Electrophoretic motion of a spherical particle in a converging-diverging nanotube

A charged spherical particle is concentrically positioned in a converging-diverging nanotube filled with an electrolyte solution, resulting in an electric double layer (EDL) forming around the particle's surface. In the presence of an axially applied electric field, the particle electrophoretically migrates along the axis of the nanotube due to the electrostatic and hydrodynamic forces acting on the particle. In contrast to a cylindrical nanotube with a constant cross-sectional area in which the electric field is almost uniform, the presence of a converging-diverging section in a nanotube alters the electric field, perturbs the charge distribution, and induces a pressure gradient and a recirculating flow that affect the electrostatic and hydrodynamic forces acting on both the particle and the fluid. Depending on the magnitude of the surface charge density along the nanotube's wall, the particle's electrophoretic motion may be significantly accelerated as the particle transverses the converging-diverging section. A continuum model consisting of the Nernst-Planck, Poisson, and Navier-Stokes equations for the ionic concentrations, electric potential, and flow field is implemented to compute the particle's velocity as a function of the particle's size, the nanotube's geometry, surface charges, electric field intensity, bulk electrolyte concentration, and the particle's location. When the particle is negatively charged and the wall of the nanotube is uncharged, the particle migrates in the direction opposite to that of the applied electric field and the presence of the converging-diverging section significantly accelerates the particle's motion. This, however, is not always true when the nanotube's wall is charged with the same sign as that of the particle. Once the ratio of the surface charge density of the nanotube's wall to that of the particle exceeds a certain value, the negatively charged particle will not translocate through the tube toward the anode and does not attain the maximum velocity at the throat of the converging-diverging section. One can envision such a device to be a nanofilter that allows molecules with surface charge densities much higher than that of the wall to go through the nanofilter, while preventing molecules with surface charge densities lower than that of the wall from passing through the nanofilter. The induced recirculating flow may be used to enhance mixing and to stretch, fold, and trap molecules in nanofluidic detectors and reactors.     

Proteomic analysis of apoptosis initiation induced by all-trans retinoic acid in human acute promyelocytic leukemia cells

The irreversible destiny of apoptosis in its early stage might play a critical role in the apoptosis of human acute promyelocytic leukemia (APL) cell line induced by all-trans retinoic acid (ATRA). To characterize protein alterations during the apoptosis-initiation phase and to understand the metabolic status at that time, we investigated the protein profiles in the apoptosis-initiation phase of APL cell line HL-60 by proteomic analysis. ATRA-withdrawal was conducted to demonstrate that there was committed initiation phase of apoptosis triggered by 10(-6) M ATRA at day 3. Only after that time point, ATRA-treated cells irreversibly went to apoptosis. Also at that time point, the positive regulators of apoptosis such as STAT3 increased at protein level, whereas negative regulators (Bcl-2 and p-STAT3) decreased. In addition, caspase-3 also increased after that time. Furthermore, comparative proteomic analysis was utilized to examine the protein expression profiles during the initiation stage of apoptosis. Our results showed 12 upregulated and 7 downregulated proteins experiencing twofold alteration, including key regulators of signal transduction such as G-proteins and nucleic receptors, proteins related with metabolism, oxidation and reduction, proteins associated with the nucleus and cytoskeleton-related proteins. Some of them could be positive modulators to trigger apoptosis, whereas others could contribute to intracellular defense against apoptosis induced by exogenous triggers. The results above suggest that there is a subtle balance between apoptosis and the intracellular defense against apoptosis. Once the balance is disturbed, cells would irreversibly initiate to undergo the execution of apoptosis.     

Basic Physicochemical Properties of Polyethylene Glycol Coated Gold Nanoparticles that Determine Their Interaction with Cells

A homologous nanoparticle library was synthesized in which gold nanoparticles were coated with polyethylene glycol, whereby the diameter of the gold cores, as well as the thickness of the shell of polyethylene glycol, was varied. Basic physicochemical parameters of this two‐dimensional nanoparticle library, such as size, ζ‐potential, hydrophilicity, elasticity, and catalytic activity ,were determined. Cell uptake of selected nanoparticles with equal size yet varying thickness of the polymer shell and their effect on basic structural and functional cell parameters was determined. Data indicates that thinner, more hydrophilic coatings, combined with the partial functionalization with quaternary ammonium cations, result in a more efficient uptake, which relates to significant effects on structural and functional cell parameters.     

Determination of organophosphorus pesticides in Lycium barbarum by gas chromatography with flame photometric detection

An analytical method was developed to determine 14 organophosphorus pesticide residues in Lycium barbarum, which is both a botanical medicine and a food. A 5 g sample is mixed with 10 mL ethyl acetate and, after shaking and centrifuging, 5 mL of the upper layer is removed, concentrated, and analyzed by gas chromatography (GC) with flame photometric detection. The essential feature of this method is that, for the purpose of reducing the burden of the GC system, 0.01 g activated carbon is used to absorb pigments during the cleanup procedure. Average recoveries of 14 organophosphorus pesticides added at 0.05, 0.1, and 0.5 mg/kg were 66.84-102.42, 71.07-97.93, and 62.50-96.24%, respectively. Limits of detection ranged from 5 to 15 microg/kg. The identities of the 14 pesticides were confirmed by GC/mass spectrometry detection in the selected-ion monitoring mode. This method is sensitive, simple, rapid, inexpensive, and safe.     

