GAOR方法的收敛性

本文导出 GAOR 迭代矩阵谱半径的表达式,给出了在 L 矩阵情况下 GAOR 与 GSOR 迭代矩阵谱半径之间的关系,并在系数矩阵为 L 矩阵,H 矩阵,Hermitian 正定矩阵,严格对角占优矩阵及不可约对角占优矩阵的条件下,讨论了 GAOR 迭代的收敛性,进一步扩充了文[2]、[3]的结果.     

Controlled growth factor release from synthetic extracellular matrices

Polymeric matrices can be used to grow new tissues and organs, and the delivery of growth factors from these matrices is one method to regenerate tissues. A problem with engineering tissues that exist in a mechanically dynamic environment, such as bone, muscle and blood vessels, is that most drug delivery systems have been designed to operate under static conditions. We thought that polymeric matrices, which release growth factors in response to mechanical signals, might provide a new approach to guide tissue formation in mechanically stressed environments. Critical design features for this type of system include the ability to undergo repeated deformation, and a reversible binding of the protein growth factors to polymeric matrices to allow for responses to repeated stimuli. Here we report a model delivery system that can respond to mechanical signalling and upregulate the release of a growth factor to promote blood vessel formation. This approach may find a number of applications, including regeneration and engineering of new tissues and more general drug-delivery applications.     

杂草稻的分类地位和利用途径探讨

对海南岛杂草稻和亚洲栽培稻及其近缘野生种的形态特征和生长习性作了对比观察,表明杂草稻虽然易落粒和种子休眠性较强,但它们与伴生的栽培稻如蕊稻（深水稻）在外部形态和叶表皮微形态等上很相似．结合前人研究结果,探讨了杂草稻的来源,指出杂草稻应归入栽培稻籼粳二亚种,作为变种,同时,观察到杂草稻与杂交稻Ｆ１等一样,在叶片远轴面脉间两气孔带之间的几行长细胞中零星分布较多气孔,简称“中气孔”,指出这种异常现象可作为杂合程度的量化指标之一,在选育杂种性品种中有应用价值,杂草稻的杂种性繁殖机制和特异基因值得鉴定、研究和利用．     

微重力细胞培养与组织工程

组织工程主要致力于组织和器官的形成和再生，其核心就是建立细胞与生物材料的三维复合体，形成具有生命力的活体组织，用于对病损组织进行形态结构和功能的重建并达到永久性替代。目前有关微重力和模拟微重力条件下细胞体外生长的研究提示微重力培养环境有利于细胞体外增生，维持有功能的细胞长期生长，并且有助于形成组织样结构，使培养得到的组织更接近于活体组织。因此微重力细胞培养为组织工程的研究开辟了新的前景。     

Scatter factor is a fibroblast-derived modulator of epithelial cell mobility

Various factors are known to regulate cell growth and differentiation, but less is known of agents which affect movement and positioning, particularly in epithelial-mesenchymal interactions. Cultured human embryo fibroblasts release a protein with a relative molecular mass (Mr) of approximately 50,000 (50K) that affects epithelial cells by causing a disruption of junctions, an increase in local motility and a scattering of contiguous sheets of cells. To investigate specificity, a range of cells has been examined for the ability to produce the factor and for sensitivity to its action. Most freshly isolated normal epithelia and epithelia from cell lines of normal tissue, but not epithelia from tumour cell lines or fibroblasts, were sensitive to scatter factor. In contrast, production of the factor, as identified by activity and by chromatography, was restricted to embryonic fibroblasts and certain variants of 3T3 and BHK21 cells and their transformed derivatives. We conclude that the scatter factor is a paracrine effector of epithelial-mesenchymal interaction, which affects the intercellular connections and mobility of normal epithelial cells. The factor might be involved in epithelial migration, such as occurs in embryogenesis or wound healing.     

Recent Advances in Hard, Tough, and Low Friction Nanocomposite Coatings

Nanocomposite coatings demonstrate improved friction and wear responses under severe sliding conditions in extreme environments. This paper provides a review how thin film multilayers and nanocomposites result in hard, tough, low-friction coatings. Approaches to couple multilayered and nanocomposite materials with other surface engineering strategies to achieve higher levels of performance in a variety of tribological applications are also discussed. Encapsulating lubricious phases in hard nanocomposite matri- ces is one approach that is discussed in detail. Results from state-of-the-art ＂chameleon＂ nanocomposites that exhibit reversible adaptability to ambient humidity or temperature are presented.     

