3‐D spatio–temporal structures of biofilms in a water channel

We develop a numerical predictive tool for multiphase fluid mixtures consisting of biofilms grown in a viscous fluid matrix by implementing a second‐order finite difference discretization of the multiphase biofilm model developed recently on a general purpose graphic processing unit. With this numerical tool, we study a 3‐D biomass–flow interaction resulting in biomass growth, structure formation, deformation, and detachment phenomena in biofilms grown in a water channel in quiescent state and subject to a shear flow condition, respectively. The numerical investigation is limited in the viscous regime of the biofilm–solvent mixture. In quiescent flows, the model predicts growth patterns consistent with experimental findings for single or multiple adjacent biofilm colonies, the so‐called mushroom shape growth pattern. The simulated biomass growth both in density and thickness matches very well with the experimentally grown biofilm in a water channel. When shear is imposed at a boundary, our numerical studies reproduce wavy patterns, pinching, and streaming phenomena observed in biofilms grown in a water channel. Copyright © 2014 John Wiley & Sons, Ltd.     

基于GPRS的输油管道阴极保护远程监测系统设计

为实现输油管道阴极保护系统的远程自动化监测与参数集中管理,开发了一种基于GPRS的分布式管道阴极保护参数远程监测系统;设计监测终端检测现场保护点的阴极电位、恒电位仪电压和阴极保护电流,采用GPRS无线网络以TCP/IP方式远传数据至监测中心工控机,实现了分布式多监测点阴极保护状态的在线监测与参数管理;运行测试结果表明,该系统稳定可靠,实现了对多站点、多通道数据的远程集中监测,阴极电位的检测精度达到了0.5%,可满足输油管线阴极保护的远程自动化监测需求。     

基于波变量补偿的阻抗匹配时延双边遥操作

通信时延是遥操作系统中固有的问题,它会严重影响遥操作的性能,降低系统的稳定性和跟踪性。基于无源理论的波变量法可以保证遥操作系统在任意时延下稳定,是解决时延问题的一个重要方法。然而,波变量法带来的波反射会阻扰有用信号的传输,降低了主从端信号的跟踪性,严重时甚至会导致整个系统振荡。针对这一问题,提出了一种基于波变量补偿的阻抗匹配双边遥操作系统结构,旨在减少波反射,提高操作者的临场感和系统的跟踪性。通过仿真实验,结果表明所提方法能够保证固定时延条件下遥操作系统的稳定性,并具有较好的跟踪性。     

Ionic liquids as precursors for highly luminescent,surface-different nitrogen-doped carbon dots used for label-free detection of Cu/Fe and cell imaging

Carbon nanodots (C-Dots) have attracted much attention in recent years due to their low cost, ready scalability, excellent chemical stability, biocompatibility and multicolor luminescence. Here, we report a facile strategy for producing highly luminescent, surface-different nitrogen-doped carbon dots (C-Dots) by using different ionic liquids (ILs). Intriguingly, the surface-different C-Dots show different selectivity for Cu²⁺ and Fe³⁺. To the best of our knowledge, this is the first example which shows that ILs are excellent precursors for producing luminescent nanomaterial used for detection of different metal ions. The resultant nitrogen-doped C-Dots are highly photoluminescent and can be used for multicolor bioimaging. Most notable, by taking different ILs as precursors, we obtain surface-different C-Dots, which can be directly used for selective detection of Cu²⁺ and Fe³⁺ without any modification. These C-Dots based sensors exhibit high sensitivity and selectivity and the sensing process can be easily accomplished with one-step rapid operation. More importantly, compared with other method using QDs, organic dyes and organic solvent, this strategy is much more eco-friendly. This work may offer a new approach for developing low cost and sensitive C-Dots-based sensors for biological and environmental applications.     

典型蓝藻多肽的浓度水平、毒性及光化学行为的研究进展

由于人为活动和气候变化,蓝藻水华污染已成为全球性环境问题。水华发生时藻类产生的毒性代谢物蓝藻多肽大量释放至水中,对生态系统和人类健康造成风险。本文系统梳理了包含微囊藻毒素在内的6种典型蓝藻多肽的浓度水平和毒性,并探讨了蓝藻多肽的光化学行为。结果显示,蓝藻多肽的浓度水平一般处于μg/L范围,其主要毒性位点为肝、肾和神经系统,致毒浓度LC₅₀在μmol/L范围。蓝藻多肽以间接光解为主,半衰期长短与蓝藻多肽本身的结构和所含的氨基酸基团种类以及环境水体pH大小等有关。本研究为解析蓝藻多肽的环境影响和环境归宿提供参考。     

On Hahn polynomial expansion of a continuous function of bounded variation

We consider the well-known method of least squares (cf., e.g., [1, p. 217]) on an equidistant grid with N + 1 nodes on the interval [−1, 1]. We investigate the following problem: For which ratio N/n, do we have pointwise convergence of the least square operator LS^N_n : C[−1,[1][→[P_n? To solve this problem we investigate the relation between the Jacobi polynomials P^α,β_k (cf., e.g., [2, p. 216]) and the Hahn polynomials Q_k (·; α, β, N) (cf., e.g., [2, p. 204]). In particular, we present the following result: Let f ∈ {g ∈ C¹[−1, 1] : g′∈ BV [−1, 1]} and let (N_n)_n be a sequence of natural numbers with n⁴/N_n → 0. Then the least square method LS^N_n [f] converges for each x ∈ [−1, 1]. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond was investigated and a series of N3-ethoxymethylated heterocyclic compounds were synthesized. A mechanism in which diethyl phosphite acts as an efficient surrogate of ethanol was proposed and supported by several evidences.     

Biosynthesis of a lactate (LA)-based polyester with a 96 mol% LA fraction and its application to stereocomplex formation

A poly(lactic acid) (PLA)-like terpolyester consisting of 96 mol% lactate (LA), 1 mol% 3-hydroxybutyrate and 3 mol% 3-hydroxyvalerate was produced in recombinant Escherichia coli LS5218 expressing LA-polymerizing enzyme (LPE). The strain was grown on glucose with a feeding of valerate as the monomer precursor. The glass transition and melting temperatures of the terpolyester were close to those of chemically synthesized poly(L-LA)s (PLLAs) having similar molecular weights. Additionally, a blend of the terpolyester, which was composed entirely of (R)-LA (D-LA) due to the strict enantiospecificity of LPE, with PLLA formed a stereocomplex with higher melting temperature (201.9 °C). These results indicate that the biological PLA-like polyester produced via this one-step microbial process has comparable thermal properties to chemically synthesized PLAs.