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A laser-irradiated surface is the paradigm of a self-organizing system, as coherent, aligned, chaotic, and complex patterns emerge at the microscale and even the nanoscale. A spectacular manifestation of dissipative structures consists of different types of randomly and periodically distributed nanostructures that arise from a homogeneous metal surface. The noninstantaneous response of the material reorganizes local surface topography down to tens of nanometers scale modifying long-range surface morphology on the impact scale. Under ultrafast laser irradiation with a regulated energy dose, the formation of nanopeaks, nanobumps, nanohumps and nanocavities patterns with 20–80 nm transverse size unit and up to 100 nm height are reported. We show that the use of crossed-polarized double laser pulse adds an extra dimension to the nanostructuring process as laser energy dose and multi-pulse feedback tune the energy gradient distribution, crossing critical values for surface self-organization regimes. The tiny dimensions of complex patterns are defined by the competition between the evolution of transient liquid structures generated in a cavitation process and the rapid resolidification of the surface region. Strongly influencing the light coupling, we reveal that initial surface roughness and type of roughness both play a crucial role in controlling the transient emergence of nanostructures during laser irradiation.

The capacity to synthesize and design highly intricated nanoscale objects of different sizes, surfaces, and shapes dramatically conditions the development of multifunctional nanomaterials. Ultrafast laser technology holds great promise as a contactless process able to rationally and rapidly manufacture complex nanostructures bringing innovative surface functions. The most critical challenge in controlling the growth of laser‐induced structures below the light diffraction limit is the absence of external order associated to the inherent local interaction due to the self‐organizing nature of the phenomenon. Here high aspect‐ratio nanopatterns driven by near‐field surface coupling and architectured by timely‐controlled polarization pulse shaping are reported. Electromagnetic coupled with hydrodynamic simulations reveal why this unique optical manipulation allows peaks generation by inhomogeneous local absorption sustained by nanoscale convection. The obtained high aspect‐ratio surface nanotopography is expected to prevent bacterial proliferation, and have great potential for catalysis, vacuum to deep UV photonics and sensing. A uniform formation of unconventional self‐organized patterns on the 100 nm scale has been generated by focused ultrafast light. Irradiated surface turns to a forest of self‐organized nanopeaks with a remarkable aspect ratio at the nanoscale. Laser beam polarization is timely controlled to prevent anisotropic energy absorption and to synchronize the laser energy delivery rate with the material dynamic response.

The formation of isotropic two-dimensional laser-induced periodic surface structures (2D-LIPSS) under circular polarization demonstrates a unique self-organization capability. In this study, we investigate LIPSS formation under both circularly and linearly polarized light, assessing the impact of polarization dynamics, from discrete rotation angles to ultrafast changes within a single optical cycle, on pattern formation. This phenomenon stems from the surface’s ability to temporally integrate all polarization states within an optical cycle, leading to a circularly oriented response. Similarly to linear polarization, the interference between the topography-induced scattered field and the incident laser field guides the process, with feedback-driven topographical evolution sustaining structure growth. However, unlike linearly polarized light, which imposes unidirectional alignment, circular polarization promotes a more symmetric arrangement. Superposed on the hexagonal lattice of pillars with short-range order, near-field interactions generate radially oriented nanostructures that interconnect the pillars via concentric filaments. By investigating these two spatial scales separately, the respective formation mechanisms and their interplay can be clarified. Supported by electromagnetic simulations, these findings offer a comprehensive framework for understanding the mechanisms behind isotropic 2D-LIPSS formation.

A self-organization hydrodynamic process has recently been proposed to partially explain the formation of femtosecond laser-induced nanopatterns on Nickel, which have important applications in optics, microbiology, medicine, etc. Exploring laser pattern space is difficult, however, which simultaneously (i) motivates using machine learning (ML) to search for novel patterns and (ii) hinders it, because of the few data available from costly and time-consuming experiments. In this paper, we use ML to predict novel patterns by integrating partial physical knowledge in the form of the Swift-Hohenberg (SH) partial differential equation (PDE). To do so, we propose a framework to learn with few data, in the absence of initial conditions, by benefiting from background knowledge in the form of a PDE solver. We show that in the case of a self-organization process, a feature mapping exists in which initial conditions can safely be ignored and patterns can be described in terms of PDE parameters alone, which drastically simplifies the problem. In order to apply this framework, we develop a second-order pseudospectral solver of the SH equation which offers a good compromise between accuracy and speed. Our method allows us to predict new nanopatterns in good agreement with experimental data. Moreover, we show that pattern features are related, which imposes constraints on novel pattern design, and suggest an efficient procedure of acquiring experimental data iteratively to improve the generalization of the learned model. It also allows us to identify the limitations of the SH equation as a partial model and suggests an improvement to the physical model itself.

