An uneven distribution of strontium in the coccolithophore Scyphosphaera apsteinii revealed by nanoscale X-ray fluorescence tomography.

Coccolithophores are biogeochemically and ecologically important phytoplankton that produce a composite calcium carbonate-based exoskeleton - the coccosphere - comprised of individual platelets, known as coccoliths. Coccoliths are stunning examples of biomineralization; their formation featuring exceptional control over both biomineral chemistry and shape. Understanding how coccoliths are formed requires information about minor element distribution and chemical environment. Here, the first high-resolution 3D synchrotron X-ray fluorescence (XRF) mapping of a coccolith is presented, showing that the lopadoliths of Scyphosphaera apsteinii display stripes of different Sr concentration. The presence of Sr stripes is unaffected by elevated Sr in the culture medium, macro-nutrient concentration, and light intensity, indicating that the observed stripiness is an expression of the fundamental coccolith formation process in this species. Current Sr fractionation models, by contrast, predict an even Sr distribution and will have to be modified to account for this stripiness. Additionally, nano-XANES analyses show that Sr resides in a Ca site in the calcite lattice in both high and low Sr stripes, confirming a central assumption of current Sr fractionation models.

Multi-resolution Correlative Ultrastructural and Chemical Analysis of Carious Enamel by Scanning Microscopy and Tomographic Imaging.

Caries, a major global disease associated with dental enamel demineralization, remains insufficiently understood to devise effective prevention or minimally invasive treatment. Understanding the ultrastructural changes in enamel is hampered by a lack of nanoscale characterization of the chemical spatial distributions within the dental tissue. This leads to the requirement to develop techniques based on various characterization methods. The purpose of the present study is to demonstrate the strength of analytic methods using a correlative technique on a single sample of human dental enamel as a specific case study to test the accuracy of techniques to compare regions in enamel. The science of the different techniques is integrated to genuinely study the enamel. The hierarchical structures within carious tissue were mapped using the combination of focused ion beam scanning electron microscopy with synchrotron X-ray tomography. The chemical changes were studied using scanning X-ray fluorescence (XRF) and X-ray wide-angle and small-angle scattering using a beam size below 80 nm for ångström and nanometer length scales. The analysis of XRF intensity gradients revealed subtle variations of Ca intensity in carious samples in comparison with those of normal mature enamel. In addition, the pathways for enamel rod demineralization were studied using X-ray ptychography. The results show the chemical and structural modification in carious enamel with differing locations. These results reinforce the need for multi-modal approaches to nanoscale analysis in complex hierarchically structured materials to interpret the changes of materials. The approach establishes a meticulous correlative characterization platform for the analysis of biomineralized tissues at the nanoscale, which adds confidence in the interpretation of the results and time-saving imaging techniques. The protocol demonstrated here using the dental tissue sample can be applied to other samples for statistical study and the investigation of nanoscale structural changes. The information gathered from the combination of methods could not be obtained with traditional individual techniques.

Differential phase contrast for quantitative imaging and spectro-microscopy at a nanoprobe beamline.

The interaction of a focused X-ray beam with a sample in a scanning probe experiment can provide a variety of information about the interaction volume. In many scanning probe experiments X-ray fluorescence (XRF) is supplemented with measurements of the transmitted or scattered intensity using a pixelated detector. The automated extraction of different signals from an area pixelated detector is described, in particular the methodology for extracting differential phase contrast (DPC) is demonstrated and different processing methods are compared across a range of samples. The phase shift of the transmitted X-ray beam by the sample, extracted from DPC, is also compared with ptychography measurements to provide a qualitative and quantitative comparison. While ptychography produces a superior image, DPC can offer a simple, flexible method for phase contrast imaging which can provide fast results and feedback during an experiment; furthermore, for many science problems, such as registration of XRF in a lighter matrix, DPC can provide sufficient information to meet the experimental aims. As the DPC technique is a quantitative measurement, it can be expanded to spectroscopic studies and a demonstration of DPC for spectro-microscopy measurements is presented. Where ptychography can separate the absorption and phase shifts by the sample, quantitative interpretation of a DPC image or spectro-microscopy signal can only be performed directly when absorption is negligible or where the absorption contribution is known and the contributions can be fitted.

The Delta Robot-A long travel nano-positioning stage for scanning x-ray microscopy.

