1,721,039 research outputs found
The specificity of chitosan in promoting branching morphogenesis of progenitor salivary tissue
No full text
Roles of tomato ERF cluster B1-a in response to bacterial wilt and abiotic stress responses
No full text各種生物性及非生物性逆境造成植物生長過程受限，而青枯病 (bacterial wilt) 是全球最嚴重的作物病害之一，但目前對於植物如何抵抗這類土壤傳播病害的防禦機制了解仍少。植物特有的乙烯反應轉錄因子 (ethylene-response factors, ERFs) 屬於 APETALA2 (AP2)/ethylene-responsive-element-binding protein (EREBP) 超級家族中的家族成員之一，在植物的逆境訊息傳遞反應中扮演重要角色。本研究針對番茄 ERF B1-a 基因群五個成員 (分別命名為 SlERF B1a-1,-2,-3,-4,-5) 在植物青枯病及缺水相關逆境反應之功能進行探討。本研究顯示番茄 ERF B1-a 蛋白群均位於細胞核內，皆具抑制轉錄活性的功能，但此五個基因的表現在植物不同組織及對青枯病菌感染、缺水逆境或植物防禦荷爾蒙處理有獨特性，且 VIGS 分析結果也顯示這些基因植物在防禦青枯病與乾旱逆境的反應上各有特殊影響。綜合SlERF B1a-1 的過量表現與短暫靜默之結果，推斷此基因在青枯病害與鹽害扮演正面角色，但在乾旱逆境扮演負面角色；然而，SlERF B1a-3 則在鹽害扮演正面角色，但在青枯病害與乾旱逆境扮演負面角色。此外，這兩個基因也參與乙烯/茉莉酸相關防禦途徑的調節。另一方面，SlERF B1a-1 在阿拉伯芥中之同源基因 At5g44210 的完全缺失突變株在鹽害、模擬乾旱、滲透壓、糖分及 ABA 之種子發芽率降低，但對青枯病、軟腐病及缺水逆境之反應則未有顯著改變。綜合目前結果顯示，五個 ERF B1a 基因可能對植物防禦反應及相關非生物逆境的耐受性各具獨特的功能。未來期望透過更深入探討 SlERF B1a 基因群在病害與非生物逆境之功能，建立 ERF B1a 基因群的抗逆境防禦機制與網絡。Plants constantly encounter a wide range of abiotic and biotic stresses, leading to tremendous crop losses. Plant bacterial wilt (BW), a serious vascular disease caused by Ralstonia solanacearum (Rs), is one of the most complex and serious crop diseases worldwide. However, information on plant defense response to systemic soil-borne diseases is very limited. Ethylene-response factors (ERFs) are a subfamily of the APETALA2 (AP2)/ethylene-responsive-element-binding protein (EREBP) transcription factor superfamily and unique to plants. ERFs play a pivotal role in plant signaling transduction pathways switching extracellular signals into cellular responses. In this study, roles of five uncharacterized members of tomato ERF cluster B1-a, namely SlERF B1a-1,-2,-3,-4,-5, in plant response to BW and water deficit (WD) are investigated. These ERFs localize in nucleus and confer transcriptional repression activity. These genes display differential transcriptional expression patterns in various tissues and under, treatments of Rs, drought and defense phytohormones, implying they may have distinct functions. VIGS assays further revealed their differential roles in tomato defense to BW and water deficit (WD) response. Results of functional analyses by VIGS and transgenic overexpression suggest that SlERF B1a-1 may play a positive role in defense to BW and salinity, and a negative role in drought. However, SlERF B1a-3 may play a negative role in defense response to BW and drought, and a positive role in salinity. Furthermore, functioning of these two genes involves ET/JA (ethylene/ jasmonic acid)-related pathways. On the other hand, reduced seed germination rates of Arabidopsis at5g44210 null mutants, an othorlogous gene of SlERF B1a-1, indicated a function of this gene in various abiotic stresses. However, mature plants of the null mutants displayed unaltered response to Rs, Pectobacterium chrysanthemi and drought treatments. Together, these results demonstrate important overlapping and differential roles of the studied ERF cluster B1-a members in plant response to biotic and abiotic stresses. These studies, along with further suggested analyses, are expected to decipher multiple functions of these proteins and to establish the related regulatory networks in plant stress responses
Characterization of Chitosan in Tissue Engineering f Salivary Gland Morphogenesis
