Multiplicity of positive solutions for a critical quasilinear elliptic system with concave and convex nonlinearities

In this paper, by using the Lusternik–Schnirelmann category, we obtain a multiplicity result for a quasilinear elliptic system with both concave and convex nonlinearities and critical growth terms in bounded domains.     

Modeling,nonlinear dynamic analysis and control of fractional PMSG of wind turbine

This study aims to reveal the laws of the relationship between fractional-order system and integer-order system. Meanwhile, delayed feedback control is introduced to control the fractional-order PMSG (permanent magnet synchronous generator) model of a wind turbine. First, the fractional-order mathematical model of PMSG is established. Next, numerical simulations under different system orders are given and the system dynamic behaviors are analyzed in detail. Then, the delayed feedback control method is introduced to control the fractional-order PMSG and the control results when different parameters vary are analyzed. Complex dynamics are presented and some interesting phenomena are discovered. It is found that the system order influences the dynamics of the system in many aspects such as chaos pattern, bifurcation behavior, period window, shape and size of strange attractor. The delayed time, feedback gain, feedback limitation, system order can obviously influence the control result except the initial state of the system. Moreover, the feedback limitation has a minimum to successfully control the system to stable states and the system order also has a maximum to do so.     

Living Carbocationic Polymerization. XLIX. Two-Stage Living Polymerization of Isobutylene to Di-tert-chlorine Telechelic Polyisobutylene

Abstract

A two-stage process was developed for the living polymerization of isobutylene (IB) employing di-tert-alcohol initiators in conjunction with BCl₃ coinitiator in the first or initiation stage, followed by TiCl₄ coinitiator in the second or propagation stage; the process was shown to yield high molecular weight (up to M ⁿ 20,000), narrow molecular weight distribution (MWD) M ^w/M ⁿ = 1.1–1.2) di-tert-chlorine telechelic polyisobutylenes (^tCl-PIB-Cl^t). The initiation stage involves the homogeneous solution living polymerization of IB induced by the di-tert-alcohol/BCl₃ combination in the presence of an electron donor such as N,N-dimethylacetamide in CH₃Cl solvent at ?80°C and proceeds up to M ⁿ < 5000; this is followed by the propagation stage in which TiCl₄ and the bulk of IB plus a sufficient amount of n-C₆H₁₄ are added to the charge to bring the solvent composition to CH₃Cl/n-C₆H₁₄ 60/40 v/v and the living polymerization is continued until high M ⁿ product is obtained. This two-stage process was developed because 1) it employs very inexpensive chemicals; 2) di-tert-alcohol/BCl₃ combinations initiate living IB polymerization in CH₃Cl but the product after reaching M ⁿ ≤ 5000 precipitates out of the CH₃Cl solution, and di-tert-alcohol/BCl₄ combinations do not initiate IB polymerization; and 3) di-tert-alcohol/BCl₃ systems do not initiate (or only very slowly) the living polymerization of IB in CH₃Cl/n-C₆H₁₄ mixtures, whereas similar TiCl₄-based systems do. The polymerization remains living during both stages although the propagating species and solvent polarity are profoundly altered. The livingness of the system has been analyzed by kinetic experiments and the structure of the ^tCl-PIB-Cl^t product by routine spectroscopic means.     

The application of an in situ karyotyping technique for mesenchymal stromal cells: a validation and comparison study with classical G-banding

The cytogenetic analysis of mesenchymal stromal cells (MSCs) is essential for verifying the safety and stability of MSCs. An in situ technique, which uses cells grown on coverslips for karyotyping and minimizes cell manipulation, is the standard protocol for the chromosome analysis of amniotic fluids. Therefore, we applied the in situ karyotyping technique in MSCs and compared the quality of metaphases and karyotyping results with classical G-banding and chromosomal abnormalities with fluorescence in situ hybridization (FISH). Human adipose- and umbilical cord-derived MSC cell lines (American Type Culture Collection PCS-500-011, PCS-500-010) were used for evaluation. The quality of metaphases was assessed by analyzing the chromosome numbers in each metaphase, the overlaps of chromosomes and the mean length of chromosome 1. FISH was performed in the interphase nuclei of MSCs for 6q, 7q and 17q abnormalities and for the enumeration of chromosomes via oligo-FISH in adipose-derived MSCs. The number of chromosomes in each metaphase was more variable in classical G-banding. The overlap of chromosomes and the mean length of chromosome 1 as observed via in situ karyotyping were comparable to those of classical G-banding (P=0.218 and 0.674, respectively). Classical G-banding and in situ karyotyping by two personnel showed normal karyotypes for both cell lines in five passages. No numerical or structural chromosomal abnormalities were found by the interphase-FISH. In situ karyotyping showed equivalent karyotype results, and the quality of the metaphases was not inferior to classical G-banding. Thus, in situ karyotyping with minimized cell manipulation and the use of less cells would be useful for karyotyping MSCs.