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Near-space hypersonic vehicles encounter significant rarefaction effects during the flight through the atmosphere, causing the classical Navier–Stokes–Fourier (NSF) equations to break down and posing challenges for the evaluation of surface drag and heat flux. In this paper, the nonlinear momentum and heat transfer in a hypersonic transitional boundary layer are analysed based on the generalized hydrodynamic equations (GHE), and the generality of the derived formulae is also discussed. The leading transport relations are obtained by estimating the relative orders of the various terms in GHE according to the hypersonic flow and boundary-layer requirements. Local non-equilibrium parameters characterising the shear non-equilibrium effect ($K_\sigma$) and thermal-gradient non-equilibrium effect ($K_q$) are introduced, and a set of correlation formulae for local surface pressure, shear stress and heat flux are proposed as corrections to continuum-based solutions. The correction function depends only on the non-equilibrium parameters $K_\sigma$ and $K_q$, and the continuous solutions can be either analytical formulae or NSF simulation results. This enables us to predict the surface aerothermodynamics with enhanced accuracy while still using the solutions of the NSF equations. The proposed formulae are carefully verified by comparing with direct simulation Monte Carlo (DSMC) results of different hypersonic rarefied flows, including flat-plate, sharp-wedge, cylinder and blunt-cone flows, and partial experimental data are also given. The results demonstrate that the proposed formulae can significantly enhance the accuracy of the continuum-based solutions, and show good agreement with DSMC simulations and experimental measurements in the near-continuum regime.
Mahaim ablation poses a significant challenge among accessory pathway ablations. This study aims to present our findings on Mahaim ablation performed using a contact force catheter, emphasizing both the effectiveness and safety of this technique.
Materials and methods:
This is a single-centre retrospective cohort study. Twenty-two consecutive patients who underwent Mahaim pathway ablation procedures between January 2017 and January 2025 were included in the study. The EnSite Precision System (Abbott, St. Paul, MN, USA) was used to facilitate mapping and to reduce or eliminate the need for fluoroscopy. Ablation was performed using the TactiCath catheter.
Results:
The median age was 11 years (range: 7–18). Antidromic tachycardia was induced in all patients with the left bundle block. All patients underwent successful ablation with the TactiCath catheter. Ablation was performed via the jugular approach in 11 patients and via the femoral region in another 11 patients. Ablation procedures were performed under atrial pacing in four patients regarding catheter stabilization. Locations of the Mahaim signals were at the right anterolateral (n = 6), right lateral (n = 7), and right posterolateral (n = 9) tricuspid annulus. The acute success rate was 100% (22/22). Fluoroscopy was not used on any patient. The median procedure time was 132 minutes (range: 72–411). No major complications were observed. One recurrent patient who presented with a tachycardia attack one month later had Ebstein’s anomaly. An ablation procedure was successfully performed from the right lateral region.
Conclusion:
In paediatric Mahaim tachycardia ablations, the use of a contact force catheter can be safe and successful.
Patients with 22q11.2 deletion are known to have immune abnormalities. Data on the immune profile of non-syndromic patients with conotruncal heart defects are limited.
Methods:
A prospective study evaluated the genetic and immunological profiles and early to mid-term postoperative outcomes of patients with conotruncal heart defects.
Results:
Infants with 22q11.2 deletion had low leukocyte counts, while low total lymphocyte counts were observed in all patients except infants without a genetic syndrome. Reduced CD3+, CD4+, and CD8+ cells were found in 22q11.2 deletion neonates and infants, as well as in infants without a genetic syndrome. Immunoglobulin G, M, and A abnormalities occurred across all groups. T cell receptor excision circle levels were lowest in patients with complex heart defects. Kappa-deleting recombination excision circle levels were increased in patients without a genetic syndrome. Early postoperative infections were frequent in all groups. Neonates with 22q11.2 deletion had longer ICU stay and higher need for antibiotics and hospital readmission at 3 and 6 months of follow-up.
Conclusion:
Neonates and infants with conotruncal heart defects have low preoperative T lymphocyte counts, reduced T cell receptor excision circle and immunoglobulin levels, and high incidence of postoperative infections. Higher kappa-deleting recombination excision circle levels compensated the T cell disbalances in patients without a genetic syndrome. The presence of a 22q11.2 deletion with conotruncal heart defects was associated with prolonged mechanical ventilation, longer ICU length of stay, higher need for antibiotic treatment after discharge from the hospital, and readmission risk in neonates after cardiac surgery.
