Three-layer composite filter media containing electrospun polyimide nanofibers for the removal of fine particles

Polyimide (P84) nanofibers of 200-500 nm were deposited uniformly on needle punched aramid felt with basis weight of 260-350 g/m² by optimized electrospinning. High temperature adhesive was then electro-sprayed on the nanofiber side deliberately to bind a thin protective layer made of temperature-resistant non-wovens. The three layer structure was afterwards enforced by hot pressing to form composite filter media. The application of the adhesive was tailored not to affect the permeability of the substrate felt while exerting adhesion strength of over 1000 kPa for the media to be suitable for flue gas dust treatment under 240 ºC. When 0.3-10 μm NaCl aerosols were used as the simulated dusts, it was found that even a small amount of P84 nanofibers could obviously elevate the filtration efficiency. The composite showed 100 % removal efficiency of particles equal and greater than 2.0 μm, and 99.5 % for particles 1.0-2.0 μm in diameter.     

Solution electrospinning of polypropylene-based fibers and their application in catalysis

Since the dissolution of polyolefins is a chronic problem, melt processing has been tacitly accepted as an obligation. In this work, polypropylene (PP) was modified on molecular level incorporating poly(ethylene glycol) (PEG) as graft segment (PP-g-PEG) in a range of 6 to 9 mol%. Gold nanoparticles were nucleated in the presence of the copolymer chains via redox reaction. The dissolution of the amphiphilic comb-type graft copolymers containing gold nanoparticles (80 nm in diameter) was achieved in toluene and successfully electrospun from its solution. The diameter of composite fibers was in the range from 0.3 to 2.5 μm. The design of the structurally organized copolymer fiber mats provided a support medium for the nanoparticles enhancing the active surface area for the catalytic applications. The resulting composite fibers exhibited rapid catalytic reduction of methylene blue (MB) dye in the presence of sodium borohydride (NaBH₄) compared to corresponding composite cast film.     

Hybrid organic-inorganic POSS (polyhedral oligomeric silsesquioxane)/polypropylene nanocomposite filaments

Octamethyl-POSS and Octaphenyl-POSS reinforced polypropylene nanocomposite monofilaments were prepared by melt blending route. It was observed that incorporation of Octamethyl-POSS and Octaphenyl-POSS in polypropylene show improvement in mechanical as well as thermal properties. Octaphenyl POSS/PP nanocomposites show significant increase in thermal stability even at very low concentration as compared to neat polymer matrix. An increase of 100 and 140 °C was observed in thermal degradation temperature at 5 wt% loss and maximum degradation over neat PP filaments respectively at low OP-POSS loadings (<5 wt%). Both Octamethyl-POSS and Octaphenyl-POSS act as lubricating agents facilitating drawing which results in improvement in orientation as well as mechanical properties.     

一种高效便捷的水稻DNA提取法及其应用

 以水稻叶片、根和种子为材料,采用高通量快速法提取基因组DNA,用稻瘟病Pita基因分子标记进行检测,获得与预期片段大小一致的特异性条带,对165份育种材料的检测结果与稻瘟病接种鉴定一致。操作方法如下：将少量水稻叶片、根或种子放入 200 μL PCR盘中,加入70 μL 缓冲液A (含NaOH和Tween20),在PCR仪中加热到95℃,保持 10 min,再加入70 μL 缓冲液B (Tris HCl和EDTA),该提取液可以直接用于PCR扩增。该方法具有几个优点：1）成本低,仅用4种化学试剂,共140 μL 提取液;2）操作简便,仅需3步,每人每天可以提取上千份样品;3）仪器设备简单,只用常规的PCR仪;4）可直接提取干种子的DNA;5）DNA质量好,能检测出水稻中的抗稻瘟病单基因Pita,并且与稻瘟病接种鉴定结果一致;6）用量少,只需要 5~20 mg 叶片、20 mg 根或半粒籽粒。尤其是检测大量样本的基因型时, 此种方法更显得高效便捷。     