Ultrafast-laser irradiated surfaces are self-organizing systems that form intricated micropatterns and nanopatterns. Different shapes of randomly and periodically dispersed nanostructures emerge from a homogenous metal surface, resulting in a remarkable display of dissipative structures. Under femtosecond laser irradiation with a controlled amount of energy, the formation of nanobreath-figure, nanocrosshatch, nanopeaks, nanohumps, nanobumps, nanocavities and nanolabyrinthine patterns are reported. The fabrication of these 2D different nanostructures may allow for novel surface functionalizations aimed at controlling mechanical, biological, optical, or chemical surface characteristics on a nanometric scale. We demonstrate that using crossed-polarized double laser pulses adds a new dimension to the nanostructuring process since the laser energy dose and multi-pulse feedback modify the energy gradient distribution, crossing key levels for surface self-organization regimes.

Ultrafast laser irradiation can induce spontaneous self-organization of surfaces into dissipative structures with nanoscale reliefs. These surface patterns emerge from symmetry-breaking dynamical processes that occur in Rayleigh-Bénard-like instabilities. In this study, we demonstrate that the coexistence and competition between surface patterns of different symmetries in two dimensions can be numerically unraveled using the stochastic generalized Swift-Hohenberg model. We originally propose a deep convolutional network to identify and learn the dominant modes that stabilize for a given bifurcation and quadratic model coefficients. The model is scale-invariant and has been calibrated on microscopy measurements using a physics-guided machine learning strategy. Our approach enables the identification of experimental irradiation conditions for a desired self-organization pattern. It can be applied generally to predict structure formation in situations where the underlying physics can be approximately described by a self-organization process and data is sparse and non-time series. Our work paves the way for supervised local manipulation of matter using timely-controlled optical fields in laser manufacturing.

How can one design complex systems capable of learning for a given functionality? In the context of ultrafast laser-surface interaction, we unravel the nature of learning schemes tied to the emergence of complexity in dissipative structures. The progressive development of learning mechanisms, from direct information storage to the development of smart surfaces, originates from the network of curvatures formed in the unstable fluid under thermoconvective instability, which is subsequently quenched and resolidified. Under pulsed laser irradiation, non-equilibrium dynamics generate intricate nanoscale patterns, unveiling adaptive process mechanisms. We demonstrate that the imprints left by light act as a form of structural memory, encoding not only local effects directed by laser field polarization but also a cooperative strategy of reliefs that dynamically adjust surface morphology to optimize light capture. By investigating how apparent complexity and optical response are intricately intertwined, shaping one another, we establish a framework that draws parallels between material adaptation and learning dynamics observed in biological systems.

Background Restrained eating disorder is prevalent worldwide across both ethnic and different cultural groups, and most importantly within the adolescent population. Additionally, comorbidities of restrained eating present a large burden on both physical and mental health of individuals. Moreover, literature is relatively scarce in Arab countries regarding eating disorders, let alone restrained eating, and among adolescent populations; hence, the aim of this study was to (1) validate the Dutch Restrained Eating Scale in a sample of Lebanese adolescents and (2) assess factors correlated with restrained eating (RE), while taking body dissatisfaction as a moderator between body mass index (BMI) and RE. Methods This cross-sectional study, conducted between May and June 2020 during the lockdown period imposed by the Lebanese government, included 555 adolescents aged between 15 and 18 years from all Lebanese governorates (mean age of 16.66 ± 1.00 years). The scales used were: Dutch Restrained Eating Scale, body dissatisfaction subscale of the Eating Disorder Inventory-Second version, Rosenberg Self-Esteem Scale, Beirut Distress Scale (for psychological distress), Hamilton Anxiety Rating Scale and Patient Health Questionnaire (for depression). Results The Confirmatory factor analysis results were obtained as follows: χ2/df = 159.88/35= 4.57, CFI= 0.96, TLI= 0.95, RMSEA = 0.08 [0.068-0.093]. Female gender (B=0.19), higher BMI (B=0.49), higher physical activity index (B=0.17), following a diet to lose weight (B=0.26), starving oneself to lose weight (B=0.13), more body dissatisfaction (B=1.09), higher stress (B=0.18) were significantly associated with more restrained eating, whereas taking medications to lose weight (B=-0.10) was significantly associated with less restrained eating. The interaction BMI by body dissatisfaction was significantly associated with restrained eating; in the group with low BMI, high body dissatisfaction was significantly associated with more restrained eating. The factor analysis yielded a one-factor solution with Eigen values > 1 (variance explained = 59.65 %; α Cronbach  = 0.924). Female gender (B = 0.19), higher BMI (B = 0.49), higher physical activity index (B = 0.17), following a diet to lose weight (B = 0.26), starving oneself to lose weight (B = 0.13), more body dissatisfaction (B = 1.09), and higher stress (B = 0.18) were significantly associated with more RE, whereas taking medications to lose weight (B=-0.10) was significantly associated with less RE. The interaction body mass index (BMI) by body dissatisfaction was significantly associated with RE; in the group with low BMI, higher body dissatisfaction was significantly associated with more RE. Conclusions Our study showed that the Dutch Restrained Eating scale is an adapted and validated tool to be used among Lebanese adolescents and revealed factors associated with restrained eating in this population. Since restrained eating has been associated with many clinically-diagnosed eating disorders, the results of this study might serve as a first step towards the development of prevention strategies targeted towards promoting a healthy lifestyle in Lebanese adolescents.

