关键词： Climate models   Reanalysis data   Climate variability   Multidecadal variability  

摘要： This paper addresses the dynamics of internal hemispheric-scale multidecadal climate variability by postulating an energy-balance (EBM) model comprising two deep-ocean oscillators in the Atlantic and Pacific basins, coupled through their surface mixed layers via atmospheric teleconnections. This system is linear and driven by the atmospheric noise. Two sets of the EBM model parameters are developed by fitting the EBM-based mixed-layer temperature covariance structure to best mimic basin-average North Atlantic/Pacific sea surface temperature (SST) covariability in either observations or control simulations of comprehensive climate models within the CMIP5 project. The differences between the dynamics underlying the observed and CMIP5-simulated multidecadal climate variability and predictability are encapsulated in the algebraic structure of the two EBM model versions so obtained: EBMCMIP5 and EBMOBS. The multidecadal variability in EBMCMIP5 is overall weaker and amounts to a smaller fraction of the total SST variability than in EBMOBS, pointing to a lower potential decadal predictability of virtual CMIP5 climates relative to that of the actual climate. The EBMCMIP5 decadal hemispheric teleconnections (and, by inference, those in CMIP5 models) are largely controlled by the variability of the Pacific, in which the ocean, due to its large thermal and dynamical memory, acts as a passive integrator of atmospheric noise. By contrast, EBMOBS features a stronger two-way coupling between the Atlantic and Pacific multidecadal oscillators, thereby suggesting the existence of a hemispheric-scale and, perhaps, global multidecadal mode associated with internal ocean dynamics. The inferred differences between the observed and CMIP5 simulated climate variability stem from a stronger communication between the deep ocean and surface processes implicit in the observational data.

关键词： Actin   Super-resolution microscopy  

摘要： Zhang et al. show that dynamin forms a helical structure with actin and, upon disruption, enhances branched actin polymerization, constituting a dynamic cycle to regulate actin cytoskeleton mechanical strength. The dynamin GTPase is known to bundle actin filaments, but the underlying molecular mechanism and physiological relevance remain unclear. Our genetic analyses revealed a function of dynamin in propelling invasive membrane protrusions during myoblast fusion in vivo. Using biochemistry, total internal reflection fluorescence microscopy, electron microscopy and cryo-electron tomography, we show that dynamin bundles actin while forming a helical structure. At its full capacity, each dynamin helix captures 12-16 actin filaments on the outer rim of the helix. GTP hydrolysis by dynamin triggers disassembly of fully assembled dynamin helices, releasing free dynamin dimers/tetramers and facilitating Arp2/3-mediated branched actin polymerization. The assembly/disassembly cycles of dynamin promote continuous actin bundling to generate mechanically stiff actin super-bundles. Super-resolution and immunogold platinum replica electron microscopy revealed dynamin along actin bundles at the fusogenic synapse. These findings implicate dynamin as a unique multifilament actin-bundling protein that regulates the dynamics and mechanical strength of the actin cytoskeletal network.

关键词： Acute myocardial infarction   Electrical storm   Late hospital presentation   Left ventricular thrombus   Systemic embolism  

摘要： The incidence of acute complications is high in patients presenting late with acute myocardial infarction (AMI). We describe the case of a patient who presented late with anterior AMI that was complicated by left ventricular (LV) thrombus and electrical storm (ES). Temporary right ventricular pacing suppressed ES under extracorporeal membrane oxygenation support but reduced cardiac function. Immediately after returning to sinus rhythm (i.e. increase in cardiac function), free-floating LV thrombus was detected by echocardiography, resulting in cerebral embolism. Rapid improvement in cardiac function related to mechanical hemodynamic support may become a trigger for embolization in patients with LV thrombus. © 2020 Japanese College of Cardiology

关键词： Sorption   Hydrocarbons   Aromatic compounds   Absorption   Polymers  

摘要： A simulation strategy encompassing different scales was applied to the systematic study of the effects of CO2 uptake on the properties of atactic polystyrene (aPS) melts. The analysis accounted for the influence of temperature between 450 and 550 K, polymer molecular weights (M-w) between 2100 and 31000 g/mol, and CO2 pressures up to 20 MPa on the volumetric, swelling, structural, and dynamic properties of the polymer as well as on the CO2 solubility and diffusivity by performing molecular dynamics (MD) simulations of the system in a fully atomistic representation. A hierarchical scheme was used for the generation of the higher M-w polymer systems, which consisted of equilibration at a coarse-grained level of representation through efficient connectivity-altering Monte Carlo simulations, and reverse-mapping back to the atomistic representation, obtaining the configurations used for subsequent MD simulations. Sorption isotherms and associated swelling effects were determined by using an iterative procedure that incorporated a series of MD simulations in the NPT ensemble and the Widom test particle insertion method, while CO2 diffusion coefficients were extracted from long MD runs in the NVE ensemble. Solubility and diffusivity compared favorably with experimental results and with predictions of the Sanchez-Lacombe equation of state, which was reparametrized to capture the M-w dependence of polymer properties with greater accuracy. Structural features of the polymer matrix were correctly reproduced by the simulations, and the effects of gas concentration and M-w on structure and local dynamics were thoroughly investigated. In the presence of CO2, a significant acceleration of the segmental dynamics of the polymer occurred, more pronouncedly at low M-w. The speed-up effect caused by the swelling agent was not limited to the chain ends but affected the whole chain in a similar fashion.