No full text唾液腺是人體分泌腺的一種，其主要的功能在掌管唾液的分泌。分泌的唾液可幫助吞嚥和消化食物，也可幫助口腔健康的維護，具有殺菌、增強免疫能力、及減少蛀牙的功能。因此，若失去唾液腺功能，在生活品質上以及生理健康方面，均會受到相當大的影響。唾液腺功能的損失，可由唾液腺本身的疾病所造成，也可因接受醫療而導致，如頭頸部癌症的患者。當這類病患接受手術與後續的化學和放射線治療，唾液腺的功能會受到嚴重影響。這些病人因無充足的唾液分泌，常常會有口乾的症狀，因而伴隨生活上許多不便和健康的危害。然而，目前在臨床上，對於唾液腺功能缺損的症狀並無根本的治療方法。許多現有的治療方法多只針對症狀的暫時緩解，故很少能藉此得到口乾症狀的舒緩。有鑑於此，如何利用組織工程的技術，重現體內自然發育時唾液腺生成的過程，為重建唾液腺功能最理想的解決方式。液腺的發育起源於口腔的黏膜上皮。在組織生成初期，特定的口腔上皮層會進行組織特化。由於唾液腺為分枝之分泌管腺，故在發育過程中，分枝形態的建立是重要的階段。藉此過程，唾液腺得以利用有限的細胞數，在有限的生長空間中，發育出大量具有功能的唾液腺組織，以滿足體內生理上的需求。此外，這個分枝發育的過程也確立了唾液腺分泌唾腺的運送管道。經由精細連結的管道網路，使產生的大量唾液腺得以順暢地排至口腔，發揮唾液的功能。而在形態建立後的唾液腺發育，特化的唾液腺上皮層會進行分化，進而發育成完整的唾液腺體。去對於唾液腺的組織工程的研究，大多侷限於唾液腺的細胞層次。對具有複雜組織構造的唾液腺，這樣的組織工程技術尚未提供真正有效的解決方法。在這些具有複雜組織構造的分泌腺體，他們的功能大半決定於組織結構的形成，而非由單獨的細胞作用即可完成。故對於這些器官的再生，組織工程的研究必須去考量組織間結構形態的生成，及不同組織和細胞間的交互作用。然而，過去對於唾液腺的組織和其結構的再生，並無任何研究提出相關的進展。因此，在本研究中，我們採取組織工程的方法，去探討是否有適合的生醫材料，可用於體外培養系統中，重現或是促進唾液腺組織結構的生成。首先，我們觀察不同生醫材質對於唾液腺組織的影響。我們發現，唾液腺的上皮和間葉組織，其本身的組織特性會受培養時接觸的生醫材質影響。在適當的材料上，不但組織可維持其生物特性，而且組織間的交互作用亦可被引發，而促使形態生長分子和基質分泌，進而促進組織形態的發生。根據這樣的結果，我們進一步採取大規模的篩檢，藉由之前發現的一些材料特性和原則，去尋找最適當唾液腺發育的材料。對於唾液腺的組織，不同的生醫材料展現不同的特性，有些不但不會促使組織的交互作用，甚至影響組織的存活，我們嘗試過的材質包括人工合成或天然的，生物可分解性或非分解性的，以及生物來源的高分子。我們的結果顯示，具有幾丁聚醣材質的培養環境具有促使唾液腺組織形態發育的特質。們嘗試先用薄膜培養系統來觀察唾液腺組織的生成情形。在多方的嘗試下，幾丁聚醣所形成的薄膜對於唾液腺組織結構的再生有助益。唾液腺組織培養在這種系統的薄膜之上，可維持其原來的生存能力，並可增生及進行結構發育，而其效率遠大於其他的生醫材料。在詳細的機轉探討中發現，幾丁聚醣的薄膜可提供唾液腺組織一個良好的生存環境，這樣的組織支架可和培養的組織間產生互動，促使培養的組織分泌結構生成和形態發育所需的細胞外基質和相關分子，而且分泌出的細胞外基質可排列成組織在形態發育過程所需的特殊形態。除此之外，我們又研發出另一含幾丁聚醣的唾液腺組織培養系統，而使生醫材料形成的組織支架混合於組織培養液中。在這個方法中，我們發現唾液腺的結構，如分枝發育的形態，可在培養系統中，得到有效率的提升。在幾丁聚醣的培養系統上，這些和唾液腺組織互動所產生的形態決定因子仍保有其活性，可促使後續培養於上之唾液腺組織發育出相關的組織結構，而重現胚胎發育器官形成的過程。外，針對聚丁聚醣在唾液腺分枝結構形成的特異性，我們也進而加以比較。我們的結果發現，形態發生的效果和幾丁聚醣的濃度成正比，而且相似的化學結構物並不能重現幾丁聚醣的性質。而幾丁聚醣的單體也無法呈現這樣的效果，且高分子結構也非唯一的因素。然而，這樣的形態生成效果和聚丁聚醣的分子量有直接相關。當幾丁聚醣的高分子鍵結被打斷，形態發生的效果就會消失，這樣的結果告訴了我們有關幾丁聚醣的特異性和應用於組織形態再生的條件。液腺發育主要源自於唾液上皮細胞。在我們的系統中，一些已知的唾液腺上皮的形態決定因子，如纖維生長因子及肝素生長因子的功能均會被加強。這些因子不只在細胞增生的能力被提升，而且組織移動和趨化的能力也被向上調控，而得以促使唾液腺上皮更有效率地針對這些形態因子的調控加以反應。由於這樣含幾丁聚醣的唾液腺組織培養系統不含血清，因此可降低血清的製備和生物相容性的問題，減少了未來直接應用於臨床的阻礙。而且混合培養液的生醫材料，可使相關的培養條件不受空間的限制，增加其應用的可能性。這樣的結果提出了對構成組織支架的生醫材料一個新的發現，也首度利用組織工程的方法去重現唾液腺結構的生成。由於這樣的系統可更有效率的增進形態決定因子和生長因子的功能，使得往後的臨床應用問題得以解決，進而縮小實驗室成果與臨床運用、甚至規模量產的差距。液腺組織的再生和重建，是現今再生醫學和組織工程的重大挑戰。唾液腺是個主要負責唾液生產和調控的器官，其複雜的分枝結構形成了一個有效率的分泌管道。在這個系統中，每個負責細胞各司其職，藉由精密串連的管路，準確而足量地將唾液送至我們的口腔和上消化道去執行功能。我們的研究提出了對於模擬這些精細管路結構生成，首度有了組織工程的初步方法。然而利用組織工程的概念去重建細胞和組織功能，是一個重要但又相當複雜的研究方向。吾人期待藉由類似組織構造層面的研究突破，使得具有完整的結構和功能的組織器官可以生成。如此對於複雜器官再生醫學的進步，及利用組織工程技術重建人類器官的夢想，將踏出了邁向實現的一大步。Salivary gland is an exocrine gland that is responsible for saliva production, absorption, and regulation. In histology, salivary is a ramified tissue formed by interconnecting branches and ducts. The arborized architecture, which is formed by the developmental process of branching morphogenesis, is essential for salivary function. Branching morphogenesis is an efficient and ubiquitous process for creating a larger cellular area for metabolic requirement in developing many glandular organs. To regenerate the glandular organ, such as salivary glands, recapitulation of branching processes may be requisite. At present, though with the progress in preserving phenotypes and promoting differentiation of salivary cells for regenerative purpose, to facilitate the morphogenesis of salivary tissue by tissue-engineering approaches has never been thoroughly explored. In this study, the possibility of promoting salivary gland morphogenesis is explored by tissue-engineering approach step by step, and the way that the chitosan-based biomaterial affects salivary tissue morphogenesis is characterized. or the purpose of recapitulating salivary gland morphogenesis, the interaction between epithelia and mesenchyme is required. During the development of ectodermal