Labeling of Adipose‐Derived Stem Cells by Oleic‐Acid‐Modified Magnetic Nanoparticles

The in vivo tracking of adipose derived stem cells (ASCs) is of essential concern when they are used as seed cells in tissue engineering. This study explores the feasibility of using magnetic nanoparticles (MNs), a type of contrast agents in magnetic resonance imaging (MRI), to label ASCs such that the labeled ASCs could be tracked in vivo by MRI non‐invasively and repeatedly. To do this, MNs of <10 nm surface‐coated with oleic acid are synthesized via a high‐temperature solution‐phase reaction. Cytotoxicity of the as‐synthesized MNs at concentrations up to 0.1 mg mL^?1 on 10⁴ cells mL^?1 ASCs is evaluated by LDH release. Since only minor cytotoxicity is detected, the effects of the labeling technique on cellular behaviors and uptake by labeled cells are investigated. Cell proliferation and differentiation with and without MNs are compared. The results show that proliferation of ASCs (10⁴ cells mL^?1) labeled by MNs (0.05 mg mL^?1) is significantly enhanced and dependent on the labeling time. The MNs are located in the vesicles within cytoplasm of ASCs. The cellular uptake reaches as high as ～180 pg/cell. Nevertheless, the labeled ASCs still maintained adipogenic and osteogenic differentiation. Hence, the feasibility of labeling ASCs by oleic acid coated MNs is ascertained and it was better to label the cells during their quiescent stage. The labeled ASCs can also be in vivo detected by MRI in a subcutaneous model in vivo. Further MRI tracking of the labeled ASCs in long‐term follow‐up would thus follow this current study.     

Theoretical Study on Destruction Mechanism of 2,3,7,8-TCDD by O3 and NO3

采用B3LYP/6-31G(d)方法优化获得O₃及NO₃降解2,3,7,8-TCDD反应通道上驻点的几何构型, 得到微观反应进程,并采用MP2/6-311G(d,p)//B3LYP/6-31G(d)方法计算得到相关反应的活化能. 研究表明,O₃和NO₃采用不同的方式对2,3,7,8-TCDD进行降解. O₃通过臭氧加成及碳碳双键断裂使2,3,7,8-TCDD降解,而NO₃通过氯取代反应使得2,3,7,8-TCDD上2,3,7,8取代位置上的氯原子被取代为氧原子,从而达到有效降解的目的. O₃降解2,3,7,8-TCDD的反应能垒显著小于NO₃降解2,3,7,8-TCDD的反应能垒,表明O₃降解2,3,7,8-TCDD的能力显著高于NO₃.     

A robust finite difference scheme for pricing American put options with Singularity-Separating method

In this paper we present a stable numerical method for the linear complementary problem arising from American put option pricing. The numerical method is based on a hybrid finite difference spatial discretization on a piecewise uniform mesh and an implicit time stepping technique. The scheme is stable for arbitrary volatility and arbitrary interest rate. We apply some tricks to derive the error estimates for the direct application of finite difference method to the linear complementary problem. We use the Singularity-Separating method to remove the singularity of the non-smooth payoff function. It is proved that the scheme is second-order convergent with respect to the spatial variable. Numerical results support the theoretical results.     

High‐Fidelity End‐Functionalization of Poly(ethylene glycol) Using Stable and Potent Carbamate Linkages

Commercial PEG‐amine is of unreliable quality, and conventional PEG functionalization relies on esterification and etherification steps, suffering from incomplete conversion, harsh reaction conditions, and functional‐group incompatibility. To solve these challenges, we propose an efficient strategy for PEG functionalization with carbamate linkages. By fine‐tuning terminal amine basicity, stable and high‐fidelity PEG‐amine with carbamate linkage was obtained, as seen from the clean MALDI‐TOF MS pattern. The carbamate strategy was further applied to the synthesis of high‐fidelity multi‐functionalized PEG with varying reactive groups. Compared to with an ester linkage, amphiphilic PEG‐PS block copolymers bearing carbamate junction linkage exhibits preferential self‐assembly tendency into vesicles. Moreover, nanoparticles of the latter demonstrate higher drug loading efficiency, encapsulation stability against enzymatic hydrolysis, and improved in vivo retention at the tumor region.     

A Compact Difference Scheme on Graded Meshes for the Nonlinear Fractional Integro-differential Equation with Non-smooth Solutions

Acta Mathematicae Applicatae Sinica, English Series - In this paper, a compact finite difference scheme for the nonlinear fractional integro-differential equation with weak singularity at the...     

基于B/S技术的校园网络视频系统设计

随着高校教育事业的飞速发展,如何利用现有的卫星电视资源、FTP云存储资源、高速网络带宽资源来丰富师生们的课余生活成了加强高校自身建设、提高竞争力的重要课题。文章结合我校现有网络环境和信息资源,提出了基于B/S技术的校园网络视频系统设计方案,并利用中心服务器平台对音频资源进行编码、压缩处理。测试证明,该设计有效地解决了设备间跨平台交互的问题,实现了卫星电视转播、高清视频现场直播和FTP资源点播三大功能,对提高校园宽带利用率及构建数字化校园具有重要的意义。     