The evolution of the flow structure around an impulsively stopped sphere is investigated in an incompressible viscous fluid under a transverse magnetic field. The study focuses on the wake structure and drag force over the range of Reynolds numbers $60 \leqslant {\textit{Re}}_{\!D} \leqslant 300$ and $ {\textit{Re}}_{\!D}=1000$, with the interaction parameters $0 \leqslant N \leqslant 10$, where $N$ characterises the strength of the magnetic field. The wake is fully developed before the impulsive stop, after which it moves downstream and interacts with the sphere under the influence of a transverse magnetic field. The complex flow structures are characterised by skin friction lines on the downstream side of the sphere and categorised into five regimes in the $\{N, {\textit{Re}}_{\!D}\}$ phase diagram based on nearly 200 cases. The drag force generally decays over time following the impulsive stop. A drag decomposition model based on the vorticity diffusion scale is proposed, attributing the drag decay to three components: the original Stokes contribution, an inertia correction at high Reynolds numbers and a magnetohydrodynamic (MHD) correction, where the inertia and MHD effects both contribute a temporal power-law decay with an exponent of $-1/6$. Temporal scaling laws of the drag decay are derived by coupling these three different effects, considering flow structures at short and long time scales, as well as the dependence on ${\textit{Re}}_{\!D}$ and $N$. The prediction results are consistent with present simulations. Furthermore, the proposed drag decomposition model is successfully extended to complex vortex flow past a sphere at ${\textit{Re}}_{\!D}=1000$, to an anisotropic ellipsoidal particle and to different magnetic field orientations.
International travel is thought to be a major risk factor for developing gastrointestinal illness in England. Transmission is thought to be more likely in countries which have lower food hygiene standards, poorer sanitation, and lack of access to clean water. However, many studies are conducted within travel clinic settings which may bias findings. Here, we present a case–control study undertaken in returning English travellers in the community conducted with cases of gastrointestinal illness notified to UKHSA.
All Cryptosporidiosis, Giardiasis, non-typhoidal Salmonellosis, and Shigellosis cases notified to the UK Health Security Agency (UKHSA) between 01 July 2023 and 15 October 2023 were asked to complete an anonymous electronic questionnaire if travelling during their incubation period. Asymptomatic travellers were recruited as controls via a market research panel and asked to complete the same questionnaire. A destination water, hygiene, and sanitation score were derived from the WHO ‘Attributable fraction of diarrhoea to inadequate WASH’ dataset. Demographics, travel details, and exposures while travelling were compared by Pearson’s chi-squared test, and pathogen and destination specific multivariable analyses were performed using a forward stepwise approach.
A total of 653 cases and 483 controls were included. The odds of being a case were significantly higher when travelling to countries outside of the EU (OR:4.6, 95%CI:3.5–6.0; p = <0.001) and to countries with high-risk WASH score (OR 6.6, 95%CI:4.9–9.1; p = <0.001), particularly Egypt, Mexico, Tunisia, and Turkey. For those travelling to a low-risk destination, eating undercooked meat or fish and swallowing water from environmental water sources were significantly associated with higher odds of illness by multivariable analysis (p < 0.05). At high-risk destinations, eating foods consumed on excursions, swallowing water from environmental sources, and eating foods from hotel buffets were significantly associated with higher odds of being a case.
Travel to popular tourist destinations is a potentially under-recognized risk factor for acquiring gastrointestinal infections. Exposures at low-risk destinations were broadly similar to risk factors in the UK. Exposures in high-risk destinations highlighted potential risks associated with catered hotels and tourist excursions which should be explored further.
