Precambrian olistoliths masquerading as sills from Death Valley, California

Olistolith production and magmatism are processes commonly associated with extensional tectonic settings, such as rift basins. We present a cautionary exemplar from one such Precambrian basin, in which we reinterpret metabasite bodies, previously documented as sills, to be olistoliths. We nevertheless demonstrate that, on the basis of field observation alone, the previous but erroneous sill interpretation is parsimonious. Indeed, it is only by using isotopic age and compositional analysis that the true identities of these metabasite olistoliths are revealed. We present new data from metabasites and metasedimentary strata of the Kingston Peak Formation (Cryogenian) and Crystal Spring Formation (Mesoproterozoic) of Death Valley, USA. These include field observations, U?Pb apatite ages, U?Pb zircon ages (detrital and igneous) and whole-rock geochemistry. These data also provide a new maximum age for the base of the Pahrump Group and suggest that the Crystal Spring Diabase was more tholeiitic than previously thought. Similar sill/olistolith misinterpretations may have occurred elsewhere, potentially producing erroneous age and tectonic-setting interpretations of surrounding strata. This is particularly relevant in Precambrian rocks, where fossil age constraints are rare. This is illustrated herein using a potential example from the Neoproterozoic literature of the Lufilian belt, Africa. We caution others against Precambrian olistoliths masquerading as sills.publishersversionPeer reviewe

Cloning of mnuA, a Membrane Nuclease Gene of Mycoplasma pulmonis, and Analysis of Its Expression in Escherichia coli

Membrane nucleases of mycoplasmas are believed to play important roles in growth and pathogenesis, although no clear evidence for their importance has yet been obtained. As a first step in defining the function of this unusual membrane activity, studies were undertaken to clone and analyze one of the membrane nuclease genes from Mycoplasma pulmonis. A novel screening strategy was used to identify a recombinant lambda phage expressing nuclease activity, and its cloned fragment was analyzed. Transposon mutagenesis was used to identify an open reading frame of 1,410 bp, which coded for nuclease activity in Escherichia coli. This gene coded for a 470-amino-acid polypeptide of 53,739 Da and was designated mnuA (for “membrane nuclease”). The MnuA protein contained a prolipoprotein signal peptidase II recognition sequence along with an extensive hydrophobic region near the amino terminus, suggesting that the protein may be lipid modified or that it is anchored in the membrane by this membrane-spanning region. Antisera raised against two MnuA peptide sequences identified an M. pulmonis membrane protein of approximately 42 kDa by immunoblotting, which corresponded to a trypsin-sensitive nucleolytic band of the same size. Maxicell experiments with E. coli confirmed that mnuA coded for a nuclease of unknown specificity. Hybridization studies showed that mnuA sequences are found in few Mycoplasma species, suggesting that mycoplasma membrane nucleases display significant sequence variation within the genus Mycoplasma

Five common pitfalls in mixed methods systematic reviews: lessons learned.

Objective: Mixed methods systematic reviews (MMSR) combine quantitative and qualitative evidence within a single review. Since the revision of the JBI Methodology for MMSRs in 2020, there has been an increasing number of reviews published that claim to follow this approach. A preliminary examination of these indicated that authors frequently deviated from the methodology. This paper outlines five common ‘pitfalls’ associated with undertaking MMSR and provides direction for future reviewers attempting MMSR. Methods: Forward citation tracking identified 17 reviews published since the revision of the JBI mixed methods methodological guidance. Methods used in these reviews were then examined against the JBI methodology to identify deviations. Results: The issues identified related to the rationale for choosing the methodological approach; incorrect synthesis and integration approach chosen to answer the review question/s posed; the exclusion of primary mixed methods studies in the review; the lack of detail regarding the process of data transformation and a lack of ‘mixing’ of the quantitative and qualitative components. Conclusion: This exercise was undertaken to assist systematic reviewers considering conducting a MMSR as well as MMSR users to identify potential areas where authors tend to deviate from the methodological approach. Based on these findings a series of recommendations are provided

Air Afrique: The demise of a continental icon

Although the rationale for multi-flag airlines' formation is rooted in contemporary strategic thinking, our understanding of their emergence and subsequent mass disappearances in the twentieth century remains an elusive issue. This article seeks to fill this void by examining the emergence, ascendency and demise of Air Afrique, an airline once seen as a symbol of regional integration in Africa. This examination takes a historical perspective and covers the period from 1961 to 2002. On the basis of this historical analysis, five distinct stages have been identified reflecting the firm's glorious days, precipitous decline and subsequent collapse. These are: the golden age; Africanisation; escalating indecision, escalating commitment and dissolution phases. Each phase provides insights into the deterministic and voluntaristic perspectives of organisational failure. The implications of the findings of this research for theory and practice are discussed. © 2013 Taylor & Francis