organ, the epithelium interacts with the surrounding mesenchyme to form specific phenotypes by receiving the guiding morphogenetic information. We first use murine fetal submandibular gland (SMG) model and the biomaterials which had been explored for salivary cells regeneration to study the biomaterial effects on epithelial-mesenchymal interaction and salivary morphogenesis. It is found that viability, migratory ability, and tissue interaction of salivary tissue are largely affected by different biomaterials. When salivary tissue is cultured on an appropriate substratum, the epithelial-mesenchymal interaction and the tissue-specific morphogenesis could be induced. ext, we perform global screening to find out the best cultured biomaterial which is capable of promoting morphogenesis of salivary tissue. It shows that the biomaterial effects still exist when whole salivary progenitor tissues are used in the survey. Numerous biomaterials, including synthetic, natural, biodegradable, non-biodegradable, and biological-origin polymers have been investigated. It is found that the cell behaviors as well as the tissue morphogenesis of salivary origin are biomaterial-dependent. Among them, chitosan shows a superior morphogenesis-promoting capacity, which maintains tissue viability and promotes an appropriate tissue interaction for morphogenesis. hen chitosan is prepared in the membranous form, it is capable of providing a more preferential environment for salivary gland branch formation. After culturing SMG explants on chitosan membranes, secreted extracellular matrices distribute in a reticular manner and form thicker fibers beyond the extents of cell attachment, which are not found in other biomaterials. In addition, the conditioned chitosan membranes are able to further enhance SMG branching. The fact that the promoting effects are eliminated with collagenase treatment and that type I and III collagen are identified within the adherent fibrillar extracellular matrix raise the possibility that the stimulating factors are collagen-originated. Furthermore, when chitosan is prepared in a soluble form, the morphogenesis-promoting effects are also observed. This result indicates that chitosan is a bioactive substratum for salivary tissue morphogenesis which enables active interaction between cultured salivary tissue and biomaterial. Next, the specificity of chitosan’s morphogenesis-promoting effects is further investigated. It is found that chitosan is able to promote SMG branching in a dose-dependent manner. The effect is chitosan-specific and is not reproduced by substrates with similar chemical structures or by other polymeric molecules of natural or synthetic origin. Furthermore, the branch-promoting effect is molecular weight-dependent. In addition, following digestion with lysozyme, chitinase, or chitosanase, digested chitosan is unable to reproduce the similar effects. This study clarifies the specificity and preferential activity of chitosan in enhancing branching morphogenesis of progenitor salivary tissue. ith chitosan, the morphogenesis-promoting effects of mesenchymal tissue on SMG are further enhanced. Chitosan is also competent to induce recombined SMG epithelium to form branches in the serum-free condition. In the presence of chitosan, the morphogenetic efficacy of mesenchyme-derived growth factors responsible for epithelial morphogenesis increases. The specific epithelial phenotype induced by individual growth factor is promoted by chitosan as well. Moreover, the proliferative and the chemotactic properties