Background: Studies have found similar rates of functional independence for men and women after endovascular thrombectomy (EVT). Less is known regarding EVT-related procedural complications and symptomatic intracerebral hemorrhage (sICH) between sexes. Methods: Using the OPTIMISE registry including data from 20 comprehensive stroke centers across Canada between 1/1/2018 and 12/31/2022, we performed a retrospective descriptive analysis of patients divided between men and women. Hemorrhagic transformation on follow-up imaging with associated clinical deterioration was required to define sICH. Results: 3631 patients were included (1778 men and 1853 women) for analysis. Female patients were older (71.8±14.6 vs 68.0±13.1 years, p<0.001). There were no differences in sICH rates (2.5% men vs. 2% women, p= 0.388}. Procedural complication rates were not different between men and women (5.8 vs 5.6% p=0.76): dissection {26 (1.5%) vs. 30 (1.6%), p=0.804}, perforation {11 (0.6%) vs. 7 (0.4%), p=0.426}, embolization {25 (1.4%) vs. 25 (1.3%), p=0.996} and arterial access complications {45 (2.5%) vs. 43 (2.3%), p=0.761}. Conclusions: In this large multicentre registry of stroke patients undergoing EVT, men and women had similarly low and reassuring rates of sICH and procedural complications. This complements previous data showing similar functional outcomes for men and women after EVT.

Background: Anterior (ACS) and posterior circulation (PCS) stroke patients have different clinical presentations and prognoses, though both benefit from endovascular thrombectomy (EVT). We sought to determine whether ACS and PCS patients treated with EVT differed with regards to treatment metrics and functional outcomes. Methods: We retrospectively analysed theCanadian OPTIMISE registry which included data from 20 comprehensive stroke centers across Canada between January 1, 2018, and December 31, 2022. We performed a descriptive analysis of patients divided in two groups (ACS= carotid artery and its branches, PCS= vertebrobasilar system). Results: Of the 6391 patients included (5929 ACS and 462 PCS), PSC patients were younger (67 vs. 71.3, p<0.001), more often male (61.9% vs. 48.6%, p<0.001), had longer (in minutes) onset-to-door (362 vs. 256, p<0.001), door-to-needle (172 vs. 144, p=0.0016), and onset-to-puncture (459 vs. 329, p<0.001) times. They were less often thrombolyzed (39.8% vs. 50.4%, p<0.001), and more frequently underwent general anesthesia (47.6% vs. 10.6%, p<0.001). Successful reperfusion and functional independence at 90 days were similar between the two groups. Conclusions: Patients with PCS had worst treatment metrics than ACS. Strategies to improve PCS management times are critical to decrease these disparities, including faster pre-hospital recognition and in-hospital workflows.

Background: We evaluated (1) the predictive accuracy and (2) multi-observer reliability of non-contrast CT markers of hematoma expansion (HE). Methods: In 124 patients with spontaneous intracerebral hemorrhage, two investigators documented the presence of six density (Barras density, hypodensity, black hole, swirl, blend, fluid level) and three shape (Barras shape, island, satellite) expansion markers, with discrepancies resolved by a third rater. We defined HE as any one of (1) >6 mL absolute or >33% relative growth of the intraparenchymal hematoma or (2) an absolute growth of >1 mL or new development of intraventricular hematoma. A subsample of 60 patients was used for the inter-observer reliability study in 13 raters. Seven raters participated in the intra-rater study. Results: The sensitivity of markers for HE varied between 4% (fluid level) and 78% (satellite), while specificity ranged from 37% (swirl) to 97% (black hole). Almost perfect inter-rater agreement was observed for the swirl (0.89) and fluid level (0.83) markers, while hypodensity (0.65) showed substantial agreement. Only the blend and fluid level markers achieved substantial intra-rater agreement (> 0.6) in all raters. Conclusions: Non-contrast CT markers of HE showed lower reliability and predictive accuracy than previously reported. Future studies should address means to improve NCCT-based HE prediction.

We investigate optimal perturbation in the flow past a finite aspect ratio ($AR$) wing. The optimization is carried out in the regime where the fully developed flow is steady. Parametric study over time horizon ($T$), Reynolds number ($Re$), $AR$, angle of attack and geometry of the wing cross-section (flat plate and NACA0012 airfoil) shows that the general shape of linear optimal perturbation remains the same over the explored parameter space. Optimal perturbation is located near the surface of the wing in the form of chord-wise periodic structures whose strength decreases from the root towards the tip. Direct time integration of the disturbance equations, with and without nonlinear terms, is carried out with linear optimal perturbation as initial condition. In both cases, the optimal perturbation evolves as a downstream travelling wavepacket whose speed is nearly the same as that of the free stream. The energy of the wavepacket increases in the near wake region, and is found to remain nearly constant beyond the vortex roll-up distance in nonlinear simulations. The nonlinear wavepacket results in displacement of the tip vortex. In this situation, the motion of the tip vortex resembles that observed during vortex meandering/wandering in wind tunnel experiments. Results from computation carried out at higher $Re$ suggest that, even beyond the steady flow regime, a perturbation wavepacket originating near the wing might cause meandering of tip vortices.