关键词： multilayer MoS2   mechanical properties   potential   molecular dynamics  

摘要： Experiments and simulations have shown that molybdenum disulfide (MoS2) has unique mechanical and electrical properties that make it promising for application as a flexible material in microscopic and nanoscopic electronic devices. In this paper, the molecular dynamics method is used to study the mechanical properties of multilayer MoS2 during compression and stretching under different intra-layer and inter-layer potentials to choose the most suitable ones. The results show that the increase in the inter-layer repulsive force during compression was all provided by sulfur atoms in the adjacent layer. The two intra-layer potentials represented two forms of tensile fracture: plastic fracture with structural holes or lattice distortions, and brittle fracture with instantaneous destruction. The chosen inter-layer potential had a significant influence on the structure of the multilayer MoS2 but the effect of inter-layer potential during stretching was not prominent. By comparing these results with reference values, the most suitable intra-layer and inter-layer potentials for the multilayer MoS2 were selected, and can serve as a reliable reference for subsequent simulations.

关键词： ICU机械通气   右美托咪定   镇静效果   血流动力学影响  

摘要： 探析右美托咪定临床应用时选择不同剂量的效果。方法:抽选我院行ICU机械通气患者70例,镇静药物选择右美托咪定,根据给药剂量差异分组,给予小剂量者35例纳入观察组,给予大剂量者35例纳入对照组,评估用药后的镇静效果,观察血流动力学的改变情况。结果:T1、T2与T3时间点,两组患者的SBP、DBP、HR、SaO2等指标差异明显(P<0.05)。结论:ICU机械通气患者选择右美托咪定镇静时,以小剂量给药方式即可达到良好的镇静效果,对血流动力学的影响最小。

关键词： Pulmonary mechanical prosthesis   Doppler-echocardiographic   Congenital heart diseases   Normal hemodynamic profile  

摘要： Objectives Very few reports have described the Doppler-derived echocardiographic parameters for mechanical pulmonary valve prosthesis (MPVP). This study aims to describe the normal Doppler hemodynamic profile of MPVP using Doppler echocardiography. Methods The current prospective, single center observational study enrolled 108 patients who underwent pulmonary valve replacement (PVR) surgery for the first time and had a normally functioning prosthesis post-operation. The hemodynamic performance of MPVPs, considering flow dependent and flow independent parameters, was evaluated at two follow-up points, at week one and week four post-operation. All assessments were conducted by an experienced echocardiographer. Results The mean age (+/- SD) of the participants was 26.4 (+/- 8.98). Tetralogy of Fallot (ToF) was the most common underlying disease leading to PVR, with a prevalence of 88%. At first week post-operation, measurement of indices reported the following values (+/- SD): peak pressure gradient (PPG): 18.51(+/- 7.64) mm Hg;mean pressure gradient (MPG): 10.88(+/- 5.62) mm Hg;peak velocity (PV): 1.97(+/- 0.43)m/s;doppler velocity index (DVI): 0.61(+/- 18);pulmonary velocity acceleration time (PVAT): 87.35(+/- 15.16) ms;effective orifice area (EOA): 2.98(+/- 1.02) cm(2);and effective orifice area to body surface area ratio (EOA/ BSA): 1.81(+/- 0.62) cm(2)/m(2). Comparing these measurements with those obtained from the second follow-up (at week four post-op) failed to hold significant difference in all values except for PVAT, which had increased from its primary value (p = 0.038). Also, right ventricular (RV) function showed significant improvement throughout the follow up period. Conclusion The findings of this study help strengthen the previously scarce data pool and better establish the normal values for Doppler hemodynamics in mechanical pulmonary prosthesis.

关键词： Solvation   Co(3+)ion   Ir3+ ion   Ammonia   Ab initio simulation   QMCF MD  

摘要： The solvation properties of Co3+ and Ir3+ in pure liquid ammonia have been investigated via ab initio quantum mechanical charge field molecular dynamics (QMCF MD) simulations. During the simulation time of 20 ps, octahedral [Co(NH3)(6)](3+) and [Ir(NH3)(6)](3+) complexes were formed in the first solvation shell without the occurance of ligand exchange. The respective average first shell ion distance of Co3+ and Ir3+ were found to be 2.07 and 2.18 angstrom. respectively. The solvation properties in the first shells of each system are found in excellent agreement with experimental data. A number of ligands were exchanged between the second solvation shell and the bulk phase in both systems along the simulation. The associated mean residence times of NH 3 ligands in the second shell are 3.06 and 2.47 ps for Co3+ and Ir3+, respectively. (C) 2020 Published by Elsevier B.V.

关键词： Void   Dislocation evolution   Mechanical properties   Real model   Nickel-base superalloys   Molecular dynamics simulation  

摘要： It is acknowledged that voids are unavoidable manufacture defects influencing the microstructure evolution and mechanical properties of nickel-based superalloys. The present work investigates the influences of void on the dislocation evolution and mechanical properties of nickel-based superalloys under different thermal conditions and strain rates. The simulation uses an embedded cubic model with voids in which the gamma' phase with L1(2) structure is surrounded by gamma phase with FCC structure to represent the real microstructure of single crystal superalloys. A model without voids is also studied. The existence of voids changes the misfit dislocation network by introducing cylindrical dislocation network around the voids which play a vital role on preventing the void coalescence at low strain. Dislocation extraction algorithm (DXA) analysis finds that new type of dislocation appears in the model with voids and the dislocation length is longer. The elastic modulus and yield strength are decreased by voids, as well as the ductility of the material. This paper demonstrates that the accumulation and reaction between dislocations are the most direct reason for declining the mechanical properties of nickel-based superalloys with void defects. (C) 2020 Published by Elsevier Ltd.