A new stage design concept, the Delta Robot, is presented, which is a parallel kinematic design for scanning x-ray microscopy applications. The stage employs three orthogonal voice coils, which actuate parallelogram flexures. The design has a 3 mm travel range and achieves rms position jitter, integrated from 1 Hz to 1 kHz, of 2.8 and 1.3 nm perpendicular to the beam and 5.6 nm along the beam direction with loads up to 350 g. The Delta Robot design process used a mechatronics approach of iterative modeling and simulation to develop the system and validate performance. The design considerations, design process, stability, and operational performance on the hard x-ray nanoprobe at Diamond Light Source are presented.

Explaining the negative impact of workplace incivility on work and non-work outcomes: The roles of negative rumination and organizational support.

Research studies have shown that workplace incivility is associated with numerous negative work and non-work outcomes. The underlying mechanisms explaining why workplace incivility is associated with these outcomes, as well as contextual buffers of these relationships, have received less attention. This study extends workplace incivility research by examining the mediating role of negative rumination as a potential factor undergirding the relationship between experiences of incivility from colleagues at work and detrimental outcomes. We also investigated perceived organizational support and family supportive work environment as potential mitigators of the indirect relationship between incivility and negative outcomes. Data were collecfrom 154 university faculty members on two occasions. The results showed that negative rumination mediated the relationships between workplace incivility and both work (job satisfaction, burnout) and non-work (work-to-family conflict, life satisfaction) outcomes. Furthermore, results from the moderated mediation analyses revealed that perceived organizational support buffered the mediated effect of negative rumination and job satisfaction and a family-supportive work environment buffered the mediated effect of negative rumination on work-to-family conflict. Overall, the results demonstrate that negative rumination helps explain why workplace incivility negatively affects both work and non-work outcomes and underscores the important role of organizational context as buffers for these relationships.

Political identity dissimilarity, workplace incivility, and declines in well-being: A prospective investigation.

The workplace is an environment where individuals have little choice about with whom they interact. As such, employees may find themselves engaged in conversations with coworkers whose political opinions and perspectives are divergent from their own. In the present study, we examined how coworkers' (dis)similarity in political identity is related to the quality of their interpersonal interactions and subsequent well-being. We predicted that political identity dissimilarity is associated with experiences of workplace incivility and, in turn, declines in psychological and occupational well-being. We tested our hypotheses in a four-wave survey study conducted during the 2012 U.S. presidential election using structural equation modeling. Consistent with our expectations, results indicated that political identity dissimilarity was associated with increased reports of incivility experiences instigated by coworkers, which, in turn, was associated with increased burnout and turnover intentions and diminished job satisfaction. The relationship between incivility and well-being was mediated by psychological distress. Overall, the findings demonstrate that political identity dissimilarity is detrimentally related to job attitudes and well-being via triggering workplace incivility, which provides meaningful implications for organizations on how to mitigate the negative influences of identity dissimilarity.

Solid-State Transformation of Amorphous Calcium Carbonate to Aragonite Captured by CryoTEM.

Early-stage reaction mechanisms for aragonite-promoting systems are relatively unknown compared to the more thermodynamically stable calcium carbonate polymorph, calcite. Using cryoTEM and SEM, the early reaction stages taking place during aragonite formation were identified in a highly supersaturated solution using an alcohol-water solvent, and an overall particle attachment growth mechanism was described for the system. In vitro evidence is provided for the solid-state transformation of amorphous calcium carbonate to aragonite, demonstrating the co-existence of both amorphous and crystalline material within the same aragonite needle. This supports non-classical formation of aragonite within both a synthetic and biological context.

Competence and performance in causal learning.

The dominant theoretical approach to causal learning postulates the acquisition of associative weights between cues and outcomes. This reduction of causal induction to associative learning implies that learners are insensitive to important characteristics of causality, such as the inherent directionality between causes and effects. An ongoing debate centers on the question of whether causal learning is sensitive to causal directionality (as is postulated by causal-model theory) or whether it neglects this important feature of the physical world (as implied by associationist theories). Three experiments using different cue competition paradigms are reported that demonstrate the competence of human learners to differentiate between predictive and diagnostic learning. However, the experiments also show that this competence displays itself best in learning situations with few processing demands and with convincingly conveyed causal structures. The study provides evidence for the necessity to distinguish between competence and performance in causal learning.