Bioactive Molecules in Soil Ecosystems: Masters of the Underground

Complex biological and ecological processes occur in the rhizosphere through ecosystem-level interactions between roots, microorganisms and soil fauna. Over the past decade, studies of the rhizosphere have revealed that when roots, microorganisms and soil fauna physically contact one another, bioactive molecular exchanges often mediate these interactions as intercellular signal, which prepare the partners for successful interactions. Despite the importance of bioactive molecules in sustainable agriculture, little is known of their numerous functions, and improving plant health and productivity by altering ecological processes remains difficult. In this review, we describe the major bioactive molecules present in below-ground ecosystems (i.e., flavonoids, exopolysaccharides, antibiotics and quorum-sensing signals), and we discuss how these molecules affect microbial communities, nutrient availability and plant defense responses.     

Preparation,structure and properties of thermoplastic olefin nanocomposites containing functionalized carbon nanotubes

The morphology and properties of multiwalled carbon nanotube modified polypropylene (PP)/ethylene–octene copolymer blends were studied. Polypropylene chains are covalently grafted onto the surface of carbon nanotubes (CNTs) in order to improve their interaction with the polymer matrix. It is observed that functionalization of CNTs improves their dispersion and increases the interfacial bonding between CNTs and polymer matrix. The functionalized CNTs are selectively distributed in the continuous polypropylene phase. The size of the dispersed elastomer phase decreases after the addition of CNTs. Functionalized CNTs act as a nucleating agent and increase the crystallinity of the polypropylene. More importantly, an important increase in impact strength, stiffness and toughness can be achieved through introducing functionalized CNTs. Copyright © 2011 Society of Chemical Industry     

Preparation and characterization of star-shaped nylon 6 with high flowability

Three kinds of star-shaped nylon 6 samples with different branched-chain length were prepared by the hydrolytic polymerization of ε-caprolactam using trimesinic acid as trifunctional reactant. The structure of prepared star-shaped nylons was characterized by infrared spectroscopy and ¹H-NMR. Compared with linear-chain nylon 6, star-shaped nylons with the equivalent molecular weight present higher melt flow indices and lower relative viscosities due to decreased molecular dimensions and reduced hydrogen bond interactions between neighboring molecules. The molecular weights of the products were determined by end-group titration and ¹H-NMR, and the molecular weight distributions (MWDs) were evaluated by gel permeation chromatography. The results show that the molecular weight decreased and the MWD narrowed as the concentration of trimesinic acid increased. Wide-angle X-ray diffraction patterns of star-shaped and linear-chain nylons show that increasing the concentration of trimesinic acid leads to good symmetry and high crystallizability, but this also degrades crystal perfection as observed using a polarized optical microscope. The viscosity of nylon 6 can be significantly reduced while maintaining its mechanical performance through the use of star-branching and an appropriate concentration of trimesinic acid.     

Modeling reaction kinetics of rigid polyurethane foaming process

A theoretical model was developed to simulate the polyurethane foaming process for a rigid foam. In the model, multiple ordinary differential equations were solved by MATLAB and the model was able to predict temperature profiles by inputting foam recipe information. This initial study on foam modeling focusses on reaction kinetic parameters that were fitted to experimental temperature data as a function of time. The modeling was able to accurately model temperature profiles of single‐polyol polyurethane formulations and was able to accurately predict temperature profiles of mixtures based on pure component kinetic parameters. A primary goal of this work is to expedite the ability to develop new foam formulations by simulation—especially for incorporation of new bio‐based polyols into formulations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1131‐1138, 2013     

Enhanced interfacial adhesion via interfacial crystallization between sisal fiber and isotactic polypropylene: direct evidence from single‐fiber fragmentation testing

Bioresource natural sisal fiber (SF) was used to prepare single fiber‐reinforced isotactic polypropylene (iPP) composites. Three kinds of interfacial crystalline morphologies, spherulites, medium nuclei density transcrystallinity (MD‐TC) and high nuclei density transcrystallinity (HD‐TC), were obtained in the single fiber‐reinforced composites by implementing quiescent or dynamic shear‐enhanced crystallization and by modulating the compatibility interaction between SF and iPP. The development of interfacial shear strength (IFSS) during the interfacial crystallization process was demonstrated for the first time using a combination of single‐fiber fragmentation testing and optical microscope observation. A close correlation between IFSS and morphological characteristics of interfacial crystallization was well elucidated. The increases in IFSS were very different for spherulitic, MD‐TC and HD‐TC morphologies. The highest IFSS obtained was 28 MPa, after the formation of HD‐TC, which was about 62% of the tensile strength of neat iPP (45 MPa). These results offer powerful and direct evidence that interfacial crystallization could play an important role in the enhancement of interfacial adhesion of real SF/iPP composites. © 2013 Society of Chemical Industry     

Novel ultraviolet-opaque, visible-transparent and light-emitting ZnO-QD/silicone composites with tunable luminescence colors

Multifunctional, ultraviolet (UV)-opaque, visible-transparent and light-emitting materials with tunable luminescence colors are highly desirable for many applications in areas of ultraviolet shielding, light-emitting diodes and optical lenses etc. In this work, ZnO quantum dots (ZnO-ODs) with various sizes are first synthesized using a simple sol-gel route and novel multifunctional ZnO-QD/silicone composites with tunable luminescence colors are then prepared via a simple direct mixing method by uniformly dispersing ZnO-QDs in the silicone matrix. The structure and morphology of the ZnO-QD/silicone composites are characterized using high resolution transmission electron microscopy and attenuated total reflection Fourier transform infrared spectroscopy. UV-vis spectrometer and fluorescent photometer are used to study the optical properties of ZnO-QD/silicone composites. The results show that the ZnO-QD/silicone composites are opaque in the UV region, transparent in the visible region and also light-emitting with tunable luminescence colors from blue to yellow-green.     

一种生长延缓剂对早熟巨峰生长的调控作用

以早熟巨峰为试材,采用南开大学研制的一种生长延缓剂,于花前10 d和花后10 d进行2种浓度的处理,测定主梢和副梢生长量及果实品质,发现该制剂能够抑制葡萄新梢生长,对副梢的抑制作用强于主梢,并且随处理浓度的增加,抑制作用增强。0.5 mL/L浓度处理后的副梢长度、质量及节数分别比对照减少41.84%、54.90%、36.22%,节间长度和粗度分别比对照减少32.77%和19.28%;各处理对14节以下主梢节间长度没有明显抑制作用,对上部节位节间抑制减少2.4%～5.5%。0.25 mL/L和0.5 mL/L浓度处理分别使穗重比对照增加了20.79%和52.53%,使果实可滴定糖含量分别比对照增加3.1 g/L和5.4 g/L;高浓度处理增加了果实可滴定酸含量,降低了花青素含量,但差异不显著。各处理显著增加了枝条中的束缚水/自由水,降低了游离氨基酸含量,但对枝条的可溶性糖和淀粉含量没有显著影响。