Incorporation of Sphingosine 1-Phosphate Loaded Mesoporous Silica Nanoparticles into Poly( L-lactic acid ) Nanofibrous Scaffolds for Bone Tissue Engineering

Controlled release of the functional factors is the key to improve clinical therapeutic efficacy during the tissue repair and regeneration.The three-dimensional(3D)scaffold can provide not only physical properties such as high strength and porosity but also an optimal environment to enhance tissue regeneration.Sphingosine1-phosphate(S1P),an angiogenic factor,was loaded into mesoporous silica nanoparticles(MSNs)and then incorporated into poly(L-lactic acid)(PLLA)nanofibrous scaffold,which was fabricated by thermally induced phase separation(TIPS)method.The prepared scaffolds were examined by attenuated total reflection Fourier transform infrared spectroscopy(ATR-FTIR),scanning electron microscopy(SEM),and transmission electron microscopy(TEM)and compressive mechanical test.The ATR-FTIR result demonstrated the existence of MSNs in the PLLA nanofibrous scaffold.The SEM images showed that PLLA scaffold had regular pore channel,interconnected pores and nanofibrous structure.The addition of MSNs at appropriate content had no visible effect on the structure of scaffold.The compressive modulus of scaffold containing MSNs was higher than that of the scaffold without MSNs.Furthermore,fluorescein isothiocyanate(FITC)was used as model molecule to investigate the release behavior of S1P from MSNsincorporated PLLA(MSNs/PLLA)nanofibrous scaffold.The result showed that the composite scaffold largely reduced the initial burst release and exhibited prolonged release of FITC than MSNs.Thus,these results indicated that S1P-loaded composite nanofibrous scaffold has potential applications for bone tissue engineering.     

对称及反对称三对角矩阵的特征向量

本文集中讨论了对称三角矩阵及反对称三对角矩阵的特征值、特征向量的性质,得到了由低阶对称三对角矩阵的特征向量构造反对称三对角矩阵的特征向量的方法,它们在矩阵计算中有着重要应用.     

亚正定阵的张量积初探

本文通过亚正定阵的标准形,得出了两个亚正定阵的张量积仍为亚正定阵的一个充要条件。     

Patterning the neuronal cells via inkjet printing of self-assembled peptides on silk scaffolds

The patterning of neuronal cells and guiding neurite growth are important for neuron tissue engineering and cell-based biosensors. In this paper, inkjet printing has been employed to pattern self-assembled I₃QGK peptide nanofibers on silk substrates for guiding the growth of neuron-like PC12 cells. Atomic force microscopy (AFM) confirmed the dynamic self-assembly of I₃QGK into nanofiber structures. The printed self-assembled peptide strongly adheres to regenerated silk fibroin (RSF) substrates through charge-charge interactions. It was observed that in the absence of I₃QGK, PC12 cells exhibited poor attachment to RSF films, while for RSF surfaces coated or printed with peptide nanofibers, cellular attachment was significantly improved in terms of both cell density and morphology. AFM results revealed that peptide nanofibers can promote the generation of axons and terminal buttons of PC12 cells, indicating that I₃QGK nanofibers not only promote cellular attachment but also facilitate differentiation into neuronal phenotypes. Inkjet printing allows complex patterning of peptide nanofibers onto RSF substrates, which enabled us to engineer cell alignment and provide an opportunity to direct axonal development in vitro. The live/dead assay showed that printed I₃QGK patterns exhibit no cytotoxicity to PC12 cells demonstrating potential for future nerve tissue engineering applications.     

DiI荧光标记示踪兔皮肤成纤维细胞修复前交叉韧带损伤的研究

体内采用组织工程方法构建前交叉韧带种子细胞筛选研究,提供了一种理想的细胞标记的方法.体外分离培养兔皮肤成纤维细胞(SF),比较皮肤成纤维细胞使用荧光染料CM-DiI体外标记前后细胞的生长状态、增殖活性以及检测SF复合纤维生物蛋白胶植入前交叉韧带上12周后的荧光表达情况.结果表明CM-Dil标记SF效果良好,标记阳性率高于95%.而标记前后SF增殖活性无明显变化,荧光标记在体内实验12周后仍有表达.从而证实CM-DiI是筛选前交叉韧带组织工程种子细胞筛选研究中细胞标记、示踪的良好标记物.     

岩石工程系统理论在边坡稳定性评价中的应用

现有的边坡稳定性评价方法不能考虑参数间的作用机理，和施工对整个边坡岩体天然性质的影响。而岩石工程系统理论将整个岩石工程视作一个系统来处理，能考虑岩石工程中各种不同因素，及其因素间的相互影响和施工对工程状态的影响。鉴此，在岩石工程系统理论的基础上，运用智能方法并结合样本，生成一个动态的网络结构，建立各边坡样本的岩石工程系统矩阵，然后求解各矩阵，并得出稳定状态边坡与非稳定状态边坡矩阵解的规律，以此提出边坡稳定性指数的概念。最后，利用此方法对福建紫金山金矿露天边坡稳定性进行了评价，并与极限平衡法得出的结果进行比较，得到一致的结论。     

稻属基因组间相关性的AFLP分析

应用AFLP（amplified restriction fragment length polymorphism)－银染法对2种栽培稻和21种野生稻的基因组多态性进行了检测,共计使用了9对选择性引物组合,扩增出602个遗传位点,通过Jacard的方法将电泳带矩阵转化为遗传相似性系数矩阵,并进行了聚类分析和主成分分析,结果表明,稻属植物按其亲缘关系的远近被分为三个大的类群：O.sativa群,O.officinalis群和其它远缘混合群,本文还对两种栽培稻的起源途径以及稻属物种的不同类型基因组间的缘关系进行了初步的探讨,为深入研究稻属物种间的进化关系提供参考。     

