Diffusion-controlled and replacement microtextures in alkali feldspars from two pegmatites: Perth, Ontario and Keystone, South Dakota

Macro- and micro-perthitic microclines from pegmatites from Perth, Ontario (Wards catalogue 46 E 0510) and Keystone, South Dakota (Wards 46 E 5125) have been studied using light and electron microscopy. A sample of the type perthite from Perth, Ontario (Hunterian Museum, Glasgow, M2361) was compared using light microscopy. It differs in bulk composition and microtexture from the Wards sample. The Perth sample from Wards is a mesoperthite, with sub-periodic ~mm-thick albite veins near (100), with irregular surfaces. The microcline has regular tartan twins and formed from orthoclase by a continuous process. The Keystone sample is a microperthite, with non-periodic albite veins mainly in {110}. Irregular tartan twins, volumes of irregular microcline and subgrains suggest that the microcline formed by dissolution–reprecipitation. Microcline in both samples contains semicoherent cryptoperthitic albite films that formed after the development of tartan twins. The bulk compositions of these intergrowths imply exsolution below ~400°C. Diffusion parameters imply sustained heating for between 0.11 My at 400°C, 1.5 GPa and 8.4 My at 300°C, 1 GPa. Unrealistic times are required at 200°C. Subsequently, the crystals reacted with a fluid leading to replacive growth of the vein perthites. Unusually, Albite twin composition planes in replacive subgrains have sub-periodic dislocations, formed by coalescence of advancing growth twins. Processes that might lead to periodic, replacive intergrowths are discussed. The Perth and Keystone feldspars have been used for experimental work on dissolution during weathering and on anomalous thermoluminescence fading. Their microtextures make them unsuitable for obtaining properties that can be extrapolated to feldspars in general

Routine characterization and interpretation of complex alkali feldspar intergrowths

Almost all alkali feldspar crystals contain a rich inventory of exsolution, twin, and domain microtextures that form subsequent to crystal growth and provide a record of the thermal history of the crystal and often of its involvement in replacement reactions, sometimes multiple. Microtextures strongly influence the subsequent behavior of feldspars at low temperatures during diagenesis and weathering. They are central to the retention or exchange of trace elements and of radiogenic and stable isotopes. This review is aimed at petrologists and geochemists who wish to use alkali feldspar microtextures to solve geological problems or who need to understand how microtextures influence a particular process. We suggest a systematic approach that employs methods available in most well founded laboratories. The crystallographic relationships of complex feldspar intergrowths were established by the 1970s, mainly using single-crystal X-ray diffraction, but such methods give limited information on the spatial relationships of the different elements of the microtexture, or of the mode and chronology of their formation, which require the use of microscopy. We suggest a combination of techniques with a range of spatial resolution and strongly recommend the use of orientated sections. Sections cut parallel to the perfect (001) and (010) cleavages are the easiest to locate and most informative. Techniques described are light microscopy; scanning electron microscopy using both backscattered and secondary electrons, including the use of surfaces etched in the laboratory; electron-probe microanalysis and analysis by energy-dispersive spectrometry in a scanning electron microscope; transmission electron microscopy. We discuss the use of cathodoluminescence as an auxiliary technique, but do not recommend electron-backscattered diffraction for feldspar work. We review recent publications that provide examples of the need for great care and attention to pre-existing work in microtextural studies, and suggest several topics for future work

The forgotten fifth: examining the early education trajectories of teenagers who fall below the expected standards in GCSE English language and maths examinations at age 16

Successive Governments have failed to address an issue that continues to plague the British education system: many teenagers leave secondary school without the ‘expected standard’ of a grade 4 pass in GCSE English language and maths. We use the UK Millennium Cohort Study (MCS) to assess the antecedents and academic trajectories of the 1 in 5 (18%) of teenagers in England who did not achieve these two thresholds, despite benefitting from many education reforms. We find that identification of falling below expected standards in pre-school assessment of ‘school readiness’ (age 3) and in teacher assessment of literacy and number skills at school entrance (age 5) are both highly predictive of failure to attain a grade 4 or higher in GCSE English language and maths at age 16, even after controlling for family background and individual characteristics. One in 4 children below expected levels at age 5 fail to achieve a grade 4 pass or above in their English language and maths GCSE at age 16 compared with 1 in 10 children above expected levels at age 5. Half of pupils who fail at age 16 were judged to be behind at age 5. We conclude that future attempts to improve standards in English and maths will likely only succeed if high quality support is provided during the pre-school years, support is provided to improve the home learning environment, and teachers are able to identify, diagnose and respond appropriately to children falling behind at early education stages

Systematic Routine for Setting Confidence Levels for Mean Time to Failure (MTTF)

There are circumstances where an item is intentionally tested to destruction.  The purpose of this technique is to determine the failure rate (λ) of a tested item.  For these items, the quality attribute is defined as how long the item will last until failure.  Once the failure rate is determined from the number of survivors and total time of all items tested the mean time to failure (MTTF) which is a typical statistic for survival data analysis issues.  MTTF is calculated by dividing one by failure rate (λ).  From this one obtains the reliability function R(t) = e-λt where t is time.  This allows the cumulative density function F(t) = 1- e-λt  to be determined.  This density function, f(t) = λe-λt is a negative exponential with a standard deviation (σ) = 1/λ.  Thus setting a warranty policy for the tested item is difficult for the practitioner.  An important property of the exponential distribution is that it is memory less.  This means its conditional probability follows P(T > s + t |T > s)=P(T > t) for all s, t ≥0.  The exponential distribution can be used to describe the interval lengths between any two consecutive arrival times in a homogeneous Poisson process.  The purpose of this research paper is to present a simple technique to determine a realistic confidence level. Using the same technique the warranty level for the tested item can be predicted