of these growth factors toward SMG epithelia are also reinforced by chitosan. Therefore, in orchestrating and intensifying the essential mesenchyme-derived growth factors, chitosan is versatile in mediating SMG epithelium to form a predetermined phenotype more efficiently and comprehensively. n all, the current study demonstrates that the morphogenesis of salivary tissue could be regulated by tissue-engineering approaches. It is suggested that, for salivary tissue, chitosan is a morphogenesis-regulating biomaterial. We design a novel methodology to facilitate salivary tissue morphogenesis by enhancing branch formation. The results provide a novel insight into the role of chitosan in salivary tissue morphogenesis and highlight the potential for future application in salivary tissue investigation and regeneration.中文摘要 1bstract 6hapter 1. Introduction 10-1. Salivary gland 10-2. Xerostomia and treatment of salivary gland dysfunction 12-3. Branching morphogenesis and salivary gland development 13-4. Tissue engineering of salivary gland 15-5. Aims and study design of the dissertation 16hapter 2. The effect of biomaterials on epithelial-mesenchymal interaction and morphogenesis of progenitor salivary tissue 19-1. Introduction 19-2. Materials and Methods 22-2-1. Preparation and characterization of biomaterials 22-2-2. Culture of isolated salivary epithelia and mesenchyme 22-2-3. 3-(4,5-dimethylthiazol-2-yl)-diphenyl tetrazolium bromide (MTT) assay 23-2-4. Scanning electron microscopy 24-2-5. Salivary tissue recombination assay 24-2-6. Immunohistochemistry of type III collagen expression 25-2-7. Immunofluorescence of collagen expression and basement membrane formation 26-3. Results 28-3-1. Characterization of membranes 28-3-2. The biomaterial effects on the isolated salivary epithelia and mesenchyme 28-3-3. The interaction between biomaterial surface and salivary tissue 32-3-4. Type III collagen expression in the salivary epithelial-mesenchymal interface 34-3-5. De novo basement membrane synthesis in the salivary epithelial-mesenchymal interface 36-3-6. The morphogenesis of salivary tissue recombinants on biomaterials 38-4. Discussion 40hapter 3. Screening of biomaterials for branch enhancement of salivary gland 45-1. Introduction 45-2. Materials and Methods 47-2-1. Preparation and characterization of membranes 47-2-2. Organotypic culture of salivary gland 47-2-3. Degradation test 48-2-4. 3-(4,5-dimethylthiazol-2-yl)-diphenyl tetrazolium bromide (MTT) assay 49-2-5. Immunohistochemistry of collagen deposition 49-3. Results 51-3-1. Salivary gland morphogenesis on different biomaterials 51-3-2. Substrates degradation and associated effects on salivary gland morphogenesis 56-3-3. Salivary gland viability on different biodegradable biomaterials 58-3-4. Cell migration of salivary cells on biomaterials 60-3-5. Deposition of extracellular matrix of salivary gland on different biomaterials 62-4. Discussion 64hapter 4. The effects of chitosan on salivary gland branching morphogenesis 68-1. Introduction 68-2. Materials and Methods 70-2-1. Preparation and characterization of membranes 70-2-2. Medium and Reagents 70-2-3. Ex vivo organ culture of SMG explants 71-2-4. Scanning electron microscopy 72-2-5. Preparation and culture of SMG explants on conditioned membranes 72-2-6. Immunohistochemistry and quantification of collagen deposition 73-3. Results 75-3-1. Branching morphogenesis of SMG explants on PVA, chitosan and PC membranes 75-3-2. Extracellular matrix deposition on substrates after cultured with SMG explants 77-3-3. SMG