Sorbiterrin A,a novel sorbicillin derivative with cholinesterase inhibition activity from the marine-derived fungus Penicillium terrestre

A novel sorbicillinoid named sorbiterrin A (1), possessing an unprecedented skeleton was isolated from a marine sediment derived fungus Penicillium terrestre. The structure including absolute stereochemistries was elucidated by analysis of NMR, MS data and TDDFT CD calculations. Sorbiterrin A showed moderate acetylcholinesterase (AChE) inhibitory effect with IC₅₀ 25 μg/mL.     

Laser-driven synthesis and magnetic properties of iron nanoparticles

Nanoparticles of iron have been prepared by laser-driven decomposition of iron pentacarbonyl vapor. In this method, an infrared laser rapidly heats a dilute mixture of precursor vapors to decompose the precursor and initiate particle nucleation. It was found that when using SF₆ as a photosensitizer during the synthesis, ferrous fluoride (FeF₂) was produced as an undesired byproduct in the product powder. The particle size, composition, and crystalline structure have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS). Results of magnetization measurements for small iron nanoparticles (about 5 nm diameter) are also presented, showing superparamagnetic behavior at room temperature, and a blocking temperature near 125 K.     

Mesenchymal‐Mode Migration Assay and Antimetastatic Drug Screening with High‐Throughput Microfluidic Channel Networks

Increasing evidence shows that activated mesenchymal migration is a key process of the metastatic cascade. Cancer cells usually gain such migratory capability through an epithelial‐to‐mesenchymal transition. Herein we present a high‐throughput microfluidic device with 3120 microchambers to specifically monitor mesenchymal migration. Through imaging of the whole chip and statistical analysis, we can evaluate the two key factors of velocity and percentage related to cell migratory capacity at different cell densities in culture. We also used the device to screen antimetastatic drugs for their inhibition of mesenchymal migration and prevention of metastatic malignancy. This device will provide an excellent platform for biologists to gain a better understanding of cancer metastasis.     

Preparation of a novel pH-responsive silver nanoparticle/poly(HEMA-PEGMA-MAA) composite hydrogel

In this paper, series of novel pH-responsive silver (Ag) nanoparticle/poly(2-hydroxyethyl methacrylate (HEMA)-poly(ethylene glycol) methyl ether methacrylate (PEGMA)-methacrylic acid (MAA)) composite hydrogel were successfully prepared by in situ reducing Ag⁺ ions anchored in the hydrogel by the deprotonized carboxyl acid groups. X-ray diffraction (XRD), UV-vis spectrophotometry, transmission electron microscopy (TEM) and electric conductivity tests were used to characterize the composite system. It was found that the size and morphology of the reduced Ag nanoparticles in the composite hydrogels could be changed by loading the Ag⁺ ions at various swelling ratios of hydrogel. Moreover, compared to the pure poly(HEMA-PEGMA-MAA) hydrogel, not only did the Ag nanoparticle/poly(HEMA-PEGMA-MAA) composite hydrogels exhibit much higher swelling ratio and faster deswelling rate, but also higher pH switchable electrical properties upon controlling the interparticle distance under pH stimulus. The pH responsive nanocomposite hydrogel reported here might be a potentially smart material in the range of applications including electronics, biosensors and drug-delivery devices.     

简单级数反应的特征时间法

在化学反应的热动力学研究中,建立适宜的研究方法从热谱曲线上获得动力学参数是其中心内容．目前,已先后建立了无量纳参数法［‘j,对比进度法［‘］,模拟热谱曲线法［’］等并已得到广泛应用［‘j．这些方法均未直接利用到时间参量,热谱解析过程都较为复杂．我们在前文［到将时间作为已知参数,建立一种不需要反应进行到底就可获得化学反应速率常数的简单级数反应的时间变量法．但是,该法数据处理时需要取三个时间点以及相应的热谱数据,而时间滞后效应对于取多个时间点所带来的动力学计算误差有时是不能忽略的．因此,本文基于热动力…     

分光光度法测定芦笋中总黄酮的含量

黄酮类化合物与铝盐形成配合物,该配合物在紫外可见光区有吸收,选择510nm为测定波长,芦丁作为对照品,用分光光度法测定芦笋中的总黄酮,平均回收率为97．23％,测定结果的相对标准偏差为2.13％(n=5)。     

薄层扫描法考查沉香细胞级微粉碎工艺

以沉香3个特征性组分的相对浸出率及挥发油提取率为指标，用薄层扫描法考查细胞级微粉碎工艺对沉香特征性组分溶出行为的影响。沉香经细胞级微粉碎后，有关特征性组分的相对浸出率及样品挥发油的提取率均有大幅度的提高，并且相关组分得到了有效的保护。该方法直观、简便、快捷、重复性好，可为沉香药材微粉碎工艺的选择提供依据。     

Li吸附对双层α-硼烯功函调控作用的理论研究

硼烯基纳米复合体是一种极具潜力的电极材料,因此硼烯的功函调控对于最大化器件的能量转换效率及性能至关重要.本工作基于第一性原理密度泛函理论,研究了Li吸附对双层α-硼烯(DBBP)的结构、电子性质和功函的影响及影响Lin/DBBP功函变化的因素(如基底变形、电子转移、真空和费米能级).结果表明, Li吸附可将DBBP的功函从4.65e V调低至1.96～4.46 e V,优于文献报道的Li吸附单层BBP (从4.16 e V调至2.31～3.67 e V)、双层石墨烯中插入Li (3.4～3.9 e V)和K (3.3～3.8 e V)的功函调控效果.其中, Li₍2(D))/DBBP (3.73 e V)和Li₍3(D))/DBBP的功函(2.91 e V)分别与常用的电极材料Mg (3.68 e V)和Ca (2.90 e V)相近, Li₍4(D))/DBBP的功函(1.96e V)甚至低于Ca.本研究表明Li吸附是降低DBBP功函的一种简单而有效的方法,具有金属性和低功函的Li吸附DBBP纳米材料在电子器件中的阴极...     

计算动脉血管发展流动的新差分格式

在引用守恒型N—S方程和SIMPLE方法的基础上,对血管发展流动的控制方程提出了新的差分格式。算例结果表明：本差分格式对血管发展流动的数值研究是可行的。     

边值问题的变结构控制法

本文试图利用变结构控制方法来确保微分方程边值问题的解的唯一存在性,得到一些简明结果。此方法具有简单易行,可处理对象多样化,抗干扰性强的特点。