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The highly nonlinear evolution of the single-mode stratified compressible Rayleigh–Taylor instability (RTI) is investigated via direct numerical simulation over a range of Atwood numbers ($A_T=0.1$–$0.9$) and Mach numbers ($Ma=0.1$–$0.7$) for characterising the isothermal background stratification. After the potential stage, it is found that the bubble is accelerated to a velocity which is well above the saturation value predicted in the potential flow model. Unlike the bubble re-acceleration behaviour in quasi-incompressible RTI with uniform background density, the characteristics in the stratified compressible RTI are driven by not only vorticity accumulation inside the bubble but also flow compressibility resulting from the stratification. Specifically, in the case of strong stratification and high $A_T$, the flow compressibility dominates the bubble re-acceleration characters. To model the effect of flow compressibility, we propose a novel model to reliably describe the bubble re-acceleration behaviours in the stratified compressible RTI, via introducing the dilatation into the classical model that takes into account only vorticity accumulation.
Chronic inflammation exerts pleiotropic effects in the aetiology and progression of chronic obstructive pulmonary disease (COPD). Glucosamine is widely used in many countries and may have anti-inflammatory properties. We aimed to prospectively evaluate the association of regular glucosamine use with incident COPD risk and explore whether such association could be modified by smoking in the UK Biobank cohort, which recruited more than half a million participants aged 40–69 years from across the UK between 2006 and 2010. Cox proportional hazards models with adjustment for potential confounding factors were used to calculate hazard ratios (HR) as well as 95 % CI for the risk of incident COPD. During a median follow-up of 8·96 years (interquartile range 8·29–9·53 years), 9016 new-onset events of COPD were documented. We found that the regular use of glucosamine was associated with a significantly lower risk of incident COPD with multivariable adjusted HR of 0·80 (95 % CI, 0·75, 0·85; P < 0·001). When subgroup analyses were performed by smoking status, the adjusted HR for the association of regular glucosamine use with incident COPD were 0·84 (0·73, 0·96), 0·84 (0·77, 0·92) and 0·71 (0·62, 0·80) among never smokers, former smokers and current smokers, respectively. No significant interaction was observed between glucosamine use and smoking status (Pfor interaction = 0·078). Incident COPD could be reduced by 14 % to 84 % through a combination of regular glucosamine use and smoking cessation.
Intestinal stem cells, which are capable of both self-renewal and differentiation to mature cell types, are responsible for maintaining intestinal epithelial homeostasis. Recent evidence indicates that these processes are mediated, in part, through nutritional status in response to diet. Diverse dietary patterns including caloric restriction, fasting, high-fat diets, ketogenic diets and high-carbohydrate diets as well as other nutrients control intestinal stem cell self-renewal and differentiation through nutrient-sensing pathways such as mammalian target of rapamycin and AMP-activated kinase. Herein, we summarise the current understanding of how intestinal stem cells contribute to intestinal epithelial homeostasis and diseases. We also discuss the effects of diet and nutrient-sensing pathways on intestinal stem cell self-renewal and differentiation, as well as their potential application in the prevention and treatment of intestinal diseases.
The novel coronavirus disease 2019 (COVID-19) pandemic has spread to over 213 countries and territories. We sought to describe the clinical features of fatalities in patients with severe COVID-19.
We conducted an Internet-based retrospective cohort study through retrieving the clinical information of 100 COVID-19 deaths from nonduplicating incidental reports in Chinese provincial and other governmental websites between January 23 and March 10, 2020.
Approximately 6 of 10 COVID-19 deaths were males (64.0%). The average age was 70.7 ± 13.5 y, and 84% of patients were elderly (over age 60 y). The mean duration from admission to diagnosis was 2.2 ± 3.8 d (median: 1 d). The mean duration from diagnosis to death was 9.9 ± 7.0 d (median: 9 d). Approximately 3 of 4 cases (76.0%) were complicated by 1 or more chronic diseases, including hypertension (41.0%), diabetes (29.0%) and coronary heart disease (27.0%), respiratory disorders (23.0%), and cerebrovascular disease (12.0%). Fever (46.0%), cough (33.0%), and shortness of breath (9.0%) were the most common first symptoms. Multiple organ failure (67.9%), circulatory failure (20.2%), and respiratory failure (11.9%) are the top 3 direct causes of death.