branching on conditioned membranes 79-3-4. SMG branching on conditioned membranes treated with collagenase 81-3-5. Expression and quantification of collagen on conditioned membranes 83-3-6. Soluble chitosan promotes branching morphogenesis of SMG explants 86-4. Discussion 88hapter 5. The specificity of chitosan in promoting branching morphogenesis of salivary gland 93-1. Introduction 93-2. Materials and Methods 95-2-1. SMG ex vivo organ culture 95-2-2. Preparation of chitosan-containing culture medium 95-2-3. Preparation of chitosan monomers, analogues, and related polymeric substrates 96-2-4. Enzyme digestion assay 96-3. Results 98-3-1. Chitosan promotes SMG branching morphogenesis in a dose-dependent manner 98-3-2. Effects of GAGs on SMG branching morphogenesis 100-3-3. Effects of chitosan monomers and analogues on SMG branching morphogenesis 101-3-4. The effects of natural and synthetic polymers on SMG explant branching 103-3-5. The effect of chitosan molecular weight on SMG explants branching 105-3-6. The effect of lysozyme, chitinase, and chitosanase on the chitosan-mediating SMG branching morphogenesis 107-4. Discussion 112hapter 6. Mechanism of chitosan branch-promoting effects in salivary gland morphogenesis 116-1. Introduction 116-2. Materials and Methods 118-2-1. Submandibular glands ex vivo organ culture 118-2-2. Antisense oligodeoxynucleotides assay and the rescue experiments with fresh medium 119-2-3. Supplement of exogenous branching morphogens 119-2-4. Culture of SMG epithelium 120-2-5. Mesenchyme recombination assay 121-2-6. Cell proliferation assay 121-2-7. Chemotactic assay with HGF soaked beads 122-3. Results 124-3-1. Chitosan effects on the SMG morphogenesis with morphogen down-regulation 124-3-2. Synergism of chitosan and exogenous morphogens on SMG morphogenesis 127-3-3. The branching-promoting effects of mesenchyme were enhanced by chitosan 130-3-4. Chitosan effects on SMG epithelium morphogenesis with homotypic mesenchymal recombination in serum-free culture 132-3-5. Chitosan effects on SMG epithelial morphogenesis induced by FGF7, FGF10, and HGF 135-3-6. Chitosan effects on SMG cell proliferation induced by FGF7, FGF10, and HGF 140-3-7. The chemotactic capacity of HGF beads with chitosan 142-4. Discussion 145hapter 7. Conclusion and Perspective 150-1. Conclusion 150-2. Perspective 151eferences 153ppendix 16
Spin-Exchange Relaxation Free Potassium Atomicagnetometer in the Un-Shielded Environment
No full text精準測磁計的應用範圍相當的廣泛-從測試基本物理對稱性到生物磁場的測量。低溫導體量子干涉裝保持著最低的磁場雜訊的紀錄 － 1 fT / Hz 。然而超導體量子干裝置具巨大的儀器體積和昂貴的降溫系統限制了這項儀器的運用。近年來，利用鉀銣的鹼金屬的光學測磁計已經接近了超導體量子干涉裝置的磁場雜訊。這類型的光測磁計是利用量測金屬原子自旋極化的拉馬進動進而得到磁場的大小。而這類型光測磁計的基本雜訊限制就是量子雜訊，其大小和垂直磁場方向的自旋緩和速率有。 在零磁場附近操作的金屬原子測磁計可以減低此種自旋緩和的影響，進而得約0.3 fT / Hz 的磁場雜訊。為了屏蔽環境的磁場，有些系統使用高磁導率的金屬蔽或是使用荷姆霍茲線圈去抵銷外在磁場[8]。此論文利用參考文獻[8]的基，提出一個改進過後的無屏蔽系統，此系統改進要項為:資料利用電腦跟資料擷取處理、使用電光晶體雷射功率穩定器來降低系統雜訊，還有減少地磁抵銷所需的時等項目。Sensitive magnetometers find wide range of applications, from tests of fundamentalymmetries to measurements of biological magnetic fields. Low temperature SQUIDetector presently hold the record as the most sensitive magnetometers with a noise levelf about 1fT / Hz . However, its huge bulk due to the complex structure and high cost ofryogenic cooling confine its applications. Recently years, Alkali-metal magnetometerssing Potassium and Rubidium approach this level of sensitivity. The mechanism oftomic magnetometers relies on a measurement of Larmor precession of spin-polarizedtoms in a magnetic field. The fundamental noise is limited by the quantum shot noisehich is related to the