A class of exact Navier-Stokes solutions for homogeneous flat-plate boundary layers and their linear stability

We introduce a new boundary layer formalism on the basis of which a class of exact solutions to the Navier–Stokes equations is derived. These solutions describe laminar boundary layer flows past a flat plate under the assumption of one homogeneous direction, such as the classical swept Hiemenz boundary layer (SHBL), the asymptotic suction boundary layer (ASBL) and the oblique impingement boundary layer. The linear stability of these new solutions is investigated, uncovering new results for the SHBL and the ASBL. Previously, each of these flows had been described with its own formalism and coordinate system, such that the solutions could not be transformed into each other. Using a new compound formalism, we are able to show that the ASBL is the physical limit of the SHBL with wall suction when the chordwise velocity component vanishes while the homogeneous sweep velocity is maintained. A corresponding non-dimensionalization is proposed, which allows conversion of the new Reynolds number definition to the classical ones. Linear stability analysis for the new class of solutions reveals a compound neutral surface which contains the classical neutral curves of the SHBL and the ASBL. It is shown that the linearly most unstable Görtler–Hämmerlin modes of the SHBL smoothly transform into Tollmien–Schlichting modes as the chordwise velocity vanishes. These results are useful for transition prediction of the attachment-line instability, especially concerning the use of suction to stabilize boundary layers of swept-wing aircraft.

On degeneracy and invariances of random fields paths with applications in Gaussian process modelling

We study pathwise invariances and degeneracies of random fields with motivating applications in Gaussian process modelling. The key idea is that a number of structural properties one may wish to impose a priori on functions boil down to degeneracy properties under well-chosen linear operators. We first show in a second order set-up that almost sure degeneracy of random field paths under some class of linear operators defined in terms of signed measures can be controlled through the two first moments. A special focus is then put on the Gaussian case, where these results are revisited and extended to further linear operators thanks to state-of-the-art representations. Several degeneracy properties are tackled, including random fields with symmetric paths, centred paths, harmonic paths, or sparse paths. The proposed approach delivers a number of promising results and perspectives in Gaussian process modelling. In a first numerical experiment, it is shown that dedicated kernels can be used to infer an axis of symmetry. Our second numerical experiment deals with conditional simulations of a solution to the heat equation, and it is found that adapted kernels notably enable improved predictions of non-linear functionals of the field such as its maximum.

Wound models for periodontal and bone regeneration: the role of biologic research

The ultimate goals of periodontal therapy remain the complete regeneration of those periodontal tissues lost to the destructive inflammatory-immune response, or to trauma, with tissues that possess the same structure and function, and the re-establishment of a sustainable health-promoting biofilm from one characterized by dysbiosis. This volume of Periodontology 2000 discusses the multiple facets of a transition from therapeutic empiricism during the late 1960s, toward regenerative therapies, which is founded on a clearer understanding of the biophysiology of normal structure and function. This introductory article provides an overview on the requirements of appropriate in vitro laboratory models (e.g. cell culture), of preclinical (i.e. animal) models and of human studies for periodontal wound and bone repair. Laboratory studies may provide valuable fundamental insights into basic mechanisms involved in wound repair and regeneration but also suffer from a unidimensional and simplistic approach that does not account for the complexities of the in vivo situation, in which multiple cell types and interactions all contribute to definitive outcomes. Therefore, such laboratory studies require validatory research, employing preclinical models specifically designed to demonstrate proof-of-concept efficacy, preliminary safety and adaptation to human disease scenarios. Small animal models provide the most economic and logistically feasible preliminary approaches but the outcomes do not necessarily translate to larger animal or human models. The advantages and limitations of all periodontal-regeneration models need to be carefully considered when planning investigations to ensure that the optimal design is adopted to answer the specific research question posed. Future challenges lie in the areas of stem cell research, scaffold designs, cell delivery and choice of growth factors, along with research to ensure appropriate gingival coverage in order to prevent gingival recession during the healing phase.

Are there signs of change in gendered language use in children's early reading material?

In this study we investigate the relative frequencies of female and male terms in early reading material for children using the Children’s Printed Word Database as a resource. As roles of females and males have changed over time it is of interest to see if there has been a corresponding change in representations of females and males in children’s books. We carried out analyses regarding different words related to gender. Except for nouns referring to relatives, we found in all word groups a preponderance of male terms. The imbalance of male and female pronouns is equivalent to that reported by Carroll, Davies, and Richman (1971) in a frequency count of printed words in children’s book in the USA conducted some 40 years ago. The results are discussed in terms of gender inequality in reading materials and the development of social mores and stereotypical ideas.

The spatial and linguistic division of the city of Malaga

The city of Malaga underwent considerable growth in the 19th and 20th centuries. The territorial expansion paired with a massive influx of immigrants occurred in three waves and as a consequence the city of Malaga remains divided into three different parts up to today. The differences between these three neighbourhoods of the city lie in the type of houses, different cultural and industrial activities, socioeconomic level, and very interestingly, also in speech. Thus, the aim of this study is an examination of the interrelation between speech (phonetic features) and urban space in Malaga. A combination of quantitative and qualitative analysis was used, based on two types of data: 1) production data stemming from recordings of 120 speakers; 2) perception data (salience, estimated frequency of use, attitude, spatial and social perception, imitation) which was collected from several surveys with 120 participants each. Results show that the speech production data divides the city of Malaga clearly into three different parts. This tripartition is confirmed by the analysis of the perception data. Moreover, the habitants of these three areas are perceived as different social types, to whom a range of social features is attributed. That is, certain linguistic features, the different neighbourhoods of the city and the social characteristics associated with them are undergoing a process of indexicalization and iconization. As a result, the linguistic features in question function as identity markers on the intraurban level.