共查询到19条相似文献，搜索用时 93 毫秒
1.
杨春蓉 《福建工程学院学报》2010,8(1)
通过模拟体液的特征配制特殊生理溶液,并以此生理溶液和胶原基质为矿化系统,观察和分析胶原基质在体外的矿化;结果发现:胶原在体外仿生矿化生成的矿物相为具有规则叶片状结构、低结晶度的碳酸羟基磷灰石;表明了羟基磷灰石矿物晶体在胶原的反应成核位点通过化学键合作用进行自组装,这种自组装结构受胶原大分子与羟基磷灰石晶体之间的相互反应以及胶原分子的自组装能力诱导。 相似文献
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杨春蓉 《福建工程学院学报》2018,(3):215-218
以透明质酸、胶原和生物玻璃为原料制备复合支架材料,并对其矿化性能进行研究。实验将透明质酸、胶原和生物玻璃按比例混合,再进行交联处理,冷冻干燥得到支架材料,最后将其浸入模拟体液进行矿化,分析生物分子在矿化过程中的作用机制。研究发现,该复合支架材料具有三维多孔的微观结构; 在模拟体液中的矿化产物为羟基磷灰石。胶原蛋白和透明质酸对溶液中钙、磷离子的亲和力构成了矿化机制的基础。且两种生物分子可相互键合,促进钙化。该支架具有良好的矿化性能,可用于骨缺损的修复。 相似文献
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胶原-磷酸钙复合物是最有应用前景的骨组织工程框架材料.论文通过扫描电镜、红外光谱等方法证明了复合物中的胶原与钙离子间存在配位作用.结果表明:矿化反应体系通过载钙胶原的自组装、磷酸钙矿化的相继过程,形成具有层状结构的复合物.分析了胶原生物矿化的机制. 相似文献
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生物模仿自装配的无机化胶原的纳米纤维(英文) 总被引：1，自引：0，他引：1
有序排列的纳米纤维集合体在自然界中普遍存在,例如骨骼、肌肉、头发.天然骨骼是一种复杂的生物无机化系统,它具有错综复杂的有序排列结构[1].它的集合形成是通过羟基磷灰石(HA)矿物在I型胶原有机间质中有序沉积而成.羟基磷灰石的晶形模型c轴取向与胶原纤维的取向一致.本文目标是制备一种似骨骼的磷灰石和磷灰石/胶原复合体.HA/胶原复合体的合成是用生物模仿策略,使复合体能与天然骨骼相似而能在临床广泛应用.复合体合成的关键步骤是在含水介质中胶原间质控制磷酸钙的成核和生长.但制备与骨骼相似而具有纳米尺度的任何材料,即使是最低等级有序排列组织的材料,也是一个挑战性问题.因为所制备的材料具有两种不相同的纳米相,有机和无机纳米相.已经研究出确定自装配HA/胶原复合体中胶原与矿物结晶之间的超结构关系.首次观测到一种新的胶原与羟基磷灰石复合体的自装配有序结构.已经研究成一种新型的骨骼代用材料,成功地进行了超过150例的临床实验. 相似文献
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脊椎动物通过进化选择了磷酸钙类磷灰石矿物来构建其牙齿和骨骼。本文描述了磷灰石在生物矿化过程中的关键特征,揭示了生物如何调制磷灰石的结构来控制矿物的组成和功能。通过以应用目的而进行的磷酸钙的合成与性能测试进行的研究,加深人们对磷灰石的化学和物理性质与其生长条件的敏感性有了更深刻的理解。 相似文献
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根据胶原生物矿化的原理和方法,制备不同条件下的明胶生物矿化样品,通过红外光谱分析,发现磷酸钙、氯化镁的存在引起明胶分子中酰胺Ⅰ、Ⅱ、Ⅲ带显著褪化,明胶生物矿化与胶原生物矿化的紫外光谱曲线也有相似之处,表明明胶与钙、镁离子存在配位作用,明胶也可能作为生物矿化的模板材料。 相似文献
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羟基磷灰石是人体硬组织中主要的无机成分,与人体组织具有良好的生物相容性,并能与骨组织形成骨性结合.对不同配方的原料预先进行压制成型,采用原位反应法在1 100℃烧结70 min制备多孔生物陶瓷,并对陶瓷的物相、微观相貌及吸水率进行了研究.实验结果表明:添加Y2O3,对合成HA的反应的催化效果最好,生成的生物陶瓷性能最佳. 相似文献
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李燕怡 《商洛师范专科学校学报》2014,(4):49-53
通过制备模拟体液来模拟人体环境对制备的多孔生物活性陶瓷进行生物相容性测试,将模拟体系温度、pH分别控制在36．5±1．5℃、7．3±1．5。将制备的多孔生物陶瓷浸泡在1．0倍与1．5倍的模拟体液中,分别培养2,4,6d。通过SEM观察培养之后多孔陶瓷材料的表面发现：培养生物玻璃多孔材料生长的羟基磷灰石状况良好,随着在模拟体液中生长时间的增加,生物玻璃矿化产生羟基磷灰石含量剧增以及磷灰石形貌发生变化。培养2d磷灰石在材料表面以及多孔内部延伸,羟基磷灰石生长尺寸可达到20μm,随时间延长玻璃表面生长出尺寸为10—100μm的树枝状结构磷灰石,培养6d有形状规则的片状磷灰石生成,尺寸达到100μm以上。 相似文献
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目的:对应用接枝的羟基磷灰石(g-HA)/聚乳酸-羟基乙酸共聚物(PLGA)纳米复合支架接种自体骨髓间充质干细胞(MSCs)和骨形态发生蛋白2(BMP-2)治疗重症骨缺损的新的治疗策略进行评估,并通过肌肉内移植研究人工骨的组织相容性和移植物在体内的矿化和缺损骨的愈合。创新点:改性的PLGA接种自体MSCs的组织工程骨加速了骨缺损的愈合,使临床重症骨缺损的治疗有了新的手段。方法:应用溶剂浇铸和粒子沥滤方法将PLGA和g-HA制备成复合支架g-HA/PLGA。在g-HA/PLGA支架上接种兔自体MSCs制成组织工程移植物。取宽0.3 cm长2.0 cm的上述移植物埋入兔背部肌肉内,8周后取出移植物,使用扫描式电子显微镜(SEM)检测人工骨的组织相容性(图3a),X射线能量色散谱(EDX)分析钙浓度。然后,用锯锯掉兔前肢桡骨骨干2.0 cm,取同样长度的上述移植物放置于骨缺损处(图4)。术后2、4、8周应用计算机X线摄影(CR)检测骨缺损愈合情况(图5),组织学分析愈合组织结构(图6),SEM检测人工骨与周围组织的相容性(图7),反转录聚合酶链式反应(RT-PCR)检测愈合组织Collagen I、Collagen II和Bmp-2基因的表达。结论:PLGA掺入g-HA主要改善了矿化作用,有益于骨相关基因的表达和骨形成。自体MSCs的应用增强了骨形成和PLGA支架的矿化作用,并加速了支架的吸收。 相似文献
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This study examined the effects of metacognitive scaffolds on learning outcomes of collaborating students in an innovative
learning arrangement. The triads were supported by computerized scaffolds, which were dynamically integrated into the learning
process and took a structuring or problematizing form. In an experimental design the two experimental groups receiving scaffolds
were compared with a control group. The experimental groups differed in the form of scaffolding used: structuring scaffolds
versus problematizing scaffolds. We analyzed the effects of metacognitive scaffolding and of different forms of scaffolds
on the learning outcomes at group and individual level. The results showed no effect of scaffolding on group performance,
nor on the acquired individual domain knowledge, but a small effect on acquired individual metacognitive knowledge. With respect
to the effects of different forms of scaffolds, we found a small effect on group performance, on transfer of individual domain
knowledge and on the individual metacognitive knowledge acquired. 相似文献
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Martina S. J. van Uum Roald P. Verhoeff Marieke Peeters 《International Journal of Science Education》2013,35(18):2461-2481