Calcium Signaling is Involved in Negative Phototropism ofRice Seminal Roots简

Calcium ions(Ca2+) act as an intracellular second messenger and affect nearly all aspects of cellular life. They are functioned by interacting with polar auxin transport, and the negative phototropism of plant roots is caused by the transport of auxin from the irradiated side to the shaded side of the roots. To clarify the role of calcium signaling in the modulation of rice root negative phototropism, as well as the relationship between polar auxin transport and calcium signaling, calcium signaling reagents were used to treat rice seminal roots which were cultivated in hydroculture and unilaterally illuminated at an intensity of 100–200 μmol/(m2·s) for 24 h. Negative phototropism curvature and growth rate of rice roots were both promoted by exogenous CaCl2 lower than 100 μmol/L, but inhibited by calcium channel blockers(verapamil and LaCl3), calcineurin inhibitor(chlorpromazine, CPZ), and polar auxin transport inhibitor(N-1-naphthylphthalamic acid, NPA). Roots stopped growing and negative phototropism disappeared when the concentrations increased to 100 μmol/L verapamil, 12.500 μmol/L LaCl3, 60 μmol/L CPZ, and 6 μmol/L NPA. Moreover, 100 μmol/L CaCl2 could relieve the inhibition of LaCl3, verapamil and NPA. The enhanced negative phototropism curvature was caused by the transportation of more auxin from the irradiated side to the shaded side in the presence of exogenous Ca2+. Calcium signaling plays a key role as a second messenger in the process of light signal regulation of rice root growth and negative phototropism.     

Polycarbazole modified carbon fiber microelectrode: Surface characterization and dopamine sensor

Electropolymerization of carbazole (Cz) by cyclic voltammetry (CV) onto carbon fiber microelectrodes (CFME) (diameter ∼7 μm) in dichloromethane (CH₂Cl₂) solution of 0.1 mol·dm⁻³ tetraethyl ammonium perchlorate (TEAP) results in the formation of polycarbazole (PCz) thin film coatings. CV results showed that these PCz thin films have reversible redox behavior in monomer-free electrolyte solution. The resulting thin polymer films were characterized using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) and atomic force microscopy (AFM). Results performed at optimum experimental conditions indicate that electrodes show a reversible and stable behavior over sixty eight days of testing for dopamine in 100 μmol·dm⁻³ buffer solution. A detection limit for PCz thin films as low as 0.1 μM (3S/N) was obtained for the polycarbazole (PCz) thin films formed using CV. Hence, this novel sensor can be considered as promising sensor for dopamine detection.     

Electrical properties of ultrafine nylon-6 nanofibers prepared via electrospinning

We report on the preparation and electrical characterization of nylon-6 nanofibers via electrospinning technique. During electrospinning, the polymer solution became highly ionized and emerging out of the micro-tip syringe by forming mesh-like ultrafine nanofibers structure in between the main fibers. The resultant nylon-6 nanofibers were well-oriented with uniform structure. The diameter of the ultrafine nanofibers (7 to 40 nm) is one order less than those of main fibers (100 to 200 nm). The current-voltage (I-V) measurements revealed a linear curve with an occurrence of negative differential resistance (NDR) behavior. The existence of NDR region in the nylon-6 nanofibers can be attributed to the tunneling current through the ultrafine structures. The fabrication of nanofibers, in the form of ultrafine mesh-like form, is relatively fast and inexpensive, and it paves the way to build up of new dimension for nano device applications.     

Spray Drying of Chitosan Acid Salts: Process Development,Scaling Up and Physicochemical Material Characterization

We investigated a spray drying process for preparing water-soluble salts of high molecular weight chitosan (CH) intended for pharmaceutical excipient applications. CH was derived from chitin of marine lobster origin (Panulirus argus). The effects of organic acid (acetic or lactic acid) and the ratio (difference) of inlet/outlet air temperature (140/90 °C or 160/100 °C) on spray drying were studied. The yield of spray-dried CH salt powders ranged from 50% to 99% in laboratory and industrial-scale processes. The spray-dried dry powder of CH salts consisted of spherical agglomerated particles with an average diameter of 36.2 ± 7.0 µm (CH acetate) and 108.6 ± 11.5 µm (CH lactate). After dispersing the spray-dried CH salt powder samples in purified water, the mean particle sizes obtained for the CH acetate salts were 31.4 nm (batch A001), 33.0 nm (A002) and 44.2 nm (A003), and for the CH lactate salts 100.8 nm (batch L001), 103.2 nm (L002) and 121.8 nm (L003). The optimum process conditions for spray drying were found: an inlet air temperature of 160 ± 5 °C, an outlet temperature of 100 ± 5 °C and an atomizer disk rotational speed of 18,200 min⁻¹. The X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) results confirmed the amorphous state of the CH salts. The ¹H nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectra of CH acetate and lactate salts verified that the spray drying process does not affect the polymer backbone. In conclusion, both laboratory and industrial-scale spray drying methods for preparing water-soluble acid salts of CH are reproducible, and the physicochemical properties of the corresponding CH acid salts are uniform.     

