Flow-induced vibration in the compressible cavity flow

The cavity plays an important role in the fuel-air mixing and combustion stability inside the hypersonic scramjet. However, the high levels of time-dependent loading resulting from the supersonic cavity flow can cause intense structural vibration even damage. Experiments and numerical simulations were performed to understand the complex fluid-structure interaction in this paper. A cantilever plate with a cavity was installed as a splitter plate in the supersonic mixing layer wind tunnel. The response displacements of this cantilever plate were measured by a non-intrusive laser vibrometer. Large eddy simulation (LES) was applied to calculate the aerodynamic loading. Results show that the St number of time-dependent surface-averaged pressure difference agrees well with semi-empirical relation of Heller used to predict the resonance mode. The cantilever plate exhibits a directly dependent response to self-oscillation of supersonic cavity flow. Measurement results of displacement indicate that the vibration shape of this plate is dominantly two-dimensional

Conducción entre la vena pulmonar superior izquierda, la aurícula izquierda y la fibrilación auricular bajo el estímulo del tronco cervico-vagal

Objective: The effect of cervical vagal trunk stimulation on conduction between left superior pulmonary vein and left atria and atria fibrillation have not been systematically studied. We attempted to investigate the electrical conduction between LA and LSPV in dogs with cervical vagal trunk stimulation and evaluate the possible underline substrates for local reentry and initiation and maintenance of AF. Methods:12 mongrel dogs (18-25 kg) underwent cervical vagal trunk stimulation at high-frequency (60 ms, 1-4V) to produce sinus arrest lasting >2 seconds,complete atrioventricularAV blocking or the sinus rate decreasing more than 50%. Left lateral thoracotomy was performed and the heart was exposed in a pericardial cradle. The HRA, LAA, PV-LAJ, LSPVm and LSPVd was locally stimulated (100 ms, 2-8V). ERP of HRA, LAA, PV-LAJ and within LSPV, ERP heterogeneity within LSPV and conduction between left superior pulmonary vein and left atria and atrial fibrillation inducing rate with vagal response was analyzed. Results: 1. During cervical vagal stimulation, the heart rate was reduced significantly from baseline 156±34 bpm to 75±34 bpm (p<0.05, n=12), ERP of HRA, LAA, PV-LAJ, LSPVm and LSPVd sites was shortened locally in all animals, ERP heterogeneity (COV-ERP ) was increased from baseline 3±3% to 30±13% (on average, p<0.05; n=12) and inducibility of AF was increased from baseline 49.9% to 70.9% with S1S1stimulation (100 ms, 2-8V) and from baseline 3.7% to 43.5% with S1S2 (5 ms decremented stepwise S1S2 300/200 ms, 2-8V, n=12; 2. LA and PV potentials at LA, PV-LAJ, LSPVm and LSPVd was overlapped during sinus rate and separated remarkably by stimulating at distal part of LSPV (n=9); 3. Unidirectional and bi-directional conduction(n=9), bi-directional decremented conduction (n=6), delayed conduction from LSPVp to LSPVd (n=12) and slow conduction from stimulating signal to local tissue potential (n=9) before onset of AF were recorded by pacing from both LSPV and LA. Conclusion: Our study strongly suggested that fast ectopic beating, abnormal vagal nerve activation as well as remodeling conduction between left superior pulmonary vein and left atria might are the common underline substrates for local reentry and AF initiation and maintenance. Objetivo: El efecto del estímulo del tronco nervioso cervico-vagal sobre la conducción entre la vena pulmonar superior izquierda (LSPV, siglas en inglés), la aurícula izquierda (LA, siglas en inglés) y la fibrilación auricular (AF, siglas en inglés), no se ha estudiado sistemáticamente. Se intentó investigar la conducción eléctrica entre la LA y la LSPV, con el estímulo del tronco nervioso cervico-vagal y evaluar los posibles substratos subyacentes para la reentrada local, la iniciación y el mantenimiento de la AF. Métodos: En 12 perros sin raza (18-25 kg), se estimuló el tronco cervico-vagal con alta frecuencia (60ms, 1-4V) para producir detenimiento sinusal con duración >2 s, completo bloqueo atrio-ventricular (AV) o un descenso superior a 50% en el ritmo sinusal. Se hizo una toracotomía lateral izquierda y se expuso el corazón en la malla pericárdica. Los HRA, LAA, PV-LAJ, LSPVm y LSPVd se estimularon localmente (100 ms, 2-8V). El de HRA, LAA, PV-LAJ y dentro de la LSPV, la heterogeneidad dentro de la LSPV y la conducción entre la vena pulmonar superior izquierda, la aurícula izquierda y la fibrilación auricular que induce un ritmo con respuesta vagal, también se analizaron. Resultados: 1. Durante el estímulo vago-cervical, el ritmo cardíaco se redujo significativamente desde la línea basal 156±34 bpm a 75±34bpm (p<0.05, n=12); los sitios ERP de HRA, LAA, PV-LAJ, LSPVm y LSPVd se acortaron localmente en todos los animales. La heterogeneidad (COV-ERP) aumentó desde la línea basal 3±3% A 30±13% (en promedio, p<0.05, n012) y la capacidad de ser inducida la AF aumentó desde la línea base 49.8% a 70.9% con un estímulo S1S1 (100 ms, 2-8V) y desde la línea basal 3.7% a 43.5% con S1S2 5ms reducido paso a paso S1S2 300/200ms, 2-8V, n=12. 2. Los potenciales de la LA y la PV en LA, PV-LAJ, LSPVm y LSPVd, se sobrepusieron durante el ritmo sinusal y se separaron notablemente por el estímulo en la porción distal de LSPV (n=9). 3. La conducción uni-direccional y bi-direccional (=9), la conducción disminuida (n=6), la conducción retardada de LSPVp a LSPVD (n=12) y la conducción lenta desde la señal estímulo hasta el potencial tejido local (n=9), antes del comienzo de la AF se registraron paso a paso tanto desde la LSPV como desde la LA. Conclusión: Este estudio sugirió con mucho vigor que los latidos ectópicos, la activación anormal del vago, así como la conducción remodelante entre la vena pulmonar superior izquierda y la aurícula izquierda son substratos comunes subyacentes para el reingreso local, la iniciación y el mantenimiento de la fibrilación auricular

