may be considered in the design process, which becomes an optimization problem. The maximum current density is additionally optimized in this work and the resultant coils are investigated for performance and practicality. Coils with minimax current density were found to exhibit maximally spread wires and may help disperse localized regions of Joule heating. They also produce the highest possible magnetic field strength per unit current for any given surface and wire size. Three different flavours of boundary element method that employ different basis functions (triangular elements with uniform current, cylindrical elements with sinusoidal current and conic section elements with sinusoidal-uniform current) were used with this approach to illustrate its generality.Comment: 24 pages, 6 figures, 2 tables. To appear in Journal of Physics D: Applied Physic

Base metal sulphide geochemistry of southern African mantle eclogites (Roberts Victor): Implications for cratonic mafic magmatism and metallogenesis

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordPlatinum-group elements (PGE) display a chalcophile behaviour and are largely hosted by base metal sulphide (BMS) minerals in the mantle. During partial melting of the mantle, BMS release their metal budget into the magma generated. The fertility of magma sources is a key component of the mineralisation potential of large igneous provinces (LIP) and the origin of orthomagmatic sulphide deposits hosted in cratonic mafic magmatic systems. Fertility of mantle-derived magma is therefore predicated on our understanding of the abundance of metals, such as the PGE, in the asthenospheric and lithospheric mantle. Estimations of the abundance of chalcophile elements in the upper mantle are based on observations from mantle xenoliths and BMS inclusions in diamonds. Whilst previous assessments exist for the BMS composition and chalcophile element budget of peridotitic mantle, relatively few analyses have been published for eclogitic mantle. Here, we present sulphide petrography and an extensive in situ dataset of BMS trace element compositions from Roberts Victor eclogite xenoliths (Kaapvaal Craton, South Africa). The BMS are dominated by pyrite-chalcopyrite-pentlandite (± pyrrhotite) assemblages with S/Se ratios ranging 1200 to 36,840 (with 87% of analyses having S/Se this editing is incorrect. This should read "(with 87% of analyses having S/Se 100 ppm) and are characteristically enriched in Os, Ir, Ru and Rh. Nano- and micron-scale Pd-Pt antimonide, telluride and arsenide platinum-group minerals (PGM) are observed spatially associated with BMS. We suggest that the predominance of pyrite in the xenoliths reflects the process of eclogitisation and that the trace element composition of the eclogite BMS was inherited from oceanic crustal protoliths of the eclogites, introduced into the SCLM via ancient subduction during formation of the Colesberg Magnetic Lineament c. 2.9 Ga and the cratonisation of the Kaapvaal Craton. Crucially, we demonstrate that the PGE budget of eclogitic SCLM may be substantially higher than previously reported, akin to peridotitic compositions, with significant implications for the PGE fertility of cratonic mafic magmatism and metallogenesis. We quantitatively assess these implications by modelling the chalcophile geochemistry of an eclogitic melt component in parental magmas of the mafic Rustenburg Layered Suite of the Bushveld Complex.Natural Environment Research Council (NERC)Russian Science Foundatio

Dual Bronchodilator Therapy as First-Line Treatment in Maintenance-Naïve Patients with Symptomatic COPD: A Pre-Specified Analysis of the EMAX Trial.

Introduction: Limited prospective evidence is available to guide selection of first-line maintenance therapy in patients with COPD. This pre-specified analysis of the EMAX trial explored the efficacy and safety of dual- versus mono-bronchodilator therapy in maintenance-naïve and maintenance-treated patients. Methods: The 24-week EMAX trial evaluated lung function, symptoms (including rescue medication use), exacerbations, and safety with umeclidinium/vilanterol, umeclidinium, and salmeterol in symptomatic patients at low exacerbation risk who were not receiving inhaled corticosteroids. Maintenance-naïve and maintenance-treated subgroups were defined by maintenance bronchodilator use 30 days before screening. Results: The analysis included 749 (31%) maintenance-naïve and 1676 (69%) maintenance-treated patients. For both subgroups, improvements from baseline in trough FEV1 at Week 24 (primary endpoint) were greater with umeclidinium/vilanterol versus umeclidinium (mean difference [95% CI]; maintenance-naïve: 44 mL [1, 87]; maintenance-treated: 77 mL [50, 104]), and salmeterol (maintenance-naïve: 128 mL [85, 171]; maintenance-treated: 145 mL [118, 172]), and in rescue medication inhalations/day over 24 weeks versus umeclidinium (maintenance-naïve: -0.44 [-0.73, -0.16]; maintenance-treated: -0.28 [-0.45, -0.12]) and salmeterol (maintenance-naïve: -0.37 [-0.66, -0.09]; maintenance-treated: -0.25 [-0.41, -0.08]). In maintenance-naïve patients, umeclidinium/vilanterol numerically improved scores at Week 24 for Transition Dyspnea Index versus umeclidinium (0.37 [-0.21, 0.96]) and versus salmeterol (0.47 [-0.10, 1.05]) and Evaluating Respiratory Symptoms-COPD versus umeclidinium (-0.26 [-1.04, 0.53]) and versus salmeterol (-0.58 [-1.36, 0.20]), with similar improvements seen in maintenance-treated patients. All treatments were well tolerated across both subgroups. Conclusion: Similar to maintenance-treated patients, maintenance-naïve patients receiving umeclidinium/vilanterol showed greater improvements in lung function and symptoms compared with patients receiving umeclidinium or salmeterol. These findings provide support for the consideration of dual bronchodilator treatment in symptomatic maintenance-naïve patients with COPD