transverse relaxation time of the spin polarized atoms.Thetomic magnetometers operating near zero field which eliminates spin exchange collisions the source of relaxation shows a fundamental noise limit which is about 0.3 fT / Hz .o block out environmental tray field, these systems apply μ -metal shield orelmholtz coil compensate system. This thesis proposes an improved version of then-shielded system in reference : the optical detection of the signals is processed by aAQ card and a computer to simplify the system, an EO stabilizer is introduced to lowerhe optical noise level in the detection, and a improved method is developed to reduce theime spent in field compensating.摘要 ..ibstract iiiontents vigures viihapter 1 Introduction to Electro-Optical Effects ...1.1. Introduction to Atomic Magnetometer ...1.2. Introduction to Linear Magneto-Optical Effects ...2.3. Introduction to Pump-Probe System ...5hapter 2 Experiment Setup and Apparatus ...11 .1. Experiment Setup Overall Diagram ...11.2. Probe and Pump Laser ...13.2.1. Probe Laser ... 13.2.2. Pump Laser ....14.3. EO Modulation and EO Feedback Power Control ...15.3.1. EO Modulation ... 15.3.2. EO Feedback Power Stablizer ...22.4. Lock-in Hardware, Software and DAQ (Data Acqusition) ..24.5. Current Source and Three Axis Helmholtz Coils ...27.6. Cell and Cell Holder and Heating ...28hapter 3 Experiment Method...29.1. Earth Field Compensate 29.2. Z- axis Field measurement 33.3. Vector Mode ...34.3.1. Theoritical Derivatoin ... 34.3.2. Experimental Setup ...35.3.3. Field Response and an alternative field compensation method ...39.3.4. Result ...42hapter 4 Summary ...46ibliography ... 4
Cladding of Cobalt-based and Nickel-based Alloy on Steel Surface Using High Frequency Induction Heating
No full text本研究是將Stellite 6鈷基合金粉末(Co-28Cr-4W-1.1C)和NiCrBSi型的鎳基合金粉末(Ni-14.4Cr-3.2B-4.4Si)事先預敷於中碳鋼及高碳鋼的表面，再用高週波感應加熱進行被覆處理。配合不同的製程參數，利用光學顯微鏡(OM)、電子微探儀(EPMA)與X光繞射分析儀(XRD)分析合金層顯微組織、化學組成以及相的鑑定，並以微硬度試驗機量測合金層的硬度分佈，之後再將試片浸泡於腐蝕液中，觀察其耐腐蝕能力。
研究結果顯示鈷基合金被覆層的組織可以區分為樹狀晶、樹枝間共晶組織及針狀組織三種。被覆層為樹狀晶與樹枝間共晶組織時，樹狀晶內為富鈷相固溶Cr、Fe等元素，共晶組織則為鈷的固溶體與碳化物M7C3，被覆層的硬度會隨著加熱時間增長而降低。但當被覆層中的Fe含量超過40％之後，被覆層組織會轉變為針狀組織，硬度則會隨著加熱時間增長而有升高的趨勢。
鎳基合金被覆層是由γ-Ni、Ni3B、Ni31Si12、CrB、Cr7C3及Ni-Cr-Fe化合物所組成。隨著加熱時間的增長，交界處的Ni-Cr-Fe化合物數量有變多，而CrB與Cr7C3數量則有減少的的趨勢，使得交界處的硬度略微降低。而被覆層中的CrB與Cr7C3隨著加熱時間的增長有粗大化的現象，使得強化相佔的比例增加，造成被覆層的硬度有上升的趨勢。而以高功率短時間進行被覆處理，被覆層中的CrB與Cr7C3數量較多，且單位面積中γ-Ni＋Ni3B佔的比例也比較多，使得被覆層的硬度較以低功率長時間進行被覆處理的為高。
經被覆鈷基或鎳基合金的試片對鹽酸、硝酸與硫酸的耐蝕能力都有顯著提升。不論是被覆鈷基或鎳基合金，隨著加熱時間的增長，被覆層的耐腐蝕能力會因為Fe的稀釋率上升而下降。In this research, Co-based alloy Stellite6（Co-28Cr-4W-1.1C）and Ni-based alloy Deloro60（Ni-14.4Cr-3.2B-4.4Si）were clad on carbon steel using high frequency induction heating. With different processing parameters, the properties of the clad layer were studied through observing the microstructure, measuring the chemical composition and hardness distribution, indentifying the phases in the layer, and conducting the corrosion test.
The results show that the microstructure of Co-based alloy layer can be divided into dendrite, interdendritic eutectics and needle structure. If the microstructure of the clad layer is dendrite and interdendritic eutectics, the matrix is Co-rich solid solution containing chromium, iron and other elements with network M7C3 carbide distributed along the grain boundary. The hardness of the clad layer will decrease with increasing the heating time. However, when the content of iron is more than 40％, the microstructure will transform into needle structure, and the hardness of the clad layer will increase with increasing the heating time.
