Growth dynamics and amorphous-to-crystalline phase transformation in natural nacre.

Biominerals, such as nacreous bivalve shells, are important archives of environmental information. Most marine calcifiers form their shells from amorphous calcium carbonate, hypothesised to occur via particle attachment and stepwise crystallisation of metastable precursor phases. However, the mechanism of this transformation, including the incorporation of trace elements used for environmental reconstructions, are poorly constrained. Here, using shells of the Mediterranean mussel, we explore the formation of nacre from the meso- to the atomic scale. We use a combination of strontium pulse-chase labelling experiments in aquaculture and correlated micro- to sub-nanoscale analysis to show that nacre grows in a dynamic two-step process with extensional and space-filling growth components. Furthermore, we show that nacre crystallizes via localised dissolution and reprecipitation within nanogranules. Our findings elucidate how stepwise crystallization pathways affect trace element incorporation in natural biominerals, while preserving their intricate hierarchical ultrastructure.

Development of ELIP to Assess Physical Literacy for Emerging Adults: A Methodological and Epistemological Challenge.

Purpose: Following increased interest in physical literacy (PL), development of appropriate tools for assessment has become an important next step for its operationalization. To forward the development of such tools, the objective of this study was to build the foundations of the Évaluation de la Littératie Physique (ELIP), designed to help reduce existing tensions in approaches to PL assessment that may be resulting in a low uptake into applied settings. Methods: We followed two steps: (1) the development of the first version of ELIP by deploying a Delphi method (n = 30); and (2) the modification of items through cognitive interviews with emerging adults (n = 32). Results: The expert consensus highlighted four dimensions of PL to be assessed-physical; affective; cognitive; and social-with new perspectives, including a preference for broad motor tests over fitness. Conclusion: Results offer new insights into the assessment of emerging adults' PL, but ELIP still requires further work concerning validity, reliability, and sensitivity.

A longitudinal examination of changes in mental health among elite Canadian athletes.

This study explored how athletes' symptoms of mental disorders changed over the course of pandemic year. Predictors of baseline levels and changes in symptoms of mental disorders were also examined. Surveys were completed four times throughout a year by Canadian athletes training for the 2020 Olympics/Paralympics (ntime1 = 186, ntime2 = 142, ntime3 = 123, ntime4 = 108). Surveys included demographics questions, measures of perceived stress, training load, social support, coping, self-esteem, depression, anxiety, and disordered eating. Data were analysed using descriptive statistics and latent growth modelling. The prevalence of mental disorder symptoms was high at baseline and there was no significant change over time. Scores for the three disorders were significantly correlated. Female athletes had higher scores for disordered eating at baseline. Higher levels of perceived stress predicted higher scores on mental disorder measures. Longitudinal tracking of symptoms of mental disorders among elite athletes is important because it allows researchers to explore whether disorder symptomologies change; rates of mental disorder symptoms were high at baseline and stayed high over the course of a year. More research is needed to explore possible gender differences in rates of disorder symptoms, and to understand how those symptoms change over time.

Laser ablation sample preparation for atom probe tomography and transmission electron microscopy.

Laser ablation is capable of removing large volumes of material with micron scale precision at very high speeds. This makes it an ideal tool for the initial stage of preparation of samples for atom probe and electron microscopy studies. However, the thermal nature of the laser ablation process is such that thermal and mechanical damage is induced in the samples in the form of zones of recrystallisation and stress induced deformation. For the analysis of nanometer-sized samples, such as those required for atom probe tomography and transmission electron microscopy, it is necessary to ensure that any damage induced during sample preparation will not introduce artefacts and that specimens are representative of the microstructure of the bulk sample. Here we have undertaken an analysis of the damage caused during sample preparation through a study of pure aluminium and phosphorous doped silicon wafers. Our findings indicate that recrystallisation and stress induced misorientations occur in pure aluminium at the micron scale, however, no detectable damage is observed in the silicon sample.

New frontiers in atom probe tomography: a review of research enabled by cryo and/or vacuum transfer systems.

There has been a recent surge in the use of cryo and/or vacuum specimen preparation and transfer systems to broaden the scope of research enabled by the microscopy technique of atom probe tomography. This is driven by the fact that, as for many microscopes, the application of atom probes to air- and temperature-sensitive materials or wet biological specimens has previously been limited by transfer through air at room temperature. Here we provide an overview of areas of research that benefit from these new transfer and analysis protocols, as well as a review of current advances in transfer devices, environmental cells, and glove boxes for controlled specimen manipulation. This includes the study of catalysis and corrosion, biological samples, liquid-solid interfaces, natural aging, and the distribution of hydrogen in materials.

