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Hot-electron devices are emerging as promising candidates for the transduction of optical radiation into electrical current, as they enable photodetection and solar/infrared energy harvesting at sub-bandgap wavelengths. Nevertheless, poor photoconversion quantum yields and low bandwidth pose fundamental challenges to fascinating applications of hot-electron optoelectronics. Based on a novel hyperbolic metamaterial (HMM) structure, we theoretically propose a vertically-integrated hot-electron device that can efficiently couple plasmonic excitations into electron flows, with an external quantum efficiency approaching the physical limit. Further, this metamaterial-based device can have a broadband and omnidirectional response at infrared and visible wavelengths. We believe that these findings may shed some light on designing practical devices for energy-efficient photodetection and energy harvesting beyond the bandgap spectral limit. [ABSTRACT FROM AUTHOR]

• Cavitating flow over a foil is studied using experiments and numerical simulations. • The studied cavitating flow exhibits both large and small-scale shedding behaviors. • Three small-scale shedding mechanisms of cavitating structures are identified. • The small-scale shedding mechanisms are described in detail. Leading-edge cavitation is responsible of the generation of transient cavities, usually made of clouds of bubbles. These transient cavities travel downstream to high-pressure regions and collapse violently, leading to noise and vibration as well as erosion. In the present paper, the focus is on the mechanisms generating transient cavities to better understand the starting point of the erosion process. The case studied is the cavitating flow over a NACA0009 hydrofoil which is investigated using experiments and numerical simulation. In the experimental part, which is conducted in EPFL high-speed cavitation tunnel, the shedding behavior is studied using high-speed visualization (HSV). In the numerical part, the cavitating flow is simulated using an incompressible solver coupled with isothermal homogeneous two-phase mixture cavitation model and Implicit Large Eddy Simulation (ILES) turbulence modelling. Owing to high speed visualization and numerical simulations, we identified two shedding mechanisms of transient cavities: (i) A primary shedding, characterized by a periodic generation of large cloud cavities and (ii) a secondary shedding of small-scale horse-shoe vortices, which are revealed for the first time. These small-scale structures, which are believed to play a major role in the erosion process, result from a complex interaction between the sheet cavity, the cloud cavity and re-entrant jets of different types. Furthermore, the detailed comparison between HSV and simulation confirms that the current numerical approach is capable of capturing the two types of shedding mechanisms very well. [ABSTRACT FROM AUTHOR]

We present a retrospective analysis of clinical symptoms and echocardiographic features in 14 patients having cardiac hydatic cysts and screened during the 18 last years, with surgical correlations in 13. The heart was the sole location of the cyst in six patients. The revealing symptoms were precordial pain (six patients), dyspnea (two patients). A systolic murmur of false pulmonic stenosis was present in three patients. In 13 patients, two-dimensional echocardiographic images of hydatic cysts were those of masses of liquid content with a well-contrasted capsule, which was single in eight patients and multiple in five, one of which had a honeycomb appearance. The mass was solid and calcified in one patient. The outlines of the cysts were particularly sharp on transesophageal echocardiograms (six patients). The cyst size ranged from 1.8 to 11 cm in diameter. Cysts were located in the intramyocardium in 10 patients (left ventricle in four patients, interventricular septum in four patients, right ventricle in two patients), the pericardium in three and the mediatinum in one. There were a Doppler pulmonary valve gradient in three patients. Computed tomography (eight patients) and coronary arteriography (seven patients) have no additional diagnosis value than echocardiography. Nuclear magnetic resonance imaging (three patients) was helpful in determining extracardiac extension of the cysts. Transthoracic and transesophageal two-dimensional echocardiography have a central role in diagnosing cardiac hydatic cysts. [Copyright &y& Elsevier]

Cavitating tip-leakage vortices appear in several hydrodynamic flows such as marine propellers or Kaplan turbines. Cavitating computations are a challenging topic since several keys issues are an ongoing work such as the definition of a universal mass source term. The present study focuses on the computations of the tip-leakage vortex including the gap between the blade tip and the side wall. Two computations are performed, one without cavitation and a second one with cavitation. In both cases, the results are compared with experimental data. The cavitation influence is investigated by comparing the cavitating and the non-cavitating cases. A particular attention is focused on the vortex core trajectory, the vorticity field and the vortex core identification. It is shown that, compared to the non-cavitating case, cavitation leads to a vortex trajectory closer to the suction side and the side wall, which can be of importance regarding the cavitation erosion. Furthermore, cavitation modified the vorticity field in the vortex core region. The main feature is a misalignment between the high vorticity region and the cavitating region, which opens a discussion regarding the definition of the vortex core. [ABSTRACT FROM AUTHOR]

