Sonic hedgehog-expressing cells in the developing limb measure time by an intrinsic cell cycle clock

How time is measured is an enduring issue in developmental biology. Classical models of somitogenesis and limb development implicated intrinsic cell cycle clocks, but their existence remains controversial. Here we show that an intrinsic cell cycle clock in polarizing region cells of the chick limb bud times the duration of Sonic hedgehog (Shh) expression, which encodes the morphogen specifying digit pattern across the antero-posterior axis (thumb to little finger). Timing by this clock starts when polarizing region cells fall out of range of retinoic acid signalling. We found that timing of Shh transcription by the cell cycle clock can be reset, thus revealing an embryonic form of self-renewal. In contrast, antero-posterior positional values cannot be reset, suggesting that this may be an important constraint on digit regeneration. Our findings provide the first evidence for an intrinsic cell cycle timer controlling duration and patterning activity of a major embryonic signalling centre

Human optional stopping in a heteroscedastic world

When making decisions, animals must trade off the benefits of information harvesting against the opportunity cost of prolonged deliberation. Deciding when to stop accumulating information and commit to a choice is challenging in natural environments, where the reliability of decision-relevant information may itself vary unpredictably over time (variable variance or "heteroscedasticity"). We asked humans to perform a categorization task in which discrete, continuously valued samples (oriented gratings) arrived in series until the observer made a choice. Human behavior was best described by a model that adaptively weighted sensory signals by their inverse prediction error and integrated the resulting quantities with a linear urgency signal to a decision threshold. This model approximated the output of a Bayesian model that computed the full posterior probability of a correct response, and successfully predicted adaptive weighting of decision information in neural signals. Adaptive weighting of decision information may have evolved to promote optional stopping in heteroscedastic natural environments. (PsycInfo Database Record (c) 2021 APA, all rights reserved)

Supporting induction: relationships count

This article examines the structural changes to the induction of teachers in Scotland using the perceptions of a group of final year student teachers. This group would be the first probationer teachers to experience revised arrangements for new teacher induction in 37 years. Their preferences and concerns are highlighted, as the new procedures roll out in schools nationwide, in an attempt to stress the importance of relationships to the success of the induction scheme. The argument put forward in this article is based on the notion that personal intelligence is central to effective relationships and therefore crucially important in the context of this mentoring relationship. The views of our sample provide evidence to suggest that the quality of interactions between the mentor and the probationer teacher are paramount in providing a good induction experience. These views are substantiated by experiences in England and in induction literature elsewhere. A synthesis of this evidence is used to make recommendations for those involved in supporting induction in schools, local authorities or teacher education institutions

'Can you recommend any good STI apps?' A review of content, accuracy and comprehensiveness of current mobile medical applications for STIs and related genital infections.

OBJECTIVE: Seeking sexual health information online is common, and provision of mobile medical applications (apps) for STIs is increasing. Young people, inherently at higher risk of STIs, are avid users of technology, and apps could be appealing sources of information. We undertook a comprehensive review of content and accuracy of apps for people seeking information about STIs. METHODS: Search of Google Play and iTunes stores using general and specific search terms for apps regarding STIs and genital infections (except HIV), testing, diagnosis and management, 10 September 2014 to 16 September 2014. We assessed eligible apps against (1) 19 modified Health on The Net (HON) Foundation principles; and (2) comprehensiveness and accuracy of information on STIs/genital infections, and their diagnosis and management, compared with corresponding National Health Service STI information webpage content. RESULTS: 144/6642 apps were eligible. 57 were excluded after downloading. 87 were analysed. Only 29% of apps met ≥6 HON criteria. Content was highly variable: 34/87 (39%) covered one or two infections; 40 (46%) covered multiple STIs; 5 (6%) focused on accessing STI testing. 13 (15%) were fully, 46 (53%) mostly and 28 (32%) partially accurate. 25 (29%) contained ≥1 piece of potentially harmful information. Apps available on both iOS and Android were more accurate than single-platform apps. Only one app provided fully accurate and comprehensive information on chlamydia. CONCLUSIONS: Marked variation in content, quality and accuracy of available apps combined with the nearly one-third containing potentially harmful information risks undermining potential benefits of an e-Health approach to sexual health and well-being

A mechanism for morphogen-controlled domain growth

Many developmental systems are organised via the action of graded distributions of morphogens. In the Drosophila wing disc, for example, recent experimental evidence has shown that graded expression of the morphogen Dpp controls cell proliferation and hence disc growth. Our goal is to explore a simple model for regulation of wing growth via the Dpp gradient: we use a system of reaction-diffusion equations to model the dynamics of Dpp and its receptor Tkv, with advection arising as a result of the flow generated by cell proliferation. We analyse the model both numerically and analytically, showing that uniform domain growth across the disc produces an exponentially growing wing disc

Homogenization in magnetic-shape-memory polymer composites

Magnetic-shape-memory materials (e.g. specific NiMnGa alloys) react with a large change of shape to the presence of an external magnetic field. As an alternative for the difficult to manifacture single crystal of these alloys we study composite materials in which small magnetic-shape-memory particles are embedded in a polymer matrix. The macroscopic properties of the composite depend strongly on the geometry of the microstructure and on the characteristics of the particles and the polymer. We present a variational model based on micromagnetism and elasticity, and derive via homogenization an effective macroscopic model under the assumption that the microstructure is periodic. We then study numerically the resulting cell problem, and discuss the effect of the microstructure on the macroscopic material behavior. Our results may be used to optimize the shape of the particles and the microstructure.Comment: 17 pages, 4 figure

Using the eSexual Health Clinic to access chlamydia treatment and care via the internet: a qualitative interview study.

OBJECTIVE: We developed the eSexual Health Clinic (eSHC), an innovative, complex clinical and public health intervention, embedded within a specialist sexual health service. Patients with genital chlamydia access their results online and are offered medical management via an automated online clinical consultation, leading to antibiotic collection from community pharmacy. A telephone helpline, staffed by Sexual Health Advisers, is available to support patients and direct them to conventional services if appropriate. We sought to understand how patients used this ehealth intervention. METHODS: Within exploratory studies of the eSHC (2014-2015), we conducted in-depth interviews with a purposive sample of 36 patients diagnosed with chlamydia, who had chosen to use the eSHC (age 18-35, 20 female, 16 male). Thematic analysis was conducted. RESULTS: Participants described choosing to use this ehealth intervention to obtain treatment rapidly, conveniently and privately, within busy lifestyles that hindered clinic access. They described completing the online consultation promptly, discreetly and with ease. The information provided online was considered comprehensive, reassuring and helpful, but some overlooked it in their haste to obtain treatment. Participants generally described being able to collect treatment from pharmacies discreetly and promptly, but for some, poor awareness of the eSHC by pharmacy staff undermined their ability to do this. Those unsuitable for remote management, who were directed to clinic, described frustration and concern about health implications and clinic attendance. However, the helpline was a highly valued source of information, assistance and support. CONCLUSION: The eSHC is a promising adjunct to traditional care. Its users have high expectations for convenience, speed and privacy, which may be compromised when transitioning from online to face-to-face elements of the eSHC. Managing expectations and improving implementation of the pharmacy process, could improve their experiences. Positive views on the helpline provide further support for embedding this ehealth intervention within a specialist clinical service