Search Results (811)

Transpiration cooling that utilizes the phase change of a liquid coolant is recognized as an effective thermal protection technique for extreme environments. However, the introduction of phase change within the porous structure brings about challenges, such as vapor blockage, pressure fluctuations, and temperature inversion, which critically influence system reliability. This study conducts numerical analyses of coupled processes of heat transfer, flow, and phase change in transpiration cooling using a Two-Phase Mixture Model. The simulation incorporates a Local Thermal Non-Equilibrium approach to capture the distinct temperature fields of the solid and fluid phases, enabling accurate prediction of the thermal response within two-phase and single-phase regions. The results reveal that under low heat flux, dominant capillary action suppresses dry-out and expands the two-phase region. Conversely, high heat flux causes vaporization to overwhelm the capillary supply, forming a superheated vapor layer and constricting the two-phase zone. The analysis also explains a paradoxical pressure drop, where an initial increase in flow rate reduces pressure loss by suppressing the high-viscosity vapor phase. Furthermore, a local temperature inversion, where the fluid becomes hotter than the solid matrix, is identified and attributed to vapor counterflow and its subsequent condensation. Full article

‘Black hole’ is the denomination of the most extreme prediction of the General Theory of Relativity made popular by J. A. Wheeler in the late sixties of the twentieth century, having now entered widely into the collective imagination. Nonetheless, the term is somewhat misleading since there is nothing that tears apart in black holes, which, furthermore, are not even black. Thus, the new name pyknons, from the ancient Greek word for ‘compact; constricted; close-packed’, is proposed for them since it captures a key distinctive feature of theirs. In deference to the objects thus renamed, it also has the merit of introducing a greater compactness in the terms denoting them. Full article

Background: Arachnoid cysts are typically benign and asymptomatic, but large cysts can exert a mass effect on adjacent neural structures. Based on the available literature, no cases of cortical visual impairment (CVI) in an adolescent caused by posterior fossa arachnoid cysts have been reported. Case presentation: We report the case of a previously healthy 16-year-old girl who presented with sudden and rapidly progressive bilateral visual loss due to a large retrocerebellar arachnoid cyst. She reported blurred vision, tunnel vision-like, and decreased visual acuity. Although neuro-ophthalmologic and imaging workup revealed no damage to the anterior visual pathways, she exhibited progressive visual decline. Functional tests confirmed bilateral cortical visual impairment: pattern-reversal visual evoked potentials (VEPs) showed preserved and symmetric P100 latencies and amplitudes, while automated perimetry revealed bilateral concentric visual field constriction with preserved central islands. Following cystoperitoneal drainage, her vision rapidly and completely recovered. Conclusions: To the best of our knowledge, this is the first reported case of reversible CVI in an adolescent caused by a posterior fossa arachnoid cyst without intracranial pressure (ICP) elevation or optic nerve involvement, and with tunnel vision-like. Our findings emphasize the role of posterior fossa lesions in visual dysfunction and highlight the potential reversibility of cortical visual loss when timely decompression is achieved. This case underscores the importance of including posterior fossa lesions in the differential diagnosis of unexplained bilateral visual loss, even in the absence of elevated intracranial pressure or anterior visual pathway involvement. Full article

What can hybridity teach us? The answer I posit is–like water–to embrace movement in all its forms. We are currently experiencing the sixth mass extinction event on earth and yet few scholars give prolonged attention to how we are to sustainably move our human inheritances forward on this increasingly uninhabitable planet. Reflecting on the work of transnational poets, specifically South Korean poet Kim Hyesoon translated through Korean American poet Don Mee Choi and Lebanese American poet Etel Adnan, we are reminded of the myriad ways in which humans can move and survive in a foreign yet familiar world. This paper finds its support in the confluence of transnational contemporary feminist poetics, formalism, environmentalism, and posthumanism. Through the use of various critical discourses, this paper considers how movement and its hybrid capacities offer a new understanding of contemporary North American poetics. In this sense, a poem should be viewed as a dynamic temporal cybernetic system, a vessel, full of energy, simultaneously pulsing with the changing movements and constrictions of everyday life. Full article