A two-dimensional analysis of the resolvent spectrum of a Mach 1.6 transitional boundary layer impacted by an oblique shock wave is carried out. The investigation is based on a two-dimensional mean flow obtained by a RANS model that includes a transition criterion. The goal is to evaluate whether such a low cost RANS based resolvent approach is capable of describing the frequencies and physics involved in this transitional boundary layer/shock-wave interaction. Data from an experiment and a companion large eddy simulation (LES) are utilized as reference for the validation of the method. The flow is characterized by a laminar boundary layer upstream, a laminar separation bubble (LSB) in the interaction region and a turbulent boundary layer downstream. The flow exhibits low amplitude unsteadiness in the LSB and at the reflected shock wave with three particular oscillation frequencies, qualified as low, medium and high in reference to their range in Strouhal number, here based on free stream velocity and LSB length ($S_{t}=0.03{-}0.11$, 0.3–0.4 and 2–3 respectively). Through the resolvent analysis this dynamics is found to correspond to an amplifier behaviour of the flow. The resolvent responses match the averaged Fourier mode of the time dependent flow field, here described by the LES, with a close agreement in frequency and spatial distribution, thereby validating the resolvent approach. The low frequency dynamics relates to a pseudo-resonance process that sequentially implies the amplification in the separated shear layer of the LSB, an excitation of the shock foot and a backward travelling density wave. As this wave hits back the separation point the amplification in the shear layer starts again and loops. The medium and high frequency modes relate to the periodic expansion/reduction of the bubble and to the turbulent fluctuations at the reattachment point of the bubble, respectively.

We investigate perturbations that maximize the gain of disturbance energy in a two-dimensional isolated vortex and a counter-rotating vortex pair. The optimization is carried out using the method of Lagrange multipliers. For low initial energy of the perturbation ($E(0)$), the nonlinear optimal perturbation/gain is found to be the same as the linear optimal perturbation/gain. Beyond a certain threshold $E(0)$, the optimal perturbation/gain obtained from linear and nonlinear computations are different. There exists a range of $E(0)$ for which the nonlinear optimal gain is higher than the linear optimal gain. For an isolated vortex, the higher value of nonlinear optimal gain is attributed to interaction among different azimuthal components, which is otherwise absent in a linearized system. Spiral dislocations are found in the nonlinear optimal perturbation at the radial location where the most dominant wavenumber changes. Long-time nonlinear evolution of linear and nonlinear optimal perturbations is studied. The evolution shows that, after the initial increment of perturbation energy, the vortex attains a quasi-steady state where the mean perturbation energy decreases on a slow time scale. The quasi-steady vortex state is non-axisymmetric and its shape depends on the initial perturbation. It is observed that the lifetime of a quasi-steady vortex state obtained using the nonlinear optimal perturbation is longer than that obtained using the linear optimal perturbation. For a counter-rotating vortex pair, the mechanism that maximizes the energy gain is found to be similar to that of the isolated vortex. Within the linear framework, the optimal perturbation for a vortex pair can be either symmetric or antisymmetric, whereas the structure of the nonlinear optimal perturbation, beyond the threshold $E(0)$, is always asymmetric. No quasi-steady state for a counter-rotating vortex pair is observed.

Freshwater gammarids infected with the acanthocephalan parasite Polymorphus minutus show behavioural alterations but also differ from uninfected individuals in their appearance because of the carotenoid-based colouration of the parasite visible through the cuticle. However, it's not clear whether this phenotypic alteration is an adaptation favouring parasite transmission to the definitive host. To test this hypothesis, we investigated the selective preference of mallard towards two prey types: uninfected gammarids on which we applied a dot of inconspicuous brown paint, and uninfected gammarids on which we applied a dot of bright orange paint to mimic the change in appearance due to P. minutus without changes in host behaviour. Mallards showed a significant preference for orange-painted gammarids regardless of how gammarids were distributed (isolated or aggregated). This suggests that parasite's colouration may play a role in enhanced transmission to definitive avian hosts. The role of P. minutus’ colouration in the conspicuousness of gammarids has however to be balanced by the extent to which mallards use visual cues to forage in the field. From the perspective of a multidimensional manipulation, this study suggests that the change in appearance may act synergistically with the changes in behaviour to promote transmission to waterbirds.

The near field of a Reynolds number and low-Mach-number cylindrical jet has been investigated by means of a high-speed stereo PIV setup that provides the spatio-temporal velocity field in a transverse plane, two diameters downstream of the jet exit. Proper orthogonal decomposition (POD) and spatio-temporal correlations are used to identify some of the main dynamical features of this flow. We show that the flow is dominated by streamwise vortices whose production and spatial organization can be related to and perturbations, and to the mean shear of the mixing layer. A dynamical scenario is proposed which describes this interaction, in accordance with our observations.

Turbulence in solid-body rotation is generated by a flow of air passing through a rotating cylinder containing a dense honeycomb structure and a turbulence-producing grid. The velocity field is probed downstream of this device by hot-wire probes. Using the statistical quantities characterizing the fluctuating field, we show that the rotation affects mainly the components normal to the rotation axis and that these effects are triggered when the Rossby numbers constructed from macroscopic turbulent quantities, are less than unity. These results are discussed in the framework of other available experimental results on the subject. A theoretical interpretation, chiefly based on spectral analysis, is then proposed to explain the trends of the observations.

The non-isotropic effects of solid-body rotation on homogeneous turbulence are investigated in this paper. A spectral formalism using eigenmodes introduces the spectral Coriolis effects more easily and leads to simpler expressions for the integral quadratic terms which come mostly from classical two-point closures. The analysis is then applied to a specific eddy damped quasi-normal Markovian model, which includes the inertial waves regime in the evaluation of triple correlations. This procedure allows for a departure from isotropy by external rotation effects. When started with rigorously isotropic initial data, the various trends observed on the Reynolds stresses and the integral lengthscales remain in accordance with the results from direct simulations; moreover they reflect a very specific spectral angular distribution. Such an angular dependence allows a drain of spectral energy from the parallel to the normal wave vectors (with respect to the rotation axis), and thus appears consistent with a trend toward two-dimensionality.