Elevated serum ferritin levels in the pediatric intensive care unit

Background:   Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening inflammatory condition caused by dysregulation of the immune system. HLH can develop in children with a variety of underlying causes including genetic cause, infection, autoimmune diseases, malignancy, etc. The symptoms of HLH are often similar to other conditions such as bacterial sepsis or systemic inflammatory response syndrome. This is a problem as the similarities among those different diseases make it difficult for the doctors to diagnose HLH and this can possibly lead to a delay in treatment. 50-75% mortality is reported in patients with secondary HLH (non-inherited) who do not receive treatment. Elevated serum ferritin level, referred to as hyperferritinemia, is the most characteristic feature of HLH and may be helpful in diagnosing HLH apart from other illnesses. This research investigates the incidences of patients with elevated serum ferritin level at the pediatric intensive care unit (PICU) of Alberta Children’s Hospital from 2014-2018 to gain a better understanding of HLH and hyperferritinemia.   Objectives:   The objectives of the study are i. identify diseases associated with hyperferritinemia on the PICU; ii. predict which PICU patient with hyperferritinemia is at risk to develop HLH during PICU admission; and iii. determine mortality risk in patients with hyperferritinemia and HLH at the PICU. Methods: This project is a retrospective chart review. A literature review was performed on the topic of hyperferritinemia and HLH, and relevant variables were identified for creating a Redcap database. Patient charts and medical records were examined for data collection of different elements including diagnosis, laboratory values, treatments, and survival status. Data of 91 patients who presented with hyperferritinemia in PICU from 2014 to 2018 is being examined. Results: Although this study is currently in progress, it is anticipated to provide insight into the features associated with hyperferritinemia and determine patients with hyperferritinemia who are at risk of developing HLH. Conclusion: Overall, the findings from this study may contribute to better understanding of hyperferritinemia and HLH in pediatric patients and contribute to decreasing mortality and morbidity of patients with hyperferritinemia and HLH. &nbsp

Detection of lithium in nearby young late-M dwarfs

Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs which is difficult to disentangle due to the lack of constraints on their age such as trigonometric parallax, lithium detection and space velocity. We search for young brown dwarf candidates among a sample of 28 nearby late-M dwarfs with spectral types between M5.0 and M9.0, and we also search for debris disks around three of them. Based on theoretical models, we used the color $I-J$, the $J$-band absolute magnitude and the detection of the Li I 6708 $\AA$ doublet line as a strong constraint to estimate masses and ages of our targets. For the search of debris disks, we observed three targets at submillimeter wavelength of 850 $\mu$m. We report here the first clear detections of lithium absorption in four targets and a marginal detection in one target. Our mass estimates indicate that two of them are young brown dwarfs, two are young brown dwarf candidates and one is a young very low-mass star. The closest young field brown dwarf in our sample at only $\sim$15 pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100$-$150 Myr. We did not detect any debris disks around three late-M dwarfs, and we estimated upper limits to the dust mass of debris disks around them.Comment: 10 pages, 5 figures, accepted for publication in Astronomy and Astrophysic

The prevalence of co-administration of clopidogrel and proton pump inhibitors

Background: Recent studies have suggested that proton pump inhibitors (PPIs) may inhibit the antiplatelet activity of clopidogrel, increasing the risk of major cardiovascular events in patients taking clopidogrel and PPIs together. Aim The primary aim of this study was to determine the prevalence of co-prescription of clopidogrel and PPIs amongst residents of aged-care facilities in New South Wales, Australia. Methods: One-year prescription records of 791 aged-care residents were analysed for prevalence of co-prescribing of clopidogrel and PPIs, and aspirin with clopidogrel and PPIs. Prevalence of co-prescribing of clopidogrel, aspirin and PPI in diabetic patients and clopidogrel with various CYP2C19 inhibitors was also examined. Results: Of the 791 residents studied, 60 were prescribed clopidogrel, 248 were on aspirin and 326 were prescribed a PPI.Among residents who were prescribed PPIs, 155 were prescribed omeprazole, 72 pantoprazole, 15 lansoprazole, 44 esomeprazole and 51 rabeprazole. Eleven of these residents had taken more than one PPI during the study period. Thirty-nine residents took a combination of clopidogrel and a PPI (any PPI) for a mean 203 days (SD 12). Thirteen residents were on the combination of aspirin and clopidogrel for a mean of 202 days (SD 111). Nine residents took the combination of clopidogrel, aspirin and a PPI (any PPI) for a mean of 173 days (SD 81). Only one patient on clopidogrel was receiving a CYP2C19 inhibitor in addition to a PPI. Conclusions: A significant number of residents in this cohort were taking a combination of clopidogrel and a PPI, mainly omeprazole. Residents who were on the combination of clopidogrel and a PPI, with or without aspirin,were on these combinations for a significantly long duration, which could increase their risk of adverse cardiovascular events