PLGA多孔支架降解与成骨细胞相互作用的影响

研究聚丙交酯-乙交酯(PLGA)多孔支架降解和大鼠股骨成骨细胞生理活性之间的相互影响.将大鼠股骨成骨细胞接种于PLGA多孔支架上,观察4周降解时间内成骨细胞增殖活性、碱性磷酸酶(ALP)活性和钙浓度的变化以及PLGA相对分子质量损失、拉伸性能和压缩性能的变化.实验结果表明,支架降解初期,成骨细胞增殖活性较高,ALP活性和分泌钙的浓度较低;支架降解中后期,细胞增殖速度明显减慢,ALP活性和分泌钙的浓度明显下降.接种有细胞的支架降解过程中相对分子质量减小的速度快于对照组,力学拉伸强度和压缩杨氏模量低于对照组.支架材料中后期降解对细胞产生的影响大于降解初期,细胞附着于支架的生理活动加快了支架降解速度.     

氨水改性对PGA/PLGA编织型输尿管支架管降解性能的影响

将聚乙交酯(PGA)和聚丙交酯乙交酯(PLGA)复丝在32锭编织机进行带芯编织后,经热定型处理得到编织型输尿管支架管,再对支架管进行氨水浸渍处理,得到改性PGA/PLGA输尿管支架管试样.将支架管试样置于人工尿液中,在温度为37℃、转速为60r/min恒温摇床中进行为期5星期的降解试验.通过测定降解过程中支架管拉伸强度和模量、压缩强度和模量、纤维表面形态、质量损失率,对支架管降解性能进行探讨.研究结果表明:支架管结构中膜结构的降解速度快于纤维结构;降解过程中经氨水处理的支架管的质量损失率大于未经氨水处理的支架管,经氨水处理支架管降解速率较快.     

PLGA的合成、表征及其导管支架的制备

用质量百分比为80％的L-丙交酯与20％的乙交酯进行开环聚合,得到聚（L-丙交酯-CO-乙交酯）（80／20）,并用红外光谱和氢核磁共振光谱进行了表征．对合成条件与PLGA相对分子量的关系进行了研究．研究结果表明,合成高分子量PLGA的最优条件是：聚合温度为140℃,反应时间为48h,单体与引发剂的摩尔比（n（M）／n（I））为8000／1．结合溶液浇铸与盐沥滤技术,PLGA被制作成多孔导管支架．PLGA导管支架具有相互连通的孔墙结构．     

新型生物降解材料输尿管支架的动物实验研究

探讨生物降解材料丙交酯／乙交酯共聚物（PLGA80：20）输尿管内支架的可行性,以16只家犬为实验动物,一侧输尿管施以离断吻合术,将PLGA支架管植于输尿管吻合局部支撑引流,分别于术后2、4、6、8及12周行静脉肾盂分泌造影检查,并取术侧输尿管行组织病理学分析。得到以下结果（1）10只实验动物术后支架管引流效果良好,支架管（6—8）周完全降解,术后肾盂分泌造影检查显示术侧肾盂、输尿管形态正常,无显影延迟;输尿管病理学改变轻微,主要镜下改变为移行上皮增生和固有层增厚。（2）3只实验动物术后早期支架管gI流效果良好,（6—8）周时一度出现术侧肾盂及中上段输尿管扩张积水、显影延迟,在术后12周缓解;输尿管病理学改变轻微。（3）2只实验动物术后早期即出现支架管移位,最终输尿管吻合处不同程度狭窄;解剖术区输尿管粘连,管腔变窄,管壁增厚;组织病理学检查发现输尿管全层炎症反应严重。（4）1只实验动物术侧肾盂输尿管始终不显影;解剖发现输尿管吻合口尿外渗,周围形成尿性囊肿。证明PLGA材料支架管生物相容性良好,降解时间适宜,尿液内引流效果尚可,但有关支架管的外型设计、固定方式等尚需进一步研究和改进。     

壳聚糖与端羧基PLGA接枝共聚物的制备与表征

壳聚糖与聚乳酸是具有良好生物相容性的高分子材料,已被广泛应用于生物材料,特别是作为组织工程支架.采用三甲基硅烷基(vMs)改性壳聚糖,4-二甲氨基吡啶(DMAP)催化,制备壳聚糖与端羧基PLGA的接枝共聚物.傅立叶变换红外光谱、核磁共振氢谱证实了共聚物的形成.热分析测试表明,共聚物具有不同于聚乳酸的热特性.接触角测试表明共聚物具有较好的亲水性.壳聚糖与端羧基PLGA的接枝共聚物具有较壳聚糖及聚乳酸更为优良的性能,可作为组织工程支架材料.     