ABSTRACTThis paper describes a multiple case study on open inquiry-based learning in primary schools. During open inquiry, teachers often experience difficulties in balancing support and transferring responsibility to pupils’ own learning. To facilitate teachers in guiding open inquiry, we developed hard and soft scaffolds. The hard scaffolds consisted of documents with explanations and/or exercises regarding difficult parts of the inquiry process. The soft scaffolds included explicit references to and additional explanations of the hard scaffolds. We investigated how teacher implementation of these scaffolds contributed to pupils’ self-directed learning during open inquiry. Four classes of pupils, aged 10–11, were observed while they conducted an inquiry lesson module of about 10 lessons in their classrooms. Data were acquired via classroom observations, audio recordings, and interviews with teachers and pupils. The results show that after the introduction of the hard scaffolds by the teacher, pupils were able and willing to apply them to their investigations. Combining hard scaffolds with additional soft scaffolding promoted pupils’ scientific understanding and contributed to a shared guidance of the inquiry process by the teacher and her pupils. Our results imply that the effective use of scaffolds is an important element to be included in teacher professionalisation. 相似文献
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Chia‐Yen Feng Ming‐Puu Chen 《British journal of educational technology : journal of the Council for Educational Technology》2014,45(2):285-302
The purpose of this study was to investigate the influence of goal specificity and scaffolding on the programming performance and self‐regulation of elementary students engaged in learning game design. This study recruited 232 students for the experimental activities. Two levels of goal specificity were employed: specific and nonspecific. Structuring and problematizing scaffolds were also used to support students in the process of learning. Our results reveal the following: (1) nonspecific goals and structuring scaffolds led to superior comprehension of programming, (2) nonspecific goals with problematizing scaffolds led to better problem‐solving performance, (3) problematizing scaffolds were more effective than structuring scaffolds in the development of self‐regulation behavior, and (4) nonspecific goals were more effective than specific goals in the promotion of resource management associated with self‐regulation. 相似文献
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Saniye Tugba Bulu Susan Pedersen 《Educational technology research and development : ETR & D》2010,58(5):507-529
This study investigated the effects of domain-general and domain-specific scaffolds with different levels of support, continuous
and faded, on learning of scientific content and problem-solving. Students’ scores on a multiple-choice pretest, posttest,
and four recommendation forms were analyzed. Students’ content knowledge in all conditions significantly increased from pretest
to posttest. However, the continuous domain-specific condition outperformed the other conditions on the posttest. Although
domain-general scaffolds were not as effective as domain-specific scaffolds on learning content and problem representation,
they helped students develop solutions, make justifications, and monitor learning. Unlike domain-specific scaffolds, domain-general
scaffolds helped students transfer problem-solving skills when they were faded. Several suggestions are discussed for making
improvements in the design of scaffolds to facilitate ill-structured problem solving. 相似文献
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Asmalina Saleh Chen Yuxin Cindy E. Hmelo-Silver Krista D. Glazewski Bradford W. Mott James C. Lester 《科学教学研究杂志》2020,57(9):1490-1518
