Structure Mediation and Properties of Poly(l-lactide)/Poly(d-lactide) Blend Fibers

Poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) blend as-spun fibers (50/50, wt.%) were prepared by melt spinning. Structure mediation under temperature and stress and properties of poly(l-lactic acid)/poly(d-lactic acid)(PLLA/PDLA) as-spun fibers were investigated by wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC). The results show that highly oriented stereocomplex (SC) crystals can be formed in PLLA/PDLA blend fibers drawn at 60 °C and annealed at 200 °C. However, at drawn temperature of 80 °C, only lower oriented SC crystals can be formed. For PLLA/PDLA blend fibers drawn twice at 60 °C (PLLA/PDLA-60-2), the crystallinity of SC crystals increases with annealing temperature in the range of 200 to 215 °C, while the degree of orientation decreases slightly. When the annealing temperature is 210 °C, the crystallinity and orientation of SC crystals in PLLA/PDLA-60-2 fibers reach 51% and −0.39, respectively. Moreover, PLLA/PDLA-60-2-210 fibers exhibit excellent heat-resistant property even at 200 °C. The results indicate that the oriented PLLA/PDLA blend fibers with high SC crystals content can be regulated in a short time

Formation of forest gaps accelerates C, N and P release from foliar litter during 4 years of decomposition in an alpine forest

Relative to areas under canopy, the soils in forest gaps receive more irradiance and rainfall (snowfall); this change in microclimate induced by forest gaps may influence the release of carbon (C) and nutrients during litter decomposition. However, great uncertainty remains about the effects of forest gaps on litter decomposition. In this study, we incubated foliar litters from six tree and shrub species in forest gaps and canopy plots and measured the release of C, nitrogen (N) and phosphorus (P) in different snow cover periods in an alpine forest from 2012 to 2016. We found that N was retained by 24-46% but that P was immediately released during an early stage of decomposition. However, forest gaps decreased litter N retention, resulting in more N and P being released from decomposing litters for certain species (i.e., larch, birch and willow litters). Moreover, the release of C and nutrients during litter decomposition stimulated by forest gaps was primarily driven by warmer soil temperature in this high-altitude forest. We conclude that gap formation during forest regeneration may accelerate C turnover and nutrient cycling and that this stimulation might be regulated by the litter species in this seasonally snow-covered forest.Peer reviewe

Structural and Electrical Properties of the YSZ/STO/YSZ Heterostructure

The heterostructure thin films of yttria-stabilized zirconia (YSZ)/strontium titanate (STO)/YSZ with various thicknesses were deposited on MgO single crystal substrate by pulsed laser deposition (PLD) method. The structural and electrical properties of the YSZ/STO/YSZ heterostructure were studied through X-ray diffraction (XRD) and electrical conductivity measurements. The in-plane conductivities of the thin films were measured and compared with that of the bulk sample. The highest conductivities were reported for those samples with the thinnest YSZ (220) layers. The observed enhancement in the lateral ionic conductivity was probably caused by the combination of the misfit dislocation density and elastic strain in the interfaces. The enhanced ionic mobility was discussed in terms of the disorder introduced in the oxygen sublattice through the epitaxial strain at the interfaces

Effect of molecular distillation on the anti-inflammatory activity and neurotoxicity of Asarum essential oil

Asarum essential oil (AEO) has been shown to have good pharmacological activities for the anti-inflammatory and analgesic effects, but increasing the dose may cause toxicity. Therefore, we studied the toxic and pharmacodynamic components of AEO by molecular distillation (MD). Anti-inflammatory activity was assessed using RAW264.7 cells. Neurotoxicity was assessed in PC12 cells and the overall toxicity of AEO was evaluated in the mouse acute toxicity assay. The results showed that AEO is primarily composed of safrole, methyl eugenol, and 3,5-dimethoxytoluene. After MD, three fractions were obtained and contained different proportions of volatile compounds relative to the original oil. The heavy fraction had high concentrations of safrole and methyl eugenol, while the light fraction contained high concentrations of α-pinene and β- pinene. The original oil and all three fractions exhibited anti-inflammatory effects, but the light fraction demonstrated more excellent anti-inflammatory activity than the other fractions. Asarum virgin oil and MD products are all neurotoxic. The exposure of PC12 cells to high concentrations of AEO resulted in abnormal nuclei, an increased number of apoptotic cells, increased ROS formation, and decreased SOD levels. Moreover, the results of acute toxicity tests in mice revealed that the light fractions were less toxic than virgin oils and other fractions. In summary, the data suggest that the MD technology enables the enrichment and separation of essential oil components and contributes to the selection of safe concentrations of AEO

Position Tracking of a Pneumatic-Muscle-Driven Rehabilitation Robot by a Single Neuron Tuned PID Controller

Pneumatic muscle actuators (PMAs) own compliant characteristics and are suitable for use in rehabilitation equipment. This paper introduces a rehabilitation robot driven by PMAs devised in the Rehabilitation and Medical Robot Laboratory. Considering high nonlinearities inside PMAs, a single neuron tuned PID controller is carefully designed. Experimental setup is built up and trials are performed. Results demonstrate the proposed advanced PID algorithm can achieve better capacity in position tracking than the conventional PID controller

Cleavage of the C= N Bond in Carbodiimides via Release of High Ring Strain: A New Strategy for the Selective Synthesis of 2-Aminoaryl Alkynyl Imines

A novel pattern of the cleavage and reorganization of CN bond in the multicomponent reaction (MCR) of terminal alkynes or haloalkynes, carbodiimides, and benzynes is achieved for the first time to construct efficiently 2-aminoaryl alkynyl imines. The selective formation and ring-opening of the azetine intermediate with the high ring strain is essential for this reaction. Further transformation of 2-aminoaryl alkynyl imines via the Cu-catalyzed cycloisomerization is explored to provide steroselectively the bi-, tri-, and tetracyclic fused pyrrolines

Oxidant-Switchable Selective Synthesis of 2‑Aminobenzimidazoles via C–H Amination/Acetoxylation of Guanidines

The iodine­(III) compound promoted C–H amination and tandem C–H amination/acetoxylation of guanidines are achieved for the first time to provide efficiently 2-aminobenzimidazoles and acetoxyl-substituted 2-aminobenzimidazoles, respectively. The amount and type of iodine­(III) compounds control the selective syntheses of two types of 2-aminobenzimidazoles. This reaction shows good regioselectivity when unsymmetrical substrates are used

Accelerating the photocatalytic degradation of toluene by unidirectional electron transfer via FRET strategy

Humanity's need for clean air has stimulated their research interest in the remediation of volatile organic compounds (VOCs). As an environmentally friendly pollution control technology, photocatalysis can easily generate oxidative free radicals for the mineralization of VOCs. Herein, we report a Förster resonance energy transfer (FRET)-inspired Ag/SrSO4/TiO2 photocatalyst with 2.5-fold higher activity for toluene degradation than pristine TiO2. The study of the catalyst reaction mechanism shows that the interlayer SrSO4 between the plasmonic Ag and the photocatalyst TiO2 is the key factor to guide the unidirectional transfer of electrons. A proper thickness of the insulator interlayer (whether SrSO4 or BaSO4) can reduce the recombination efficiency of photo-generated electrons and holes, resulting in an excellent toluene degradation ability. This finding demonstrates the excellent versatility of the catalyst system, which provides a novel direction for the modification of typical photocatalysts