Obstructive sleep apnea syndrome (OSAS) in children and adolescents is a prevalent and multifactorial disorder associated with significant short- and long-term health consequences. While adenotonsillectomy (AT) remains the first-line treatment, a substantial proportion of patients—especially those with obesity, craniofacial anomalies, or comorbid conditions—exhibit persistent or recurrent symptoms, underscoring the need for individualized and multimodal approaches. This review provides an updated and comprehensive overview of current and emerging treatments for pediatric OSAS, with a focus on both surgical and non-surgical options, including pharmacological, orthodontic, and myofunctional therapies. A narrative synthesis of recent literature was conducted, including systematic reviews, randomized controlled trials, and large cohort studies published in the last 10 years. The review emphasizes evidence-based indications, mechanisms of action, efficacy outcomes, safety profiles, and limitations of each therapeutic modality. Adjunctive and alternative treatments such as rapid maxillary expansion, mandibular advancement devices, myofunctional therapy, intranasal corticosteroids, leukotriene receptor antagonists, and hypoglossal nerve stimulation show promising results in selected patient populations. Personalized treatment plans based on anatomical, functional, and developmental characteristics are essential to optimize outcomes. Combination therapies appear particularly effective in children with residual disease after AT or with specific phenotypes such as Down syndrome or maxillary constriction. Pediatric OSAS requires a tailored, multidisciplinary approach that evolves with the child’s growth and clinical profile. Understanding the full spectrum of available therapies allows clinicians to move beyond a one-size-fits-all model, offering more precise and durable treatment pathways. Emerging strategies may further redefine the therapeutic landscape in the coming years. Full article

Tectonic activity in the Mediterranean region has been driven by the convergence of the confining plates (Nubia, Arabia and Eurasia). This convergence has been accommodated by the consumption of the oceanic domains that were present in the late Oligocene. It is suggested that this process has been enabled by the lateral escape of orogenic belts in response to constrictional contexts. Where this condition was not present, subduction did not occur. This interpretation can plausibly and coherently account for the very complex pattern of tectonic processes in the whole area since the early Miocene. It is also suggested, by providing some examples, that the geodynamic context proposed here might help us to recognize the connection between the ongoing tectonic processes and the spatio-temporal distribution of past major earthquakes. A discussion is then reported about the incompatibilities of the main alternative geodynamic interpretation (slab pull) with the observed deformation pattern. Full article

Ferroelectric materials, characterized by spontaneous electric polarization, exhibit remarkable parallels with fluid dynamics, where polarization flux behaves similarly to fluid flow. Understanding polarization distribution in confined geometries at the nanoscale is crucial for both fundamental physics and technological applications. Here, we show that the classical Bernoulli principle, which describes the conservation of the energy flux along velocity streamlines in a moving fluid, can be extended to the conservation of polarization flux in ferroelectric nanorods with varying cross-sectional areas. Geometric constrictions lead to an increase in polarization, resembling fluid acceleration in a narrowing pipe, while expansions cause a decrease. Beyond a critical expansion, phase separation occurs, giving rise to topological polarization structures such as polarization bubbles, curls and Hopfions. This effect extends to soft ferroelectrics, including ferroelectric nematic liquid crystals, where polarization flux conservation governs the formation of complex mesoscale states. Full article

Peripheral nerve injury initiates a complex cascade of events coordinating immune responses, extracellular matrix (ECM) remodeling, and neuronal repair. While β2-microglobulin (B2M) is well known for its role in MHC class I-mediated antigen presentation and CD8⁺ T-cell differentiation, its potential contributions to non-immune processes remain underexplored. In this study, we investigated the role of B2M in peripheral nerve regeneration using a chronic constriction injury (CCI) model in wild-type and B2M-deficient (B2M-KO) mice. Flow cytometry, RNA sequencing (RNA-seq), and quantitative PCR (qPCR) were performed to assess T-cell subset dynamics and gene expression following injury. Flow cytometric analysis showed that CD3⁺CD4⁺ and CD3⁺CD8⁺ T-cell populations increased by day 7 post-injury. While CD3⁺CD4⁺ T-cell expansion occurred in both groups, a significant increase in CD3⁺CD8⁺ T cells was observed only in wild-type mice. RNA-seq analysis at 3 days post-injury—prior to substantial T-cell accumulation—revealed marked downregulation of ECM-related genes in B2M-KO mice, including collagens, matrix-associated proteins, and other key ECM components. KEGG analysis identified suppression of ECM–receptor interaction, PI3K-Akt, and TGF-β signaling pathways. qPCR confirmed reduced expression of Thbs1 in B2M-KO mice. These findings suggest that B2M plays a critical, CD8⁺ T-cell-independent role in regulating ECM dynamics and regenerative signaling during early nerve repair, expanding the conceptual framework of B2M’s function beyond classical immune roles. Full article

Stenosis geometries are constrictions of a biological tube that can be found in many forms in the human body. Capturing the flow field in such geometries is important. For this purpose, simulations were performed using the generalised k-$\omega$ (GEKO) turbulence model to study flow through stenosis geometries with throat constrictions of 75, 50 and 25% area reduction. Laminar flow conditions of Re = 2000 and 1000 were applied and the results were compared with experimental data. The effect of four GEKO parameters ($C_{SEP}$, $C_{NW}$, $C_{JET}$ and $C_{MIX}$) on flow in the post-stenotic region was investigated by simulating a wide range of parameter values. Results showed that the $C_{MIX}$ parameter, combined with a modified GEKO blending function, had the greatest effect on axial velocity, velocity fluctuations and the location of the jet breakdown region. A $C_{MIX}$ value of 0.4 closely matched the experimental results for a 75% area reduction stenosis at $Re=2000$ and showed significant improvements over existing Reynolds-averaged Navier–Stokes models. The GEKO model was also able to closely match the axial velocity results predicted by previously published large-eddy simulation models under the same flow conditions. Furthermore, the GEKO model was applied to a realistic oral-to-tracheal airway model for a Reynolds number of 2000 and produced results consistent with the idealised stenotic tube. Full article