Inappropriateness of health care in Canada: a systematic review protocol

Background: There is increasing recognition in Canada and globally that a substantial proportion of health care delivered is inappropriate as evidenced by (1) harmful and/or ineffective practices being overused, (2) effective clinical practices being underused, and (3) other clinical practices being misused. Inappropriate health care leads to negative patient experiences, poor health outcomes, and inefficient use of scarce health care resources. The purpose of this study is to conduct a systematic review of inappropriate health care in Canada. Our specific objectives are to (1) systematically search and critically review published and grey literature for studies on inappropriate health care in Canada; (2) estimate the nature and magnitude of inappropriate health care in Canada and its provincial and territorial jurisdictions. Methods: We will include all quantitative study designs reporting objective or subjective measurements of inappropriate health care in Canada over the last 10 years. We will search the following online databases: MEDLINE, Cochrane Central Register of Controlled Trials, EconLit, and ISI-Web of Knowledge, which contains Web of Science Core Collection-Citation Indexes, Science Citation Index Expanded, Conference Proceedings Citation Index-Science, and Conference Proceedings Citation Index-Social Science & Humanities. We will also search grey literature sources to identify provincial and national audits of inappropriate health care. Two authors will independently screen, assess data quality, and extract data for synthesis. Study findings will be synthesized narratively. We will organize our data into three care categorizations: preventive care, acute care, and chronic care. We will provide a compendium of inappropriate health care for each care category for Canada and each Canadian province and territory, where sufficient data exists, by calculating (1) overall medians of underuse, overuse, and misuse of clinical practices and (2) the range of medians of underuse, overuse, and misuse for each clinical practice investigated. Discussion: This review will result in the first-ever evidence-based compendium of inappropriate health care in Canada. We will also develop detailed reports of inappropriate health care for each Canadian province and territory. Systematic review registration: PROSPERO CRD42018093495Medicine, Faculty ofNon UBCPopulation and Public Health (SPPH), School ofReviewedFacult

An appraisal of respiratory system compliance in mechanically ventilated covid-19 patients

BackgroundHeterogeneous respiratory system static compliance (CRS) values and levels of hypoxemia in patients with novel coronavirus disease (COVID-19) requiring mechanical ventilation have been reported in previous small-case series or studies conducted at a national level.MethodsWe designed a retrospective observational cohort study with rapid data gathering from the international COVID-19 Critical Care Consortium study to comprehensively describe CRS—calculated as: tidal volume/[airway plateau pressure-positive end-expiratory pressure (PEEP)]—and its association with ventilatory management and outcomes of COVID-19 patients on mechanical ventilation (MV), admitted to intensive care units (ICU) worldwide.ResultsWe studied 745 patients from 22 countries, who required admission to the ICU and MV from January 14 to December 31, 2020, and presented at least one value of CRS within the first seven days of MV. Median (IQR) age was 62 (52–71), patients were predominantly males (68%) and from Europe/North and South America (88%). CRS, within 48 h from endotracheal intubation, was available in 649 patients and was neither associated with the duration from onset of symptoms to commencement of MV (p = 0.417) nor with PaO2/FiO2 (p = 0.100). Females presented lower CRS than males (95% CI of CRS difference between females-males: − 11.8 to − 7.4 mL/cmH2O p RS was marginal (p = 0.139). Ventilatory management varied across CRS range, resulting in a significant association between CRS and driving pressure (estimated decrease − 0.31 cmH2O/L per mL/cmH20 of CRS, 95% CI − 0.48 to − 0.14, p RS (+ 10 mL/cm H2O) was only associated with being discharge from the ICU within 28 days (HR 1.14, 95% CI 1.02–1.28, p = 0.018).ConclusionsThis multicentre report provides a comprehensive account of CRS in COVID-19 patients on MV. CRS measured within 48 h from commencement of MV has marginal predictive value for 28-day mortality, but was associated with being discharged from ICU within the same period. Trial documentation: Available at https://www.covid-critical.com/study.Trial registration: ACTRN12620000421932