An electron microscopy study of the crystal growth of schwertmannite needles through oriented aggregation of goethite nanocrystals

The formation of their onoxyhydroxide schwertmannite has been monitored by time-resolved transmission electronmicroscopy (TEM) studies. Schwertmannitea ggregates are found to form initially as spherical agglomerates offer rihydrite crystallites, which then begin to grow characteristic needles on their surfaces. High-resolution images of the needles show that they are initially comprised of aligned goethite nanocrystals, which subsequently coarsen to form crystallographically coherent needles of goethite. Thus, needle formation on schwertmannite aggregates can be considered as the first stage in the phase transformation from schwertmannite to goethite. The results of this study suggest that schwertmannite is not a distinct mineral phase, but may be a mixture of ferrihydrite and poorly crystalline goethite with a distinctive morphology directed by the presence of surface-adsorbed sulfate anions

Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

Catalysis and synthesis are intimately linked in modern organic chemistry. The synthesis of complex molecules is an ever evolving area of science. In many regards, the inherent beauty associated with a synthetic sequence can be linked to a certain combination of the creativity with which a sequence is designed and the overall efficiency with which the ultimate process is performed. In synthesis, as in other endeavors, beauty is very much in the eyes of the beholder.† It is with this in mind that we will attempt to review an area of synthesis that has fascinated us and that we find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences

Avatars of Eurocentrism in the critique of the liberal peace

Recent scholarly critiques of the so-called liberal peace raise important political and ethical challenges to practices of postwar intervention in the global South. However, their conceptual and analytic approaches have tended to reproduce rather than challenge the intellectual Eurocentrism underpinning the liberal peace. Eurocentric features of the critiques include the methodological bypassing of target subjects in research, the analytic bypassing of subjects through frameworks of governmentality, the assumed ontological split between the ‘liberal’ and the ‘local’, and a nostalgia for the liberal subject and the liberal social contract as alternative bases for politics. These collectively produce a ‘paradox of liberalism’ that sees the liberal peace as oppressive but also the only true source of emancipation. However, the article suggests that a repoliticization of colonial difference offers an alternative ‘decolonizing’ approach to critical analysis through repositioning the analytic gaze. Three alternative research strategies for critical analysis are briefly developed

Statistical analysis plan for the OPTIMUM study: optimising immunisation using mixed schedules, an adaptive randomised controlled trial of a mixed whole-cell/acellular pertussis vaccine schedule

Objective: The purpose of this double-blind, randomised, controlled trial is to compare allergic outcomes in children following vaccination with acellular pertussis (aP) antigen (standard of care in Australia) given at 2 months of age versus whole cell pertussis (wP) in the infant vaccine schedule. Participants: Up to 3000 Australian infants 6 to <12 weeks of age born ≥32 weeks gestation. Interventions: The intervention is a wP containing vaccine as the first scheduled pertussis vaccine dose instead of an aP containing vaccine. Outcomes: The primary outcome is a binary indicator of history of IgE-mediated food allergy at the age of 12 months confirmed, where necessary, with an oral food challenge before 18 months of age. Secondary outcomes include (1) history of parent-reported clinician-diagnosed new onset of atopic dermatitis by 6 or 12 months of age with a positive skin prick test to any allergen before 12 months of age, (2) geometric mean concentration in pertussis toxin-specific IgG before and 21 to 35 days after a booster dose of aP at 18 months of age, and (3) sensitisation to at least one allergen by 12 months of age. Results: Operating characteristics of trial decision rules were evaluated by trial simulation. The selected rules for success and futility approximately maintain type I error of 0.05 and achieved power 0.85 for a reduction in the primary outcome from 10% in the control group to 7% in the intervention group. Discussion: A detailed, prospective statistical analysis plan (SAP) is presented for this Bayesian adaptive design. The plan was written by the trial statistician and details the study design, pre-specified adaptive elements, decision thresholds, statistical methods, and the simulations used to evaluate the operating characteristics of the trial. Application of this SAP will minimise bias and supports transparent and reproducible research. Trial registration: Australia & New Zealand Clinical Trials Registry, ACTRN12617000065392. Registered on 12 January 2017 Study protocol: https://doi.org/10.1136/bmjopen-2020-04283

The many roles of mellitic acid during barium sulfate crystallization

The various roles of mellitic acid during barium sulfate crystallization from nucleation to mesocrystal formation are explored and elucidated

Detecting Transits in Sparsely Sampled Surveys

The small sizes of low mass stars in principle provide an opportunity to find Earth-like planets and "super-Earths" in habitable zones via transits. Large area synoptic surveys like Pan-STARRS and LSST will observe large numbers of low mass stars, albeit with widely spaced (sparse) time sampling relative to the planets' periods and transit durations. We present simple analytical equations that can be used to estimate the feasibility of a survey by setting upper limits to the number of transiting planets that will be detected. We use Monte Carlo simulations to find upper limits for the number of transiting planets that may be discovered in the Pan-STARRS Medium Deep and 3-pi surveys. Our search for transiting planets and M-dwarf eclipsing binaries in the SDSS-II supernova data is used to illustrate the problems (and successes) in using sparsely sampled surveys.Comment: 7 pages, 2 figures, published in Proceedings of the Conference on Classification and Discovery in Large Astronomical Surveys, 200