Relative age effects in the Movement Assessment Battery for Children-2: age banding and scoring errors.

AIM: The Movement Assessment Battery for Children-2 (MABC-2) uses age-grouped scoring, which will result in relative motor functioning being overestimated for some children and underestimated for others. In this paper, we measure these errors and discuss their consequences. METHOD: We pool data from two validation studies to obtain a sample of 278 children assessed with the MABC-2 (mean (SD) age: 5 years, 0 months (9.6 months); 142 female). We used regression to measure the association between standard score and relative age, and used these results to estimate misclassification rates at the MABC-2's recommended thresholds. RESULTS: Movement Assessment Battery for Children-2 scores were distributed as expected (mean (SD) = 10.4 (2.8)). We estimated that the standard score varied by 2.76 units (0.92 SDs) per year of relative age. Depending on threshold and age bandwidth, this implies overall misclassification rates from 9% to 23%. INTERPRETATION: Relative age differences in MABC-2 scores led to substantial systematic error for young children. These errors can affect MABC-2 validity, longitudinal stability and agreement with other tools, which may reduce the appropriateness of care offered to children. Scoring approaches that may reduce or eliminate these errors are outlined.

Validity of the Ages and Stages Questionnaire to detect risk of Developmental Coordination Disorder in preschoolers.

BACKGROUND: A reliable and valid screening tool for detecting children at risk for Developmental Coordination Disorder (DCD) is needed. The purpose of this study was to evaluate the ability of the Ages and Stages Questionnaire-Third Edition (ASQ-3) motor scales to detect children at risk for DCD in a community-based sample of children aged 3.5-5.5 years. METHODS: One hundred and sixty parent-child pairs were recruited from community-based organizations. Children were eligible if they spoke English and had no known physical impairments. Eligible parents were asked to fill out the ASQ-3, following which their child's fine motor and gross motor proficiency was assessed using the Movement Assessment Battery for Children-Second Edition (MABC-2). DCD risk was defined as those children scoring at or below the 16th percentile on the MABC-2. Sensitivity and specificity of the fine and gross motor areas of the ASQ-3 were examined and referenced against the DCD risk classification. RESULTS: The ASQ-3 total motor score correlated moderately with overall standard score on the MABC-2 (r = 0.41; p < 0.001). Regardless of the ASQ-3 cut-off used, sensitivities of the ASQ-3 fine motor or gross motor scale to detect DCD risk were low at 21-47%, whereas specificities were high at 89-96%. CONCLUSION: Early identification of motor skill delays is important in order to intervene and hopefully prevent the associated negative health consequences. However, because of the low sensitivity of the ASQ-3 motor scales, these results suggest that the ASQ-3 is not an appropriate screening tool to identify children at risk for DCD in the preschool population.

New approaches to nanoparticle sample fabrication for atom probe tomography.

Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the atomic scale, especially in three dimensions (3D). Atom probe tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome. In order to achieve this, the nanomaterial needs to be positioned within the end of a tip and fixed there so the sample possesses sufficient structural integrity for analysis. Here we provide a detailed description of various techniques that have been used to position nanoparticles on substrates for atom probe analysis. In some of the approaches, this is combined with deposition techniques to incorporate the particles into a solid matrix, and focused ion beam processing is then used to fabricate atom probe samples from this composite. Using these approaches, data has been achieved from 10-20 nm core-shell nanoparticles that were extracted directly from suspension (i.e. with no chemical modification) with a resolution of better than ± 1 nm.

Increasing the strength of nanocrystalline steels by annealing: Is segregation necessary?

Hardening phenomena in nanocrystalline metals after annealing have been widely reported, and the subject of much recent debate. Solute segregation to grain boundaries and dislocation source hardening have been proposed to cause the strengthening. To shed light on the dominant mechanisms, we present results from mechanical experiments and atom probe tomography on samples with similar grain size but different amounts of solute segregation and different boundary chemistries.

Detecting and extracting clusters in atom probe data: a simple, automated method using Voronoi cells.

The analysis of the formation of clusters in solid solutions is one of the most common uses of atom probe tomography. Here, we present a method where we use the Voronoi tessellation of the solute atoms and its geometric dual, the Delaunay triangulation to test for spatial/chemical randomness of the solid solution as well as extracting the clusters themselves. We show how the parameters necessary for cluster extraction can be determined automatically, i.e. without user interaction, making it an ideal tool for the screening of datasets and the pre-filtering of structures for other spatial analysis techniques. Since the Voronoi volumes are closely related to atomic concentrations, the parameters resulting from this analysis can also be used for other concentration based methods such as iso-surfaces.

