Effects ofIn Vitro degradation on the weight loss and tensile properties of PLA/LPCL/HPCL blend fibers

PLA/LPCL/HPCL blend fibers composed of poly (lactic acid) (PLA), low molecular weight poly (ɛ-caprolactone) (LPCL), and high molecular weight poly (ɛ-caprolactone) (HPCL) were prepared by melt blending and spinning for bioabsorbable filament sutures. The effects of blending time and blend composition on the X-ray diffraction patterns and tensile properties of PLA/LPCL/HPCL blend fibers were characterized by WAXD and UTM. In addition, the effect ofin vitro degradation on the weight loss and tensile properties of the blend fibers hydrolyzed during immersion in a phosphate buffer solution at pH 7.4 and 37°C for 1–8 weeks was investigated. The peak intensities of PLA/LPCL/HPCL blend fibers in X-ray diffraction patterns decreased with an increase of blending time and LPCL contents in the blend fibers. The weight loss of PLA/LPCL/HPCL blend fibers increased with an increase of blending time, LPCL contents, and hydrolysis time while the tensile strength and modulus of the blend fibers decreased. The tensile strength and modulus of the blend fibers were also found to be increased with an increase of HPCL contents in the blend fibers. The optimum conditions to prepare PLA/LPCL/HPCL blend fibers for bioabsorbable sutures are LPCL contents of 5 wt%, HPCL contents of 35 wt%, and blending time of 30 min. The strength retention of the PLA/LPCL/HPCL blend fiber prepared under optimum conditions was about 93.5% even at hydrolysis time of 2 weeks.     

Assessment of Eicosapentaenoic Acid (EPA) Production from Filamentous Microalga Tribonema aequale: From Laboratory to Pilot-Scale Study

It has long been explored to use EPA-rich unicellular microalgae as a fish oil alternative for production of the high-value omega-3 fatty acid eicosapentaenoic acid (EPA, 20:5, n-3). However, none of the efforts have ever reached commercial success. This study reported a filamentous yellow-green microalga Tribonema aequale that possesses the ability to grow rapidly and synthesize significant amounts of EPA. A series of studies were conducted in a glass column photobioreactor under laboratory culture conditions and in pilot-scale open raceway ponds outdoors. The emphasis was placed on the specific nutrient requirements and the key operational parameters in raceway ponds such as culture depth and mixing regimes. When optimized, T. aequale cells contained 2.9% of EPA (w/w) and reached a very high biomass concentration of 9.8 g L⁻¹ in the glass column photobioreactor. The cellular EPA content was increased further to 3.5% and the areal biomass and EPA productivities of 16.2 g m⁻² d⁻¹ and 542.5 mg m⁻² d⁻¹, respectively, were obtained from the outdoor pilot-scale open raceway ponds, which were the record high figures reported thus far from microalgae-based EPA production. It was also observed that T. aequale was highly resistant to microbial contamination and easy for harvesting and dewatering, which provide two additional competitive advantages of this filamentous microalga over the unicellular counterparts for potential commercial production of EPA and other derived co-products.     

图书馆核心竞争力的研究与我馆核心竞争力构建的思考

对国内有关图书馆核心竞争力的研究进展进行了介绍,对解放军医学图书馆核心竞争力的构建进行了思考。

     

水稻类树状突变体s2-21的遗传分析与精细定位

叶序和出叶间隔期是叶片生长发育的基本生物学特性和水稻的重要农艺性状之一。对叶序或出叶间隔期突变体的研究,可以帮助我们了解叶片的形成机制。本研究以甲基磺酸乙酯(EMS)诱变粳稻品种日本晴,获得一个稳定遗传的类树状突变体s2-21。该突变体出叶间隔期变短、节间缩短、植株矮化、分蘖数减少、叶片数增加、不能正常进行生殖生长。将该突变体与籼稻品种Dular杂交,遗传分析表明该突变体性状受1对隐性基因控制。通过InDel分子标记对s2-21/Dular F₂群体进行遗传定位,将该基因初步定位在第1染色体InDel标记C1-15和S1-17之间。利用本实验已测序的籼稻品种Dular全基因组序列与NCBI (http://www.ncbi.nlm.nih.gov/)上提供的粳稻品种日本晴基因组序列比对,发展了6个新的InDel标记,最终将该基因定位在W25和W26之间约88 kb的区间内。测序结果表明该突变体中PLA2基因的第4个内含子的第5位碱基由G突变为A。     