Preparation of thiophilic paramagnetic adsorbent for separation of antibodies

The micron-sized microspheres with superparamagnetic property were synthesized with vinyl acetate and divinylbenzene by microsuspension polymerization. After the complete alcoholysis, these hydroxyl-functionalized microspheres were activated by divinylfone and modified with mercaptoethanol to prepare the thiophilic magnetic adsorbent, which was used to specifically isolate immunoglobulin G （IgG） from human serum. This thiophilic magnetic adsorbent performed an evident salt-dependent adsorption behavior for IgG. Due to their salt-promoted adsorption towards IgG under high salt concentration, the absorbed antibodies could be extracted in low salt concentration with high purity.     

并行FORTRAN程序设计技术探索

简要叙述了并行程序设计语言ＣＭＦｏｒｔｒａｎ的计算模式、并行数据结构及其主要特征．并对Ｆｏｒｔｒａｎ７７和Ｆｏｒｔｒａｎ９０上的扩展部分作了概要描述．     

New Strategy for the Synthesis of Phosphonyl Pyrazoles

Phosphonyl hydrazones react with DMF/POC1₃ to afford 3-phosphonyl pyrazoles. Phosphonyl methylene hydrazones react with DMF/POC1₃ to provide 4-phosphonyl pyrazoles. 5-Phosphonyl pyrazoles are obtained from the reaction of phosphonyl chlorovinylaldehydes with phenylhydrazine.     

Si doping effect on self-organized InAs/GaAs quantum dots

In situ ultra high vacuum scanning probe microscopy (SPM) and low-temperature photoluminescence (PL) studies have been performed on Si-doped self-organized InAs/GaAs quantum dots samples to investigate the Si doping effects. Remarkably, when Si is doped in the sample, according to the SPM images, more small dots are formed when compared with images from undoped samples. On the PL spectra, high-energy band tail which correspond to the small dots appear, with increasing doping concentration, the integral intensity of the high-energy band tail account for the whole peak increase too. We relate this phenomenon to a model that takes the Si atom as the nucleation center for QDs formation.     

烟草花叶病毒在受限空间下的自组装行为

以烟草花叶病毒(TMV)为基本构建单元,研究了其在毛细管、载玻片-载玻片和柱透镜-硅片3种不同受限空间下的自组装行为。 结果表明,由于接触线有规律、重复性的粘滑运动,在3种受限体系下TMV均可组装得到高度规整的条带结构。 在毛细管内组装可得到垂直于管的长轴方向的有序条带。 随接触线深入管中心,条带跨距(l)与带宽(w)均逐渐增大。 在2个平行载玻片所构成的可控空间内所得到的条带以2条互相垂直的中心线为轴对称排列,并沿从载玻片边缘至轴向中心方向条带跨距和带宽梯度增大。 同样,利用柱透镜 硅片所组成的体系可得到类似平行线状条带,其跨距、带宽及条带高度沿从外部边缘至柱透镜/硅片接触中心方向逐渐减小。 在3种体系下,棒状TMV粒子均平行于接触线的方向取向。 TMV浓度对组装结构具有显著影响,随着浓度的增加,条带跨距和带宽均增加,直至条带结构消失形成连续膜。     

An electrochemically prepared sky-blue light emitting ether functionalized polyfluorene as chemosensor for metal ions

Synthesis and electrochemical polymerization of 9,9-bis(2-(2-(2-methoxy ethoxy)ethoxy)ethyl)-fluorene(EO-F)into poly[9,9-bis(2-(2-(2-methoxy ethoxy)ethoxy)ethyl)-fluorene](EO-PF) films are reported. The boron trifluoride diethyl etherate electrolyte enables facile preparation of EO-PF films at lower potential compared to LiClO4/MeCN and the electrochemical polymerizations are discussed. The EO-PF shows good electrochemical behavior and can be dissolved in solvents such as DMSO and THF. The solubility of EO-PF in THF is 2 mg mL 1and the number average molecular weight is35300 with a polydispersity index of 1.65. The side chains on C9position of the monomer maintain unchanged after electrooxidation into corresponding polymer. The EO-PF dissolved in THF under 365 nm ultraviolet light is sky blue light emitting with the Commission Internationale de L Eclairage-CIE coordinates of(0.19, 0.15). The electropolymerized EO-PF is used for the first time in chemosensing metal ions, demonstrating fluorescence quenching for Mn2+and Fe3+while fluorescence enhancement for Cr6+ions.