Synthesis and Characterization of a Novel Preceramic Polymer for SiBNC Ceramic Fibers

A new approach for the synthesis of polymer precursor for quaternary SiBNC fibers is presented. The inexpensive, commercially available reactants n-propylamine (C₃H₇NH₂), trichlorosilane (SiHCl₃) and boron trichloride (BCl₃) were used in a simple one-step reaction. The reaction mainly involved the co-polymerization between Si-Cl, B-Cl and N-CH₂CH₂CH₃ with C₃H₇NH₂ evaporation. Characterization of synthesized polymer was performed by FT-IR and NMR. The polymer has a relatively linear-chain chemical structure, and could be easily converted into flexible green fibers by melt-spun with diameter of 24 μm. After pyrolysis process at 1000 °C under nitrogen atmosphere, SiBNC ceramic fibers were obtained with a diameter of about 19 μm. Those fibers showed average tensile strength of 1.05 GPa and it remained in the amorphous state up to 1600 °C, which made them as the promising candidates for reinforcements in ceramic matrix composites for hightemperature application.     

Uniaxially well-aligned nanofiber arrays fabricated by electrospinning with a stable and low moving velocity jet

Aligned fibers in micro-/nano-scale have attracted more attention especially in tissue engineering field because cells can orientation growth along the fiber. However, it is still a huge technological challenge in achieving it as a result of the inherent bending instability of an electrospinning jet. Herein, we report a novel and simple spinning approach, in which low dielectric constant of dioxane was judiciously used as solvent for spinning dope, to obtain electrospinning jet with low induced charge, therefore eliminating electrically and aerodynamically driven bending instability, and forming a stable and low forward-moving velocity jet longer than 100 cm. This consequently allows for readily collecting and fabricating individual fibers, well-aligned ultrafine fiber arrays over large areas. Our approach has proved to be effective in preparing well-aligned ultrafine fibers from biodegradable poly(D, L-lactic acid) with different molecular mass, natural polymer acetyl cellulose and synthesized non-biodegradable polymer polystyrene.     

A comparison of flax shive and extracted flax shive reinforced PP composites

In this study, flax shive (FS) and extracted flax shive (EFS) were fully characterized. The results showed that EFS presented lower noncellulose content, smaller porous tunnels and better thermal stability than FS. The 5 % weight loss temperature of EFS was over 200 °C, which can meet the requirements of the processing conditions for the natural fiber reinforced polymer composites. Consequently, the flax shive and extracted flax shive reinforced PP composites were prepared and characterized. It was found that the thermal stability of EFS/PP composites was better than that of FS/PP composites, and both FS and EFS behaved as nucleation agents, which could accelerate the crystallization process of PP in the composites. Mechanical test showed that EFS could be used as a reinforcing material for PP composite when compatibilizer was applied. The flexural strength and modulus of the composites containing 30 % EFS were about 8 % and 100 % higher than that of pure polypropylene, respectively.     

