NONLINEAR DYNAMICS AND SYNCHRONIZATION OF TWO COUPLED PIPES CONVEYING PULSATING FLUID

In this paper, the nonlinear dynamical behavior of two coupled pipes conveying pulsating fluid is studied. The connection between the two pipes is considered as a distributed linear spring. Based on this consideration, the equations of motion of the coupled two-pipe system are obtained. The two coupled nonlinear partial differential equations, discretized using the fourth- order Galerkin method, are solved by a fourth-order Runge-Kutta integration algorithm. Results show that the connection stiffness has a significant effect on the dynamical behavior of the coupled system. It is found that for some parameter values the motion types of the two pipes might be synchronous.     

First-principles study of structural stability and elastic property of pre-perovskite PbTiO3

The structural stability and the elastic properties of a novel structure of lead titanate,which is named preperovskite PbTiO₃ （PP-PTO） and is constructed with TiO₆ octahedral columns arranged in a one-dimensional manner,are investigated by using first-principles calculations.PP-PTO is energetically unstable compared with conventional perovskite phases,however it is mechanically stable.The equilibrium transition pressures for changing from preperovskite to cubic and tetragonal phases are 0.5 GPa and 1.4 GPa,respectively,with first-order characteristics.Further,the differences in elastic properties between pre-perovskite and conventional perovskite phases are discussed for the covalent bonding network,which shows a highly anisotropic character in PP-PTO.This study provides a crucial insight into the structural stabilities of PP-PTO and conventional perovskite.     

Fabrication of Gene Carrier via Self-assembly of Poly[(dimethylamino)ethyl Methacrylate] and Poly(aspartic acid)-grafted-Poly(ethylene glycol)

A biocompatible complex has been prepared as gene carrier via electrostatic interaction, which is composed of a polycation, that is, poly[(dimethylamino)ethyl methacrylate] end-capped with cholesterol moiety (Chol-PDMAEMA₃₀), along with a polyanion named poly(aspartic acid)-grafted-poly(ethylene glycol) (PASP-g-PEG). The complexes have less cytotoxicity compared to the case of alone Chol-PDMAEMA₃₀ or branched polyethylenimine (PEI) system.

In the present study, biocompatible complexes have been prepared as gene carrier via electrostatic interaction, which is composed of a polycation, that is, poly[(dimethylamino)ethyl methacrylate] end-capped with cholesterol moiety (Chol-PDMAEMA₃₀), along with a polyanion named poly(aspartic acid)-grafted-poly(ethylene glycol) (PASP-g-PEG). We first synthesized polysuccinimide (PSI) via condensation polymerization of aspartic acid, and then used PEG-NH₂ to react with the partial pentacyclic rings of PSI to yield a kind of graft copolymer polysuccinimide-grafted-poly(ethylene glycol) (PSI-g-PEG). After hydrolysis of the residual succinimide units, a new biodegradable and biocompatible graft copolymer PASP-g-PEG was prepared successfully. Chol-PDMAEMA₃₀ was synthesized via oxyanion-initiated polymerization, as reported in our previous literature. We investigated the interactions between every pair among calf thymus DNA, Chol-PDMAEMA₃₀, and PASP-g-PEG by agarose gel retardation assay. The results indicate that the prepared complexes could completely bind DNA and may become more stable during systemic circulation. The complexes have less cytotoxicity compared to the case of alone Chol-PDMAEMA₃₀ or branched polyethylenimine (PEI) system. Furthermore, the physicochemical properties of the complexes were also investigated by zeta potential, transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. These biodegradable and biocompatible polymeric carriers have potential applications in gene delivery.     

PCR-based detection of gene transfer vectors: application to gene doping surveillance

Athletes who illicitly use drugs to enhance their athletic performance are at risk of being banned from sports competitions. Consequently, some athletes may seek new doping methods that they expect to be capable of circumventing detection. With advances in gene transfer vector design and therapeutic gene transfer, and demonstrations of safety and therapeutic benefit in humans, there is an increased probability of the pursuit of gene doping by athletes. In anticipation of the potential for gene doping, assays have been established to directly detect complementary DNA of genes that are top candidates for use in doping, as well as vector control elements. The development of molecular assays that are capable of exposing gene doping in sports can serve as a deterrent and may also identify athletes who have illicitly used gene transfer for performance enhancement. PCR-based methods to detect foreign DNA with high reliability, sensitivity, and specificity include TaqMan real-time PCR, nested PCR, and internal threshold control PCR.     

Improved staining of phosphoproteins with high sensitivity in polyacrylamide gels using Stains‐All

An improved Stains‐All (ISA) staining method for phosphoproteins in SDS‐PAGE was described. Down to 0.5–1 ng phosphoproteins (α‐casein, β‐casein, or phosvitin) can be successfully selectively detected by ISA stain, which is approximately 120‐fold higher than that of original Stains‐All stain, but is similar to that of commonly used Pro‐Q Diamond stain. Furthermore, unlike the original Stains‐All protocol that was time consuming and light unstable, ISA stain could be completed within 60 min without resorting to protect the gels from light during the whole staining procedure. According to the results, it is concluded that ISA stain is a rapid, sensitive, specific, and economic staining method for a broad application to the research of phosphoproteins.