Treatment of COPD with Long-Acting Bronchodilators: Association Between Early and Longer-Term Clinically Important Improvement.

Introduction: This post hoc analysis of the "Early MAXimization of bronchodilation for improving COPD stability" (EMAX) trial investigated whether patients achieving early clinically important improvement (CII) sustained longer-term improvements and lower risk of clinically important deterioration (CID). Methods: Patients were randomized to umeclidinium/vilanterol, umeclidinium, or salmeterol for 24 weeks. The patient-reported outcomes (PROs) Transition Dyspnea Index (TDI), Evaluating Respiratory Symptoms, St George's Respiratory Questionnaire (SGRQ) and COPD Assessment Test (CAT) were assessed. CII, defined as attaining minimum clinically important differences (MCID) in ≥2 PROs, was assessed at Weeks 4, 12 and 24. CID was defined as a deterioration in CAT, SGRQ, TDI by the MCID and/or a moderate/severe exacerbation from Day 30. Results: Of 2425 patients, 50%, 53% and 51% achieved a CII at Weeks 4, 12 and 24, respectively. Patients with a CII at Week 4 versus those without had significantly greater odds of achieving a CII at Weeks 12 and 24 (odds ratio: 5.57 [95% CI: 4.66, 6.66]; 4.09 [95% CI: 3.44, 4.86]). The risk of a CID was higher in patients who did not achieve a CII at Week 4 compared with patients who did (hazard ratio [95% CI]: 2.09 [1.86, 2.34]). Patients treated with umeclidinium/vilanterol versus either monotherapy had significantly greater odds of achieving CII at Weeks 4, 12 and 24. Conclusion: Achieving a CII at Week 4 was associated with longer-term improvement in PROs and a reduced risk of deterioration. Further research is required to investigate the importance of an early response to treatment on the long-term disease course

Confident and sensitive phosphoproteomics using combinations of collision induced dissociation and electron transfer dissociation

We present a workflow using an ETD-optimised version of Mascot Percolator and a modified version of SLoMo (turbo-SLoMo) for analysis of phosphoproteomic data. We have benchmarked this against several database searching algorithms and phosphorylation site localisation tools and show that it offers highly sensitive and confident phosphopeptide identification and site assignment with PSM-level statistics, enabling rigorous comparison of data acquisition methods. We analysed the Plasmodium falciparum schizont phosphoproteome using for the first time, a data-dependent neutral loss-triggered-ETD (DDNL) strategy and a conventional decision-tree method. At a posterior error probability threshold of 0.01, similar numbers of PSMs were identified using both methods with a 73% overlap in phosphopeptide identifications. The false discovery rate associated with spectral pairs where DDNL CID/ETD identified the same phosphopeptide was < 1%. 72% of phosphorylation site assignments using turbo-SLoMo without any score filtering, were identical and 99.8% of these cases are associated with a false localisation rate of < 5%. We show that DDNL acquisition is a useful approach for phosphoproteomics and results in an increased confidence in phosphopeptide identification without compromising sensitivity or duty cycle. Furthermore, the combination of Mascot Percolator and turbo-SLoMo represents a robust workflow for phosphoproteomic data analysis using CID and ETD fragmentation. Biological significance Protein phosphorylation is a ubiquitous post-translational modification that regulates protein function. Mass spectrometry-based approaches have revolutionised its analysis on a large-scale but phosphorylation sites are often identified by single phosphopeptides and therefore require more rigorous data analysis to unsure that sites are identified with high confidence for follow-up experiments to investigate their biological significance. The coverage and confidence of phosphoproteomic experiments can be enhanced by the use of multiple complementary fragmentation methods. Here we have benchmarked a data analysis pipeline for analysis of phosphoproteomic data generated using CID and ETD fragmentation and used it to demonstrate the utility of a data-dependent neutral loss triggered ETD fragmentation strategy for high confidence phosphopeptide identification and phosphorylation site localisation