We study nonlinear resonant triad interactions among flexural-gravity waves generated by a steadily moving load on a floating ice sheet. Of the many possible triad interactions involving at least one load-produced wave, we focus on the double-frequency case where the wavenumber of the leading wave is double that of the trailing wave. This case stands out because resonant interactions can occur with or without the presence of an ambient wave. Using multiple-scale perturbation analysis, we obtain amplitude evolution equations governing the leading-order, steady-state response. We complement the theoretical predictions with direct numerical simulations of the initial–boundary value problem using a high-order spectral method accurate to arbitrary order. Our results show that the double-frequency interaction can cause the trailing wave amplitude to decay with distance from the load, with its energy transferred to its second harmonic which radiates forwards to coherently interfere with the leading wave. Depending on the length and orientation of the load, the resonant interaction can in some cases cause the wave drag to become vanishingly small, or in other cases nearly double the maximum bending strain compared to the linear prediction. We also consider the effect of a small ambient wave that can initiate a resonant interaction in the leading wave field in addition to the trailing wave field interaction. This can result in a steady, localised wave packet containing two mutually trapped wave components, leading to vanishing wave drag. This work has potential implications for defining safe operating profiles for vehicles travelling on floating ice.

Previous research has shown personalised nutrition feedback is more effective than generic onesize-fits-all nutrition advice(1). Using fruit and vegetable intakes from the MyPlanetDiet randomized controlled trial, this analysis will determine if different severity of personalised nutrition feedback delivers greater dietary change.

Participants were recruited from the general public and randomised to receive personalised feedback based on a more sustainable diet (intervention) or Healthy Eating Guidelines (control). Intervention participants received feedback on total fruit, total vegetables, dark green vegetables, and/or red/orange vegetables. Control participants received feedback on total fruit and vegetables, total vegetables, citrus fruits, and/or fruit juice. Participants completed dietary assessments (3x 24-hour recalls) at baseline (Week 0) and endpoint (Week 12) using Foodbook24, a validated online dietary assessment tool(2). Mean food group intakes and Healthy Eating Index scores were calculated. Personalised feedback messaging was assessed to measure the severity of fruit and vegetable feedback, ranging from zero messages (least severe) to four messages (most severe). Data are presented as mean±standard error. Data were analysed via two-way mixed analysis of covariance and univariate general linear models using IMB SPSS Statistics (Version 29).

Participants (n = 292) were 56% female and 42.3 ± 0.7 years old. Mean fruit and vegetable intake at baseline was 325.4 ± 183.3g. Almost all participants (97%) received feedback for at least one component of fruit and vegetable intake. Control participants were more likely to receive feedback on fruit (p<0.001) while intervention participants were more likely to receive vegetable feedback (p<0.001). There was a significant time*group interaction for fruit intake (p = 0.005) with larger increases in the control (+102.3g) than the intervention group (+38.6g). The intervention group had higher vegetable intakes (200.6 ± 7.9g) compared to control (164.2 ± 7.5g) at endpoint (p<0.001). Those receiving more severe fruit and vegetable feedback had significantly lower intakes of fruit and vegetables at baseline (p<0.001) but not endpoint (p = 0.80). There was a significant time*group interaction for fruit and vegetable intake (p<0.001) between severity groups. Those with least severe feedback decreased fruit and vegetable intake (-57.4g) while those in the most severe group increased intakes by 162.2g. However, mean fruit and vegetable intake in the least severe group was still higher (472.9 ± 31.8g) at endpoint than in the most severe group (397.2 ± 23.6g). There was a significant time (p<0.001) and time*group interaction (p = 0.039) in HEI scores with the smallest increase in the least severe group (+3.7) and the largest increase in the most severe feedback group (+9.6).

More personalised nutrition feedback was associated with greater behaviour change when using fruit and vegetable intake as an example. Differences in messaging between control and intervention groups led to corresponding differences in dietary change. Different severity of personalised nutrition feedback resulted in participants having comparable fruit and vegetable intakes at endpoint.

