Ash aggregation during the 11 February 2010 partial dome collapse of the Soufrière Hills Volcano, Montserrat

On 11 February 2010, Soufrière Hills Volcano, Montserrat, underwent a partial dome collapse (~ 50 × 106 m3) and a short-lived Vulcanian explosion towards the end. Three main pyroclastic units were identified N and NE of the volcano: dome-collapse pyroclastic density current (PDC) deposits, fountain-collapse PDC deposits formed by the Vulcanian explosion, and tephra-fallout deposits associated with elutriation from the dome-collapse and fountain-collapse PDCs (i.e. co-PDC fallout deposit). The fallout associated with the Vulcanian explosion was mostly dispersed E and SE by high altitude winds. All units N and NE of the volcano contain variable amounts and types of particle aggregates, although the co-PDC fallout deposit is associated with the largest abundance (i.e. up to 24 wt%). The size of aggregates found in the co-PDC fallout deposit increases with distance from the volcano and proximity to the sea, reaching a maximum diameter of 12 mm about 500 m from the coast. The internal grain size of all aggregates have nearly identical distributions (with Mdϕ ≈ 4–5), with particles in the size categories > 3 ϕ (i.e. < 250 μm) being distributed in similar proportions within the aggregates but in different proportions within distinct internal layers. In fact, most aggregates are characterized by a coarse grained central core occupying the main part of the aggregate, coated by a thin layer of finer ash (single-layer aggregates), while others have one or two additional layers accreted over the core (multiple-layer aggregates). Calculated aggregate porosity and settling velocity vary between 0.3 and 0.5 and 11–21 m s− 1, respectively. The aggregate size shows a clear correlation with both the core size and the size of the largest particles found in the core. The large abundance of aggregates in the co-PDC fallout deposits suggests that the buoyant plumes elutriated above PDCs represent an optimal environment for the formation (particle collision) and development (aggregate layering) of particle aggregates. However, specific conditions are required, including i) a large availability of water (in this case provided by the steam plumes associated with the entrance of PDCs into the ocean), ii) presence of plume regions with different grain-size features (i.e. both median size and sorting) that allows for the development of multiple layers, iii) strong turbulence that permits both particle collision and the transition of the aggregates through different plume regions, iv) presence of hot regions (e.g. PDCs) that promote aggregate preservation (in this case also facilitated by the presence of sea salt)

Forced Chemical Vapor Infiltration of Tubular Geometries: Modeling, Design, and Scale-Up

In advanced indirectly fired coal combustion systems and externally fired combined cycle concepts, ceramic heat exchangers are required to transfer heat from the hot combustion gases to the clean air that drives the gas turbines. For high efficiencies, the temperature of the turbine inlet needs to exceed 1,100 C and preferably be about 1,260 C. The heat exchangers will operate under pressure and experience thermal and mechanical stresses during heating and cooling, and some transients will be severe under upset conditions. Silicon carbide-matrix composites appear promising for such applications because of their high strength at elevated temperature, light weight, thermal and mechanical shock resistance, damage tolerance, and oxidation and corrosion resistance. The development of thick-walled, tubular ceramic composites has involved investigations of different fiber architectures and fixturing to obtain optimal densification and mechanical properties. The current efforts entail modeling of the densification process in order to increase densification uniformity and decrease processing time. In addition, the process is being scaled to produce components with a 10 cm outer diameter

Double reading in breast cancer screening : cohort evaluation in the CO-OPS trial

Purpose: To investigate the effect of double readings by a second radiologist on recall rates, cancer detection and characteristics of cancers detected in the National Health Service Breast Screening Program in England. Materials and Methods: In this retrospective analysis we evaluated 805,206 women through screening and diagnostic test results by extracting one year of routine data from 33 English breast screening centers. Centers used double reading of digital mammograms, with arbitration if there were discrepant reads. Information on reader decisions, with results of follow-up tests, were used to explore the effect of the second reader. The statistical tests used were the test for equality of proportions, the χ2 test for independence and the t-test. Results: The first reader recalled 4·76%, (38295/805206, 95% CI 4·71%-4·80%) of women. Two readers recalled 6·19% in total, (49857/805206, 95% CI 6·14%- 6·24%), but arbitration of discordant reads reduced recall rate to 4·08%, (32863/805206, 95% CI 4·04%-4·12%, p<0.001). 7055 cancers were detected of which 627 (8·89%, 95% CI 8·22%-9·55%, p<0.001) were detected by the second reader only. These additional cancers were more likely to be ductal carcinoma in situ, (30·5% (183/600) vs 22.0% (1344/6114), p<0.001); and additional invasive cancers were smaller (mean 14·2mm vs 16·7mm, p<0.001), had fewer involved nodes, and were likely to be lower grade. Conclusion: Double reading with arbitration reduces recall and increases cancer detection compared to single reading. Cancers detected only by the second reader were smaller, lower grade, and had less nodal involvement