A combined experimental and direct numerical simulation (DNS) investigation is undertaken to study the laminar boundary-layer (BL) flow adjacent to a melting vertical ice face at two far-field water salinities ($S_\infty =0$ and 34 ‰) and a range of far-field temperatures ($T_\infty$). Wall-normal distributions of vertical velocity and temperature within the BL are measured by a modified molecular tagging velocimetry and thermometry technique. Experimental data match with DNS only when a nonlinear equation of state (EoS) for density is used rather than a linear EoS. For all $S_\infty =0$, i.e. freshwater cases, the flow remains uni-directional, although the flow reverses direction at $T_\infty =4^{\,\circ} \text{C}$. A bi-directional flow, however, exists for $S_\infty =$ 34 g kg−1, where an inner salinity-driven upward flow of fresher water is accompanied by a downward-flowing temperature-driven outer flow. Although the contribution of temperature to density relative to salinity is small $({\approx}1/40)$, the thermal BL region is larger owing to higher diffusivity. This results in increased total buoyancy force when the buoyancy is integrated across the BL, which combined with effects of wall shear stress on salinity BL and a freer thermal BL growth reveals that buoyancy from temperature contributes almost equally to the overall flow. Melt rates ($V$) also show differing features in uni- and bi-directional flows. The uni-directional flows exhibit the standard scaling of increasing velocity magnitude and BL thickness, and decreasing $V$ with distance along the flow direction. Such scalings are not followed in the bi-directional flows. These show a more uniform $V$ with height, which is attributed to the counteracting effects of an upward-growing salinity BL and a downward-growing temperature BL, combined with the necessity of maintaining salinity and temperature flux balance at the ice–water interface.
This article examines the benefits of utilizing site and orbital diversity reception techniques at Ka- and Q-bands in South Eastern Europe, comparing their performance in Cyprus and Greece. The assessment relies on measured rainfall rate statistics, collected near the selected locations in both countries. The study compares and evaluates the performance of double and triple site and orbital diversity scenarios. The simulation outcome reveals that the adoption of double and triple site, or double and triple orbital diversity configurations leads to considerable enhancements in outage performance in both frequency bands. The delivered improvements are markedly significant when specifically 3-site and 3-orbit diversities are applied, especially at Q-band. However, the orbital diversity demonstrates inferior performance compared with site diversity. Notably, for satellite systems demanding extremely high levels of service continuity, the 3-site diversity approach proves highly effective at Ka- and Q-bands, accomplishing this without necessitating overly large fade margins. Comparing Cyprus and Greece, the latter demonstrates lower outage improvements due to the higher measured rainfall rates. Finally, for a dual orbital diversity scenario in Greece, measured experimental results are presented in terms of joint attenuation and compared with the theoretical model, exhibiting noticeable accuracy.
A well-known theorem of Nikiforov asserts that any graph with a positive $K_{r}$-density contains a logarithmic blowup of $K_r$. In this paper, we explore variants of Nikiforov’s result in the following form. Given $r,t\in \mathbb{N}$, when a positive $K_{r}$-density implies the existence of a significantly larger (with almost linear size) blowup of $K_t$? Our results include:
• For an $n$-vertex ordered graph $G$ with no induced monotone path $P_{6}$, if its complement $\overline {G}$ has positive triangle density, then $\overline {G}$ contains a biclique of size $\Omega ({n \over {\log n}})$. This strengthens a recent result of Pach and Tomon. For general $k$, let $g(k)$ be the minimum $r\in \mathbb{N}$ such that for any $n$-vertex ordered graph $G$ with no induced monotone $P_{2k}$, if $\overline {G}$ has positive $K_r$-density, then $\overline {G}$ contains a biclique of size $\Omega ({n \over {\log n}})$. Using concentration of measure and the isodiametric inequality on high dimensional spheres, we provide constructions showing that, surprisingly, $g(k)$ grows quadratically. On the other hand, we relate the problem of upper bounding $g(k)$ to a certain Ramsey problem and determine $g(k)$ up to a factor of 2.
• Any incomparability graph with positive $K_{r}$-density contains a blowup of $K_r$ of size $\Omega ({n \over {\log n}}).$ This confirms a conjecture of Tomon in a stronger form. In doing so, we obtain a strong regularity type lemma for incomparability graphs with no large blowups of a clique, which is of independent interest. We also prove that any $r$-comparability graph with positive $K_{(2h-2)^{r}+1}$-density contains a blowup of $K_h$ of size $\Omega (n)$, where the constant $(2h-2)^{r}+1$ is optimal.
The ${n \over {\log n}}$ size of the blowups in all our results are optimal up to a constant factor.
Georg Lukács’s History and Class Consciousness (1923) has often been criticised for its idealism. I discuss Lukács’s critique of reification in light of these charges, identifying two different idealist vocabularies of (neo-)Kantian and Hegelian origin, respectively. I show that the function of the former is critical: refracting Marx’s analysis of social form through a Kantian form/content distinction allows Lukács to critique capitalism as the domination of form over content. Lukács’s Hegelian leanings are more problematic, however, as they constrain his own insights into the conditioned and contingent character of political practice and history.