Currently, hydrodynamic models for bay and estuarine systems involve many parameters that require proper calibration to design coastal structures effectively. However, in coastal regions with limited data availability, the implementation of such models becomes challenging. This research introduces a simplified hydrodynamic methodology designed to analyse the impact of hydraulic control structures in shallow waters. This approach offers a computationally efficient alternative that allows engineers to rapidly evaluate the impact of horizontal and vertical constrictions in shallow waters experiencing wave propagation. A practical application is demonstrated in a one-dimensional channel with a length of 200,000 m and an average depth of 5 m. The only parameter required for calibration in the proposed methodology is bed friction. The three analysed scenarios—longitudinal constriction, plan-view constriction, and the influence of bed friction—demonstrate the model’s sensitivity to these variations, highlighting its reliability as a decision-making tool for coastal engineering projects. Moreover, the comparison of the proposed hydrodynamic simulation methodology at the stabilised tidal inlet structure in Cartagena de Indias, Colombia, demonstrated its ability to reproduce observed water levels accurately, reinforcing its reliability and potential for broader application. Full article

Background/Objectives: The aim of this study was to determine the prevalence of functional cardiovascular anomalies detected on fetal echocardiography in third-trimester large-for-gestational-age (LGA) fetuses, who were subsequently born as macrosomic newborns with a birth weight exceeding 4000 g. Methods: A retrospective study was conducted on 1002 fetuses examined during the third trimester at our fetal cardiology center between 2018 and 2024. All fetuses were classified as having “normal heart anatomy” (NHA). Statistical analysis was performed using Microsoft Excel 2024, Statistica 13.1, and EasyMedStat (version 3.37.1). A p-value of <0.05 was considered statistically significant. Results: The 1002 fetuses were divided into two groups. The study group (NHA-LGA) consisted of 167 fetuses born with a weight of >4000 g and the control group (NHA-AGA) was made up of 835 fetuses with a birth weight between 2500 and 4000 g. In the NHA-LGA group, 24 fetuses (14.4%) experienced ductal constriction (DC), while in the NHA-AGA group, it was 11 (1.3%) fetuses (p < 0.00001). Myocardial hypertrophy was observed in 30 fetuses (18.0%) in the NHA-LGA group versus 72 (8.6%) in the NHA-AGA group (p < 0.0003). Additionally, cardiomegaly was noted in 95 fetuses (11.4%) in the NHA-LGA group, compared to 37 (4.4%) in the NHA-AGA group (p < 0.0004). Conclusions: LGA fetuses with normal heart anatomy may present with functional cardiovascular anomalies, including ductal constriction, myocardial hypertrophy, and cardiomegaly. In our cohort, such anomalies were identified in up to 51% of cases. These findings suggest that targeted fetal echocardiographic screening in macrosomic fetuses could be clinically valuable, even in the absence of structural heart defects, and may aid in the early identification of functional cardiac alterations that could impact perinatal management. Full article

A cheap, environmentally friendly, easily scalable post-treatment of Na-ZSM-5 (Si/Al molar ratio = 20 or 30) via electron-beam irradiation to produce hierarchical H-ZSM-5 as a propylene-increasing fluid catalytic cracking additive was performed. Higher specific surface areas and highly accessible porous systems were obtained among the irradiated samples. A combination of ²⁷Al, ¹H magic angle spinning nuclear magnetic resonance and NH₃-temperature-programmed desorption methods showed that upon irradiation, some of the framework’s tetrahedral Al atoms were removed as non-framework Al atoms via flexible coordination with Si-OH groups (either framework or non-framework defects), thus increasing the H-ZSM-5 acidity and stability during hydrothermal dealumination. The enhanced selectivity and stability toward propylene production over the irradiated H-ZSM-5 samples were attributed to the integration of the reserved population of medium acid sites into the highly accessible hierarchical network. N₂ adsorption–desorption isotherm data showed that the Si-rich H-ZSM-5 samples possessed an obvious ink-bottle-shaped micro-mesopore network and a greater degree of disordered orientation of the straight pore systems toward the exterior surfaces. Micro-activity test data suggested that with an increasing Si/Al ratio, the H-ZSM-5 additives lost some extent of their cracking activity due to the constricted hierarchical pore network toward the exterior surface but gained more stability and selectivity for propylene due to the reserved medium acid sites. Full article