Scalable preparation of multiscale carbon nanotube/glass fiber reinforcements and their application in polymer composites

The introduction of carbon nanotubes (CNTs) into conventional fiber to construct a hierarchical structure in polymer composites has attracted great interest owing to their merits of performance improvement and multiple functionalities. However, there is a challenge for realizing the scalable preparation of the multi-scale CNT-glass fiber (CNTGF) reinforcements in practical application. In this work, we present a simple and continuous method of the mass production of multiscale CNT-glass fiber (CNT-GF) reinforcements. Scanning electron microscopy and thermo gravimetric analysis indicated ~1.0 wt% CNTs were highly dispersed on the whole fiber surface through a facile surfactant-assisted process. Such hybrid CNT-GF fillers were found to effectively enhance the stiffness, strength and impact resistance of polypropylene polymer. Increased storage modulus, glass transition temperature and crystallization temperature of the composites filled with the CNT-GF fillers were also observed in the differential scanning calorimetry and dynamic mechanical analysis compared with the composites containing the pristine GF fillers. Fracture surface analysis revealed enhanced interfacial quality between CNT-GF and matrix, which is likely responsible for improved performance of the hierarchical polymer composites.     

西藏冬青稞胚乳淀粉粒发育特征研究

为了解青稞胚乳淀粉及淀粉粒形成与生长特征,以西藏育成青稞品种冬青8号为材料,对籽粒发育过程中胚乳灌浆速度、淀粉积累量及淀粉粒的产生、二维面积、粒径变化进行了分析。结果表明,胚乳发育过程中,干物质和淀粉积累量呈S型曲线,两者呈正相关。花后5d,青稞胚乳中可零星见到粒径和二维面积较小的A型小淀粉粒;花后10~15d,A型小淀粉粒数量显著增大,但粒径和二维面积增加较慢;花后20d,B型小淀粉粒可能已经形成,与A型小淀粉粒组成一个复合群体;花后25d,形成了粒径10μm的A型淀粉粒、粒径5~10μm的B型淀粉粒和粒径5μm的C型淀粉粒;花后30~55d,不同粒径的淀粉粒数量和二维面积逐渐增加,其中,C型淀粉粒数量不断增加直至籽粒成熟。青稞成熟籽粒胚乳中,淀粉粒的粒径为1.45~44.76μm,二维面积为3.56~1 750.8μm2;A型淀粉粒形状为近圆形,表面光滑,个别表面附着有C型淀粉粒,B型淀粉粒形状有近圆形、椭圆形多种类型,C型淀粉粒形状比B型淀粉粒的变异更大。     

DAC对玉米DNA甲基化影响及基因表达量变化的研究

以5-氮杂-2脱氧胞苷(DAC)处理相应对照玉米幼苗叶片为材料构建转录组测序文库,采用Illumina测序平台进行测序,对差异表达基因进行GO功能分类和KEGG通路分析.最终筛选到差异基因1072个,其中,上调表达基因为646个,下调表达基因为426个.将差异基因富集的生物过程和信号通路进行GO分析,发现主要集中于细胞...     

9种热区植物白粉病菌的rDNA-ITS序列及系统发育分析

为弄清橡胶树、野艾蒿、大尾摇、胡萝卜、车前草、马占相思、红木、苦瓜和九里香等热区植物上白粉病菌的种类和彼此之间的系统发育关系,对这些白粉病菌的rDNA-ITS序列进行扩增和测序,与GenBank上公布的序列进行同源性比对,并进行分类.结果表明:橡胶树、马占相思、红木和九里香上的白粉病菌相似性非常高,均在99％以上;野艾蒿、大尾摇和苦瓜白粉病菌与叉丝单囊壳白粉菌的亲缘关系较近,分别达到100％和99％;胡萝卜白粉病菌与白粉菌属的独活白粉菌相似性在99％以上;而车前草白粉病菌与污色白粉菌的相似性达100％.利用供试菌和GenBank上公布的rDNA-ITS序列构建了系统发育树,将供试白粉菌分为4个类群,确定供试白粉菌之间的亲缘关系.     

提高稻瘟病菌转化频率的研究

 为提高pAN7-1质粒导入稻瘟病菌建立的遗传转化体系的转化率，进行了对转化效率影响因子的研究。稻瘟病菌转化溶液中使用50 mmol/L CaCl₂浓度，PEG4000 40%或PEG80000 40%多聚物，添加30 μg鲱鱼精DNA，供体质粒DNA呈直线状都有利转化频率的提高。其中鲱鱼精DNA作用尤为显著，由于添加30 μg鲱鱼精DNA，转化频率高达71.6转化子/μg DNA。42℃热冲击对稻瘟病菌转化并非必需，转化溶液中添加受体菌2539w DNA后，反而引起转化频率的明显下降。     

