Structured illumination microscopy for super-resolution and optical sectioning

Optical microscopy plays an essential role in biological studies due to its capability and compatibility of non-contact, minimally invasive observation and mea- surement of live specimens. However, the conventional optical microscopy only has a spatial resolution about 200 nm due to the Abbe diffraction limit, and also lacks the ability of three-dimensional imaging. Super-resolution far- field optical microscopy based on special illumination schemes has been dramatically developed over the last decade. Among them, only the structured illumination microscopy （SIM） is of wide-field geometry that enables it easily compatible with the conventional optical microscope. In this article, the principle of SIM was introduced in terms of point spread function （PSF） and optical transform function （OTF） of the optical system. The SIM for super-resolution （SIM-SR） proposed by Gustafsson et al. and the SIM for optical sectioning （SIM-OS） pro- posed by Neil et al. are the most popular ones in the research community of microscopy. They have the same optical configuration, but with different data post- processing algorithms. We mathematically described the basic theories for both of the SIMs, respectively, and pre- sented some numerical simulations to show the effects of super-resolution and optical sectioning. Various approaches to generation of structured illumination patterns were reviewed. As an example, a SIM system based on DMD- modulation and LED-illumination was demonstrated. A lateral resolution of 90 nm was achieved with gold nanoparticles. The optical sectioning capability of the microscope was demonstrated with Golgi-stained mouse brain neurons, and the sectioning strength of 930 nm was obtained.     

An equivalent 1D nanochannel model to describe ion transport in multilayered graphene membranes

Multilayered graphene-based membranes are promising for a variety of applications related to ion or molecule transport, such as energy storage and water treatment. However, the complex three-dimensional cascading nanoslit-like structure embedded in the membrane makes it difficult to interpret and rationalize experimental results, quantitatively compare with the traditional membrane systems, and quantitatively design new membrane structures. In this paper, systematic numerical simulations were performed to establish an equivalent onedimensional(1 D) nanochannel model to represent the structure of multilayered graphene membranes. We have established a quantitative relationship between effective diffusion length Leffand cross-section area Aeffof the1 D model and our recently developed two dimensional(2 D) representative microstructure for graphene membranes. We find that only in the cases of a relatively large lateral size L( ~100 nm) and a small slit size h( 2 nm), the effective diffusion length Leffand Aeffcan be calculated by an over-simplified but often used model. Otherwise, they show complex dependence on all three structural parameters of the 2 D structural model.Our equivalent 1 D nano-channel model can reproduce experimental results very well except for h 0.5 nm. The discrepancy could be attributed to the anomalous behaviour of molecules under nano-confinement that is not considered in our simulations. This model can also be extended to multilayered membranes assembled by other2 D materials.     

Effect of Nb and V on the continuous cooling transformation of undercooled austenite in Cr–Mo–V steel for brake discs

The increasing speed of trains necessitates the development of brake-disc materials that meet more stringent requirements. Therefore, Nb and V have been added to Cr–Mo–V steel to improve its thermal fatigue performance when used in brake discs. In this paper, the influences of Nb and V on the static continuous cooling transformation (CCT) behaviors of undercooled austenite were studied. The microstructures, hardness, and dislocation densities at different cooling rates and with the addition of different alloying elements were also investigated. The results show that the transformation products of ferrite, granular bainite, lower bainite, and martensite form under different cooling conditions. With increasing Nb and V contents, the CCT curves are shifted to the left, ferrite and bainite transformations are promoted, and the critical cooling rate of total martensite formation is increased. The added V mainly forms V-rich M₈C₇ precipitates and reduces the dissolved C content; therefore, the A_c1, A_c3, and M_s-point temperatures increase. Moreover, the stability of retained austenite is also reduced; its content therefore decreases. Compared with V, the effect of added Nb is weaker because of its smaller content. However, the addition of Nb improves the hardness at lower cooling rates because of the precipitation of fine NbC particles and refining of the microstructure.     

Reductive recovery of manganese from low-grade manganese dioxide ore using toxic nitrocellulose acid wastewater as reductant

The hydrometallurgical strategy of extracting Mn from low-grade Mn ores has attracted attention for the production of electrolytic manganese metal (EMM). In this work, the reductive dissolution of low-grade MnO₂ ores using toxic nitrocellulose acidic wastewater (NAW) as a reductant was investigated for the first time. Under the optimized conditions of an MnO₂ ore dosage of 100 g·L-1, an ore particle size of -200 mesh, concentrated H₂SO₄-to-NAW volume ratio of 0.12, reaction temperature of 90℃, stirring speed at 160 r·min-1, and a contact time of 120 min, the reductive leaching efficiency of Mn and the total organic carbon (TOC) removal efficiency of NAW reached 97.4% and 98.5%, respectively. The residual TOC of 31.6 mg·L-1 did not adversely affect the preparation of EMM. The current process offers a feasible route for the concurrent realization of the reductive leaching of Mn and the treatment of toxic wastewater via a simple one-step process.     