The tracheostomy clinical nurse specialist: an essential member of the multidisciplinary team.

BACKGROUND: Tracheostomies are a common procedure within the specialties of otolaryngology and intensive care. The ENT department at Monklands Hospital has developed the position of tracheostomy clinical nurse specialist to improve the management of tracheostomy patients. There is evidence to support the development of a multidisciplinary team for the management of tracheostomy patients following intensive care unit treatment; however, the creation of a specific tracheostomy clinical nurse specialist position has not been widely endorsed in the literature. OBJECTIVE: This paper describes the role of the tracheostomy clinical nurse specialist, advocating this position within the multidisciplinary team.

Childhood cognitive ability and its relationship with anxiety and depression in adolescence.

BACKGROUND: Childhood cognitive ability may have protective effects against internalizing symptoms in adolescence, although this may depend on the time of symptom assessment and child gender. Also, the effects of childhood stressors on adolescent internalizing symptoms may be moderated by childhood cognitive ability. METHODS: The sample included 4405 individuals from the Canadian National Longitudinal Study of Children and Youth (NLSCY). Between ages 4-5 and 10-11, children completed a test of verbal ability and scholastic aptitude and a series of mathematics computation tests. Internalizing symptoms were assessed via self-reports at ages 12-13 and 14-15. RESULTS: Greater cognitive ability was generally associated with decreased odds of internalizing symptoms at age 12-13. However, greater cognitive ability generally increased, or had no effect on, the odds of internalizing symptoms at age 14-15. Some of the effects of childhood cognitive ability varied with child gender. Also, childhood cognitive ability attenuated the effects of family dysfunction and chronic illness throughout childhood on subsequent internalizing symptoms. LIMITATIONS: These data are largely subject to some degree of reporting bias, the tests of cognitive ability are limited and may not represent overall cognitive ability, and there may be intermediary variables that account for the relationship between childhood cognitive ability and adolescent internalizing symptoms. CONCLUSION: Results suggest that programs attempting to increase early cognitive skills may be particularly beneficial for girls. Also, an increased focus on cognitive skills may attenuate the negative effects of some stressors on subsequent anxious and depressive symptoms, regardless of child gender.

Caregiving, single parents and cumulative stresses when caring for a child with cancer.

BACKGROUND: Single parents whose children have cancer are a marginalized group who report less family centred care, and therefore, less quality cancer care for their children. As such, the aims of this study were to explore how single parents of children with cancer describe their caregiving experiences and to understand their contextual life stressors. METHODS: A constructivist grounded theory method was used. Qualitative interviews with 29 single parents of children with cancer who were at least 6 months post-diagnosis were recruited between November 2009 and April 2011 from four hospitals across Canada. Line-by-line coding was used to establish codes and themes and constant comparison was used to establish relationships among emerging codes and conceptual themes. RESULTS: The first set of findings report on caregiving duties including: emotional tasks, informational tasks and physical tasks. The second set of findings report on the contextual picture of parent's lives including their living conditions, their physical and mental health and their family histories of disruption, trauma and disease. CONCLUSIONS: Single parents caring for children with cancer were found to experience several cumulative stressors in addition to the current strain of caring for a child with cancer. The synergy of these cumulative stresses with the added strain of caregiving for a child with cancer may have long-term health and financial implications for parents. Broad-based policy interventions should focus on relieving the chronic strains associated with being a single parent of a child with cancer.

Descriptive and factor analysis of the Developmental Coordination Disorder Questionnaire (DCDQ'07) in a population-based sample of children with and without Developmental Coordination Disorder.

BACKGROUND: The Developmental Coordination Disorder Questionnaire (DCDQ'07) discriminates children with Developmental Coordination Disorder (DCD) from their peers. Studies employing the DCDQ have typically used clinical samples. To further validate the DCDQ'07, this study: (1) described its distributions in a population-based sample, and a sample of children with DCD; (2) explored sex and age differences at important cut-points; and (3) examined its factor structure. METHODS: This secondary analysis of data collected from 23 schools (n = 3151) included a sample of 3070 children (1526 boys, 1544 girls) and a sample of 122 children (73 boys, 49 girls) who met DCD diagnostic criteria. DCDQ'07 distributions were described by age and sex. Chi-square analyses were conducted using three clinically important percentile ranges; a factor analysis explored the construct validity of DCDQ scores. RESULTS: Parents of 3070 children (97.4%) completed the questionnaire independently. Significant sex differences were noted in both samples. Significant differences in proportions by sex, and DCDQ means by age were found in the population sample. A three-factor solution was found, accounting for 70.3% of the variance. CONCLUSIONS: This is one of the largest studies using the DCDQ'07 with a non-clinical sample. The three-factor solution, including item loading, was consistent with previous research. When using DCDQ cut-offs it is important to consider sex and age.