Rotating Gliding Arc Assisted Water Splitting in Atmospheric Nitrogen

In this study, hydrogen production from water splitting in N₂ using an atmospheric pressure rotating gliding arc plasma was investigated. The effect of input H₂O concentration and total flow rate on the performance of the plasma water splitting process (e.g., H₂ and O₂ yield, H₂ production rate, and energy yield of H₂) was investigated. N₂ showed a pronouncedly facilitating effect on the H₂O splitting and H₂ production process due to the reactions of the excited N₂ species [e.g., electronically excited metastable N₂(A)] with the H₂O molecules. The maximum H₂ production rate reached up to 41.3 μmols^?1, which is much higher than that of other typical non-thermal plasmas (e.g., ~0.2 μmols^?1 for a dielectric barrier discharge). Optical emission diagnostics has shown that in addition to the NO, N₂, and N₂ ⁺ that were observed in the pure N₂ spectra, strong OH and NH emission lines also appeared in the H₂O/N₂ spectra. OH radical is considered as a key intermediate species that could contribute to the formation of H₂, O₂, and H₂O₂. The increase of the H₂O concentration could lead to a continuous enhancement of the OH intensity. The rotational temperature of N₂ ⁺ dropped drastically from 2875 ± 125 to 1725 ± 25 K with the addition of 1 % (mol/mol) H₂O into the N₂ plasma.     

Co-Cr-O复合氧化物上丙烷低温完全氧化:结构效应、反应动力学和原位光谱研究（英文）

低碳烷烃是一类主要的挥发性有机污染物(VOCs),广泛生成于汽车尾气以及各种工业过程如煤处理、石油精炼以及天然气处理等.随着对环保要求的日益提高,对高效VOCs消除技术的需求愈加迫切.催化完全氧化(催化燃烧)技术具有起燃温度低、能耗低、净化效果好(无二次污染)等优点,因而极具应用潜力.对于低碳烷烃的催化燃烧,贵金属催化剂如Pt和Pd等具有很高的反应活性,但存在价格昂贵并易中毒等缺陷限制了其商业应用.另一方面,过渡金属氧化物由于其价格低廉、抗中毒性能优异及热稳定性好等特点受到广泛关注.Cu,Mn,Co,Fe等氧化物都具有良好的催化活性,其中Co氧化物由于其在丙烷催化燃烧中的高活性受到关注.而在Co氧化物中添加第二金属更能促进其反应性能.因此本文制备了一系列不同Co/Cr比例的复合氧化物用于丙烷催化燃烧,考察了催化剂结构和表面性质对其反应行为的影响,并通过反应动力学和原位光谱技术对反应机理进行了探索.实验结果表明,随着Co/Cr比例的变化,催化剂的晶相结构、颗粒尺寸、比表面积、表面酸性以及氧化还原性等特性均发生了明显变化,进而影响了其反应行为.当Co/Cr比例为1/2时(1Co2Cr),催化剂为尖晶石结构并具有最大的比表面积.该催化剂上具有最高的反应活性(250℃时反应速率为1.38μmol g^-1 s^-1),可归因于其最高的表面酸性和低温氧化还原性能的协同作用.反应动力学结果表明,1Co2Cr催化剂上丙烷和氧气的反应级数分别为0.58±0.03和0.34±0.05,低于2Co1Cr(分别为0.77±0.02和0.98±0.16)和1Co5Cr(分别为0.66±0.05和1.30±0.11),表明1122Cr催化剂相比后二者具有更高的丙烷和氧气表面覆盖度,得益于其更高的表面酸性和更好的低温氧化还原性能.此外,原位红外光谱表明,在反应过程中,1Co2Cr催化剂上的主要表面物种为多齿碳酸盐,该物种在低温时(<250℃)在表面积聚,但在高温时被分解.     

The formation mechanism and distribution of micro-aluminum oxide layer

It is of great significance to study the thermal oxidation process to understand the reaction mechanism of aluminum particle and further its applications in propellants. The physical and chemical properties of micron-aluminum particle were evaluated by scanning electron microscopy, laser particle size analyzer, X-ray diffractometer and inductively coupled plasma atomic emission spectrometer. The thermal oxidation characteristics of the sample were studied by thermal analyzer. The experimental results showed that the initial oxide thickness of the sample was about 3.96 nm, and the calculated values of the specific surface area and the active aluminum content obtained by the established mathematical model were in good agreement with the measured values. The thermal oxidation process of the sample was divided into three stages. When the temperature rose to 1100 °C, the thermal oxidation efficiency of the sample reached 98.55%. With the increase in treatment temperature, dramatic crystalline changes occurred on the surface of the sample: amorphous alumina—γ-Al₂O₃, α-Al₂O₃, and the oxide layer thickness increased from 3.96 to 5.72 nm and 31.56 nm up to 320.15 nm. When the temperature reached 700 °C, the outer surface of the oxide layer contained a small amount of α-Al₂O₃, while the interior consisted of a large amount of γ-Al₂O₃, indicating that the conversion of γ-Al₂O₃ to α-Al₂O₃ occurred from the inside out.     

One-pot,five-component 1,3-dipolar cycloaddition: A facile synthesis of spiropyrrolidine and spiropyrrolizidine derivatives

A one-pot, five-component strategy toward the synthesis of new indole substituted pyrrolidine and pyrrolizidine heterocycles through 1,3-dipolar cycloaddition reactions using ninhydrin, 1,2-phenylenediamine, amino acids, 3-cyanoacetyl indoles and aryl aldehydes is described. The features of this procedure were characterized by the mild reaction conditions, high yields, one-pot procedure, and operational simplicity.