管理层能力对企业融资约束的影响研究 ——基于内部控制质量的中介效应

针对经济转型中企业普遍面临融资约束的发展障碍,基于2013—2019年中国A股上市公司的数据,实证检验管理层能力对企业融资约束的影响及作用机理。结果显示：管理层能力越强,越有助于缓解融资约束,二者的负相关关系在非国有上市公司中尤为明显;内部控制质量在管理层能力与企业融资约束的关系中具有部分中介作用,且中介效应在非国有上市公司中更加显著。研究丰富了有关管理层能力经济后果的文献,为破解融资约束难题开拓了新的思路。     

超声波测定固相沉积点研究

目前国内外广泛采用激光刚定固相沉积点,只适用于较轻透明的油,对于较黑的油因为光无法穿透而无法测试,为适用于高含蜡及沥青的原油固相沉积点测试!,建立了超声波测试固相沉积点的方法,用柴油为溶剂,对石蜡在柴油中的析蜡点进行了研究,在将石蜡加热溶解于柴油后,测定其在不同浓度下石蜡在柴油中的析蜡点。通过实验发现,石蜡析出的温度随着石蜡浓度的增加而增加,超声波在油样中的传播速度随着石蜡浓度的增加而增加,随着温度的降低而增加。实验还发现,在出现石蜡沉积的后期,由于石蜡沉积是一个放热过程,所以在这期l’q,温度下降很缓慢,有时甚至不下降。超声波的传播时间曲线也会在这个时候出现一个水平段。     

Anti-corrosion performance of waterborne Zn-rich coating with modified silicon-based vehicle and lamellar Zn (Al) pigments

In order to develop the eco-friendly Zn-rich coatings with higher corrosion resistance and lower pigment contents, several series of coatings were designed and manufactured employing lamellar Zn (Al) pigments mixed with silicone-acrylate emulsion modified inorganic silicate vehicle, and then were evaluated by conventional methods and the electrochemical method. The results indicated that the pigment contents reduced to approximate 25 mass% with lamellar Zn or (Zn and Al) pigments as substitute for spherical Zn pigments, and pigment mixtures were homogeneously dispersed due to silicone-acrylate emulsion moistening modification. Furthermore, the optimal coating had good coating properties (adhesion grade: one), acid resistance (lower mass losses) and anti-corrosive performance (improved corrosion potential and anodic passivation). The experimental results indicated that the modified lamellar Zn (Al) coating was suitable for large-scale spread and application on protecting steel structures in the hostile environment.     

Clonally related visual cortical neurons show similar stimulus feature selectivity

A fundamental feature of the mammalian neocortex is its columnar organization. In the visual cortex, functional columns consisting of neurons with similar orientation preferences have been characterized extensively, but how these columns are constructed during development remains unclear. The radial unit hypothesis posits that the ontogenetic columns formed by clonally related neurons migrating along the same radial glial fibre during corticogenesis provide the basis for functional columns in adult neocortex. However, a direct correspondence between the ontogenetic and functional columns has not been demonstrated. Here we show that, despite the lack of a discernible orientation map in mouse visual cortex, sister neurons in the same radial clone exhibit similar orientation preferences. Using a retroviral vector encoding green fluorescent protein to label radial clones of excitatory neurons, and in vivo two-photon calcium imaging to measure neuronal response properties, we found that sister neurons preferred similar orientations whereas nearby non-sister neurons showed no such relationship. Interestingly, disruption of gap junction coupling by viral expression of a dominant-negative mutant of Cx26 (also known as Gjb2) or by daily administration of a gap junction blocker, carbenoxolone, during the first postnatal week greatly diminished the functional similarity between sister neurons, suggesting that the maturation of ontogenetic into functional columns requires intercellular communication through gap junctions. Together with the recent finding of preferential excitatory connections among sister neurons, our results support the radial unit hypothesis and unify the ontogenetic and functional columns in the visual cortex.     

Optimal operational decisions when a manufacturer offers trade credit to his retailer

In this paper,we develop models to determine operational and financial decisions of a supply chain under the condition that the retailer faces a financial constraint and the manufacturer can offer trade credit to assist the retailer.We first study the case where the retailer is risk-neutral,and derive the optimal ordering and financial decisions.Then,the case where the retailer is risk-averse(downside risk) is studied and -the effects of the risk on the retailer and manufacturer’s operational and financial decisions are discussed.Finally,numerical examples are provided to conduct managerial analysis.     

沙漠深处未来城

正为什么一个盛产石油的国家要在阿拉伯沙漠的腹地建立一座太阳能环保城市?答案是:为了改变世界。马斯达尔城给人的第一印象是仿佛海市蜃楼般不真实。从远处看,它就像是一栋多彩的建筑物孤独地矗立在天际线上。导致这种奇怪感觉的部分原因是马斯达尔城奇特的地理位置:毗邻阿布扎比机场,通往阿拉伯湾的高速公路从城中穿过,位于环境恶劣的沙漠深处。在这座城市和阿