Collaborative inquiry learning affords educators a context within which to support understanding of scientific practices, disciplinary core ideas, and crosscutting concepts. One approach to supporting collaborative science inquiry is through problem-based learning (PBL). However, there are two key challenges in scaffolding collaborative inquiry learning in technology rich environments. First, it is unclear how we might understand the impact of scaffolds that address multiple functions (e.g., to support inquiry and argumentation). Second, scaffolds take different forms, further complicating how to coordinate the forms and functions of scaffolds to support effective collaborative inquiry. To address these issues, we identify two functions that needed to be scaffolded, the PBL inquiry cycle and accountable talk. We then designed predefined hard scaffolds and just-in-time soft scaffolds that target the regulation of collaborative inquiry processes and accountable talk. Drawing on a mixed method approach, we examine how middle school students from a rural school engaged with Crystal Island: EcoJourneys for two weeks (N=45). Findings indicate that hard scaffolds targeting the PBL inquiry process and soft scaffolds that targeted accountable talk fostered engagement in these processes. Although the one-to-one mapping between form and function generated positive results, additional soft scaffolds were also needed for effective engagement in collaborative inquiry and that these soft scaffolds were often contingent on hard scaffolds. Our findings have implications for how we might design the form of scaffolds across multiple functions in game-based learning environments. 相似文献
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Scaffolding features that provide multimodal support for the pronunciation and meaning of words are increasingly common in digital reading environments. These vocabulary scaffolds are intended to aid the accurate pronunciation and understanding of individual words in context, thus supporting both vocabulary development and comprehension of text. However, the evidence on their efficacy remains inconclusive. The present study adds to the evidence base by examining: 1) whether child characteristics predict the use of vocabulary scaffolds; 2) whether the use of vocabulary scaffolds is associated with reading comprehension performance; and 3) whether the association between the use of scaffolds and reading comprehension is modulated by child and/or item characteristics. A large cohort (N ∼ 120,000) of 5- to 8-year-old children in the United States interacted with a gamified digital reading environment with embedded vocabulary scaffolds, thereby generating a large observational dataset of user log files. Confirmatory analyses with Generalized Linear Mixed Models (GLMMs) indicated that children with lower literacy skills, beginning readers, girls, and bilingual students were more likely to use the scaffold. Overall, the use of scaffolds was associated with better reading comprehension performance. The association between the use of scaffolds and reading comprehension was modulated by both child and item characteristics. We conclude that vocabulary scaffolds may be promising tools to facilitate reading comprehension and reduce performance differences amongst diverse learners in digital reading environments. Educational implications and recommendations for future research are discussed. 相似文献
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We investigated how 2 different curricular scaffolds (context-specific vs. generic), teacher instructional practices, and the interaction between these 2 types of support influenced students' learning of science content and their ability to write scientific arguments to explain phenomena. The context-specific scaffolds provided students with hints about the task and what content knowledge to use in or incorporate into their writing. The generic scaffolds supported students in understanding a general framework (i.e., claim, evidence, and reasoning) regardless of the content area or task. This study focused on an 8-week middle school chemistry curriculum that was enacted by 6 teachers with 578 students during the 2004–2005 school year. Analyses of identical pre- and posttests as well as videotapes of teacher enactments revealed that the curricular scaffolds and teacher instructional practices were synergistic in that the effect of the written curricular scaffolds depended on the teacher's enactment of the curriculum. The context-specific curricular scaffolds were more successful in supporting students in writing scientific arguments to explain phenomena, but only when teachers' enactments provided explicit domain-general support for the claim, evidence, and reasoning framework, suggesting the importance of both types of support in successful learning environments. 相似文献