不同工艺聚乳酸膜用于加热卷烟的降温性能研究

为探究不同工艺对聚乳酸膜(PLA)作为加热卷烟降温段材料的降温性能影响,采用吹塑、拉伸与流延等成型工艺制备了3种PLA膜并加工成相应的基棒,并考察了3种膜的热物性参数（热扩散系数与导热系数等）及降温段基棒对模拟热气流的降温效果。结果表明,拉伸膜在3种PLA基棒中的降温效果最优,3种基棒降温性能的优劣主要与其在成型过程中的热历史与受力史导致的分子链取向与结晶度差异有关。因此,通过调整PLA膜成型工艺可以调控其降温性能,能够为加热卷烟降温材料的设计与加工提供有益指导。     

聚乳酸纳米微球制备工艺研究

聚乳酸（PLA）由于良好的生物相容性和可降解性已被广泛应用于医学领域。以聚乳酸为载体材料制备农药传输系统可有效防止敏感型药物降解,延长农药的持效期。采用乳化-溶剂挥发法（O/W）制备了聚乳酸纳米微球,考察了表面活性剂的种类及浓度、有机相和水相体积比、聚乳酸浓度等因素对纳米微球粒径大小的影响,用扫描电子显微镜和透射电子显微镜对纳米微球的形貌进行表征,用纳米激光粒度仪对纳米微球的粒径和多分散指数进行了表征。结果表明：选择Tween20为表面活性剂,当Tween20浓度为0.01~0.03 g/mL、聚乳酸浓度为0.02 g/mL、有机相与水相比为1∶10,通过超声乳化可制得粒径为230~250 nm的纳米微球,并具有较好的分散性和成球性。进一步制备了聚乳酸-嘧菌酯纳米微球,表面活性剂的浓度是影响粒径的关键因素,当Tween20浓度为0.03 g/mL,所得纳米微球的粒径为236 nm,包封率和载药量分别可达81.38%和27.11%。本研究可为环境友好型聚乳酸纳米农药缓释微球的制备提供技术和参数支持。     

以科学发展观为指导，推进军队图书馆可持续发展

分析了制约图书馆可持续发展的主要因素,以科学发展观为指导思想,指出了军队图书馆实现可持续发展必须坚持改革创新。

     

毒死蜱-聚乳酸微球的制备及其性能评价

以毒死蜱为芯材,以生物可降解材料聚乳酸(PLA)为载体(壁材),采用溶剂挥发法制备了毒死蜱缓释微球,考察了芯壁材质量比及聚乳酸浓度对微球质量的影响。结果表明:当聚乳酸浓度增加时,载药量和包封率、粒径均随之增加;当芯壁材质量比减小(由1∶2减小至1∶5)时,微球粒 径、载药量也逐渐减小;包封率在芯壁材质量比为1∶3和1∶4时分别为89.88%±1.67%和90.55%±1.86%;当芯壁材质量比小于1∶2时,微球呈光滑完整的球形。差示扫描量热检测分析证明,毒死蜱和聚乳酸能够有机地结合为一体。表明合适的芯壁材比例和聚乳酸浓度有利于提高制备微球的质量。     

玉米秸秆纤维/聚乳酸复合材料的力学及降解性能研究

利用热压工艺制备得到了玉米秸秆纤维/聚乳酸复合材料,研究了玉米秸秆纤维的含量对复合材料力学及降解性能的影响。研究表明：随着玉米秸秆纤维含量的增加,复合材料的力学性能（拉伸强度、断裂伸长率）出现先增大后减小的变化趋势,在玉米秸秆纤维含量为10%时复合材料的断裂伸长率达到20.3%,复合材料的拉伸强度在玉米秸秆纤维含量13%时达到最大值24.38MPa;在降解120 d后,玉米秸秆纤维/聚乳酸复合材料的质量损失率变大,同时随着玉米秸秆纤维含量的增加,复合材料的质量损失逐渐变大,聚乳酸分子量的降低速度加快。     

军队院校图书馆开展深层次信息服务的必要性及方式

探讨了军队院校图书馆开展深层次信息服务的必要性和方式。