Background/Objectives: Currently, clear aligners are preferred to conventional appliances, especially among adult patients. However, the use of aligners for treating maxillary constriction is still debated in the literature. Therefore, the purpose of this study was to assess maxillary dentoalveolar expansion following clear aligner therapy in adults using CBCT scans. Methods: The study sample encompassed 50 non-growing patients (27 females and 23 males) aged 20 to 42 undergoing clear aligner orthodontics without dental extractions or auxiliaries. Transverse linear distances were measured on initial and final CBCTs and, subsequently, analysed through paired t-test and ANOVA. We considered alveolar bone measurements and interdental widths measured at the buccal apices and cusps from canines to second molars. Results: The buccal alveolar ridge width showed the greatest expansion (1.01 ± 0.38 mm), followed by the palatal alveolar ridge and maxillary alveolar bone. Statistically significant improvements were observed for all interdental measurements. The most considerable changes occurred in the interpremolar cusp distances, while the least changes were seen in the intermolar apex distances. At the cusp level, the average interpremolar widths increased by 3.44 ± 0.22 mm for the first premolars and 3.14 ± 0.27 mm for the second ones. Conclusions: Clear aligner treatment can effectively manage a constricted maxillary arch. We found significant changes in the maxillary alveolar bone. Both inter-apex and inter-cusp widths increased in all teeth, with the highest values in the premolars. Moreover, the increases in interdental distances at both apex and cusp levels were related to tooth position. Full article

Background and Objectives: Vision uses about half of the pathways within the brain, and these anatomical structures are susceptible to injury in concussion. Authors have suggested that subconcussive head impacts, common in soccer, may disrupt visual function. The following study aimed to explore and compare quantitative pupillometry and Vestibular Ocular Motor Screening (VOMS) in female soccer athletes. Materials and Methods: Twenty-six Division 1 female soccer athletes (20.46 ± 2.36 years) received baseline quantitative pupillometry and VOMS measurements. Results: Of the 26 tested athletes, 3 (11.5%) had clinically significant pupillometry findings at baseline. The mean Neurological Pupil Index or NPi, a composite generated from pupillometry, did not vary: 3.9 ± 0.4 (right eye) and 4.0 ± 0.4 (left eye). No difference in NPi was observed compared to the VOMS score (p > 0.05). Kruskal–Wallis H tests were significant in the right eye for constriction percentage (χ²(2) = 17.843, p < 0.001, E² = 0.69) and minimum pupil size (χ²(2) = 7.976, p = 0.019, E² = 0.31). A post hoc Dunn test showed significant differences in constriction percentage and minimum pupil size between low NPi and high NPi groups (p < 0.05). One athlete sustained a concussion. NPi was measured within 24 h and was normal, but VOMS was not (total score = 4). Conclusions: The components of pupillometry need more investigation, and there is a need for agreement on concussion-specific cutoffs for quantitative pupillometry for concussion assessment. The lack of a relationship between quantitative pupillometry and VOMS suggests that these tools evaluate different constructs. Athletes with an NPi < 3.8 had significantly less constriction percentage and larger minimum pupil size than athletes with higher NPi scores. More research should be carried out to determine the usefulness of the NPi score, and perhaps researchers should consider individual pupillometry components. Full article

Objectives: Mouth breathing in children may lead to craniofacial anomalies such as maxillary constriction. Pediatricians play a crucial role in recognizing early signs and making timely referrals. This study aimed to evaluate the awareness of pediatricians regarding mouth breathing and its orthodontic implications and to assess the impact of their treatment attitudes and clinical experience on referral practices. Methods: A 20-item online questionnaire was completed by 110 volunteer pediatricians from various regions of Türkiye via professional networks. The survey included items on awareness, treatment attitudes, referral behaviors, and demographics. Composite scores for awareness and orthodontic treatment attitude were calculated and included in the analysis. Data were analyzed using chi-square tests, Spearman correlation, and binary logistic regression. Results: Most pediatricians were aware of the link between mouth breathing and craniofacial issues (awareness rate: 73.6%), yet only 14.5% were familiar with specific orthodontic treatment approaches such as maxillary expansion. Although 70.9% expressed a desire for further training, only 25.5% reported frequently referring patients for orthodontic evaluation. Referral behavior was significantly associated with both clinical experience (p = 0.004) and orthodontic treatment attitude scores (p = 0.004) but not with awareness scores (p = 0.12). Conclusions: Although pediatricians in Türkiye demonstrate relatively high awareness regarding the consequences of mouth breathing, referral practices remain limited. Attitudinal orientation toward orthodontic treatment may play a more influential role in referral behavior than awareness alone. Full article