Regulation of CCL5 Expression in Smooth Muscle Cells Following Arterial Injury

Chemokines play a crucial role in inflammation and in the pathophysiology of atherosclerosis by recruiting inflammatory immune cells to the endothelium. Chemokine CCL5 has been shown to be involved in atherosclerosis progression. However, little is known about how CCL5 is regulated in vascular smooth muscle cells. In this study we report that CCL5 mRNA expression was induced and peaked in aorta at day 7 and then declined after balloon artery injury, whereas IP-10 and MCP-1 mRNA expression were induced and peaked at day 3 and then rapidly declined

Detection of Flare-induced Plasma Flows in the Corona of EV Lac with X-ray Spectroscopy

Stellar flares are characterized by sudden enhancement of electromagnetic radiation from the atmospheres of stars. Compared to their solar counterparts, our knowledge on the coronal plasma dynamics of stellar flares and their connection to coronal mass ejections (CMEs) remains very limited. With time-resolved high-resolution spectroscopic observations from the \textit{Chandra} X-ray observatory, we detected noticeable coronal plasma flows during several stellar flares on a nearby dMe star EV Lac. In the observed spectra of O~{\sc{viii}} (3 MK), Fe~{\sc{xvii}} (6 MK), Mg~{\sc{xii}} (10 MK), and Si~{\sc{xiv}} (16 MK) lines, these flare-induced upflows/downflows appear as significant Doppler shifts of several tens to \speed{130}, and the upflow velocity generally increases with temperature. Variable line ratios of the Si~{\sc{xiii}} triplet reveal that these plasma flows in most flares are accompanied by an increase of the coronal plasma density and temperature. We interpret these results as X-ray evidences for chromospheric evaporation on EV Lac. In two successive flares, the plasma flow pattern and a sharp increase of the measured coronal density are highly suggestive of explosive evaporation. The transition from redshifts to blueshifts in such an explosive evaporation occurs at a temperature of at least 10 MK, much higher than that observed in solar flares ($\sim$1 MK). However, in one flare the cool and warm upflows appear to be accompanied by a decreasing plasma density, which might be explained by a stellar filament/prominence eruption coupled to this flare. These results provide important clues to understand the coronal plasma dynamics during flares on M dwarfs.Comment: accepted by Ap

Three-dimensional topological structures and formation processes of dislocations in Au nanowire under tension loading

