Experimental characterization of dynamic behaviour of gelatin-based material using DIC

In this paper, the dynamic response of gelatin-based soft material under impact loading is investigated. The dynamic tests are principally performed by the classical SHPB (Split Hopkinson Pressure Bars) technique. However, due to the very low mechanical impedance of the specimen compared with the Hopkinson bars, the feeble impact forces are measured by highly sensitive piezoelectric polyvinylidene fluoride (PVDF) pressure sensors instead of SHPB measurement system. The PVDF pressure sensors are placed on the interfaces between the specimen and the bars. During the impact test, the non-equilibrium stress state and inhomogeneous strain fields are developed in the specimen; a digital image correlation (DIC) technique is proposed to identify the inhomogeneous displacement fields using high speed photography. A non-parametric approach based on the DIC technique is developed to deduce the transient stress fields in the longitudinal and transverse directions from the displacement fields measured by DIC. The validation of the calculated stress fields is performed by comparing them with the stress measurements from the PVDF pressure sensor at the bottom end of the specimen. Furthermore, stress-strain response is carried out using this approach throughout the specimen. It is clearly shown that the average highest strain rate varies with position in the specimen. This lead to multiple stress-strain relations determined at different strain rates by only one impact test. The significant strain rate sensitivity is observed at the tested rate range from 81/s to 269/s. Under compression loading, the axial stress state is developed as a simple compression only in the central part of the specimen due to the friction at the interfaces between the specimen and the bars. According to the calculated results based on movement of “long waves”, the region of the simple compression stress state in the central part of the specimen is localized. It is observed that the axial stress is much more important than the transverse stress in the central part and this confirms the assumption of uni-axial compression stress state in the specimen.     

Electron localization function from density components

This work addresses the decomposition of the Electron Localization Function (ELF) into partial density contributions using an appealing split of kinetic energy densities. Regarding the degree of the electron localization, the relationship between ELF and its usual spin‐polarized formula is discussed. A new polarized ELF formula, built from any subsystems of the density, and a localization function, quantifying the measure of electron localization for only a subpart of the total system are introduced. The methodology appears tailored to describe the electron localization in bonding patterns of subsystems, such as the local nucleophilic character. Beyond these striking examples, this work opens up opportunities to describe any electronic properties that depend only on subparts of the density in atoms, molecules, or solids. © 2016 Wiley Periodicals, Inc.     

On the semicontinuity problem of fibers and global F-regularity

In this article, we discuss the semicontinuity problem of certain properties on fibers for a morphism of schemes. One aspect of this problem is local. Namely, we consider properties of schemes at the level of local rings, in which the main results are established by solving the lifting and localization problems for local rings. In particular, we obtain the localization theorems in the case of seminormal and F-rational rings, respectively. Another aspect of this problem is global, which is often related to the vanishing problem of certain higher direct image sheaves. As a test example, we consider the deformation of the global F-regularity.     

Pseudo‐spherical normal Darboux images of curves on a lightlike surface

We introduce the notions of the pseudospherical normal Darboux images for the curve on a lightlike surface in Minkowski 3‐space and study these Darboux images by using technics of the singularity theory. Furthermore, we give a relation between these Darboux images and Darboux frame from the viewpoint of Legendrian dualities.     

A unifying theory of exactness of linear penalty functions II: parametric penalty functions

In this article, we develop a general theory of exact parametric penalty functions for constrained optimization problems. The main advantage of the method of parametric penalty functions is the fact that a parametric penalty function can be both smooth and exact unlike the standard (i.e. non-parametric) exact penalty functions that are always nonsmooth. We obtain several necessary and/or sufficient conditions for the exactness of parametric penalty functions, and for the zero duality gap property to hold true for these functions. We also prove some convergence results for the method of parametric penalty functions, and derive necessary and sufficient conditions for a parametric penalty function to not have any stationary points outside the set of feasible points of the constrained optimization problem under consideration. In the second part of the paper, we apply the general theory of exact parametric penalty functions to a class of parametric penalty functions introduced by Huyer and Neumaier, and to smoothing approximations of nonsmooth exact penalty functions. The general approach adopted in this article allowed us to unify and significantly sharpen many existing results on parametric penalty functions.     

