On wave-driven propulsion

A theory is presented for wave-driven propulsion of floating bodies driven into oscillation at the fluid interface. By coupling the equations of motion of the body to a quasi-potential flow model of the fluid, we derive expressions for the drift speed and propulsive thrust of the body which in turn are shown to be consistent with global momentum conservation. We explore the efficacy of our model in describing the motion of SurferBot [Rhee et al., Bioinspir. Biomim. 17 (5), 2022], demonstrating close agreement with the experimentally determined drift speed and oscillatory dynamics. The efficiency of wave-driven propulsion is then computed as a function of driving oscillation frequency and the forcing location, revealing optimal values for both of these parameters which await confirmation in experiments. A comparison to other modes of locomotion and applications of our model to competitive water-sports are discussed in conclusion

Influence of 4-vinylbenzylation on the rheological and swelling properties of photo activated collagen hydrogels

Covalent functionalisation of collagen has been shown to be a promising strategy to adjust the mechanical properties of highly swollen collagen hydrogels. At the same time, secondary interactions between for example, amino acidic terminations or introduced functional groups also play an important role and are often challenging to predict and control. To explore this challenge, 4-vinylbenzyl chloride (4VBC) and methacrylic anhydride (MA) were reacted with type I collagen, and the swelling and rheological properties of resulting photo-activated hydrogel systems investigated. 4VBC-based hydrogels showed significantly increased swelling ratio, in light of the lower degree of collagen functionalisation, with respect to methacrylated collagen networks, whilst rheological storage moduli were found to be comparable between the two systems. To explore the role of benzyl groups in the mechanical properties of the 4VBC-based collagen system, model chemical force microscopy (CFM) was carried out in aqueous environment with an aromatised probe against an aromatised gold-coated glass slide. A marked increase in adhesion force (F: 0.11±0.01 nN) was measured between aromatised samples, compared to the adhesion force observed between the non-modified probe and a glass substrate (F: 2.64±1.82 nN). These results suggest the formation of additional and reversible π-π stacking interactions in aromatic 4VBC-based networks and explain the remarkable rheological properties of this system in comparison to MA-based hydrogels

Helical glasses near ferromagnetic quantum criticality

We study the effects of quenched charge disorder on the phase reconstruction near itinerant ferromagnetic quantum critical points in three spatial dimensions. Combining a Replica-disorder average with a fermionic version of the quantum order-by-disorder mechanism, we show that weak disorder destabilizes the ferromagnetic state and enhances the susceptibility towards incommensurate, spiral magnetic ordering. The Goldstone modes of the spiral phase are governed by a 3d-XY model. The induced disorder in the pitch of the spiral generates a random anisotropy for the Goldstone modes, inducing vortex lines in the phase of the helical order and rendering the magnetic correlations short ranged with a strongly anisotropic correlation length

Time-varying covariates and semi-parametric regression in capture-recapture: an adaptive spline approach

Advances in capture–recapture methodology have allowed the inclusion of continuous, time-dependent individual-covariates as predictors of survival and capture probabilities. The problem posed by these covariates is that they are only observed for an individual when that individual is captured. One solution is to assume a model of the covariate which defines the distribution of unobserved values, conditional on the observed values, and apply Bayesian methods to compute parameter estimates and to test the covariate’s effect. Previous applications of this approach have modeled the survival probability as a linear function of the covariate on some scale (e.g. identity or logistic). In some applications a linear function may not adequately describe the true relationship. Here we incorporate semi-parametric regression to allow for more flexibility in the relationship between the covariate and the survival probabilities of the Cormack– Jolly–Seber model. A fully Bayesian, adaptive algorithm is used to model the relationship with splines, in which the complexity of the relationship is governed by the number and location of the knots in the spline. A reversible jump Markov chain Monte Carlo algorithm is implemented to explore splines with different knot configurations, and model averaging is used to compute the final estimates of the survival probabilities. The method is applied to a simulated data set and to data collected through the Dutch Constant Effort Sites ringing project to study the survival of reed warblers (Acrocephalus scirpaceus) as a function of condition.postprin

Educational needs of epileptologists regarding psychiatric comorbidities of the epilepsies: a descriptive quantitative survey.

