The role of hydrothermal activity in the formation of karst-hosted manganese deposits of the Postmasburg Mn Field, Northern Cape Province, South Africa

The Postmasburg Manganese Field (PMF), Northern Cape Province, South Africa, once represented one of the largest sources of manganese ore worldwide. Two belts of manganese ore deposits have been distinguished in the PMF, namely the Western Belt of ferruginous manganese ores and the Eastern Belt of siliceous manganese ores. Prevailing models of ore formation in these two belts invoke karstification of manganese-rich dolomites and residual accumulation of manganese wad which later underwent diagenetic and low-grade metamorphic processes. For the most part, the role of hydrothermal processes and metasomatic alteration towards ore formation has not been adequately discussed. Here we report an abundance of common and some rare Al-, Na-, K- and Ba-bearing minerals, particularly aegirine, albite, microcline, banalsite, sérandite-pectolite, paragonite and natrolite in Mn ores of the PMF, indicative of hydrothermal influence. Enrichments in Na, K and/or Ba in the ores are generally on a percentage level for most samples analysed through bulk-rock techniques. The presence of As-rich tokyoite also suggests the presence of As and V in the hydrothermal fluid. The fluid was likely oxidized and alkaline in nature, akin to a mature basinal brine. Various replacement textures, particularly of Na- and K- rich minerals by Ba-bearing phases, suggest sequential deposition of gangue as well as ore-minerals from the hydrothermal fluid, with Ba phases being deposited at a later stage. The stratigraphic variability of the studied ores and their deviation from the strict classification of ferruginous and siliceous ores in the literature, suggests that a re-evaluation of genetic models is warranted. New Ar-Ar ages for K-feldspars suggest a late Neoproterozoic timing for hydrothermal activity. This corroborates previous geochronological evidence for regional hydrothermal activity that affected Mn ores at the PMF but also, possibly, the high-grade Mn ores of the Kalahari Manganese Field to the north. A revised, all-encompassing model for the development of the manganese deposits of the PMF is then proposed, whereby the source of metals is attributed to underlying carbonate rocks beyond the Reivilo Formation of the Campbellrand Subgroup. The main process by which metals are primarily accumulated is attributed to karstification of the dolomitic substrate. The overlying Asbestos Hills Subgroup banded iron formation (BIF) is suggested as a potential source of alkali metals, which also provides a mechanism for leaching of these BIFs to form high-grade residual iron ore deposits

Mouse models of preterm birth: Suggested assessment and reporting guidelines

Preterm birth affects approximately 1 out of every 10 births in the United States, leading to high rates of mortality and long-term negative health consequences. To investigate the mechanisms leading to preterm birth so as to develop prevention strategies, researchers have developed numerous mouse models of preterm birth. However, the lack of standard definitions for preterm birth in mice limits our field\u27s ability to compare models and make inferences about preterm birth in humans. In this review, we discuss numerous mouse preterm birth models, propose guidelines for experiments and reporting, and suggest markers that can be used to assess whether pups are premature or mature. We argue that adoption of these recommendations will enhance the utility of mice as models for preterm birth

