晶状体蛋白液-液相分离及逾渗相变的分子动力学模拟研究

探究不同势场下晶状体蛋白胶体粒子的微观分布与结构特性,研究单元系晶状体蛋白体系的液-液相分离及逾渗相变过程

BP神经网络和ARIMA模型对污水处理厂出水总氮浓度的模拟预测

污水处理厂出水总氮(TN)浓度是评价水处理效果的关键指标之一,利用BP神经网络建立模型对污水处理厂脱氮工艺进行模拟,引入自回归移动平均模型(ARIMA)对污水处理厂未来短期出水TN浓度进行预测..

BP神经网络和ARIMA模型对污水处理厂出水总氮浓度的模拟预测

污水处理厂出水总氮(TN)浓度是评价水处理效果的关键指标之一。建立BP神经网络模型对污水处理厂脱氮工艺进行模拟,引入自回归整合移动平均模型(ARIMA模型)对污水处理厂未来短期出水TN浓度进行预测。结果表明:BP神经网络模型在训练集和测试集模拟结果的平均相对误差分别为15. 9%和16. 5%,模型预测结果的平稳性较差; ARIMA模型对未来7 d出水TN浓度的时序预测平均误差为4. 41%,预测精度较高; 2个模型相结合有助于实现污水处理厂快捷和高效的在线检测。福建省自然科学基金项目(2018J01016);;\n厦门大学大学生创新创业训练计划项目(2018X0256

Selective dynamical imaging of interferometric data

Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve the innermost accretion flows of the largest supermassive black holes on the sky. The sparse nature of the EHT’s (u, v)-coverage presents a challenge when attempting to resolve highly time-variable sources. We demonstrate that the changing (u, v)-coverage of the EHT can contain regions of time over the course of a single observation that facilitate dynamical imaging. These optimal time regions typically have projected baseline distributions that are approximately angularly isotropic and radially homogeneous. We derive a metric of coverage quality based on baseline isotropy and density that is capable of ranking array configurations by their ability to produce accurate dynamical reconstructions. We compare this metric to existing metrics in the literature and investigate their utility by performing dynamical reconstructions on synthetic data from simulated EHT observations of sources with simple orbital variability. We then use these results to make recommendations for imaging the 2017 EHT Sgr A* data sethttp://iopscience.iop.org/2041-8205Physic

First Sagittarius A* Event Horizon Telescope Results. VIII. Physical Interpretation of the Polarized Ring

In a companion paper, we present the first spatially resolved polarized image of Sagittarius A* on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3 mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%–28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87*, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of Sgr A* (equivalent to ≈46° ± 12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow

First Sagittarius A* Event Horizon Telescope results. II. EHT and multiwavelength observations, data processing, and calibration

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5–11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ∼50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.http://iopscience.iop.org/2041-8205Physic

Budding and rupture of the vesicle with multiple components

囊泡膜脂区的出芽和囊泡粘附于基底时的破裂普遍存在于分子生物学实验研究及临床诊断中，具有重要的科学意义和广阔的应用前景。但基底粘附对囊泡上膜脂区出芽的影响以及膜脂区存在对于囊泡在基底上破裂机制的影响，由于问题复杂，大量关键问题尚未解决。目前对于膜脂区的研究多集中于囊泡存在水溶液的情况，但在真实生理过程中细胞往往与周围不同环境发生相互作用；对于囊泡在基底上破裂的研究只关注到了囊泡上存在一种磷脂分子的情况，但真实的生物膜上往往存在多种不同的磷脂分子。耗散粒子动力学的模拟方法可以用于囊泡粘附和膜脂区的研究，且可以考虑溶液对于磷脂膜的影响。本文通过耗散粒子动力学的方法，建立粗粒化分子模型，研究膜脂区在囊泡粘附于基底时的出芽现象以及带有膜脂区囊泡在基底上的破裂过程的力学机制。重点探讨当囊泡粘附于基底时膜脂区出芽特征以及含有膜脂区时囊泡在基底上的破裂机制。 本文主要研究内容及结论如下： 1. 建立适合于表示磷脂膜粘附于基底的耗散粒子动力学模型。研究了磷脂双层膜自由以及粘附于基底时的粒子数密度分布和应力分布特征，分析两种情况下粒子数密度和应力分布的联系与区别，证明磷脂膜粘附模型的合理性。 2. 膜脂区的出芽现象。研究了囊泡内部含水量和基底对磷脂分子等效吸引力差值对于膜脂区出芽的影响。计算表明，存在一个临界体表比。若囊泡的体表比大于此临界值，膜脂区不可能在囊泡上出芽，此时等效吸引力差值只可以改变膜脂区在囊泡上的位置；若囊泡的体表比小于此临界值，膜脂区可能出芽，此时等效吸引力差值是决定膜脂区是否出芽的主要因素。当等效吸引力差值在零附近时，膜脂区可以在囊泡与基底的粘附边界出芽，当等效吸引力差值在其他区域时，出芽现象被抑制。 3. 含有膜脂区囊泡在基底上的破裂机制。以统一的囊泡初始构型为基础，研究了等效吸引力差值和囊泡含水量对囊泡破裂过程的影响。结果表明，与只有一种磷脂分子囊泡的破裂机制不同，当粘附于基底的囊泡含有膜脂区时，囊泡以膜脂区脱离囊泡并在基底上铺展的方式破裂，并且等效吸引力差值和囊泡体表比是影响膜脂区是否铺展的主要原因