Large eddy simulations of tip vortex cavitation (TVC) around an elliptical hydrofoil is performed to study its scale effect. A satisfying agreement is obtained between the numerical and experimental data. It indicates that the scale effect of TVC is remarkable. With the increase of scale ratio or incoming velocity, the intensity of TVC significantly increases. Based on our results, two mechanisms for the scale effect of TVC are proposed, i.e., the roll-up of boundary layer and the interaction between tip vortex (TV), secondary vortex and trailing vortex. As incoming velocity increases, the fusion of TV and secondary vortex enhances and the boundary layer thickness decreases, which lead to larger circulation and smaller vortex core radius, tending to intensify TV. As scale ratio increases, the fusion of TV and secondary vortex enhances and the boundary layer thickness increases slightly, which lead to much higher circulation and slight increase of vortex core radius, promoting the occurrence of TVC in general. In addition, with equal cavitation number and Reynolds number, TVC in the large scale is stronger than that in the small scale, indicating that it seems not so reasonable to equate the velocity-induced scale effect with the scale-ratio-induced one. • The scale effect of tip vortex cavitation induced by incoming velocities and scale ratios is numerically studied. • The scale ratio and incoming velocity modify the dimensionless vortex core radius and circulation. • Two mechanisms for the scale effect of tip vortex cavitation are proposed. [ABSTRACT FROM AUTHOR]

The healing process of intracranial aneurysms (IAs) treated with flow diverter stents (FDSs) depends on the IA flow modifications and on the epithelization process over the neck. In sidewall IA models with straight parent artery, two main hemodynamic regimes with different flow patterns and IA flow magnitude were broadly observed for unstented and high porosity stented IA on one side, and low porosity stented IA on the other side. The hemodynamic transition between these two regimes is potentially involved in thrombosis formation. In the present study, CFD simulations and multi-time lag (MTL) particle imaging velocimetry (PIV) measurements were combined to investigate the physical nature of this transition. Measurable velocity fields and non-measurable shear stress and pressure fields were assessed experimentally and numerically in the aneurysm volume in the presence of stents with various porosities. The two main regimes observed in both PIV and CFD showed typical flow features of shear and pressure driven regimes. In particular, the waveform of the averaged IA velocities was matching both the shear stress waveform at IA neck or the pressure gradient waveform in parent artery. Moreover, the transition between the two regimes was controlled by stent porosity: a decrease of stent porosity leads to an increase (decrease) of pressure differential (shear stress) through IA neck. Finally, a good PIV-CFD agreement was found except in transitional regimes and low motion eddies due to small mismatch of PIV-CFD running conditions. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Excess of total homocysteine (tHcy) and decrease of thiolactonase activities (HTase) have been proposed as risk factors for coronary artery diseases (CAD). Objectives: We evaluated the relationship of tHcy and HTase with paraoxonase 1 (PON1) gene polymorphism according to CAD severity. Design and methods: 118 healthy volunteers and 91 CAD patients were compared. Results: Serum levels of tHcy and oxidized LDL (ox-LDL) increased significantly by 26% and 48% in CAD patients and were associated with significantly lower levels of HDL cholesterol (p = 0.02) and 42% of decrease in HTase activities (p <0.05). In these patients the HTase activity was negatively associated with tHcy and Hs CRP levels (r =−0.622, p =0.00 and r =−0.355, p =0.007 respectively) but positively associated with apoB and triglyceride levels (r =0.35, p =0.042 and r =0.308, p=0.003 respectively). HTase activity decreased inversely to the number of affected vessels and according to PON1 polymorphism. PON1 Q192R RR and PON1 L55M MM genotypes were associated with higher HTase activities. Only PON1 L55M (MM) genotype frequency was significantly higher in CAD patients than in controls (P <0.05), while its frequency was similar between the two subgroups according to CAD severity. In a multivariate analysis, tHcy levels were the only independent factor affecting the severity of cardiovascular disease (p = 0.029). Conclusions: High tHcy levels are associated with the severity of cardiovascular disease and may be partly explained by the diminished HTase activities in these patients. [Copyright &y& Elsevier]

Abstract: Background: Aspirin (ASA) failure to inhibit in vitro platelet function had been termed ASA resistance. The prevalence of this phenomenon as measured with different platelet function tests varies widely among studies. Objectives: In this study, we propose to determine the prevalence of ASA non-responsiveness in stable coronary artery patients using three different tests. Patients and methods: One hundred ninety-one patients with a stable coronary artery disease and receiving secondary ASA prophylaxis (250 mg/day) were tested. For each patient the ASA-induced platelet inhibition was determined using three different tests: Ivy Bleeding time (BT), collagen/epinephrine closure time (CEPI-CT; PFA-100™, Dade-Behring) and urinary 11-dehydrothromboxane B2 (uTxB2) excretion level. The agreement between these tests was evaluated by kappa statistics test. Results: The prevalence of biological ASA resistance was 15.7% (n =30), 20.4% (n =39) and 24.6% (n =47) by BT, PFA-100™ and UTxB2, respectively. Only fourteen patients (7.3%) were non-responders for two tests: 6 (3.1%) BT/ PFA-100™; 1 (0.5%) BT/UTxB2; 7 (3.7%) PFA-100™/UTxB2). A poor agreement was found between these three methods and only 3 patients were resistant with all the tests (1.6%). Conclusion: The lack of agreement supposed that different types of aspirin resistance exist. Thus, combination of two tests or more could be a primary solution for a better identification of ASA resistant patients. This hypothesis must be confirmed by a large-scale randomized study with clinically well-defined endpoints. [Copyright &y& Elsevier]