Testing for lynch syndrome in people with endometrial cancer using immunohistochemistry and microsatellite instability-based testing strategies – a systematic review of test accuracy

Background Lynch syndrome is an inherited genetic condition that is associated with an increased risk of cancer, including endometrial and colorectal cancer. We assessed the test accuracy of immunohistochemistry and microsatellite instability-based testing (with or without MLH1 promoter methylation testing) for Lynch syndrome in women with endometrial cancer. Methods We conducted a systematic review of literature published up to August 2019. We searched bibliographic databases, contacted experts and checked reference lists of relevant studies. Two reviewers conducted each stage of the review. Results Thirteen studies were identified that included approximately 3500 participants. None of the studies was at low risk of bias in all domains. Data could not be pooled due to the small number of heterogeneous studies. Sensitivity ranged from 60.7–100% for immunohistochemistry, 41.7–100% for microsatellite instability-based testing, and 90.5–100% for studies combining immunohistochemistry, microsatellite instability-based testing, and MLH1 promoter methylation testing. Specificity ranged from 60.9–83.3% (excluding 1 study with highly selective inclusion criteria) for immunohistochemistry, 69.2–89.9% for microsatellite instability-based testing, and 72.4–92.3% (excluding 1 study with highly selective inclusion criteria) for testing strategies that included immunohistochemistry, microsatellite instability-based testing, and MLH1 promoter methylation. We found no statistically significant differences in test accuracy estimates (sensitivity, specificity) in head-to-head studies of immunohistochemistry versus microsatellite instability-based testing. Reported test failures were rare. Conclusions Sensitivity of the index tests were generally high, though most studies had much lower specificity. We found no evidence that test accuracy differed between IHC and MSI based strategies. The evidence base is currently small and at high risk of bias

Single-Cell Growth Rates in Photoautotrophic Populations Measured by Stable Isotope Probing and Resonance Raman Microspectrometry

A newmethod tomeasure growth rates of individual photoautotrophic cells by combining stable isotope probing (SIP) and single-cell resonance Raman microspectrometry is introduced. This report explores optimal experimental design and the theoretical underpinnings for quantitative responses of Raman spectra to cellular isotopic composition. Resonance Raman spectra of isogenic cultures of the cyanobacterium, Synechococcus sp., grown in 13C-bicarbonate revealed linear covariance between wavenumber (cm−1) shifts in dominant carotenoid Raman peaks and a broad range of cellular 13C fractional isotopic abundance. Single-cell growth rates were calculated from spectra-derived isotopic content and empirical relationships. Growth rates among any 25 cells in a sample varied considerably;mean coefficient of variation, CV, was 29±3%(s/x), of which only ∼2% was propagated analytical error. Instantaneous population growth rates measured independently by in vivo fluorescence also varied daily (CV ≈ 53%) and were statistically indistinguishable from single-cell growth rates at all but the lowest levels of cell labeling. SCRR censuses of mixtures prepared from Synechococcus sp. and T. pseudonana (a diatom) populations with varying 13C-content and growth rates closely approximated predicted spectral responses and fractional labeling of cells added to the sample. This approach enables direct microspectrometric interrogation of isotopically- and phylogenetically-labeled cells and detects as little as 3% changes in cellular fractional labeling. This is the first description of a non-destructive technique to measure single-cell photoautotrophic growth rates based on Raman spectroscopy and well-constrained assumptions, while requiring few ancillary measurements

Oxidation resistant coatings for ceramic matrix composite components

Corrosion resistant Ca{sub 0.6}Mg{sub 0.4}Zr{sub 4}(PO{sub 4}){sub 6} (CMZP) and Ca{sub 0.5}Sr{sub 0.5}Zr{sub 4}(PO{sub 4}){sub 6} (CS-50) coatings for fiber-reinforced SiC-matrix composite heat exchanger tubes have been developed. Aqueous slurries of both oxides were prepared with high solids loading. One coating process consisted of dipping the samples in a slip. A tape casting process has also been created that produced relatively thin and dense coatings covering a large area. A processing technique was developed, utilizing a pre-sintering step, which produced coatings with minimal cracking

