Traditional wavefront control in high-energy, high-intensity laser systems usually lacks real-time capability, failing to address dynamic aberrations. This limits experimental accuracy due to shot-to-shot fluctuations and necessitates long cool-down phases to mitigate thermal effects, particularly as higher repetition rates become essential, for example, in inertial fusion research. This paper details the development and implementation of a real-time capable adaptive optics system at the Apollon laser facility. Inspired by astronomical adaptive optics, the system uses a fiber-coupled 905 nm laser diode as a pilot beam that allows for spectral separation, bypassing the constraints of pulsed lasers. A graphics processing unit-based controller, built on the open-source Compute And Control for Adaptive Optics framework, manages a loop comprising a bimorph deformable mirror and a high-speed Shack–Hartmann sensor. Initial tests showed excellent stability and effective aberration correction. However, integration into the Apollon laser revealed critical challenges unique to the laser environment that must be resolved to ensure safe operation with amplified shots.

The non-dimensional energy of starting vortex rings typically converges to values around 0.33 when they are created by a piston-cylinder or a bluff body translating at a constant speed. To explore the limits of the universality of this value and to analyse the variations that occur outside of those limits, we present an alternative approach to the slug-flow model to predict the non-dimensional energy of a vortex ring. Our approach is based on the self-similar vortex sheet roll-up described by Pullin (J. Fluid Mech., vol. 88, 1978, pp. 401–430). We derive the vorticity distribution for the vortex core resulting from a spiralling shear layer roll-up and compute the associated non-dimensional energy. To demonstrate the validity of our model for vortex rings generated through circular nozzles and in the wake of disks, we consider different velocity profiles of the vortex generator that follow a power law with a variable time exponent $m$. Higher values of $m$ indicate a more uniform vorticity distribution. For a constant velocity ($m=0$), our model yields a non-dimensional energy of ${{E}^{{*}}}=0.33$. For a constant acceleration ($m=1$), we find ${{E}^{{*}}}=0.19$. The limiting value $m \rightarrow \infty$ corresponds to a uniform vorticity distribution and leads to ${{E}^{{*}}}=0.16$, which is close to values found in the literature for Hill's spherical vortex. The radial diffusion of the vorticity within the vortex core results in the decrease of the non-dimensional energy. For a constant velocity, we obtain realistic vorticity distributions by radially diffusing the vorticity distribution of the Pullin spiral and predict a decrease of the non-dimensional energy from 0.33 to 0.28, in accordance with experimental results. Our proposed model offers a practical alternative to the existing slug flow model to predict the minimum non-dimensional energy of a vortex ring. The model is applicable to piston-generated and wake vortex rings and only requires the kinematics of the vortex generator as input.

The development of maternal representations of the child during pregnancy guides a mother’s thoughts, feelings, and behavior toward her child. The association between prenatal representations, particularly those that are disrupted, and toddler social-emotional functioning is not well understood. The present study examined associations between disrupted prenatal representations and toddler social-emotional functioning and to test disrupted maternal behavior as a mediator of this association. Data were drawn from 109 women from a larger prospective longitudinal study (N=120) of women and their young children. Prenatal disrupted maternal representations were assessed using the Working Model of the Child Interview disrupted coding scheme, while disrupted maternal behavior was coded 12-months postpartum from mother-infant interactions. Mother-reported toddler social-emotional functioning was assessed at ages 12 and 24 months. Disrupted prenatal representations significantly predicted poorer toddler social-emotional functioning at 24 months, controlling for functioning at 12 months. Further, disrupted maternal behavior mediated the relation between disrupted prenatal representations and toddler social-emotional problems. Screening for disrupted representations during pregnancy is needed to facilitate referrals to early intervention and decrease the likelihood of toddler social-emotional problems.

Adverse developmental outcomes for some children following institutional care are well established. Removal from institutional care and placement into families can promote recovery. However, little is known about how positive outcomes are sustained across adolescence among children with histories of severe deprivation. The present study examined the caregiving conditions that are associated with attaining and maintaining competent functioning (i.e., outcomes within typical levels) from middle childhood to adolescence following exposure to early institutional care. The participants included children with and without a history of institutional care who had competence assessed at ages 8, 12, and 16 years across seven domains: family relationships, peer relationships, academic performance, physical health, mental health, substance use (ages 12 and 16 years only), and risk-taking behavior. The participants were grouped based on whether they were always versus not always competent and never versus ever competent at ages 8 through 16 years. Adolescents with a history of institutional care were less likely to be consistently competent than those who were family reared. Among those who were exposed to early institutional rearing, maintaining competent functioning from 8 to 16 years was associated with spending less time in institutions and receiving higher-quality caregiving early in life. Ensuring high quality early caregiving may promote competent functioning following early deprivation.