血小板上清液对家兔生长板软骨细胞增殖的影响

目的:观察人血小板上清液(hum an p latelet supernatant,hPS)对体外培养幼兔生长板软骨细胞增殖与分化的影响。方法:原代分离培养兔生长板软骨细胞并稳定传代,同时添加不同体积分数的hPS,采用W ST-8染色法检测细胞增殖倍数;A lc ian B lue法测基质蛋白多糖含量;羟脯氨酸法测定软骨细胞胶原产量,酶动力学方法测定碱性磷酸酶(ALP)活性。结果:体积分数5%hPS组显著促进软骨细胞的增殖以及基质蛋白多糖的合成,但形态上失去其软骨表型。各体积分数组hPS对总胶原的合成与对照组相比差异没有显著性意义,hPS抑制了ALP的活性。结论:hPS可以有效地促进生长板软骨细胞的增殖,抑制其肥大化。     

Cadherin-based biomaterials: Inducing stem cell fate towards tissue construction and therapeutics

The precise regulation of cell fate by biomaterials is one of the core focuses in tissue engineering and regenerative therapeutics. Cell fate is controlled by the niche signaling cues, including growth factors/morphogens, direct cell-cell contact, and extracellular matrix components. Here, we discuss how to bio-mimic cell-cell interaction by tailoring the interface of biomaterials to design effective scaffolds. Cadherins, as a key cell membrane protein family mediating the intercellular adherens junction, have attracted extensive attention in the functional modification of biomaterials. Therefore, cadherin-based biomaterials, their ability to modulate stem cell fate, and their applications in regenerative medicine are reviewed. Furthermore, we provide an outlook for exploiting the bio-mimic biomaterials in advanced cell therapeutics.     

BHK-21细胞在生物材料溶液中黏附及增殖比较

目的比较BHK-21细胞在3种生物材料溶液中黏附及增殖情况,探讨以类人胶原蛋白为基础制备组织工程材料的可行性。方法将BHK-21细胞分别种植于类人胶原蛋白、壳聚糖、透明质酸以及共混溶液中,在倒置显微镜下观察细胞的黏附和生长情况,并利用MTT方法检测种植后1～5 d细胞的增殖情况。结果BHK-21细胞种植12 h,类人胶原蛋白、壳聚糖以及两者共混溶液能显著促进BHK的黏附(P<0.01);BHK-21细胞在类人胶原蛋白溶液及类人胶原蛋白与其他生物材料共混溶液中功能活跃,维持其形态且能持续增殖,其中类人胶原蛋白/壳聚糖共混溶液促细胞增殖能力最强。结论类人胶原蛋白能够维持BHK细胞的生长与繁殖,在组织工程领域是一种极有潜力的组织工程材料。     

Haemonectin, a bone marrow adhesion protein specific for cells of granulocyte lineage

There is substantial evidence that the haematopoietic microenvironment is crucial to the growth and differentiation of haematopoietic cells. This microenvironment is composed of stromal cells, soluble factors and extracellular matrix (ECM). We have shown that a complex extract of bone marrow ECM can stimulate the growth and differentiation of haematopoietic cells in vitro. Furthermore, the use of inhibitors or stimulators of ECM synthesis in long-term marrow culture affects cell proliferation. On a molecular level, however, the interactions between ECM and haematopoietic cells are not well understood. We have investigated the adhesion between specific bone marrow ECM components and haematopoietic cells, and found a protein, 'haemonectin', of relative molecular mass 60,000 in bone marrow ECM which is a lineage- and organ-specific attachment molecule for cells of granulocyte lineage. This specificity distinguishes haemonectin from previously described adhesion proteins which have a wider tissue distribution and cell type specificity.     

Possible positive autocrine feedback in the prereplicative phase of human fibroblasts

The growth of normal diploid fibroblasts is generally thought to be tightly controlled by exogenous growth factors such as platelet-derived growth factor (PDGF) and epidermal growth factor (EGF). Subversion of a growth factor pathway at a regulatory point is considered to be a key event in neoplastic transformation and tumorigenesis. Thus, simian sarcoma virus has acquired the gene encoding the B-chain of PDGF and there is direct experimental proof that SSV-transformation is mediated by a PDGF-like growth factor. There is accumulating evidence that PDGF-like molecules are also synthesized and released by certain normal cells, suggesting an important role of cellularly produced PDGF in development and tissue regeneration. We now present evidence that a transient expression of the gene encoding the PDGF A-chain, and the synthesis and release of functional A-chain homodimers, is an early event in the prereplicative phase of normal human foreskin fibroblasts exposed to PDGF or EGF. Since these cells are PDGF-responsive, the results imply the existence of a positive autocrine signal that may serve as an amplifier of the mitogenic response under certain conditions.     

宇宙创生于真空涨落

讨论了宇宙的创生问题,发现共形不变物质场的真空单圈近似下的Brans-Dicke方程存在自洽、严格的宇宙解,且此解有初始奇点。无论是Einstein理论还是Brans-Dicke理论,都容许物质场的真空涨落创生宇宙。