Rapid antigen detection and molecular tests for group A streptococcal infections for acute sore throat : systematic reviews and economic evaluation

Background Sore throat is a common condition caused by an infection of the airway. Most cases are of a viral nature; however, a number of these infections may be caused by the group A Streptococcus bacterium. Most viral and bacterial sore throat infections resolve spontaneously within a few weeks. Point-of-care testing in primary care has been recognised as an emerging technology for aiding targeted antibiotic prescribing for sore throat in cases that do not spontaneously resolve. Objective Systematically review the evidence for 21 point-of-care tests for detecting group A Streptococcus bacteria and develop a de novo economic model to compare the cost-effectiveness of point-of-care tests alongside clinical scoring tools with the cost-effectiveness of clinical scoring tools alone for patients managed in primary care and hospital settings. Data sources Multiple electronic databases were searched from inception to March 2019. The following databases were searched in November and December 2018 and searches were updated in March 2019: MEDLINE [via OvidSP (Health First, Rockledge, FL, USA)], MEDLINE In-Process & Other Non-Indexed Citations (via OvidSP), MEDLINE Epub Ahead of Print (via OvidSP), MEDLINE Daily Update (via OvidSP), EMBASE (via OvidSP), Cochrane Database of Systematic Reviews [via Wiley Online Library (John Wiley & Sons, Inc., Hoboken, NJ, USA)], Cochrane Central Register of Controlled Trials (CENTRAL) (via Wiley Online Library), Database of Abstracts of Reviews of Effects (DARE) (via Centre for Reviews and Dissemination), Health Technology Assessment database (via the Centre for Reviews and Dissemination), Science Citation Index and Conference Proceedings [via the Web of Science™ (Clarivate Analytics, Philadelphia, PA, USA)] and the PROSPERO International Prospective Register of Systematic Reviews (via the Centre for Reviews and Dissemination). Review methods Eligible studies included those of people aged ≥ 5 years presenting with sore throat symptoms, studies comparing point-of-care testing with antibiotic-prescribing decisions, studies of test accuracy and studies of cost-effectiveness. Quality assessment of eligible studies was undertaken. Meta-analysis of sensitivity and specificity was carried out for tests with sufficient data. A decision tree model estimated costs and quality-adjusted life-years from an NHS and Personal Social Services perspective. Results The searches identified 38 studies of clinical effectiveness and three studies of cost-effectiveness. Twenty-six full-text articles and abstracts reported on the test accuracy of point-of-care tests and/or clinical scores with biological culture as a reference standard. In the population of interest (patients with Centor/McIsaac scores of ≥ 3 points or FeverPAIN scores of ≥ 4 points), point estimates were 0.829 to 0.946 for sensitivity and 0.849 to 0.991 for specificity. There was considerable heterogeneity, even for studies using the same point-of-care test, suggesting that is unlikely that any single study will have accurately captured a test’s true performance. There is some randomised controlled trial evidence to suggest that the use of rapid antigen detection tests may help to reduce antibiotic-prescribing rates. Sensitivity and specificity estimates for each test in each age group and care setting combination were obtained using meta-analyses where appropriate. Any apparent differences in test accuracy may not be attributable to the tests, and may have been caused by known differences in the studies, latent characteristics or chance. Fourteen of the 21 tests reviewed were included in the economic modelling, and these tests were not cost-effective within the current National Institute for Health and Care Excellence’s cost-effectiveness thresholds. Uncertainties in the cost-effectiveness estimates included model parameter inputs and assumptions that increase the cost of testing, and the penalty for antibiotic overprescriptions. Limitations No information was identified for the elderly population or pharmacy setting. It was not possible to identify which test is the most accurate owing to the paucity of evidence. Conclusions The systematic review and the cost-effectiveness models identified uncertainties around the adoption of point-of-care tests in primary and secondary care settings. Although sensitivity and specificity estimates are promising, we have little information to establish the most accurate point-of-care test. Further research is needed to understand the test accuracy of point-of-care tests in the proposed NHS pathway and in comparable settings and patient groups

