聚烯烃共混物分散相尺寸梯度分布形态形成速度影响因素的研究

研究了聚烯烃高分子共混物的初始相形态及相间界面张力的改变对退火热处理条件下共混物分散相尺寸分布梯度形态形成速度的影响．通过控制共混物共混过程中Ｂｒａｂｅｎｄｅｒ转子的转速来控制共混物所受的剪切力大小，可达到控制共混物初始相形态的目的．通过ＳＥＭ电镜观察相形态，并利用计算机图象分析仪得到分散粒子的粒径及其分布数据．研究结果表明，转子转速越大，即共混物所受的剪切力越大，分散相初始粒径越小，且分散也越均匀．初始粒径较小的样品退火后形成梯度的速度相对较快．选用体系聚丙烯（ＰＰ）／乙烯 醋酸乙烯酯共聚物（ＥＶＡｃ）、聚乙烯（ＰＥ）／ＥＶＡｃ及改变ＥＶＡｃ中的醋酸乙烯酯（ＶＡｃ）含量与ＰＥ共混对比研究了不同相界面张力对梯度化速度的影响．结果表明，上述各体系退火热处理后均可形成梯度相形态，且相间界面张力越大．高分子共混物中梯度相形态形成速度也越快     

Expression of human β-defensin-2 with multiple joined genes in Escherichia coli

Human β-defensin (HBD)-2 is a small cationic peptide with a broad range of antimicrobial activity. In this study, multiple copies of the hBD2 gene were linked in tandem, and a number of different Escherichia coli expression vectors were evaluated, including pQE-30, pBV220, pET-28a(+), and pGEX-4T-2. No expression of multiple joined genes was detectable in the pQE-30 expression system, whereas in pBV220 with one or two joined hBD2 genes and in pET-28a(+) with one, two, or four copies, target proteins were expressed at a low level. Only when pGEX-4T-2 was applied as expression plasmid with one or two joined hBD2 genes were target proteins expressed in high level, and the expressed fusion proteins account for 26 and 16% of the total insoluble proteins, respectively. In the pGEX-4T-2 and pET-28a(+) expression systems, the effects of multiple joined genes on the growth of host strains and plasmid stability were examined. Host cells containing plasmid carrying fewer copies of hBD2 genes were faster in cell growth. Plasmid stability decreased with an increase in multiple joined genes, which was especially noticeable in the pET-28a(+) system. Furthermore, the presence of glucose in culture medium brought about a positive effect on plasmid stability when using pET28-nhBD2 as expression vectors.     

Synthesis of thioglycoside-based UDP-sugar analogues

Arbuzov reaction of O-acetyl-protected glycosylthiomethyl chlorides with triethyl phosphite and then phosphonate ethyl ester cleavage with trimethylsilyl bromide afforded glycosylthiomethyl phosphonates 13, 18, 22, and 26. These intermediates could be readily transformed into the O-deprotected phosphonates 7-10 and into title compounds 1-4. Similarly, sulfonomethyl phosphonate moieties containing UDP-sugar analogues 5 and 6 were obtained.     

Preparation of LiCoO2 cathode materials from spent lithium–ion batteries

Preparation of LiCoO₂ cathode materials from spent lithium–ion batteries are presented. It started with the reclaim/recycle of metal values from spent lithium–ion batteries, which involves the separation of electrode materials by ultrasonic treatment, acid dissolution, precipitation of cobalt and lithium, followed by the preparation of LiCoO₂ cathode materials. Co (99.4%) and Li (94.5%) were recovered from spent lithium–ion batteries. The LiCoO₂ cathode materials prepared from the reclaimed cobalt and lithium compounds showed good elecrtochemical performance. The reclaiming of cobalt and lithium has a promising outlook for the recycling of cobalt and lithium from spent Li–ion batteries, thus reducing the cost of Li–ion batteries.     

北京切诺基吉普车点火系统工作原理与检修

本文介绍了北京切诺基吉普车点火系统的结构,工作原理及检修.     

基于实验的心肌被动力本构模型

在狗心脏外科手术和心肌力学性能试验的基础上,对心肌力学性能实验数据进行处理和拟合,并应用有限元方法对心肌的单拉实验、松弛实验进行数值模拟和计算. 得到不同心肌位点的本构模型的非线性弹性和黏性参数,从而发展了心肌被动力的非线性黏弹性本构模型,体现了心脏力学行为的非均匀性和黏弹性. 在理论模型和试验数据的基础上,开发了有限元软件ABAQUS的VUMAT材料子程序,应用于数值心脏的仿真研究.      

Synthesis of an S-linked glycopeptide analog derived from human Tamm-Horsfall glycoprotein

Direct base catalyzed S-glycosylation of a cysteine and a homocysteine containing peptide with O-acetyl protected bromides in DMF-water solution furnished two glycopeptide fragments. The two glycopeptide fragments were linked to the target glycopeptide with two S-glycosyl residues mimicking a part of Tamm-Horsfall glycoprotein.     

SmxLa1-xP5O14和DyxY1-xP5O14晶体的荧光寿命研究

本文用脉冲衰减法和时间分辨荧光光谱法测量了六种不同稀土离子浓度的SmxLa1-xP5O4晶体的4G5/2→6HJ(J=5/2,7/2,9/2,11/2)四个能级和七种不同稀土离子浓度的DyxY1-xP5O14晶体的4F9/2→6HJ(J=15/2,13/2,11/2,9/2)四个能级的荧光寿命和荧光强度。结果指出,在这类晶体中,Sm3+和Dy3+的荧光寿命随着离子的浓度增加而变短,存在着严重的荧光浓度猝灭现象。最后还讨论了浓度与寿命,寿命与荧光强度的关系。     

铕的时间分辨激光荧光光谱分析：Ⅰ方法研究

本工作是在自建装置上，利用时间分辨激光荧光光谱技术，选择Ｅｕ－ＴＴＡ－ＥｔＯＨ液体荧光体系，建立了时间分辨激光荧光测定铕的方法。该测定铕离子的线性范围为０．０００２－１０μｇ／ｍｌ检测限为１０＾－５μｇ／ｍｌ。０．０３μｇ／ｍｌＥｕ＾３＋标准样品ＥｕＴＴＡ３，测定的相对标准偏差为４．７％，该法用于实际样品的分析测定，结果满意。结合铕的分析，对本方法选择化学体系的条件、测定装置的参数进行了讨论。并获     

Poly(acrylic acid)‐chitosan @ tannic acid double‐network self‐healing hydrogel based on ionic coordination

In this work, poly(acrylic) acid‐chitosan @ tannic acid‐aluminum ion (PAA‐CS@TA‐Al³⁺) double‐network hydrogel was prepared via prefabrication, blending method, and Al³⁺ immersion method. The interaction between chitosan and tannic acid (CS@TA) was analyzed using Fourier transfer infrared spectra and UV‐Vis spectra. The UV‐Vis spectrum was also used to confirm the formation of ionic coordination in the gel. Then, the possible coordination modes were studied and analyzed. The microscopic pore structure and macroscopic strain behavior of the gel were analyzed using SEM and tensile testing, respectively, which verified that the tensile strength (≈32 KPa) and elongation at break (≈1700%) of the gel primarily resulted from its crosslinking structure. In addition, the gel also demonstrated a good self‐healing performance with recovery ≈92.2% at 60 minutes. Hence, the proposed novel self‐healing gel can provide inspiration for the preparation of future self‐healing gels.