BODIPY-based Fluorescent Probe for Fast Detection of Hydrogen Sulfide and Lysosome-targeting Applications in Living Cells

Hydrogen sulfide (H₂S) is recognized as an endogenous gaseous signaling agent in many biological activities. Lysosomes are the main metabolic site and play a pivotal role in cells. Herein, we designed and synthesized two new fluorescent probes BDP-DNBS and BDP-DNP with a BODIPY core to distinguish H₂S. The sensing mechanism is based on the inhibition-recovery of the photo-induced electron transfer (PET) process. Through comparing the responsive behaviors of the two probes toward H₂S, BDP-DNBS showed a fast response time (60 s), low limit of detection (LOD, 51 nM), high sensitivity and selectivity. Moreover, the reaction mechanism was demonstrated by mass spectrometry and fluorescence off-on mechanism was proved by density functional theory (DFT). Significantly, confocal fluorescence imaging indicated that BDP-DNBS was successfully used to visualize H₂S in lysosomes in living HeLa cells.     

Dynamic Visualization of Free Radicals at Single Oxygen Bubbles using Chemiluminescence

The generation of free radicals is a key process in the formation and the collapse of the bubbles in water, however, the direct and dynamic observation of the radicals in this process at single bubbles has never been achieved. Here, the hydroxyl (OH^.) and oxygen (O₂^.−) radicals at single oxygen bubbles are continuously traced using chemiluminescence (CL), in which these radicals at the bubble react with the surrounding luminol in the solution emitting the light. Varied increase trends of luminescence are observed in the generation of a bubble, floating, short parking at the water/air interface and the final explosion, revealing the complexity in the distribution of radicals at the bubble unprecedentedly. Despite more radicals are observed at the bubble generated at a deep position under the water for the stabilization, almost the same amount of radicals are included in the bubbles that is independent on the water pressure during the production of the bubble. This rich information collected from the dynamic study of bubbles illustrates the complicated generation and distribution process of radicals at the bubbles, and will facilitate the understanding of the function about the bubbles.     

肿瘤乏氧靶向响应的罗丹明荧光探针及其成像介导手术治疗

基于罗丹明的良好荧光性能, 经化学偶联反应制备并表征了一个偶氮乏氧特异响应的“Off-On”型荧光成像探针(FY-4). 从分子层面证实了其荧光“Off-On”性能和响应机制; 在L02正常细胞及4T1, HeLa和A549肿瘤细胞层面考察了其对受试细胞株的毒性和不同乏氧时间的荧光成像性能; 再利用4T1肿瘤模型, 分别以肿瘤原位注射和尾静脉注射的方式考察了其荧光成像性能, 并探究了其荧光成像介导切除肿瘤性能, 最后还考察了FY-4的生物安全性. 结果表明, FY-4有高的肿瘤乏氧靶向特异“关-开”响应的荧光成像差异显影及荧光成像介导切除肿瘤的潜能, 结合其良好的光物理性能、 生物安全性和明晰的给药时间等特性, 有望为生物医学荧光成像介导肿瘤切除提供新的研究工具.     

即时定位与制图辅助的INS/GPS组合导航系统

即时定位与制图可以在线构建环境特征地图同时利用所建地图辅助定位,可以建立基于特征地图的的地形辅助全自主式导航系统。当GPS信号有效时,导航系统利用INS/GPS组合方式进行精确导航,同时在线建立特征地图,并不断更新修正地图。当GPS信号无效的时候,之前建立的地图用来修正惯导误差,约束惯导误差在一定的范围内,达到精确导航的目的。将及时定位与制图在线制图的功能引入组合导航系统使得该系统具有在线跟踪路标制图和限制系统误差扩延的能力,此性能通过计算机仿真得到验证。     

The low Reynolds number turbulent flow and mixing in a confined impinging jet reactor

Turbulent mixing takes an important role in chemical engineering, especially when the chemical reaction is fast compared to the mixing time. In this context a detailed knowledge of the flow field, the distribution of turbulent kinetic energy (TKE) and its dissipation rate is important, as these quantities are used for many mixing models. For this reason we conduct a direct numerical simulation (DNS) of a confined impinging jet reactor (CIJR) at Re = 500 and Sc = 1. The data is compared with particle image velocimetry (PIV) measurements and the basic flow features match between simulation and experiment. The DNS data is analysed and it is shown that the flow is dominated by a stable vortex in the main mixing duct. High intensities of turbulent kinetic energy and dissipation are found in the impingement zone which decrease rapidly towards the exit of the CIJR. In the whole CIJR the turbulence is not in equilibrium. The strong mixing in the impingement zone leads to a rapid development of a monomodal PDF. Due to the special properties of the flow field, a bimodal PDF is generated in cross-sections downstream the impingement zone, that slowly relaxes under relaminarising conditions. The time required for meso-mixing is dominating the overall mixing performance.