The Structure of Eu-III

Previous x-ray diffraction studies have reported Eu to transform from the hcp structure to a new phase, Eu-III, at 18 GPa. Using x-ray powder diffraction we have determined that Eu remains hcp up to 33 GPa, and that the extra peaks that appear at 18 GPa are from an impurity phase with space group R-3c . Above 33 GPa the diffraction pattern becomes very much more complex, signalling a transition to a phase with a distorted hcp structure.Comment: 4 pages, 4 figures, AIRAPT-23 Conference, Mumbai, 201

Evolution of Mechanical Properties of Lava Dome Rocks Across the 1995–2010 Eruption of Soufrière Hills Volcano, Montserrat

Lava dome collapses pose a hazard to surrounding populations, but equally represent important processes for deciphering the eruptive history of a volcano. Models examining lava dome instability rely on accurate physical and mechanical properties of volcanic rocks. Here we focus on determining the physical and mechanical properties of a suite of temporally-constrained rocks from different phases of the 1995–2010 eruption at Soufrière Hills volcano in Montserrat. We determine the uniaxial compressive strength, tensile strength, density, porosity, permeability, and Young’s modulus using laboratory measurements, complemented by Schmidt hammer testing in the field. By viewing a snapshot of each phase, we find the highest tensile and compressive strengths in the samples attributed to Phase 4, corresponding to a lower permeability and an increasing proportion of isolated porosity. Samples from Phase 5 show lower compressive and tensile strengths, corresponding to the highest permeability and porosity of the tested materials. Overall, this demonstrates a reliance of mechanical properties primarily on porosity, however, a shift toward increasing prevalence of pore connectivity in weaker samples identified by microtextural analysis demonstrates that here pore connectivity also contributes to the strength and Young’s Modulus, as well as controlling permeability. The range in UCS strengths are supported using Schmidt hammer field testing. We determine a narrow range in mineralogy across the sample suite, but identify a correlation between increasing crystallinity and increasing strength. We correlate these changes to residency-time in the growing lava dome during the eruption, where stronger rocks have undergone more crystallization. In addition, subsequent recrystallization of silica polymorphs from the glass phase may further strengthen the material. We suggest the variation in physical and mechanical rock properties shown within the Soufrière Hills eruptive products be included in future structural stability models of the remaining over-steepened dome on Montserrat, and that consideration of rock heterogeneity and its temporal variation if possible, be made in other, similar systems

Optimising breast cancer screening reading: blinding the second reader to the first reader's decisions.

OBJECTIVES: In breast cancer screening, two readers separately examine each woman's mammograms for signs of cancer. We examined whether preventing the two readers from seeing each other's decisions (blinding) affects behaviour and outcomes. METHODS: This cohort study used data from the CO-OPS breast-screening trial (1,119,191 women from 43 screening centres in England) where all discrepant readings were arbitrated. Multilevel models were fitted using Markov chain Monte Carlo to measure whether reader 2 conformed to the decisions of reader 1 when they were not blinded, and the effect of blinding on overall rates of recall for further tests and cancer detection. Differences in positive predictive value (PPV) were assessed using Pearson's chi-squared test. RESULTS: When reader 1 recalls, the probability of reader 2 also recalling was higher when not blinded than when blinded, suggesting readers may be influenced by the other's decision. Overall, women were less likely to be recalled when reader 2 was blinded (OR 0.923; 95% credible interval 0.864, 0.986), with no clear pattern in cancer detection rate (OR 1.029; 95% credible interval 0.970, 1.089; Bayesian p value 0.832). PPV was 22.1% for blinded versus 20.6% for not blinded (p < 0.001). CONCLUSIONS: Our results suggest that when not blinded, reader 2 is influenced by reader 1's decisions to recall (alliterative bias) which would result in bypassing arbitration and negate some of the benefits of double-reading. We found a relationship between blinding the second reader and slightly higher PPV of breast cancer screening, although this analysis may be confounded by other centre characteristics. KEY POINTS: • In Europe, it is recommended that breast screening mammograms are analysed by two readers but there is little evidence on the effect of 'blinding' the readers so they cannot see each other's decisions. • We found evidence that when the second reader is not blinded, they are more likely to agree with a recall decision from the first reader and less likely to make an independent judgement (alliterative error). This may reduce overall accuracy through bypassing arbitration. • This observational study suggests an association between blinding the second reader and higher positive predictive value of screening, but this may be confounded by centre characteristics