COVID-19 deaths are mainly elderly and patients with chronic diseases especially cardiovascular disorders and diabetes. Multiple organ failure is the most common direct cause of death.
This study mainly focused on the key technologies, the photon dose calculation based on the Monte Carlo Finite-Size Pencil Beam (MCFSPB) model in the Accurate Radiotherapy System (ARTS). In the MCFSPB model, the acquisition of pencil beam kernel is one of the most important technologies. In this study, by analyzing the demerits of the clinical pencil beam dose calculation methods, a new pencil beam kernel model was developed based on the Monte Carlo (MC) simulation and the technology of medical accelerator energy spectrum reconstruction. which greatly improved the accuracy of calculated result. According to the axial symmetry principle, only part of simulation results was used for the data of pencil beam kernel, which greatly reduced the data quantity of the pencil beam and reduced calculated time. Based on the above studies, the MCFSPB method was designed and implemented by the Visual C++ development tool. With several tests including the comparisons among the American Association of Physicists in Medicine (AAPM) No. 55 Report sample and the ion chamber measurement of lung-simulating inhomogeneous phantom in clinical treatment plan, the results showed that the maximum error of most calculated point was less than 0.5% in the homogeneous phantom and less than 3% in the heterogeneous phantom. This method met the clinical criteria, and would be expected to be used as a fast and accurate dose engine for clinic TPS.
Electrochemically grown cadmium sulfide (CdS) nanorod arrays were studied with Raman spectroscopy. The resonant Raman spectroscopy unravels the enhanced electron-phonon interaction up to the fifth-order multiphonon process in the vertically aligned CdS nanorods after annealing. Resonant Raman scattering at room temperature reveals a surface phonon mode at 253 cm−1 in the annealed nanorod. This unprecedented observation is accounted for by the lateral confinement in the nanorod whose average aspect ratio is approximately 5. An intersubband transition near 3000 cm−1 is also observed. These results point to important optoelectronic applications of this material.
In this paper, we consider random dynamical systems (abbreviated as RDSs) generated by compositions of one-sided stationary random endomorphisms of class C^2 of a compact manifold. We will first introduce the notions of entropy and Lyapunov exponents for such RDSs, and then prove that the entropy formula of Pesin type holds if the sample measures of an invariant measure are absolutely continuous with respect to the Lebesgue measure on the manifold. Our result covers those obtained by Ledrappier and Young , and Liu  for i.i.d. random diffeomorphisms or (non-invertible) endomorphisms, and that obtained by  for two-sided stationary random endomorphisms. If the phase spaces are compact and finite-dimensional manifolds without boundary, this result may be considered as the almost-final form of Pesin entropy formula for RDSs with absolutely continuous invariant or sample measures.
Contributions of acoustical deformation scattering, ion impurity scattering and grain boundary potential scattering to the conductivity of TCO films have been calculated to discuss the predominant scattering mechanism, regardless of precise details of the preparation procedure. The results indicate that the effective mass of charge carriers has a strong dependence on carrier concentration. Based on the effective mass correction, as well as the carrier concentration-ionized impurity centers correction, scattering due to ion impurity has been developed to explain the upper limit of mobility or the lower limit of resistivity of TCO films. Two empirical expressions are introduced to depict the dependence of the upper limit of mobility and the lower limit of resistivity of TCO films on carrier concentration.
ZnO:Al (ZAO) films were deposited on quartz substrates by dc magnetron reactive sputtering from a Zn target mixed with Al. The effect of substrate temperature and Al doping content on the structural, electrical and optical properties of ZAO films were investigated. It was observed that the (002) peak position of all films shifts to lower angle comparable to that of bulk ZnO due to the residual stress change with deposition parameters. The dependences of electrical properties such as resistivity, carrier concentration and Hall mobility on substrate temperature and Al doping content were measured. The minimum resistivity is 4.23×10−4 ω.cm with the carrier concentration of 9.21×1020 cm−3 and Hall mobility of 16.0 cm2v−1s−1. The visible transmittance of above 80% was obtained. The optical band gap was observed to increase with increasing carrier concentration. The possible mechanisms are discussed.
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