Silicate glass coated microchannels through a phase conversion process for glass-like electrokinetic performance

The surface modified polydimethylsiloxane (PDMS) microchannels show a much more inferior performance to the durable and reproducible glass chip. In this paper, a facile approach to preparing a silicate glass modified PDMS microchannel for glass-like performance is presented. This glass-like performance is made possible by a phase conversion of a preceramic polymer--allylhydridopolycarbosilane (AHPCS). The, several hundred nanometer thick, polymer that coats the PDMS channel is hydrolyzed to form hydrophilic silicate glass via phase conversion under an aqueous alkali condition. It is characterized by XPS, FTIR-ATR, AFM, and contact angle measurements. The silicate glass coated PDMS channel from AHPCS has an excellent solvent resistance, delivers a high electroosmotic flow (EOF) that is stable in the long-term (4.9±0.1×10(-4) cm(2) V(-1) s(-1)) and a reliable capillary electrophoresis (CE), which are comparable to those of native glass channels. Moreover, the silicate glass PDMS channel allows easy regeneration of the electrokinetic behavior, just as in a glass channel, by a simple treatment with alkali solution. This coating approach can be applied to other polymer substrates such as polyimide (PI).     

Synthesis of monodisperse mesoporous TiO2 spheres with tunable sizes between 0.6 and 3.1 μm and effects of reaction temperature, Ti source purity, and type of alkylamine on size and monodispersity

We report a novel method for synthesizing monodisperse mesoporous TiO(2) spheres (sizes = 0.6-3.1 μm) by hydrolysis of titanium isopropoxide (TIP) in a mixture of C(8)-C(16)n-alkylamine, water, and ethanol. The size increases with decreasing temperature, TIP concentration, and water concentration, and upon purifying TIP. n-Dodecylamine gives the highest monodispersity.     

Disease-specific induced pluripotent stem cells: a platform for human disease modeling and drug discovery

The generation of disease-specific induced pluripotent stem cell (iPSC) lines from patients with incurable diseases is a promising approach for studying disease mechanisms and drug screening. Such innovation enables to obtain autologous cell sources in regenerative medicine. Herein, we report the generation and characterization of iPSCs from fibroblasts of patients with sporadic or familial diseases, including Parkinson's disease (PD), Alzheimer's disease (AD), juvenile-onset, type I diabetes mellitus (JDM), and Duchenne type muscular dystrophy (DMD), as well as from normal human fibroblasts (WT). As an example to modeling disease using disease-specific iPSCs, we also discuss the previously established childhood cerebral adrenoleukodystrophy (CCALD)- and adrenomyeloneuropathy (AMN)-iPSCs by our group. Through DNA fingerprinting analysis, the origins of generated disease-specific iPSC lines were identified. Each iPSC line exhibited an intense alkaline phosphatase activity, expression of pluripotent markers, and the potential to differentiate into all three embryonic germ layers: the ectoderm, endoderm, and mesoderm. Expression of endogenous pluripotent markers and downregulation of retrovirus-delivered transgenes [OCT4 (POU5F1), SOX2, KLF4, and c-MYC] were observed in the generated iPSCs. Collectively, our results demonstrated that disease-specific iPSC lines characteristically resembled hESC lines. Furthermore, we were able to differentiate PD-iPSCs, one of the disease-specific-iPSC lines we generated, into dopaminergic (DA) neurons, the cell type mostly affected by PD. These PD-specific DA neurons along with other examples of cell models derived from disease-specific iPSCs would provide a powerful platform for examining the pathophysiology of relevant diseases at the cellular and molecular levels and for developing new drugs and therapeutic regimens.     

Chemical Control of Yeast Cell Division by Cross‐Linked Shells of Catechol‐Grafted Polyelectrolyte Multilayers

The chemical control of cell division has attracted much attention in the areas of single cell‐based biology and high‐throughput screening platforms. A mussel‐inspired cytocompatible encapsulation method for achieving a “cell‐division control” with cross‐linked layer‐by‐layer (LbL) shells is developed. Catechol‐grafted polyethyleneimine and hyaluronic acid are chosen as polyelectrolytes for the LbL process, and the cross‐linking of polyelectrolytes is performed at pH 8.5. Cell division is controlled by the number of the LbL nanolayers and cross‐linking reaction. We also suggest a new measuring unit, , for quantifying “cell‐division timing” based on microbial growth kinetics.

     

Asymptotic Ruin Probability for Cox Risk Model with Variable Premium Rate and Constant Interest Force

This paper focuses on ruin probability for Cox model with variable premium rate and constant investment return when the claims have heavy tailed distribution. By considering the "skeleton process' of Cox risk model, a recursive equation for finite time ruin probabilities are derived in terms of "renewal techniques' and asymptotic estimation for finite time ruin probabilities and ultimate ruin probability are obtained by inductive method.     