Pteridophytes are excellent ecological indicators of habitat quality. In this study, we built a model that predicts the habitat suitability of Elaphoglossum beddomei Sledge, an epiphytic or lithophytic and endemic pteridophyte in Southern Western Ghats, by using the technique of species distribution modelling. The occurrence data of E. beddomei from field explorations as well as from various herbaria were collected during 2018–2022. These occurrence data along with climatic data were processed by R packages. The processed data were further analysed using MaxEnt software to project the distribution of E. beddomei in future climatic scenarios. After correlation analysis, five bioclimatic variables – Mean Temperature of Wettest Quarter (bio8), Precipitation of Driest Quarter (bio17), Precipitation of Warmest Quarter (bio18), Precipitation of Wettest Quarter (bio16) and Temperature Annual Range (BIO5-BIO6) (bio7) – were selected from 19 bioclimatic variables with less correlation. Precipitation of Warmest Quarter (bio18) had the most influence in determining the distribution of E. beddomei, with a permutation importance of 83%. Conversely, Temperature Annual Range (BIO5-BIO6) (bio7) and Precipitation of Driest Quarter (bio17) showed least influence in determining the distribution of E. beddomei, and hence, the models created without these variables are considered for prediction. The habitat suitability predictions of the model indicate that the potential habitats of the species may get reduced in Southern Western Ghats in future climatic scenarios. It is in tune with the predicted expansion of drier climatic zones in Southern Western Ghats, which may reduce the suitable habitats for the E. beddomei in near future. So, it demands formulating suitable strategies for reducing the emission of greenhouse gases, regenerating forests and conserving forests by implementing more stringent policies on the environment to protect such highly habitat-specific evergreen elements.

We investigate air-entraining flows where degassing, rather than fragmentation, plays a significant role. Of interest is the power-law slope $\beta$ of the bulk bubble size distribution $N(a)$ during the air-generating period, when the total volume of bubbles is increasing. We study a canonical air-entraining flow created by strong underlying free-surface turbulence. We perform analysis using the population balance equation (PBE) and computations using direct numerical simulations (DNS) with bubble tracking. We quantify the importance of degassing by the ratio of degassing flux ($Q_D$) to entrainment flux ($Q_I$), $\mathcal {D}=Q_D/Q_I$, and the ratio of degassing rate ($\varLambda (a)$) to fragmentation rate ($\varOmega (a)$) for a bubble of radius $a$, $\varLambda (a)/\varOmega (a)$. For a broad range of large Froude numbers ${{Fr}}=U/\sqrt {L g}$, DNS give $\mathcal {D}=\operatorname {O}(1)$ (independent of ${{Fr}}$), showing that degassing is relevant, and $\varLambda (a) \gg \varOmega (a)$, showing that the bubble population is degassing-dominated. In contrast to fragmentation-dominated populations, such as those due to wave breaking, where $\beta =-10/3$, degassing-dominated populations have qualitatively different $N(a)$ during air entrainment. Analysis using the PBE shows that degassing-dominated $\beta$ is a function of $\varLambda (a)$, which has a turbulence-driven regime ($a< a_\varLambda$) and a buoyancy-driven regime ($a>a_\varLambda$). Here, $a_\varLambda$ is the bubble radius where terminal buoyant rise velocity equals $u_{rms}$. Consequently, $N(a)$ exhibits a split power with $\beta (a< a_\varLambda )=-4.\bar {3}$ and $\beta (a>a_\varLambda )=-5.8\bar {3}$ for moderate bubble Reynolds numbers ${{Re}}_b$. For large ${{Re}}_b$, $\beta (a>a_\varLambda )=-4.8\bar {3}$. The DNS strongly confirm these findings for moderate ${{Re}}_b$. By identifying and describing degassing-dominated bubble populations, this work contributes to the understanding and interpretation of broad types of air-entraining problems where degassing plays a relevant role.