The Type II supernovae 2006V and 2006au: two SN 1987A-like events

Supernova 1987A revealed that a blue supergiant (BSG) star can end its life as a core-collapse supernova (SN). SN 1987A and other similar objects exhibit properties that distinguish them from ordinary Type II Plateau (IIP) SNe, whose progenitors are believed to be red supergiants (RSGs). Similarities among 1987A-like events include a long rise to maximum, early luminosity fainter than that of normal Type IIP SNe, and radioactivity acting as the primary source powering the light curves. We present and analyze two SNe monitored by the Carnegie Supernova Project that are reminiscent of SN 1987A. Optical and near-infrared (NIR) light curves, and optical spectroscopy of SNe 2006V and 2006au are presented. These observations are compared to those of SN 1987A, and are used to estimate properties of their progenitors. Both objects exhibit a slow rise to maximum and light curve evolution similar to that of SN 1987A. At the earliest epochs, SN 2006au also displays an initial dip which we interpret as the signature of the adiabatic cooling phase that ensues shock break- out. SNe 2006V and 2006au are both found to be bluer, hotter and brighter than SN 1987A. Spectra of SNe 2006V and 2006au are similar to those of SN 1987A and other normal Type II objects, although both consistently exhibit expansion velocities higher than SN 1987A. Semi-analytic models are fit to the UVOIR light curve of each object from which physical properties of the progenitors are estimated. This yields ejecta mass estimates of about 20 solar masses, explosion energies of 2 - 3 x 10^51 erg, and progenitor radii of 75 - 100 solar radii for both SNe. The progenitors of SNe 2006V and 2006au were most likely BSGs with a larger explosion energy as compared to that of SN 1987A.Comment: 21 pages,15 figures, accepted for publication in A&A, 25 October 201

Coordination of opposing sex-specific and core muscle groups regulates male tail posture during Caenorhabditis elegans male mating behavior

Background To survive and reproduce, animals must be able to modify their motor behavior in response to changes in the environment. We studied a complex behavior of Caenorhabditis elegans, male mating behavior, which provided a model for understanding motor behaviors at the genetic, molecular as well as circuit level. C. elegans male mating behavior consists of a series of six sub-steps: response to contact, backing, turning, vulva location, spicule insertion, and sperm transfer. The male tail contains most of the sensory structures required for mating, in addition to the copulatory structures, and thus to carry out the steps of mating behavior, the male must keep his tail in contact with the hermaphrodite. However, because the hermaphrodite does not play an active role in mating and continues moving, the male must modify his tail posture to maintain contact. We provide a better understanding of the molecular and neuro-muscular pathways that regulate male tail posture during mating. Results Genetic and laser ablation analysis, in conjunction with behavioral assays were used to determine neurotransmitters, receptors, neurons and muscles required for the regulation of male tail posture. We showed that proper male tail posture is maintained by the coordinated activity of opposing muscle groups that curl the tail ventrally and dorsally. Specifically, acetylcholine regulates both ventral and dorsal curling of the male tail, partially through anthelmintic levamisole-sensitive, nicotinic receptor subunits. Male-specific muscles are required for acetylcholine-driven ventral curling of the male tail but dorsal curling requires the dorsal body wall muscles shared by males and hermaphrodites. Gamma-aminobutyric acid activity is required for both dorsal and ventral acetylcholine-induced curling of the male tail and an inhibitory gamma-aminobutyric acid receptor, UNC-49, prevents over-curling of the male tail during mating, suggesting that cross-inhibition of muscle groups helps maintain proper tail posture. Conclusion Our results demonstrated that coordination of opposing sex-specific and core muscle groups, through the activity of multiple neurotransmitters, is required for regulation of male tail posture during mating. We have provided a simple model for regulation of male tail posture that provides a foundation for studies of how genes, molecular pathways, and neural circuits contribute to sensory regulation of this motor behavior

Examiners\u27 decision‐making processes in observation-based clinical examinations

Background: Objective structured clinical examinations (OSCEs) are commonly used to assess the clinical skills of health professional students. Examiner judgement is one acknowledged source of variation in candidate marks. This paper reports an exploration of examiner decision making to better characterise the cognitive processes and workload associated with making judgements of clinical performance in exit‐level OSCEs. Methods: Fifty‐five examiners for exit‐level OSCEs at five Australian medical schools completed a NASA Task Load Index (TLX) measure of cognitive load and participated in focus group interviews immediately after the OSCE session. Discussions focused on how decisions were made for borderline and clear pass candidates. Interviews were transcribed, coded and thematically analysed. NASA TLX results were quantitatively analysed. Results: Examiners self‐reported higher cognitive workload levels when assessing a borderline candidate in comparison with a clear pass candidate. Further analysis revealed five major themes considered by examiners when marking candidate performance in an OSCE: (a) use of marking criteria as a source of reassurance; (b) difficulty adhering to the marking sheet under certain conditions; (c) demeanour of candidates; (d) patient safety, and (e) calibration using a mental construct of the \u27mythical [prototypical] intern\u27. Examiners demonstrated particularly higher mental demand when assessing borderline compared to clear pass candidates. Conclusions: Examiners demonstrate that judging candidate performance is a complex, cognitively difficult task, particularly when performance is of borderline or lower standard. At programme exit level, examiners intuitively want to rate candidates against a construct of a prototypical graduate when marking criteria appear not to describe both what and how a passing candidate should demonstrate when completing clinical tasks. This construct should be shared, agreed upon and aligned with marking criteria to best guide examiner training and calibration. Achieving this integration may improve the accuracy and consistency of examiner judgements and reduce cognitive workload