随机环境中马氏链的平稳分布(英文)

本文引入了随机环境中马氏链平稳分布的概念. 在合适的条件下, 给出了随机环境中马氏链的平稳分布存在的一些充分条件. 特别地, 讨论了Cogburn链的平稳分布存在性问题. 同时, 构造了一个随机环境中马氏链的例子, 它的平稳分布是存在的.     

Thickness-dependent tunable characteristics of (Ba0.5Sr0.5)0.925K0.075TiO3 thin films prepared by pulsed laser deposition

The thickness-dependent dielectric properties and tunability of pulsed laser deposited (Ba_0.5Sr_0.5)_0.925K_0.075TiO₃ (BSKT) thin films with different thickness ranging from 80 to 300 nm has been investigated. Dielectric properties of the BSKT thin films are substantially improved as the BSKT film thickness increases, which can be explained by the model of a low-permittivity dead layer that is connected in series with the bulk region of the film. The estimated values of thickness and the average dielectric constant for the dead layer are 2.4 nm and 23.5, respectively, in a Pt/BSKT/Pt capacitor structure. The tunability and figure of merit increased with increasing film thickness, which are attributed to the change in lattice parameter and the dead layer effect.     

Elastic and inelastic scattering components in the angular intensity distribution of He scattered from graphite

The angular intensity distribution of thermal energy He beam scattered from highly oriented pyrolytic graphite (HOPG) surface has been measured by means of supersonic molecular beam scattering technique in the wide surface temperature range. To separate the elastic and inelastic scattering components, simple analysis method has been developed by applying the classical binary collision theory of the hard cube model (HCM). From the extracted elastic scattering component in the scattering distribution, the Debye temperature of the HOPG surface has been derived as 590 ± 30 K. On the basis of the HCM analysis for the extracted inelastic scattering components of He beam, the effective mass for the HOPG surface has been found to be 72 u (six carbon atoms).     

Effect of surface property of polyimide substrate on the formation of pentacene thin-film

We investigated the effect of surface property of polyimide substrate on the formation of pentacene thin-film by using atomic force microscopy (AFM) and X-ray reflectivity (XRR) and diffuse scattering (XDS). Two types of polymer films were prepared: (1) polyimide (PAA-PI) from poly(amic acid) (PAA) (2) polyimide hybrid (PAA-PI-H) prepared by hybridizing the PAA and soluble polyimide (PI) with a octadecyl side chain. The hybridization ratio of PI to PAA was 2/98 in wt%. The water contact angle for PAA-PI-H and PAA-PI were around 80° and 64°, respectively. Morphology of pentacene with a ropelike structure and (1 1 0) peak around 1.4 Å in q_z was found when it was deposited on PAA-PI thin-film. Different pentacene morphology was observed when it was deposited on PAA-PI-H thin-film. The different morphology might be due to a 5-6 nm thick additional layer (∼0.95 ρ_film) at the interface between pentacene and PAA-PI-H thin-film caused by a long alkyl side chain introduced to the polymer main chain.     

配位键驱动的多卟啉阵列结构在纳米SiO2表面的组装及光电性能

制备了吡啶功能化的纳米二氧化硅(nanoSiO₂BPy), 并利用配位键驱动的层层自组装技术, 以四吡啶基锌卟啉(ZnTPyP)为链接单元, 在nanoSiO₂BPy表面构筑了含有(Pd/ZnTPyP)_n多卟啉阵列结构的有机-无机杂化材料. 利用热重、 紫外-可见吸收光谱和X射线光电子能谱跟踪分析了nanoSiO₂BPy@(Pd/ZnTPyP)_n杂化材料的组装过程. 结果表明, nanoSiO₂BPy@(Pd/ZnTPyP)₃杂化材料在150~450 ℃升温区间内质量损失17%, 可归结为组装在纳米SiO₂表面的多卟啉阵列和少量有机物的热分解. 紫外-可见和荧光光谱表明, 在nanoSiO₂BPy@(Pd/ZnTPyP)_n杂化材料中, 锌卟啉Soret带的吸收峰出现在426 nm处, 其Q带的荧光发射峰出现在605和655 nm处, 荧光寿命约为1.78 ns, 光谱数据均与锌卟啉在稀的二甲亚砜溶液中的结果接近, 表明组装在nanoSiO₂BPy表面的锌卟啉环之间相互作用较弱, 没有形成聚集体. 场发射透射电镜照片显示, 由于Pd/ZnTPyP的组装, nanoSiO₂BPy@(Pd/ZnTPyP)₃杂化材料的平均直径由原料的10~16 nm增加到15~20 nm. 杂化材料修饰电极的循环伏安曲线在-0.6~-2.4 V(vs. Ag/AgCl)范围内出现了2对不可逆的氧化还原峰, 归属于卟啉被氧化的电子转移过程. 探讨了nanoSiO₂BPy@(Pd/ZnTPyP)_n杂化材料作为光敏剂在光电转换、 光催化乙基紫精的还原和显色方面的应用.