Psychiatric disorders are relatively frequent comorbidities in epilepsy and they have an impact on morbidity, mortality, and quality of life. This is a report from the Task Force on Education of the ILAE Commission on Neuropsychiatry based on a survey about educational needs of epileptologists regarding management of the psychiatric comorbidities of epilepsy. The Task Force designed a quantitative questionnaire to survey the self-perceived confidence of child and adult epileptologists and psychiatrists in managing major psychiatric comorbidities of epilepsy to identify: (1) critical areas of improvement from a list of skills that are usually considered necessary for effective management of these conditions, and (2) the preferred educational format for improving these skills. A total of 211 respondents from 36 different countries participated in the survey. Confidence and usefulness scores suggest that responders would most value education and training in the management of specific clinical scenarios. Child neurologists identified major Axis I disorders, such as mood and anxiety disorders, while adult neurologists identified attention deficit hyperactivity disorder, intellectual disabilities, and autistic spectrum disorder as key areas. Both adult and child neurologists identified screening skills as the priority. Psychiatrists mainly valued specific training in the management of psychiatric complications of epilepsy surgery or psychiatric adverse events of antiepileptic drugs. Sessions during congresses and face-to-face meetings represent the preferred educational format, while e-learning modules and review papers were chosen by a minority of respondents. Results of this survey identify key areas for improvement in managing the psychiatric comorbidities of epilepsy and suggest specific strategies to develop better training for clinicians involved in epilepsy care

Structure and expression of GSL1 and GSL2 genes encoding gibberellin stimulated-like proteins in diploid and highly heterozygous tetraploid potato reveals their highly conserved and essential status

Background: GSL1 and GSL2, Gibberellin Stimulated-Like proteins (also known as Snakin-1 and Snakin-2), are cysteine-rich peptides from potato (Solanum tuberosum L.) with antimicrobial properties. Similar peptides in other species have been implicated in diverse biological processes and are hypothesised to play a role in several aspects of plant development, plant responses to biotic or abiotic stress through their participation in hormone crosstalk, and redox homeostasis. To help resolve the biological roles of GSL1 and GSL2 peptides we have undertaken an in depth analysis of the structure and expression of these genes in potato. Results: We have characterised the full length genes for both GSL1 (chromosome 4) and GSL2 (chromosome 1) from diploid and tetraploid potato using the reference genome sequence of potato, coupled with further next generation sequencing of four highly heterozygous tetraploid cultivars. The frequency of SNPs in GSL1 and GSL2 were very low with only one SNP every 67 and 53 nucleotides in exon regions of GSL1 and GSL2, respectively. Analysis of comprehensive RNA-seq data substantiated the role of specific promoter motifs in transcriptional control of gene expression. Expression analysis based on the frequency of next generation sequence reads established that GSL2 was expressed at a higher level than GSL1 in 30 out of 32 tissue and treatment libraries. Furthermore, both the GSL1 and GSL2 genes exhibited constitutive expression that was not up regulated in response to biotic or abiotic stresses, hormone treatments or wounding. Potato transformation with antisense knock-down expression cassettes failed to recover viable plants. Conclusions: The potato GSL1 and GSL2 genes are very highly conserved suggesting they contribute to an important biological function. The known antimicrobial activity of the GSL proteins, coupled with the FPKM analysis from RNA-seq data, implies that both genes contribute to the constitutive defence barriers in potatoes. The lethality of antisense knock-down expression of GSL1 and GSL2, coupled with the rare incidence of SNPs in these genes, suggests an essential role for this gene family. These features are consistent with the GSL protein family playing a role in several aspects of plant development in addition to plant defence against biotic stresses. © 2014 Meiyalaghan et al.; licensee BioMed Central Ltd