Spectral analysis of boundary layers in Rayleigh-Benard convection

A combined experimental and numerical study of the boundary layer in a 4:1 aspect-ratio Rayleigh-B\'{e}nard cell over a four-decade range of Rayleigh numbers has been undertaken aimed at gaining a better insight into the character of the boundary layers. The experiments involved the simultaneous Laser Doppler Anemometry (LDA) measurements of fluid velocity at two locations, i.e. in the boundary layer and far away from it in the bulk, for Rayleigh numbers varying between $1.6 \times 10^7$ and $2.4 \times 10^9$. In parallel, direct numerical simulations (DNS) have been performed for the same configuration for Rayleigh numbers between $7.0 \times 10^4$ and $7.7 \times 10^7$. The temperature and velocity probability density functions and the power spectra of the horizontal velocity fluctuations measured in the boundary layer and in the bulk flow are found to be practically identical. Except for the smallest Rayleigh numbers, the spectra in the boundary layer and in the bulk central region are continuous and have a wide range of active scales. This indicates that both the bulk and the boundary layers are turbulent in the $\textrm{Ra}$ number range considered. However, molecular effects can still be observed and the boundary layer does not behave like a classical shear-driven turbulent boundary layer.Comment: 10 pages, 6 figures, Accepted for publication in Phys. Rev.

Nudges can be both autonomy-preserving and effective: Evidence from a survey and quasi-field experiment

Nudges are widely employed tools within organizations, but they are often criticized for harming autonomy and for being ineffective. We assess these two criticisms simultaneously: can nudges be both autonomy-preserving and effective in changing behavior? We developed three nudges - an opinion leader nudge, a rule-of-thumb and self-nudges - to reduce a particularly sticky behavior: email use. In a survey experiment of 4,112 healthcare employees, we tested their effect on perceived autonomy and subjective effectiveness. We also tested traditional policy instruments for comparison. Next, to assess objective effectiveness, we conducted a quasi-field experiment in a large healthcare organization with an estimate of 1,189 active email users. We found that each nudge in isolation, but especially when combined, was perceived to be both autonomy-preserving and effective, and more so than traditional policy instruments like an access limit or a monetary reward. We also found some evidence that the combination of all nudges decreased actual email use. This paper advances the literature by showing how innovations in nudge design improve nudges' ability to be autonomy-preserving and effective

p63 regulates multiple signalling pathways required for ectodermal organogenesis and differentiation

Heterozygous germline mutations in p63, a transcription factor of the p53 family, result in abnormal morphogenesis of the skin and its associated structures, including hair follicles and teeth. In mice lacking p63, all ectodermal organs fail to develop, and stratification of the epidermis is absent. We show that the ectodermal placodes that mark early tooth and hair follicle morphogenesis do not form in p63-deficient embryos, although the multilayered dental lamina that precedes tooth placode formation develops normally. The N-terminally truncated isoform of p63 (?Np63) was expressed at high levels in embryonic ectoderm at all stages of tooth and hair development, and it was already dominant over the transactivating TAp63 isoform prior to epidermal stratification. Bmp7, Fgfr2b, Jag1 and Notch1 transcripts were co-expressed with ANp63 in wild-type embryos, but were not detectable in the ectoderm of p63 mutants. In addition, ?-catenin and Edar transcripts were significantly reduced in skin ectoderm. We also demonstrate that BMP2, BMP7 and FGF10 are potent inducers of p63 in cultured tissue explants. Hence, we suggest that p63 regulates the morphogenesis of surface ectoderm and its derivatives via multiple signalling pathways

Handling stress during policy implementation: Developing a classification of “coping” by frontline workers based on a systematic review

Stress is endemic to street-level work. How frontline workers handle conflicting pressures and changes in their environment bears substantially on policy performance and the delivery of human services. ‘Coping’ is the current term for understanding frontline workers responses to stress. Coping in the field of policy implementation is a sensitizing concept, not yet harmonized with extensive coping literature in clinical psychology nor operationalized to enable its measurement of its prevalence in the context of policy implementation. This paper takes steps to close that gap. Our main objective is to define coping and build a classification model. To this end, we conduct a systematic review of the literature on coping during policy implementation. After discussing ways that technology and new forms of public administration may bear on coping, we build a classification model of coping during policy implementation, comprised of three main families of coping (negotiation, problem solving and opposition) and multiple ways of coping (such as blaming others, routinizing services and whistleblowing). Our ultimate goal is to operationalize coping in the context of frontline work so that it can advance our understanding of human service delivery and serve as a diagnostic tool for practitioners seeking to improve policy performance as everyday practice