Self-efficacy toward physical activity and the physical activity behavior of children with and without Developmental Coordination Disorder.

PURPOSE: Affecting 5-6% of children, Developmental Coordination Disorder (DCD) is a prevalent chronic condition. The nature of the disorder - impaired motor coordination - makes avoidance of physical activity (PA) common. The purpose of this study was to examine the effect of barrier and task self-efficacy on PA behavior in children with DCD and a group of typically developing (TD) children. METHODS: Children were compared on their perceived ability to complete different intensities and duration of PA (task efficacy) and their confidence in completing PA when faced with everyday barriers (barrier efficacy). An accelerometer was used to record their activity over the subsequent week. RESULTS: Children with DCD were found to have significantly lower task efficacy and barrier efficacy. They also spent significantly less time in moderate to vigorous physical activity (MVPA). Multivariate analyses revealed that gender modified the relationship for both groups. Separate multivariate regressions, were therefore conducted by gender. A direct effect of DCD on PA was observed for boys, but not for girls. Further analyses showed that neither task efficacy nor barrier efficacy influenced the relationship between DCD and PA. CONCLUSION: Results from this study confirm that children with DCD have lower task and barrier self-efficacy than TD children and that males have lower PA levels than their TD peers; however neither task or barrier self-efficacy mediated the relationship between DCD and PA.

New atom probe approaches to studying segregation in nanocrystalline materials.

Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping.

Three-dimensional nanofabrication of polystyrene by focused ion beam.

Focused ion beam micromachining provides a maskless and resistless technique for prototyping of structures from thermoplastic polymers, an example being the production of polystyrene microcantilevers with potential applications as micro/nanoelectromechanical systems sensors and actuators. The applicability of FIB technology is, however, often restricted by the damage created by high energy gallium ion bombardment and local beam heating, which can affect the desired properties and limit the minimum achievable size of the fabricated structure. To investigate the ion-induced damage and determine the limitations of the technique for polymer nanofabrication, we have exposed thin polystyrene film to the ion beam at varying ion doses, ion energies and specimen temperatures. Ion doses ranging from 10(16) to 10(18) ions cm(-2) show significant gallium implantation, redeposition of sputtered material and chemical degradation in the polymer. Raman results show that the local heating in polymer during milling is severe at room temperature, damaging the aromatic carbon bonding (C = C) in particular. These observations are supported by the results of a beam heating model and Monte Carlo simulations. The chemical degradation caused by local beam heating is found to be significantly reduced by cooling the specimen to -25°C during milling. This is consistent with observations that reversible and repeatable thermal actuation of a fabricated polystyrene-platinum microcantilever is only observed when the cantilever is prepared at low temperature milling. Using this cooling approach, polymer structures can be fabricated with dimensions as low as 200 nm and still retain a sufficient volume of material unaffected by the ion beam.

Shaping the lens of the atom probe: fabrication of site specific, oriented specimens and application to grain boundary analysis.

The random sampling provided by classical atom probe sample preparation methods is one of the major factors limiting the types of problems that can be addressed using this powerful technique. A focused ion beam enables not only site-specific preparation, but can also be used to give the specimen, which acts as the lens in an atom probe experiment, a specific shape. In this paper we present a technique that uses low accelerating voltages (10 and 5 kV) in the focused ion beam (FIB) to reproducibly produce specimens with selected grain boundaries <100 nm from the tip at any desired orientation. These tips have a high rate of successfully running in the atom probe and no Ga contamination within the region of interest. This technique is applied to the analysis of grain boundaries in a high purity iron wire and a strip-cast steel. Lattice resolution is achieved around the boundary in certain areas. Reconstruction of these datasets reveals the distribution of light and heavy elements around the boundary. Issues surrounding the uneven distribution of certain solute elements as a result of field-induced diffusion are discussed.

Optimisation of specimen temperature and pulse fraction in atom probe microscopy experiments on a microalloyed steel.

This paper details the effects of systematic changes to the experimental parameters for atom probe microscopy of microalloyed steels. We have used assessments of the signal-to-noise ratio (SNR), compositional measurements and field desorption images to establish the optimal instrumental parameters. These corresponded to probing at the lowest possible temperature (down to 20K) with the highest possible pulse fraction (up to 30%). A steel containing a fine dispersion of solute atom clusters was used as an archetype to demonstrate the importance of running the atom probe at optimum conditions.