Strong shear-flow modulation of instabilities in rapid directional solidification

We examine the effect of a strong shear flow on morphological instabilities that occur in the directional solidification of a dilute, binary alloy when the interface departs from local thermal equilibrium in a frozen-temperature, one-sided model. In particular, the flow velocity U∞ is much larger than the rate of solidification V and the Schmidt number is arbitrary. In contrast to solidification processes under small or no flow, for which both a cellular and an oscillatory mode of instability appear, the liquid-solid interface under flows of large magnitude is susceptible to a single mode of instability. All experiments on banding occur in the overlap region between these modes under no flow and since these two primary modes coalesce into one time-dependent, spatially-dependent mode, there is no mechanism for the production of bands anymore in the large-flow regime. No experiments have been conducted to date on this rapid solidification under flow and this suggests that such experiments would show no bands. The flow significantly stabilizes and selects higher wavenumbers for the preferred form of instability in comparison to systems involving small or no flow. The introduction of a strong flow provides an effective mechanism to eliminate instabilities at high solidification rates. However, stability thresholds at low solidification rates remain mainly indifferent to the presence of flow.This work is supported by the National Institute of Stan- dards and Technology (Grant No. 70NANB14H012) as part of the Center for Hierarchical Material Design (CHiMaD)

Using a model of group psychotherapy to support social research on sensitive topics

This article describes the exploratory use of professional therapeutic support by social researchers working on a sensitive topic. Talking to recently bereaved parents about the financial implications of their child's death was expected to be demanding work, and the research design included access to an independent psychotherapeutic service. Using this kind of professional support is rare within the general social research community, and it is useful to reflect on the process. There are likely to be implications for collection and interpretation of data, research output and the role and experience of the therapist. Here, the primary focus is the potential impact on researcher well-being

Thermocapillary instabilities in a horizontal liquid layer under partial basal slip

We investigate the onset of three-dimensional hydrothermal waves in a low-capillary-number liquid layer of arbitrary depth, bounded by a free liquid–gas interface from above and a partial slip, rigid surface from below. A selection of two- and three-dimensional hydrothermal waves, longitudinal rolls and longitudinal travelling waves, form the preferred mode of instability, which depends intricately on the magnitude of the basal slip. Partial slip is destabilizing for all modes of instability. Specifically, the minimal Marangoni number required for the onset of instability follows M_{m}\sim a(\unicode[STIX]{x1D6FD}^{-1}+b)^{-c} for each mode, where a,b,c>0 and \unicode[STIX]{x1D6FD}^{-1} is the slip parameter. In the limit of free slip, longitudinal travelling waves disappear in favour of longitudinal rolls. With increasing slip, it is common for two-dimensional hydrothermal waves to exchange stability in favour of longitudinal rolls and oblique hydrothermal waves. Two types of oblique hydrothermal waves appear under partial slip, which exchange stability with increasing slip. The oblique mode that is preferred under no slip persists and remains near longitudinal for small slip parameters.This work is supported by the National Institute of Stan- dards and Technology (Grant No. 70NANB14H012) as part of the Center for Hierarchical Material Design (CHiMaD)

Detecting delirium superimposed on dementia: diagnostic accuracy of a simple combined arousal and attention testing procedure

Detecting delirium superimposed on dementia (DSD) can be challenging because assessment partly relies on cognitive tests that may be abnormal in both conditions. We hypothesized that a combined arousal and attention testing procedure would accurately detect DSD. Patients aged ≥70 years were recruited from five hospitals across Europe. Delirium was diagnosed by physicians using DSM-5 criteria using information from nurses, carers, and medical records. Dementia was ascertained by the Informant Questionnaire on Cognitive Decline in the Elderly. Arousal was measured using the Observational Scale of Level of Arousal (OSLA), which assesses eye opening, eye contact, posture, movement, and communication. Attention was measured by participants signaling each time an “A” was heard when “S-A-V-E-A-H-A-A-R-T” was read out. The sample included 114 persons (mean age 82 years (SD 7); 54% women). Dementia alone was present in 25% (n = 28), delirium alone in 18% (n = 21), DSD in 27% (n = 31), and neither in 30% (n = 34). Arousal and attention was assessed in n = 109 (96%). Using OSLA, 83% participants were correctly identified as having delirium (sensitivity 85%, specificity 82%, AUROC 0.92). The attention task correctly classified 76% of participants with delirium (sensitivity 90%, specificity 64%, AUROC 0.80). Combining scores correctly classified 91% of participants with delirium (sensitivity 84%, specificity 92%, AUROC 0.94). Diagnostic accuracy remained high in the subgroup with dementia (93% correctly classified, sensitivity 94%, specificity 92%, AUROC 0.98). This combined arousal–attention assessment to detect DSD was brief yet had high diagnostic accuracy. Such an approach could have clinical utility for diagnosing DSD

Flexible production and entry: institutional, technological, and organizational determinants

Academics, the media, and policymakers have all raised concerns about the implications of human workers being replaced by machines or software. Few have discussed the implications of the reverse: firms’ ability to replace capital with workers. We show that this flexibility can help new firms overcome uncertainty and increase entrepreneurial entry. We develop a simple real options model where permissive labor regulations allow firms to take advantage of capital-labor substitutability by replacing ‘rigid’ capital with ‘flexible’ labor. The model highlights institutional, technological, and organizational preconditions to using this flexibility. Using a large and comprehensive dataset on entry by standalone firms and group affiliates, we provide evidence in support of the model

Fluctuations of a holographic quantum Hall fluid

We analyze the neutral spectrum of the holographic quantum Hall fluid described by the D2-D8' model. As expected for a quantum Hall state, we find the system to be stable and gapped and that, at least over much of the parameter space, the lowest excitation mode is a magneto-roton. In addition, we find magneto-rotons in higher modes as well. We show that these magneto-rotons are direct consequences of level crossings between vector and scalar modes.Comment: 20 pages, 8 figures; v.2 figures improved, 2 figures added, and text clarified particularly in Sec. 5, to appear in JHE

Moving from evidence-based medicine to evidence-based health.

While evidence-based medicine (EBM) has advanced medical practice, the health care system has been inconsistent in translating EBM into improvements in health. Disparities in health and health care play out through patients' limited ability to incorporate the advances of EBM into their daily lives. Assisting patients to self-manage their chronic conditions and paying attention to unhealthy community factors could be added to EBM to create a broader paradigm of evidence-based health. A perspective of evidence-based health may encourage physicians to consider their role in upstream efforts to combat socially patterned chronic disease