Eosinophilic meningitis or meningoencephalitis caused by Angiostrongylus cantonensis is endemic to the Pacific area of Asia, especially Taiwan, Thailand, and Japan. Although eosinophilia is an important clinical manifestation of A. cantonensis infection, the role of eosinophils in the progress of the infection remains to be elucidated. In this experiment, we show that A. cantonensis-induced eosinophilia and inflammation might lead to the induction of IAP/NF-κB, JAK/STAT1 and MEKK1/JNK signals. The phosphorylation levels of JAK and JNK, STAT1, IAP, NF-κB and MEKK1 protein products were significantly increased after 12 days or 15 days of A. cantonensis infection. However, no significant differences in MAPKs such as Raf, MEK-1, ERK1/2 and p38 expression were found between control and infected mice. The activation potency of JAK/STAT1, IAP/NF-κB and MEKK1/JNK started increasing on day 3, with significant induction on day 12 or day 15 after A. cantonensis infection. Consistent results were noted in the pathological observations, including eosinophilia, leukocyte infiltration, granulomatous reactions, and time responses in the brain tissues of infected mice. These data suggest that the development of brain injury by eosinophilia of A. cantonensis infection is associated with activation of JAK/STAT1 signals by cytokines, and/or activation of MEKK1/JNK by oxidant stress, and/or activation of NF-κB by increasing IAP expression.

We study nonlinear resonant wave–wave interactions which occur when ocean waves propagate into a thin floating ice sheet. Using multiple-scale perturbation analysis, we obtain theoretical predictions of the wave amplitude evolution as a function of distance travelled past the ice edge for a semi-infinite ice sheet. The theoretical predictions are supported by a high-order spectral (HOS) method capable of simulating nonlinear interactions in both open water and the ice sheet. Using the HOS method, the amplitude evolution predictions are extended to multiple (coupled) triad interactions and a single ice sheet of finite length. We relate the amplitude evolution to mechanisms with strong frequency dependence – ice bending strain, related to ice breakup, as well as wave reflection and transmission. We show that, due to sum-frequency interactions, the maximum strain in the ice sheet can be more than twice that predicted by linearised theory. For an ice sheet of finite length, we show that nonlinear wave reflection and transmission coefficients depend on a parameter in terms of wave steepness and ice length, and can have values significantly different than those from linear theory. In particular, we show that nonlinear sum-frequency interactions can appreciably decrease the total wave energy transmitted past the ice sheet. This work has implications for understanding the occurrence of ice breakup, wave attenuation due to scattering in the marginal ice zone and the resulting ice floe size distribution.

A fundamental open problem in the mechanics of granular media is the determination of the stress in the static state. It is known that the static stress depends strongly on how the grain assembly is created and the nature of confining boundaries. Non-trivial spatial variations have been observed even in simple geometries, posing long-standing challenges to continuum modelling. In this paper, we create gravity-deposited grain packings computationally and devise a method to visualise the paths of load transmission, which we call force lines. We show that the force lines reflect the flow during deposition, thereby encoding preparation history. We then show that the force lines coincide with ensemble averaged biased random walks in the particle contact network; this identification yields a closure relation for the stress, which together with the static momentum balances fully determines the stress field. The model makes accurate predictions for the stress in piles and silos, even for unusual deposition methods, thereby showing promise for more general scenarios.

This work investigates the stability and transition to turbulence in a diverging channel subjected to a time-varying trapezoidal-shaped inflow boundary condition. Numerical simulations are performed for different deceleration rates and Reynolds numbers while maintaining a constant acceleration rate. The flow transition begins with two-dimensional primary instability with the formation of inflectional velocity profiles, followed by local separation and the emergence of an array of shear layer vortices. We divide simulation cases systematically into three categories based on the onset of secondary instability and the generation of streamwise vorticity. At low and medium Reynolds numbers (type I), the spanwise vortex rolls formed by inflectional instability remain two-dimensional and diffuse at the channel centre without exhibiting further instabilities. At high Reynolds numbers and deceleration rates (type II), the rolled shear layer exhibits secondary instability during the zero mean inflow phase, followed by local incipient turbulent structure formation. The streamwise vorticity that develops over the shear layer structures causes oscillations with a spanwise wavelength similar to those associated with the elliptic instability in a counter-rotating vortex pair. Using the Lamb–Oseen approximation of vortices in conjunction with the dynamic mode decomposition algorithm of the three-dimensional flow field, we captured successfully the characteristics of the secondary instability. The third category (type III) is characterized by periodic unsteady separation, secondary instability, and merging of shear layer vortices, which occurs when Reynolds numbers are high and deceleration rates are low.