Several matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) have been implicated in the development and outcome of coronary artery disease (CAD). We investigated whether MMP-12 and TIMP-1 levels were associated with risk, severity, and outcome of CAD. Plasma MMP-12 and TIMP-1 levels are measured in 50 and 44 patients with CAD, respectively, by enzyme-linked immunosorbent assay. Of all patients, 16 were taking statins. Patients who were not on statins were classified into 3 groups according to number of >50% stenotic vessels. Compared with 29 volunteers without CAD, patients without statins (n = 34) had higher MMP-12 concentrations (1.71 vs 1.08 ng/ml, p = 0.021). MMP-12 levels were significantly lower in patients with than in those without statin treatment (0.99 vs 1.71 ng/ml, p = 0.008). There was no association between MMP-12 levels and number of >50% stenotic vessels. MMP-12 concentrations were not associated with outcome of CAD. However, plasma TIMP-1 levels were associated with restenosis independently of number of stenotic vessels and age (p = 0.035) but not with risk or severity of CAD. In conclusion, plasma MMP-12 concentration was associated with the presence of CAD. Statin therapy decreases plasma MMP-12 levels in patients with CAD. Increased TIMP-1 levels may prevent restenosis after angioplasty. [Copyright &y& Elsevier]

• The cavitating flow around a tip vortex is simulated with LES. • The reason for the discrepancy between the predicted and observed TVC is discussed. • An Euler-Lagrangian cavitation model is proposed to improve the accuracy of TVC. Numerical simulation of tip vortex cavitation (TVC) remains a challenging task in a variety of applications, such as axial turbines and pumps as well as marine propellers. Although it is well known that TVC is highly sensitive to gas content, be it dissolved or not, numerical models do not consider this aspect so far. As a result, numerical simulations usually underestimate the development or the intensity of TVC. In the present paper, we propose an new Euler-Lagrangian cavitation model based on Rayleigh-Plesset (R-P) equation, taking into account the non-condensable gas. In this model, the Euler method is used to solve the global flow field and the Lagrangian method is used to track the migration of non-condensable gas bubbles into the vortex core. Based on the simplified R-P equation, the connection between local gas concentration and its effect on cavitation is modeled and the mass source terms in the original Schnerr-Sauer (S-S) cavitation model are modified. We applied the new cavitation model to a simplified case study, made of an elliptical NACA-16020 hydrofoil and compared the results with experimental observation. We obtained a significant improvement of the TVC prediction. Our work illustrates the major role of the gas content in sustaining cavitation downstream of the hydrofoil through an efficient attraction of nuclei, fueled by the low pressure induced by the vortex flow. [ABSTRACT FROM AUTHOR]

In the present paper, Large Eddy Simulations combined with the Zwart-Gerber-Belamri cavitation model are conducted to study the flow characteristics in a tip-leakage flow. A reasonable agreement is obtained between the numerical and experimental data. With the numerical results, the influence of cavitation in a tip-leakage flow on the gross features of tip-leakage vortex (TLV) and tip-separation vortex (TSV), the behavior of tip-leakage jet, the time-averaged vorticity field and turbulent kinetic energy (TKE) distributions are discussed in detailed. Our results demonstrate that more complex induced vortexes are observed in the non-cavitation case when compared with the cavitation case. Moreover, the results indicate that cavitation promotes the fusion of TLV and TSV. The narrower passageway in the gap when cavitation occurs increases the strength of tip-leakage jet, which leaves significant influence on local vorticity and turbulent kinetic energy. Cavitation trends to suppress the production of spanwise and pitchwise vorticity and promotes the TKE production. Further analysis shows that the spanwise and pitchwise flow patterns are mainly responsible for the TKE production. The fluctuations of v and w velocity and the corresponding spanwise and pitchwise velocity gradient components need to be controlled if a decrease in the viscous losses is desired. • The tip-leakage cavitating flow is simulated by LES. • Evolution and dynamic behavior of TLV and TSV are identified and discussed. • The mechanism of cavitation on TKE is clarified. [ABSTRACT FROM AUTHOR]