BackgroundOcular toxoplasmosis is common across all regions of the world. Understanding of the epidemiology and approach to diagnosis and treatment have evolved recently. In November 2020, an international group of uveitis-specialised ophthalmologists formed the International Ocular Toxoplasmosis Study Group to define current practice.Methods192 Study Group members from 48 countries completed a 36-item survey on clinical features, use of investigations, indications for treatment, systemic and intravitreal treatment with antiparasitic drugs and corticosteroids, and approach to follow-up and preventive therapy.ResultsFor 77.1% of members, unilateral retinochoroiditis adjacent to a pigmented scar accounted for over 60% of presentations, but diverse atypical presentations were also reported. Common complications included persistent vitreous opacities, epiretinal membrane, cataract, and ocular hypertension or glaucoma. Most members used clinical examination with (56.8%) or without (35.9%) serology to diagnose typical disease but relied on intraocular fluid testing—usually PCR—in atypical cases (68.8%). 66.1% of members treated all non-pregnant patients, while 33.9% treated selected patients. Oral trimethoprim–sulfamethoxazole was first-line therapy for 66.7% of members, and 60.9% had experience using intravitreal clindamycin. Corticosteroid drugs were administered systemically by 97.4%; 24.7% also injected corticosteroid intravitreally, almost always in combination with an antimicrobial drug (72.3%). The majority of members followed up all (60.4%) or selected (35.9%) patients after resolution of acute disease, and prophylaxis against recurrence with trimethoprim–sulfamethoxazole was prescribed to selected patients by 69.8%.ConclusionOur report presents a current management approach for ocular toxoplasmosis, as practised by a large international group of uveitis-specialised ophthalmologists.

BackgroundNon-infectious uveitis is a diverse group of inflammatory conditions that collectively account for substantial blindness worldwide. Expert guidelines and results of clinical trials guide treatment, but real-world clinical care is impacted by additional factors. In 2023, an international group of uveitis-specialised ophthalmologists formed the International Study Group for Systemic Immunomodulatory Drug Treatment of Non-Infectious Uveitis to report current practice.Methods221 study group members from 53 countries completed a 30-item questionnaire on their management of non-infectious uveitis including: indications for and investigations prior to initiating systemic immunomodulatory drugs, use of conventional and biological drugs, and follow-up of treated patients.ResultsMajor indications to initiate systemic immunomodulatory drugs were: uveitis not controlled with oral prednis(ol)one (n=208, 94.1%), specific uveitis diagnosis (n=197, 89.1%), and patient intolerance of oral prednis(ol)one (n=186, 84.2%). All members (n=221, 100%) performed pretreatment screens including: blood chemistry (n=217, 98.2%), blood examination (n=207, 93.7%), and Quantiferon assay (n=196, 88.7%). Eight conventional and 14 biological drugs were prescribed: methotrexate was the preferred conventional drug overall (n=126, 57.0%) and for 9 of 11 uveitides, and adalimumab was the preferred biological drug overall (n=216, 97.7%) and for 11 of 11 uveitides. When drugs were combined, methotrexate plus adalimumab was most popular (n=158 of 188 members, 84.0%). Patients with inactive uveitis were typically evaluated and screened for drug toxicity every 6–12 weeks (n=161, 72.9%, and 165, 74.7%, respectively).ConclusionOur report describes practice patterns of a large international group of uveitis specialists treating non-infectious uveitis with systemic immunomodulatory drugs.