Physical activity for women with breast cancer after adjuvant therapy

© 2018 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd. Background: Women with a diagnosis of breast cancer may experience short- and long-term disease and treatment-related adverse physiological and psychosocial outcomes. These outcomes can negatively impact prognosis, health-related quality of life (HRQoL), and psychosocial and physical function. Physical activity may help to improve prognosis and may alleviate the adverse effects of adjuvant therapy. Objectives: To assess effects of physical activity interventions after adjuvant therapy for women with breast cancer. Search methods: We searched the Cochrane Breast Cancer Group (CBCG) Specialised Registry, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Physiotherapy Evidence Database (PEDro), SPORTDiscus, PsycINFO, ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform, on 18 September 2015. We also searched OpenGrey and Healthcare Management Information Consortium databases. Selection criteria: We searched for randomised and quasi-randomised trials comparing physical activity interventions versus control (e.g. usual or standard care, no physical activity, no exercise, attention control, placebo) after adjuvant therapy (i.e. after completion of chemotherapy and/or radiation therapy, but not hormone therapy) in women with breast cancer. Data collection and analysis: Two review authors independently selected studies, assessed risk of bias, and extracted data. We contacted trial authors to ask for additional information when needed. We calculated an overall effect size with 95% confidence intervals (CIs) for each outcome and used GRADE to assess the quality of evidence for the most important outcomes. Main results: We included 63 trials that randomised 5761 women to a physical activity intervention (n = 3239) or to a control (n = 2524). The duration of interventions ranged from 4 to 24 months, with most lasting 8 or 12 weeks (37 studies). Twenty-eight studies included aerobic exercise only, 21 involved aerobic exercise and resistance training, and seven used resistance training only. Thirty studies described the comparison group as usual or standard care, no intervention, or control. One-fifth of studies reported at least 20% intervention attrition and the average physical activity adherence was approximately 77%. No data were available on effects of physical activity on breast cancer-related and all-cause mortality, or on breast cancer recurrence. Analysis of immediately postintervention follow-up values and change from baseline to end of intervention scores revealed that physical activity interventions resulted in significant small-to-moderate improvements in HRQoL (standardised mean difference (SMD) 0.39, 95% CI 0.21 to 0.57, 22 studies, 1996 women; SMD 0.78, 95% CI 0.39 to 1.17, 14 studies, 1459 women, respectively; low-quality evidence), emotional function (SMD 0.21, 95% CI 0.10 to 0.32, 26 studies, 2102 women, moderate-quality evidence; SMD 0.31, 95% CI 0.09 to 0.53, 15 studies, 1579 women, respectively; low-quality evidence), perceived physical function (SMD 0.33, 95% CI 0.18 to 0.49, 25 studies, 2129 women; SMD 0.60, 95% CI 0.23 to 0.97, 13 studies, 1433 women, respectively; moderate-quality evidence), anxiety (SMD -0.57, 95% CI -0.95 to -0.19, 7 studies, 326 women; SMD -0.37, 95% CI -0.63 to -0.12, 4 studies, 235 women, respectively; low-quality evidence), and cardiorespiratory fitness (SMD 0.44, 95% CI 0.30 to 0.58, 23 studies, 1265 women, moderate-quality evidence; SMD 0.83, 95% CI 0.40 to 1.27, 9 studies, 863 women, respectively; very low-quality evidence). Investigators reported few minor adverse events. Small improvements in physical activity interventions were sustained for three months or longer postintervention in fatigue (SMD -0.43, 95% CI -0.60 to -0.26; SMD -0.47, 95% CI -0.84 to -0.11, respectively), cardiorespiratory fitness (SMD 0.36, 95% CI 0.03 to 0.69; SMD 0.42, 95% CI 0.05 to 0.79, respectively), and self-reported physical activity (SMD 0.44, 95% CI 0.17 to 0.72; SMD 0.51, 95% CI 0.08 to 0.93, respectively) for both follow-up values and change from baseline scores. However, evidence of heterogeneity across trials was due to variation in intervention components (i.e. mode, frequency, intensity, duration of intervention and sessions) and measures used to assess outcomes. All trials reviewed were at high risk of performance bias, and most were also at high risk of detection, attrition, and selection bias. In light of the aforementioned issues, we determined that the evidence was of very low, low, or moderate quality. Authors' conclusions: No conclusions regarding breast cancer-related and all-cause mortality or breast cancer recurrence were possible. However, physical activity interventions may have small-to-moderate beneficial effects on HRQoL, and on emotional or perceived physical and social function, anxiety, cardiorespiratory fitness, and self-reported and objectively measured physical activity. The positive results reported in the current review must be interpreted cautiously owing to very low-to-moderate quality of evidence, heterogeneity of interventions and outcome measures, imprecision of some estimates, and risk of bias in many trials. Future studies with low risk of bias are required to determine the optimal combination of physical activity modes, frequencies, intensities, and durations needed to improve specific outcomes among women who have undergone adjuvant therapy.Published versio