We investigate the fundamental time scales that characterise the statistics of fragmentation under homogeneous isotropic turbulence for air–water bubbly flows at moderate to large bubble Weber numbers, $We$. We elucidate three time scales: $\tau _r$, the characteristic age of bubbles when their subsequent statistics become stationary; $\tau _\ell$, the expected lifetime of a bubble before further fragmentation; and $\tau _c$, the expected time for the air within a bubble to reach the Hinze scale, radius $a_H$, through the fragmentation cascade. The time scale $\tau _\ell$ is important to the population balance equation (PBE), $\tau _r$ is critical to evaluating the applicability of the PBE no-hysteresis assumption, and $\tau _c$ provides the characteristic time for fragmentation cascades to equilibrate. By identifying a non-dimensionalised average speed $\bar {s}$ at which air moves through the cascade, we derive $\tau _c=C_\tau \varepsilon ^{-1/3} a^{2/3} (1-(a_{max}/a_H)^{-2/3})$, where $C_\tau =1/\bar {s}$ and $a_{max}$ is the largest bubble radius in the cascade. While $\bar {s}$ is a function of PBE fragmentation statistics, which depend on the measurement interval $T$, $\bar {s}$ itself is independent of $T$ for $\tau _r \ll T \ll \tau _c$. We verify the $T$-independence of $\bar {s}$ and its direct relationship to $\tau _c$ using Monte Carlo simulations. We perform direct numerical simulations (DNS) at moderate to large bubble Weber numbers, $We$, to measure fragmentation statistics over a range of $T$. We establish that non-stationary effects decay exponentially with $T$, independent of $We$, and provide $\tau _r=C_{r} \varepsilon ^{-1/3} a^{2/3}$ with $C_{r}\approx 0.11$. This gives $\tau _r\ll \tau _\ell$, validating the PBE no-hysteresis assumption. From DNS, we measure $\bar {s}$ and find that for large Weber numbers ($We>30$), $C_{\tau }\approx 9$. In addition to providing $\tau _c$, this obtains a new constraint on fragmentation models for PBE.

An aorto-ventricular tunnel is a rare congenital cardiac defect, where a channel connects the lumen of the ascending aorta to the left or right ventricle. Four patients presented with an aorto-left ventricular tunnel over two decades at a median age of 8 months (range 0.1–10 months). Two patients (50%) had associated cardiac anomalies including hypoplastic left heart syndrome and left ventricular noncompaction/hypertrophic cardiomyopathy with aortic/pulmonary valve dysplasia in one patient each. Although traditionally surgical treatment has addressed this problem, management has evolved to transcatheter closure with excellent outcomes in appropriately selected patients at our national centre.

Many adaptations of the lifting-line theory have been developed since its conception to aid in preliminary aerodynamic wing design, but they typically fall into two main formulations, named $\alpha $- and $\Gamma $-formulation, which differ in terms of the control points chordwise location and the variable updated during the iterative scheme. This paper assess the advantages and drawbacks of both formulations through the implementation of the respective methods and application of standard verification and validation procedures. Verification showed that the $\Gamma $-method poorly converges for wings with nonstraight quarter-chord lines, while the $\alpha $-method presents adequate convergence rates and uncertainties for all geometries; it also showed that the $\Gamma $-method agrees best with analytic results from the cassic lifting-line theory, indicating that it tends to overpredict wing lift. Validation and comparison to other modern lifting-line methods was done for similar geometries, and not only corroborated the poor converge and lift overprediction of the $\Gamma $-method, but also showed that the $\alpha $-method presented the closest results to experimental data for almost all cases tested, concluding that this formulation is typically superior regardless of the wing geometry. These results indicate that the implemented $\alpha $-method has a greater potential for the extension of the lifting-line theory to more geometrically complex lifting surfaces other than fixed wings with straight quarter-chord lines and wakes constrained to the planform plane.

During the high velocity impact of an object on a solid covered with a thin fluid layer, a lubricated contact exists within the short time in which the liquid is squeezed out from the contact. This is important for e.g. the grip of shoes on wet surfaces. We experimentally study the squeeze flow of such layers and find that the amount of viscous dissipation determines how much fluid remains in the contact after the kinetic energy of the impacting object is absorbed. For impacts with sufficient amount of kinetic energy, it is possible to completely drain a Newtonian or shear thinning fluid from the contact on a short time scale. Viscoelastic liquids, however, cannot be drained by increasing impact velocity, because of the fluids’ elastic tendency to retract back into the contact after rapid squeezing. This explains why the presence of polymeric fluids can lead to extreme slipperiness of surfaces. Furthermore, we show that all our experimental results agree with the predictions given by hydrodynamic theory applied to the fluid flow in the gap.

