Morphological Control of Anisotropic Self-Assemblies from Alternating Poly(p-dioxanone)-poly(ethylene glycol) Multiblock Copolymer Depending on the Combination Effect of Crystallization and Micellization.

A novel and facile method was developed for morphological controlling of self-assemblies prepared by crystallization induced self-assembly of crystalline-coil copolymer depending on the combination effect of crystallization and micellization. The morphological evolution of the self-assemblies of alternating poly(p-dioxanone)-block-poly(ethylene glycol) (PPDO-PEG) multiblock copolymer prepared by different solvent mixing methods in aqueous solution were investigated. "Chrysanthemum"-like and "star anise"-like self-assemblies were obtained at different rates of solvent mixing. The results suggested gradually change in solvent quality (slowly dropping water into DMF solution) leaded to a hierarchical micellization-crystallization process of core-forming PPDO blocks, and flake-like particles were formed at the initial stage of crystallization. Meanwhile, crystallization induced micellization process occurred when solvent quality changed drastically. Shuttle-like particles, which have much smaller size than those of flake-like particles, were formed at the initial stage of crystallization when quickly injecting water into DMF solution of the copolymer. Therefore, owing to the different changing rate of solvent quality, which may result in different combination effect of crystallization and micellization during self-assembly of the copolymer, PPDO-PEG self-assemblies with different hierarchical morphology in nano scale could be obtained.

Preparation of core-shell nanofibers with selectively localized CNTs from Shish Kebab-like hierarchical composite micelles.

A novel and facile bottom-up strategy for preparing core-shell nanofibers with selectively localized carbon nanotubes is developed using hierarchical composite micelles of crystalline-coil copolymer and carbon nanotubes as the building blocks. An amphiphilic di-block copolymer of poly (p-dioxanone) (PPDO) and PEG (polyethylene glycol) functionalized with pyrene moieties at the chain ends of PPDO blocks (Py-PPDO-b-PEG) is designed for constructing composite micelles with multiwalled carbon nanotubes (MWCNTs). The self-assembly of Py-PPDO-b-PEG and MWCNTs is co-induced by the crystallization of PPDO blocks and the π-π stacking interactions between pyrene moieties and MWCNTs, resulting in composite micelles with "shish kebab"-like nanostructure. A mixture of composite micelles and polyvinyl alcohol (PVA) water solution is then used as the spinning solution for preparing electrospun nanofibers. The morphologies of the nanofibers with different composition are investigated by SEM and TEM. The results suggest that the MWCNTs selectively localized in the core of the nanofibers of MWCNTs/Py-PPDO-b-PEG/PVA. The alignment and interfusion of composite micelles during the formation of nanofibers may confine the carbon nanotubes in the hydrophobic core region. In contrast, the copolymer without pyrene moieties cannot form composite micelles, thus these nanofibers show selective localization of MWCNTs in the PVA shell region.

[Effects of straw returning on maize yield and root system spatial distribution under water stress]. / æ°´åˆ†èƒè¿«ä¸‹ç§¸ç§†è¿˜ç”°å¯¹çŽ‰ç±³äº§é‡å’Œæ ¹ç³»ç©ºé—´åˆ†å¸ƒçš„å½±å“.

To investigate the effects of straw amendments on the yield and root spatial distribution of maize under water stress, an experiment with rainproof shelter was conducted in the field experimental station of Shenyang Agricultural University in 2016 and 2017. The drip irrigation facilities were used to perform water stress treatments. Straw burying (T1) and straw incorporation (T2) as two approaches of straw amendments were conducted combined with three depths of 15 cm (D1), 30 cm (D2), and 45 cm (D3) for straw returning, ploughing tillage at above three depths without straw presence as control in this study. During seedling and silking stages of maize, drought and water logging stresses were introduced respectively to the plants. Our results showed that the yield of maize under S1T1D2 treatment in 2016 was significantly increased by 5.7%-7.1%. Compared with all the rest treatments, the dry weights of lateral roots and deep roots under S1T1D2 treatment were increased by 67.3%-149.9% and 17.9%-116.4%, respectively. The dry matter accumulation in shoot of maize observed from S1T1D2 treatment was significantly lower than those under other treatments, with 2.1%-35.8% reduction. Our results indicated that S1T1D2 could significantly promote the growth and spatial distribution of maize root, accounting to release water stress and keep yield stabilization or promotion. Therefore, 30 cm of straw burying could be used as a suitable approach of straw returning for maize production in northeastern China, where the climate is with a pattern of drought first and waterlogging in later stage.