Ni-based alloy layer consists of γ-Ni matrix, Ni3B, Ni31Si12, CrB, Cr7C3 and Ni-Cr-Fe compounds. The interface compound of Ni-Cr-Fe will increase and both CrB and Cr7C3 will decrease with increasing the heating time, leading to a slightly decrease in the hardness near the interface. In the clad layer, the coarsening of CrB and Cr7C3 becomes more obvious as the heating time increases. In other words, the volume fraction of hardening phases（CrB and Cr7C3）increases and lead to the increasing of hardness. High heating power and short heating time will increase the compounds of CrB and Cr7C3 as well as the volume fraction ofγ-Ni and Ni3B ,and lead to increase in hardness of the clad layer.
The specimen clad with Co-based alloy or Ni-based alloy has excellent resistance to the corrosion of hydrochloric acid, nitric acid and sulfuric acid. No matter which alloy is clad, the ability of anti-corrosion will decrease with increasing the heating time, owing to the dilution of iron in the clad layer
臺灣股票市場錯置效果之研究
No full text本研究主要利用臺灣某券商交易資料庫，仿造Odean(1998)之研究方法，檢定臺灣股票市場投資人是否有太快出售手中獲利的股票，傾向繼續持有損失的股票之現象，文獻上稱為『錯置效果』，並且考慮投資人有該行為可能的原因是為了要調整投資組合，樣本經假設與處理後，進行錯置效果之檢定，並且利用不同的區隔變數將投資人區隔成若干群體，分別對不同群體作錯置效果之檢定。
研究發現臺灣股票市場存在有錯置效果，與國外論文不同處是錯置效果的存在不會影響投資人的投資績效，經過檢定後發現，臺灣股票市場投資人發生錯置效果的原因可能是為了調整投資組合，經股齡與年齡分群後發現股齡最高的投資人有顯著的錯置效果，可能的解釋為臺灣股票市場散戶投資人較多，週轉率高，所以股齡較高的投資人投資經驗豐富，對投資組合的調整也較迅速。若是經有無信用交易戶與期貨交易戶分群後，發現有信用交易戶與期貨交易戶的投資人有顯著的錯置效果，因為信用交易是具有槓桿作用的投資工具，根據展望理論將會加深錯置效果。根據擇股擇時能力將投資人區分後，發現績效較好的投資人有顯著的錯置效果，這表示擇股擇時能力較佳的投資人調整投資組合的能力出色，享有較高的投資報酬，但受限於資料的完整性，無法進一步分析擇股擇時能力的準則。The tendency to hold losers too long and sell winners too soon has been labeled the Disposition Effect. The purpose of this thesis is test the hypothesis of the existing of Disposition Effect in Taiwan stock market by learning the research method of Odean(1998) and analyzing the trading records at a local brokerage house. These investors demonstrate a preference for realizing winner rather than loser. Their behavior may be motivated by a desire of rebalance portfolios. A different result shows no negative relation between disposition effect and investment returns opposite from Odean(1998). Then I segment the samples by some variables s, and verify the said Disposition Effect on each segment.
From this research it is realized that the Disposition Effect does exist in Taiwan stock market, however its existence shows no influence to investors’ performances, this result apparently differs from the one overseas. The segments of experience and age shows that the much more experience the investors have, the more obvious Disposition Effect appears on them. The majority of Taiwan stock market is currently individual investors, and features high turnover rate, therefore the investors experienced more makes a prompter portfolios re-balance. The segments of marginal trading and future trading shows that Disposition Effect appears on both these accounts, since the margin trading is an investment tool featured leverage, depending on prospect theory enhances the Disposition Effect. The segments of investors’ timing and selection ability shows that Disposition Effect appears on those investors having superior performances, which also implies that these investors seems to be specialized in portfolios re-balance and attains higher investment return. Unfortunately, due to the difficulty on gathering the source, it cannot go further to analyze the criteria of timing and selection ability verification.目錄 ....................................................Ⅰ
圖(表)次 ................................................Ⅱ
第一章 序論 ............................................. 1
第一節 研究背景與動機 ......................................... 1
第二節 研究目的 ............................................... 2
第三節 研究架構 ............................................... 3
第二章 文獻探討 .................................. 4
第一節 行為財務理論發展 ....................................... 4
第二節 文獻回顧 ............................................... 8
第三章 研究方法 ................................. 49
第一節 資料來源與處理 ........................................ 49
第二節 資料假設與限制 ........................................ 51
第三節 變數定義與檢定統計量 .................................. 52
第四節 資料分析方法 .......................................... 54
第四章 實證結果分析 ............................. 57
第一節 臺灣股票市場錯置效果 .................................. 57
第二節 依變數分群後之錯置效果 ................................ 61
第五章 結論與建議 ............................... 67
第一節 研究發現與投資策略 .................................... 67
第二節 研究限制 .............................................. 69