Numerical simulations of turbulent flows at realistic Reynolds numbers generally rely on filtering out small scales from the Navier–Stokes equations and modelling their impact through the subgrid-scale stress tensor ${\tau }_{\textit{ij}}$. Traditional models approximate ${\tau }_{\textit{ij}}$ solely as a function of the filtered velocity gradient, leading to deterministic subgrid-scale closures. However, small-scale fluctuations can locally exhibit instantaneous values whose deviation from the mean can have a significant influence on the flow dynamics. In this work, we investigate these effects by employing direct numerical simulations combined with Gaussian filtering to quantify subgrid-scale effects and evaluating the local energy flux in both space and time. The mean performance of the canonical Clark model is assessed by conditioning the energy flux distributions on the invariants of the filtered velocity gradient tensor, $Q$ and $R$. The Clark model captures to a good degree the mean energy flux. However, the fluctuations around these mean values for given ($Q,R$) are of the order of the mean, displaying fat-tailed distributions. To be more precise, we examine the joint distributions of true energy flux and the predictions from both the Clark and the Smagorinsky models. This approach mirrors the strategy adopted in early stochastic subgrid-scale models. Clear non-Gaussian characteristics emerge from the obtained distributions, particularly through the appearance of heavy tails. The mean, the variance, the skewness and the flatness of these distributions are quantified. Our results emphasise that fluctuations are an integral component of the small-scale feedback onto the large-scale dynamics and should be incorporated into subgrid-scale modelling through an appropriate stochastic framework.
In cultural heritage projects and artistic documentation, motion capture has emerged as a key archival strategy that is promised to be a “next stage” solution in preserving and accessing the past. However, motion capture is not an objective recording; it transposes a technological bodily imaginary onto the bodies whose movements it documents. This essay is situated at the intersection of current critical discourses on archives, dance and AI, bringing domain-specific knowledge to reimagine biased algorithmic systems. Although there is substantial risk for representational harms in how current AI motion models are used to render dancing bodies as data, recent projects show that retaining the entanglement of expert practitioners can refine data processing. We argue that incorporating the specificity of dance-based knowledge can support more meaningful historical research practices, in particular when understanding how bodies are themselves also archives. This contributes to identifying and countering the harms that arise from the mismatch between what automated motion extraction systems purport to accomplish and what they actually represent. The article outlines questions and guidelines that reimagine motion data through a visceral approach for an era of AI.
Online synchronous chat, or ‘Live Chat’, is distinguished by its real-time, anonymous, and text-based nature. There is limited understanding of the characteristics of those who choose Live Chat services compared to Blended Services. This study examined the demographic, psychosocial, and service engagement profiles of young people using the Irish Live Chat service, Jigsaw Live Chat, compared with those attending Jigsaw’s Blended (in-person and/or video) support Service. Routine service-based data were analysed from 1,313 Live Chat and 3,604 Blended Service users. Reasons for attendance among Live Chat users seeking mental health support were analysed using content analysis. Live Chat users were more likely to be gender-diverse, older, and to report higher psychological distress than Blended Service users. Anxiety and low mood were common presenting issues. Attendance reasons varied, with over one-third citing multiple issues and many experiencing persistent distress. A minority attended for information or while waiting for other support. Overall, users reported high satisfaction. Live Chat users waited an average of 2.5 minutes, compared with typical waits of 1–2 months for the Blended Service. These findings highlight Live Chat as a distinct and essential access point for highly distressed and underserved youth, particularly those with minority gender and sexual identities.
In this paper, a dual concentric square-loop dual-polarized reconfigurable frequency selective surface with a high tuning ratio of 2.02 operating in the 1.53–3.10 GHz band is proposed. This high tuning ratio has been achieved by using four SMV1430-LF varactor diodes, which have been actuated using a simple biasing arrangement made of stubs and four metallic vias per unit-cell. The unit-cell has been rigorously analyzed, and an equivalent circuit (EC) model has been developed for the physical insight. The proposed EC model also demonstrates the reconfigurability of the unit-cell and thus predicts its behavior. The effect of the angular incidence of the impinging electromagnetic wave on the structure up to a 45º has been experimentally verified, which demonstrates its angular stability and polarization insensitive behavior. The structure may find applications in the electromagnetic spectrum’s L, S, and 2.45 GHz ISM bands.