POSS/polypropylene hybrid nanocomposite monofilaments by reactive extrusion

The Allyl-heptaisobutyl-polyhedral oligomeric silsesquioxane (AHO-POSS) grafted polypropylene (PP) was prepared by reactive extrusion and by physical blending routes. The structure and properties of physically blended and reactively blended POSS/PP nanocomposites were investigated by FTIR, wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis, SEM, spherutlic growth and mechanical properties studies. Chemical bonding of POSS with PP in reactive extrusion was confirmed by FT-IR spectroscopy. DSC and TGA studies showed that the thermal stability of AHO-POSS/PP nanocomposite prepared by reactive extrusion improved significantly as compared to only physically blended nanocomposites. WAXD studies showed decrease in crystallinity of the AHO-POSS/PP nanocomposites prepared by reactive extrusion. SEM studies showed aggregation tendency in case of physically blended AHO-POSS/PP nanocomposites. Spherulite growth studies show reactive blending retards spherulite growth in PP polymer.     

Preparation of Cu-BTC/PVA Fibers with Antibacterial Applications

In this study, a metal-organic framework (MOF)/polymer electrospun fiber was prepared. The MOF, copper-1,3,5- benzenetricarboxylate (Cu-BTC), was synthesized using a sonochemical method at 25 °C, with a 1:1:1 mixture of dimethylformamide, ethanol, and deionized water as solvent. The sonication time was shown to have a pronounced effect on the morphology and structure of the Cu-BTC. A square pyramid shape with sides of 100 nm was obtained after 2 h of sonication. Extending the sonication time provided a lower amount of unknown phase and produced a uniform Cu-BTC framework. The Cu-BTC-modified PVA fibers were then fabricated by electrospinning. The effect of the Cu-BTC and PVA concentration was investigated at 25 kV, a flow rate of 10 μl/min, and a working distance of 150 mm. FTIR spectra and FESEM images showed good dispersion of the Cu-BTC on the PVA fiber. The as-prepared Cu-BTC-modified PVA fibers exhibited excellent antibacterial effectiveness against S. aureus.     

茉莉花茶香气的SPME/GC-MS检测方法

为建立茉莉花茶香气的固相微萃取/气相色谱-质谱(SPME/GC-MS)联用的快速检验方法,以"春毫茉莉花茶"为材料,研究萃取头类型、吸附温度、吸附时间和样品量对SPME吸附茉莉花茶香气的影响,同时研究脱附时间对SPME中茉莉花茶香气脱附效果的影响.结果表明:应用SPME/GC-MS技术检测茉莉花茶香气,具有简便、快速、准确和灵敏度高等特点;测定茉莉花茶香气的推荐条件为用150 g茉莉花茶样品量、PDMS-100μm萃取头、在60℃下吸附2 h、脱附时间5 min.     

微型DPSA-1仪-SPCE微分电位溶出法同步快速检测茶叶中的铅、镉、铜

用微型DPSA-1仪结合丝网印刷碳电极(SPCE),以微分电位溶出法对茶叶中的铅、镉、铜进行同步快速检测。优化的试验参数如下:Hg2+浓度为3×10-4 mol/L,支持电解质为1.5 mol/L pH4.0的氯化铵溶液,富集电位-1.1 V,终止电位-0.2 V,富集时间200 s。在此条件下获得的检测结果在20～840μg/L(相当于茶叶中铅含量为1～42 mg/kg)范围内呈现良好的线性关系,铅的相关系数为r=0.99749,检出限为1.12μg/L(S/N=3);镉的相关系数为r=0.99740,检出限为1.09μg/L(S/N=3);铜的相关系数为r=0.99612,检出限为1.23μg/L(S/N=3)。研究了检测过程中存在多种干扰离子对于铅、镉、铜检测的干扰情况。试验所得检测结果与国标检测法进行t检验,无显著差异。比较常规的检测技术,微型DPSA-1型仪结合SPCE微分电位溶出法同步检测茶叶中的铅、镉、铜,是更加经济的一种快速检测方法,可实现样品的高比例筛检,还可推广应用于其他类型食品和环境样品中铅、镉、铜的同步快速检测。