The nativist ideology of ivoirité of the 1990s generated brutal discriminatory policies against those labelled as ‘strangers’, especially Muslims. Reversing that perspective, this article focuses on the interface between religion and national identity in twentieth-century Côte d'Ivoire from within Muslim society. The argument is divided into two parts. The first puts forward the counter-hegemonic, patriotic-cum-cosmopolitan narratives that a new Muslim leadership formulated in order to write Islam into national history. The second focuses on grass-roots, demotic, day-to-day realities. It explores Muslim takes on belonging and alienation in practice, paying careful attention to the community's internal diversity. It shows how, over time, Ivorian Muslims have showcased varying degrees of cosmopolitan patriotism but also of their own, local xenophobia. The concluding section returns to the new Muslim leadership and its multifaceted endeavours to reconcile Muslim lived experiences with their cosmopolitan patriotic aspirations. The article ends with a short epilogue surveying the violent armed conflicts of the period 2002 to 2011 and how Muslims were a part of them.

Drops impacting at low velocities onto a pool surface can stretch out thin hemispherical sheets of air between the drop and the pool. These air sheets can remain intact until they reach submicron thicknesses, at which point they rupture to form a myriad of microbubbles. By impacting a higher-viscosity drop onto a lower-viscosity pool, we have explored new geometries of such air films. In this way we are able to maintain stable air layers which can wrap around the entire drop to form repeatable antibubbles, i.e. spherical air layers bounded by inner and outer liquid masses. Furthermore, for the most viscous drops they enter the pool trailing a viscous thread reaching all the way to the pinch-off nozzle. The air sheet can also wrap around this thread and remain stable over an extended period of time to form a cylindrical air sheet. We study the parameter regime where these structures appear and their subsequent breakup. The stability of these thin cylindrical air sheets is inconsistent with inviscid stability theory, suggesting stabilization by lubrication forces within the submicron air layer. We use interferometry to measure the air-layer thickness versus depth along the cylindrical air sheet and around the drop. The air film is thickest above the equator of the drop, but thinner below the drop and up along the air cylinder. Based on microbubble volumes, the thickness of the cylindrical air layer becomes less than 100 nm before it ruptures.

We present new on-sky results for the Subaru Coronagraphic Extreme Adaptive Optics imager (SCExAO) verifying and quantifying the contrast gain enabled by key components: the closed-loop coronagraphic low-order wavefront sensor (CLOWFS) and focal plane wavefront control (“speckle nulling”). SCExAO will soon be coupled with a high-order, Pyramid wavefront sensor which will yield > 90% Strehl ratio and enable 106–107 contrast at small angular separations allowing us to image gas giant planets at solar system scales. Upcoming instruments like VAMPIRES, FIRST, and CHARIS will expand SCExAO's science capabilities.

We present a new ground-based technique to detect or follow-up long-period, potentially habitable exoplanets via precise relative astrometry of host stars using Multi-Conjugate Adaptive Optics (MCAO) on 8 meter telescopes equipped with diffractive masks. MCAO improves relative astrometry both by cancellation of high-altitude atmospheric layers, which induce dynamic focal-plane distortions, and the improvement of centroiding precision with sharper PSFs. However, mass determination of habitable exoplanets requires multi-year reference grid stability of ~1–10 μas or nanometer-level stability on the long-term average of out-of-pupil phase errors, which is difficult to achieve with MCAO (e.g., Meyer et al. 2011). The diffractive pupil technique calibrates dynamic distortion via extended diffraction spikes generated by a dotted primary mirror, which are referenced against a grid of background stars (Guyon et al. 2012). The diffractive grid provides three benefits to relative astrometry: (1) increased dynamic range, permitting observation of V < 10 stars without saturation; (2) calibration of dynamic distortion; and (3) a spectrum of the target star, which can be used to calibrate the magnitude of differential atmospheric refraction to the microarcsecond level. A diffractive 8-meter telescope with diffraction-limited MCAO in K-band reaches < 3–5 μas relative astrometric error per coordinate perpendicular to the zenith vector in one hour on a bright target star in fields of moderate stellar density (~10–40 stars arcmin−2). We present preliminary on-sky results of a test of the diffractive mask on the Nickel telescope at Lick Observatory.

The permeability of rocks fractured by random, planar cracks, is expressed as a classical bond percolation problem on a random lattice, by Voronoi partition of space. The percolation threshold is determined as a function of the statistical characteristics of the cracks, or of their traces on an arbitrary face of the rock, by using an empirical quasi-invariant of percolation theory.

Detailed observations have been performed on the evolution of a viscous catenary, a rope of high-viscosity fluid suspended from two points falling under gravity. Stroboscopic imaging techniques are used to obtain the position and shape of the strand as a function of time. Depending on their initial thickness and profile, the filaments are observed to evolve into either a quasi-catenary, or other, more complex shapes. A conceptually simple, energy-based theory is developed and compared with observations. It is shown to describe reasonably, except for a scaling in the time scale, the catenary-like regime.