缓慢成孔型磷酸钙复合材料的性能研究

目的制备并检测CPC—PLGA复合物,为骨组织工程研究提供新的支架材料．方法制备CPC—PLGA复合物,筛选最佳配比并检测其性能;将人骨髓间充质干细胞种植于CPC—PLGA复合物上并体外培养,然后进行扫描电镜观察．结果CPC-30％vol％PLGA力学性能最好,抗压强度40．5MPa,弹性模量13．8Gpa;模拟体液下降解6周材料形成100～300μm相互连通孔隙;骨髓间充质干细胞在支架材料表面生长良好,并通过降解产生的孔洞内材料深部长人．结论CPC—PLGA复合支架材料具有优良特性,适于骨组织工程支架．     

氯乙烯—丙烯酸丁酯共聚物热降解动力学的研究

用TG－DSC法研究氯乙烯（VC）－丙烯酸西酯（BA）共聚物的热降解动力学。考察了升温速率（β）、气氛对热降解的影响,在氮气气氛中,共聚物（VC－BA）的热降解反应是吸热反应,降解反应分两步进行。第一步是脱除支基,反应级数（n）为1.2级,活化能（E）为113KJ／mol;第二步是主链断裂,反应级数（n）随升温速率（β）的增大而减小,在空气气氛中,共聚物（VC－BA）的热降解反应是放热反应,降解分三步进行（第三步未完成）。第一步也是脱除支基,反应级数（n)为１.0级,活化能（Ｅ）为１１１.2KJ/mol;第二步亦是主链断裂,反应级数也随β增大而减小。     

氯乙烯-丙烯酸T酯共聚物热降解动力学的研究

用TG-DSC法研究氯乙烯(VC)-丙烯酸丁酯(BA)共聚物的热降解动力学.考察了升温速率(p)、气氛对热降解的影响.在氮气气氛中,共聚物(VC-BA)的热降解反应是吸热反应.降解反应分两步进行.第一步是脱除支基,反应级数(n)为1.2级,活化能(E)为113 KJ/mol;第二步是主链断裂,反应级数(n)随升温速率(β)的增大而减小.在空气气氛中,共聚物(VC-BA)的热降解反应是放热反应,降解分三步进行(第三步未完成).第一步也是脱除支基,反应级数(n)为1.0级,活化能(E)为111.2 KJ/mol;第二步亦是主链断裂,反应级数也随β增大而减小.     

制备附载rhTGF-β1的PLGA缓释支架及其对MSCs细胞形态的影响

为探讨自制的附载转化生长因子-β1(rhTGF-β1)的D,L-乳酸-CO-乙醇酸(PLGA)体外缓释生物支架对人骨髓间充质干细胞(MSCs)细胞形态的影响,制备了附载rhTGF-β1的PLGA生物支架,并检测了在PLGA的降解过程中rhTGF-β1的释药规律;同时分离培养人骨髓间充质干细胞,体外培养后分别接种于附载和未附载rhTGF-β1的PLGA支架上.通过扫描电镜观察不同时间段MSC在支架上的生长情况,实验结果表明,rhTGF-β1能被包裹进PLGA支架中,而且可在PLGA支架降解过程中持续释放出来.通过扫描电镜还观察到实验组支架上细胞呈多角或梭形,且有较多基质分泌,而对照组细胞较少.因此附载转化生长因子-β1的PLGA复合载体是一种较为理想的新型生物支架.     

无催化剂直接熔融缩聚合成聚乳酸-乙醇酸

以乳酸(LA)、乙醇酸(GA)为原料,在无催化剂、高真空条件下直接熔融缩聚合成聚乳酸-乙醇酸(PLGA)无规共聚物,对产物进行了GPC、FTIR、1H-NMR表征,并研究了反应时间、聚合温度、LA/GA投料比对PLGA分子质量的影响.结果表明:在所研究的聚合温度范围内,PLGA分子质量随聚合时间的延长先增大后减小;聚合温度越高,PLGA所能达到的最高分子质量越小,最佳聚合温度范围为160～170 ℃,最佳反应时间范围为57～69 h;在相同反应条件下,LA/GA投料比越小,PLGA分子质量越大.该研究为PLGA的合成提供一种安全、经济、有效的新途径.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.