Efficacy of Drug-Eluting Balloons for Patients With In-Stent Restenosis: A Meta-Analysis of 8 Randomized Controlled Trials.

The optimal treatment for in-stent restenosis (ISR) of both bare-metal stent (BMS) and drug-eluting stent (DES) is currently unclear. The aim of this meta-analysis was to assess the role of drug-eluting balloon (DEB) as an optional treatment for ISR. We searched PubMed, MEDLINE, EMBASE, BIOS, and Web of Science from 2005 to July 2014. Eight studies, enrolling 1413 patients were included. Main end points were late lumen loss (LLL), binary in-segment restenosis (BR), major adverse cardiac events (MACEs), target lesion revascularization (TLR), death, myocardial infarction (MI), and stent thrombosis (ST). When compared to plain old balloon angioplasty (POBA), DEB treatment significantly reduced the risk of MACE (risk rato [RR] 0.37, P < .01), death (RR 0.44, P = .04), TLR (RR 0.27, P < .01), BR (RR [95% CI]: 0.23[0.12 to 0.43], P < .01) and associated with better outcomes of LLL ( 0.50 [ 0.65 to 0.35] mm, P < .01). However, the differences were not significant between DEB treatment and DES treatment in all primary and secondary end points. The DEB was a better option to treat ISR when compared to POBA. However, it had similar effects as DES.

[Preliminary study on using acousto-optic tunable filter as wavelength selector for atomic absorption spectrometry].

An acousto-optic tunable filter (AOTF) is an all-solid-state, electronic monochromator that is based on the diffraction of light by an acoustic wave in an anisotropic crystal. It is a new kind of tunable small filter with narrow band compared with traditional unicolor filter. The filter can diffract incident white light at a specific wavelength when a specific radio frequency is applied into it. An AAS experimental setup using a microwave plasma torch (MPT) as the atomizer, and a visible AOTF as the wavelength selector was developed and the analytical performance was evaluated by determination of Na. The effect on the absorption signal of some operating conditions, including the observation height, the microwave forward power and the carrier and support gas flow rates for MPT, were investigated. The detection limit for Na was shown to be 0.23 microgram.mL-1 and the relative standard deviation was 2.6% (n = 6).

Nanofibers with very fine core-shell morphology from anisotropic micelle of amphiphilic crystalline-coil block copolymer.

A novel and facile strategy, combining anisotropic micellization of amphiphilic crystalline-coil copolymer in water and reassembly during single spinneret electrospinning, was developed for preparing nanofibers with very fine core-shell structure. Polyvinyl alcohol (PVA) and polyethylene glycol-block-poly(p-dioxanone) (PEG-b-PPDO) were used as the shell and the crystallizable core layer, respectively. The core-shell structure could be controllably produced by altering concentration of PEG-b-PPDO, and the chain length of the PPDO block. The morphology of the nanofibers was investigated by Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). X-ray rocking curve measurements were performed to investigate the degree of ordered alignment of the PPDO crystalline lamellae in the nanofiber. The results suggested that the morphology of nanoparticles in spinning solution plays very important role in determining the phase separation of nanofibers. The amphiphilic PEG-b-PPDO copolymer self-assembled into star anise nanoaggregates in water solution induced by the crystallization of PPDO blocks. When incorporated with PVA, the interaction between PVA and PEG-b-PPDO caused a morphological transition of the nanoaggregates from star anise to small flake. For flake-like particles, their flat surface is in favor of compact stacking of PPDO crystalline lamellae and interfusion of amorphous PPDO in the core of nanofibers, leading to a relatively ordered alignment of PPDO crystalline lamellae and well-defined core-shell phase separation. However, for star anise-like nanoaggregates, their multibranched morphology may inevitably prohibit the compact interfusion of PPDO phase, resulting in a random microphase separation.