Parameters of hemocyte populations have been considered as relevant indicators of bivalve health and are currently used in immunotoxicological studies. Hemocytes in hemolymph can be collected by puncturing either the pericardial cavity or the adductor muscle sinus with a syringe. Flow cytometry is a methodological approach that is increasingly being used in laboratories for the study of hemocyte parameters in aquatic invertebrates. However, various protocols for hemocyte processing in laboratories equipped with different types of cytometers have been published. In this context, two flow cytometers (EPICS XL4®, Beckman Coulter and FacsCalibur®, Becton Dickinson) and two sites of hemocyte collection (pericardial cavity and adductor muscle sinus) were compared for the analysis of hemocyte parameters in the Pacific oyster, Crassostrea gigas. Hemolymph cells were analyzed in terms of their number and organelle contents. Cell mortality, phagocytosis, non specific esterase, extension of the lysosomal compartment and production of reactive oxygen species were quantified. The results showed that the phagocytic index was higher for hemocytes obtained in the muscle sinus hemolymph. The results are discussed with respect to the potential use of flow cytometry as a tool for hemocyte studies in bivalves.

In this article, we describe an optical set-up designed to measure directly velocity gradients (strophometry). This strophometer is based on the analysis of the distortions of a fringe pattern ‘written’ instantaneously in a flow field. We apply it to study the transverse velocity-gradient component ∂u/∂y in a plane Poiseuille flow at moderate Reynolds numbers. Mean values and different moments of the fluctuating gradient distribution related to viscous dissipation, vorticity dynamics and intermittency are obtained. These results are interpreted in terms of the large-scale structures which are present in the flow.

The thermal convective instability of a nematic layer aligned perpendicular to horizontal plates displays original characteristics, due to the coupling of the nematic distortion with the temperature gradient; in particular the adverse temperature gradient threshold ΔTc can be modified by the application of a vertical (stabilizing) or horizontal (destabilizing) magnetic field. In addition, the application of a magnetic field H controls both the threshold of this instability and the geometric form of the instabilities above ΔTc.

We present experimental results on the modified Stokes force F exerted on a sphere in magnetic levitation whose position is kept fixed by an optical feedback system. A Newtonian liquid moves at a constant velocity U relative to the sphere. We consider the motion in two different situations.

(i) When the sphere approaches a wall perpendicular to U, the increase in |F| due to lubrication agrees quantitatively with theoretical results such as those of Brenner (1961) and Maude (1961), obtained neglecting the unsteadiness of the flow field.

(ii) In the complementary situation of a sphere moving along the axis of a cylindrical tube, our results expressed as a function of the eccentricity of the trajectory and of the ratio of the two radii confirm and extend previous theoretical analyses. They show in particular the existence of a minimum of |F| away from the axis of the cylinder and a sharp increase in |F| when the sphere approaches the sidewall. By comparing with the results for a sphere moving parallel to a flat wall, we analyse the effect of the curvature of the cylindrical tube.

In nematic homeotropic films (director n perpendicular to the horizontal limiting plates) heated from below, the distortion of the director which is coupled to the ordinary heat convection mechanism responsible for the Rayleigh–Bénard instability exerts a strongly stabilizing influence. Owing to the difference in time scales, an oscillatory instability results whose characteristics are investigated experimentally here. An inverted bifurcation with an associated hysteresis is also obtained and this was studied in some detail. A vertical magnetic field H is also used to align the sample. The decrease of the orientational time constant when H increases leads to marked changes in the overstable regime, which are well described by a simple analysis.

This paper exposes a method for evaluating the performances of a systemdedicated to exoplanet direct imaging. It is based on the use of a statisticaldescription of a somewhat ideal star/planet couple in terms of contrast and angular separation.Among many already available techniques, the Phase Induced Amplitude ApodizationCoronagraph (PIAAC) seems to gather all the necessary qualities to performdirect imaging of hypothetical Earth-like exoplanets in the close Solarneighbourhood (30 pc).After a quick description of its concept, the proposed evaluation method is used and provides an original set of criteria to classify concepts.

The high contrast (typically $10^{10}$) and small angular separation between a planet and its parent star are the main challenges that need to be overcome to detect and characterize Earth-like planets around the nearest stars. Therefore, exoplanet imaging requires the use of a coronagraph, that ideally efficiently cancels the light from the star and has minimal influence on the planet image. The Phase Induced Amplitude Apodization Coronagraph relies on pupil apodization by geometrical remapping of the flux in the pupil plane. This method combines the advantages of classical pupil apodization with high throughput ($\approx$100%) and high angular resolution (${\approx}\lambda/D$), and has some unique advantages over most coronagraphs, such as low chromaticity, low sensitivity to stellar angular size and to small pointing errors. As a result, planet detection time is about 50–100 times shorter in comparison with classical coronagraphic techniques (Martinache et al. 2005).

Both the advantages of the PIAAC and the main factors affecting the performance of the coronograph will be examined in our laboratory experiment in which high quality PIAA optics wilkl be combined with wavefront control to demonstrate achromatic high contrast imaging ($10^6$ or more) at small angular separation (less than $2\lambda/D$). We present here a description and current status of this experiment together with a short analyses of the main factors affecting the performance of the coronograph.