Designing to Debias: Measuring and Reducing Public Managers’ Anchoring Bias

Public managers’ decisions are affected by cognitive biases. For instance, employees’ previous year's performance ratings influence new ratings irrespective of actual performance. Nevertheless, experimental knowledge of public managers’ cognitive biases is limited, and debiasing techniques have rarely been studied. Using a survey experiment on 1,221 public managers and employees in the United Kingdom, this research (1) replicates two experiments on anchoring to establish empirical generalization across institutional contexts and (2) tests a consider-the-opposite debiasing technique. The results indicate that anchoring bias replicates in a different institutional context, although effect sizes differ. Furthermore, a low-cost, low-intensity consider-the-opposite technique mitigates anchoring bias in this survey experiment. An exploratory subgroup analysis indicates that the effect of the intervention depends on context. The next step is to test this strategy in real-world settings

Decision‐making at the frontline: exploring coping with moral conflicts during public service delivery

Moral conflicts, where a person is confronted with two or more clashing values, norms or responsibilities, are common in public service delivery. Choosing one is realized at the cost of the other(s). Frontline professionals, such as physicians and police officers, often experience clashes over the right thing to do as new policies, organisational rules, professional obligations and clients’ demands come together. Stress may be a consequence. This chapter aims to increase our understanding of moral conflicts and coping with stress in regard to public service delivery and explore how morality and coping strategies are interconnected in the policy context.<

De “ultieme HRM-vraag”: Zou jij je werkgever aanbevelen aan familie en vrienden?

Organisaties streven daarom naar 'loyale' werknemers. Er zijn al verschillende manieren om loyaliteit te meten, zoals via 'organisatiebetrokkenheid'. Maar is er niet één ultieme vraag die we kunnen stellen? Misschien kunnen we deze loyaliteit meten via de zogenaamde 'Werkgever Net Promotor Score'. Deze vraag is afgeleid van het artikel van Frederick Reichfeld uit de Harvard Business Review, getiteld "The one number you need to grow". Reichfeld stelt er een 'ultieme vraag' is die bedrijven aan hun klanten kunnen stellen. Deze vraag: "In welke mate beveelt u deze organisatie aan bij vrienden en familie?" wordt in klanttevredenheidsonderzoeken gebruikt gebruikt om de loyaliteit van klanten te meten

Consistent alleviation of abiotic stress with silicon addition: a meta-analysis

1. Hundreds of single species studies have demonstrated the facility of silicon (Si) to alleviate diverse abiotic stresses in plants. Understanding of the mechanisms of Si-mediated stress alleviation is progressing, and several reviews have brought information together. A quantitative assessment of the alleviative capacity of Si, however, which could elucidate plant Si function more broadly, was lacking. 2. We combined the results of 145 experiments, predominantly on agricultural species, in a meta-analysis to statistically assess the responses of stressed plants to Si supply across multiple plant families and abiotic stresses. We interrogated our database to determine whether stressed plants increased in dry mass and net assimilation rate, oxidative stress markers were reduced, antioxidant responses were increased and whether element uptake showed consistent changes when supplied with Si. 3. We demonstrated that across plant families and stress types, Si increases dry weight, assimilation rate and chlorophyll biosynthesis and alleviates oxidative damage in stressed plants. In general, results indicated that plant family (as a proxy for accumulator type) and stress type had significant explanatory power for variation in responses. The consistent reduction in oxidative damage was not mirrored by consistent increases in antioxidant production, indicative of the several different stress alleviation mechanisms in which Si is involved. Silicon addition increased K in shoots, decreased As and Cd in roots and Na and Cd in shoots. Silicon addition did not affect Al, Ca or Mn concentration in shoots and roots of stressed plants. Plants had significantly lower concentrations of Si accumulated in shoots but not in roots when stressed. 4. Meta-analyses showed consistent alleviation by Si of oxidative damage caused by a range of abiotic stresses across diverse species. Our findings indicate that Si is likely to be a useful fertilizer for many crops facing a spectrum of abiotic stresses. Similarities in responses across families provide strong support for a role of Si in the alleviation of abiotic stress in natural systems, where it has barely been explored. We suggest this role may become more important under a changing climate and more experiments using non-agricultural species are now needed