Dislocation is an important microstructural configuration in most crystalline materials, but it is still difficult for experiments to detect its local atomic structures and formation processes. Molecular dynamics simulation provides a powerful tool to investigate the dislocation by means of some geometrical structural analysis methods, but most of these methods cannot accurately distinguish the nuances of local configurations. Herein, we propose a new microstructural analysis method of cluster-type-index method (CTIM). The three-dimensional (3D) topological structures and formation processes of dislocations during tensioning Au nanowire are illuminated by means of CTIM. It is found that the favourite local atomic structures in dislocations are the defective FCC clusters represented by the CTIM indexes (13, 3/1421 2/1431 2/1441 4/1541 2/1661). The vector analysis method based on the accumulation of lattice distortions cannot identified the aggregation of disordered atoms in the initial nucleation of dislocation. In the formation processes of dislocation atoms, three trajectories of T1: FCC→(13, 3/1421 2/1431 2/1441 4/1541 2/1661), T2: FCC→(12, 2/1311 1/1411 9/1421) and T3: FCC→(11, 4/1311 7/1421) are favorite. The dislocation atoms following the T1 trajectory are mainly located at the core of dislocations, while that following the T2 and T3 trajectories is at the front of dislocations. CTIM would provide an effective tool to investigate the defective structures and their interactions in nanocrystalline structures

CO2 dissociation activated through electron attachment on reduced rutile TiO2(110)-1x1 surface

Converting CO$_2$ to useful compounds through the solar photocatalytic reduction has been one of the most promising strategies for artificial carbon recycling. The highly relevant photocatalytic substrate for CO$_2$ conversion has been the popular TiO$_2$ surfaces. However, the lack of accurate fundamental parameters that determine the CO$_2$ reduction on TiO$_2$ has limited our ability to control these complicated photocatalysis processes. We have systematically studied the reduction of CO2 at specific sites of the rutile TiO$_2$(110)-1x1 surface using scanning tunneling microscopy at 80 K. The dissociation of CO2 molecules is found to be activated by one electron attachment process and its energy threshold, corresponding to the CO$_2^{\dot-}$/CO$_2$ redox potential, is unambiguously determined to be 2.3 eV higher than the onset of the TiO$_2$ conduction band. The dissociation rate as a function of electron injection energy is also provided. Such information can be used as practical guidelines for the design of effective catalysts for CO$_2$ photoreduction

A First-principles Prediction of Two-Dimensional Superconductivity in Pristine B2C Single layer

Based on first-principles lattice dynamics and electron-phonon coupling calculations, B2C sheet is predicted to be a two-dimensional (2D) phonon-mediated superconductor with a relatively high transition temperature (Tc). The electron-phonon coupling parameter calculated is 0.92, and it is mainly contributed by low frequency out-of-plane phonon modes and electronic states with a {\pi} character. When the Coulomb pseudopotential is set to 0.10, the estimated temperature Tc is 19.2 K. To be best of our knowledge, B2C is the first pristine 2D superconductor with a Tc higher than the boiling point of liquid helium.Comment: accepted by Nanoscal

Mental health status and its associated factors among female nurses in the normalization of COVID-19 epidemic prevention and control in China

ObjectiveTo investigate mental health status and its associated factors among female nurses in the normalization of COVID-19 epidemic prevention and control in China.MethodsRandom cluster sampling was applied to recruit 740 female nurses in China. The respondents completed the survey with mobile devices. Demographic questionnaire, Generalized Anxiety Disorder-7, Patient Health Questionnaire-9, Insomnia Severity Index, and The Impact of Event Scale-Revised were used to assess demographic Information, anxiety, depression, insomnia and PTSD symptoms, respectively. The associated factors of mental health status were identified by binary logistic regression analysis.ResultsThe prevalence of anxiety and depression was 7.9 and 17.8%, respectively. Insomnia was an associated factor of anxiety (OR = 6.237, 95%CI = 6.055–23.761, P &lt; 0.001) and depression (OR = 9.651, 95%CI = 5.699–22.370, P &lt; 0.001), while PTSD was an associated factor of anxiety (OR = 11.995, 95%CI = 2.946–13.205, P &lt; 0.001) and depression (OR = 11.291, 95%CI = 6.056–15.380, P &lt; 0.001), Being married was a protective factor of depression (OR = 0.811, 95%CI = 1.309–6.039, P &lt; 0.01).ConclusionFemale nurses showed problems in mental health. Insomnia, PTSD and marital status were associated with mental health. The hospital management should pay more attention to the unmarried groups, and strive to improve the sleep quality of female nurses and reduce their stress caused by traumatic events