第三節 後續研究建議 .......................................... 70
參考文獻 ........................................ 72
圖(表)次
圖2-1 價值函數..............................................13
圖2-2 決策權重函數..........................................13
圖2-3 價值函數-1............................................15
圖2-4 價值函數-2............................................15
圖3-1 臺灣加權股價日線圖，2000年1月至2000年6月 ..........50
圖4-1 投資人年齡層分布百分比................................57
圖4-2 投資人股齡分布百分比..................................58
圖4-3 有無使用期貨交易戶與信用交易戶之比例..................58
圖4-4 依股齡分類後之PGR/PLR.................................61
圖4-5 依年齡分類後之PGR/PLR.................................62
圖4-6 依有無期貨交易與有無信用交易分類後之PGR/PLR...........64
圖4-7 依同時具有與同時不具有期貨、信用交易戶分類之PGR/PLR...64
圖4-8 依擇時擇股能力分群後之PGR/PLR.........................66
圖4-9 投資人擇時擇股能力區隔命名............................66
表4-1 整體資料庫PGR與PLR...................................59
表4-2 10個交易日內沒有買入新股之PGR和PLR...................59
表4-3 剔除10個交易日內沒有買入新股之PGR和PLR..............59
表4-4 調整投資組合與非調整投資組合投資人獲利率比較...........60
表4-5 賣出獲利股票與帳上損失股票10、20個交易日後之平均報酬率....60
表4-6 依股齡分群後之PGR與PLR...............................61
表4-7 依年齡分群後之PGR與PLR...............................62
表4-8 依信用交易、期貨交易分群後之PGR與PLR.................63
表4-9 依信用交易與期貨交易分群後之PGR與PLR.................64
表4-10 依擇股擇時能力分群後之PGR與PLR.......................6
Vestibular-Evoked Myogenic Potentials in Patients with Otosclerosis Using Air- and Bone-Conducted Tone-Burst Stimulation
No full textObjective: Otosclerosis is a progressive disease with a remodeling process causing ossicular malformation and conductive hearing loss. The aim of this study was to investigate whether vestibular-evoked myogenic potential ( VEMP) correlates with the progression of otosclerosis. Design: Fifteen patients with otosclerosis (21 ears) without operation and 10 healthy subjects (20 ears) underwent VEMP test using air-conducted (AC) and bone-conducted (BC) tone- burst stimulation. Setting: Tertiary referral university hospital. Results: In 21 unoperated otosclerotic ears, 5 ears (24%) showed present AC-VEMPs, and 16 ears had absent ACVEMPs. Conversely, 16 ears (76%) displayed present BC- VEMPs and 5 ears with absent BC-VEMPs. In those with both AC - and BC-VEMPs, none of them showed air-bone gap greater than 30 dB; in those with absent AC-VEMPs but present BC- VEMPs, 27% of the ears had air-bone gap greater than 30 dB; and in those with absence of both AC- and BC-VEMPs, 80% of the ears revealed air-bone gap greater than 30 dB. Thus, a significant relationship existed among the presence of AC- VEMPs, BC-VEMPs, and magnitude of conductive hearing loss. Conclusion: The presence of an AC-VEMP may indicate an earlier stage of otosclerosis, although absent BC-VEMP infers a later stage. Restated, AC-VEMPs may complement the results obtained with BC-VEMPs to classify the stage of otosclerosis
Chitosan Cooperates with Mesenchyme-Derived Factors Inregulating Salivary Gland Epithelial Morphogenesis
No full textChitosan is a widely used biocompatible biomaterial in the tissue regeneration, but its utility and application in the tissue morphogenesis of salivary gland remains unclear. The study aimed to explore the effects of chitosan on the epithelial morphogenesis of submandibular gland (SMG). With chitosan, the branching morphogenesis of the whole SMG explant was facilitated, and the morphogenetic-promoting effects of mesenchymal tissue on SMG were further enhanced. Furthermore, chitosan was competent to induce recombined SMG epithelium to form branches in the serum-free condition independently. In the presence of chitosan, the morphogenetic efficacy of mesenchyme-derived growth factors responsible for epithelial morphogenesis including fibroblast growth factors 7, fibroblast growth factor 10 and hepatocyte growth factor increased. The specific epithelial phenotype induced by individual growth factor, which was required for the accomplishment of salivary epithelial morphogenesis, was promoted by chitosan. Moreover, the proliferative and the chemotactic properties of these growth factors towards the SMG epithelia were also reinforced by chitosan. Therefore, in orchestrating and intensifying the essential mesenchyme-derived growth factors, chitosan is versatile in mediating SMG epithelium to form a predetermined phenotype more efficiently and comprehensively . This study suggested that chitosan is a morphogenetic- regulating biomaterial for salivary tissue, which might be useful for the future salivary gland investigation and regeneration
- …