We consider the entrainment volume that results from the quasi-two-dimensional interactions of rising surface-parallel vorticity with an air–water interface. Based on systematic (three-dimensional) direct numerical simulations (DNS) of the canonical problem of a rectilinear vortex pair impinging on and entraining air at the free surface, we develop a phenomenological model to predict the resulting entrainment volume in terms of four key parameters. We identify a new parameter, a circulation flux Froude number $Fr^2_\Xi =|\varGamma |W/a^2\,g$, that predicts the dimensionless volume $\forall$ of entrained air initiated by a coherent vortical structure of circulation $\varGamma$, effective radius $a$, vertical rise velocity $W$ with gravity $g$. For $Fr^2_\Xi$ below some critical value $Fr^2_{\Xi cr}$, no air is entrained. For $Fr^2_\Xi >Fr^2_{\Xi cr}$, the average initial entrainment $\overline {\forall }_o$ scales linearly with ($Fr^2_\Xi -Fr^2_{\Xi cr}$). We also find that $\overline {\forall }_o$ is linearly dependent on circulation Weber number $We_{\varGamma }$ for a range of vortex Bond number $5 \lesssim Bo_{\varGamma } \lesssim 50$, and parabolically dependent on circulation Reynolds $Re_{\varGamma }$ for $Re_{\varGamma }\lesssim 2580$. Outside of these ranges, surface tension and viscosity have little effect on the initial entrainment volume. For the canonical rectilinear vortex problem, the simple model predicts $\overline {\forall }_o$ extremely well for individual coherent structures over broad ranges of $Fr^2_\Xi$, $We_{\varGamma }$, $Bo_{\varGamma }$ and $Re_{\varGamma }$. We evaluate the performance of this parameterisation and phenomenological entrainment model for air entrainment due to the complex periodic vortex shedding and quasi-steady wave breaking behind a fully submerged horizontal circular cylinder. For the range of parameters we consider, the phenomenological model predicts the event-by-event dimensionless entrainment volume measured in the DNS satisfactorily for this complex application.

We study the effect of random perturbations of body positions in large uniformly spaced arrays of axisymmetric wave energy converters (WECs). We perform systematic computational simulations of ensembles of randomized array configurations that are obtained by introducing zero-mean position perturbations (characterized by randomness parameter $\varepsilon$) to line arrays of uniform spacing $d$. Of special interest are the conditions under which these randomized arrays can extract more energy than the underlying uniform arrays. We find that random WEC arrays achieve substantial energy extraction gains over the same number of isolated bodies in monochromatic and irregular incident seas. Introducing $\varepsilon >0$ acts to smooth out the uneven performance of uniformly spaced arrays over varying incident wavenumber. In the low-scattering regime, the standard deviation of array gain grows with the square of wavenumber, for which we provide a theoretical explanation. We show that the uniform line array with spacing optimized for a given incident spectrum generally outperforms randomized arrays of any mean $d$ and $\varepsilon$ in that spectrum, and we offer a heuristic explanation. This holds for a wide range of incident spectra.

Backstepping represents a promising control law for fixed-wing Unmanned Aerial Vehicles (UAVs). Its non-linearity and its adaptation capabilities guarantee adequate control performance over the whole flight envelope, even when the aircraft model is affected by parametric uncertainties. In the literature, several works apply backstepping controllers to various aspects of fixed-wing UAV flight. Unfortunately, many of them have not been implemented in a real-time controller, and only few attempt simultaneous longitudinal and lateral–directional aircraft control. In this paper, an existing backstepping approach able to control longitudinal and lateral–directional motions is adapted for the definition of a control strategy suitable for small UAV autopilots. Rapidly changing inner-loop variables are controlled with non-adaptive backstepping, while slower outer loop navigation variables are Proportional–Integral–Derivative (PID) controlled. The controller is evaluated through numerical simulations for two very diverse fixed-wing aircraft performing complex manoeuvres. The controller behaviour with model parametric uncertainties or in presence of noise is also tested. The performance results of a real-time implementation on a microcontroller are evaluated through hardware-in-the-loop simulation.