Institutional Repository of Kyoto Institute of Technology
Not a member yet
1100 research outputs found
Sort by
Preparation of CaCO3?Polymer Composites by Bio-inspired Control Crystallization
Get PDF京都工芸繊維大学博士（工学）Natural composite materials produced by living organisms such as teeth, bone, nacre, and eggshells have attracted significant interest over the last few decades because such materials seem to provide new pathways for producing light-weight materials with excellent mechanical properties. In spite of the intensive works, further investigation is still required for understanding the mechanism behind natural biomineralization processes as well as the development novel industrial applications based on the bio-inspired techniques. This thesis describes the bio-inspired control crystallization of CaCO3 under the participation of hydrophilic polymers at the points of the development of novel composite materials as well as the development of novel methods for the morphological control of CaCO3. In a general introduction part, the author has introduced the reviews about biominerallization, CaCO3, crystallography, and the current status of biomimetic approaches, and has described the outline of this thesis. In Part 1 (Chapter 1), poly(p-phenylene-sulfoterephthalamide) (PPST), which has a lyotropic liquid crystalline (LC) nature in water, was used to a template mineralization of CaCO3 for the preparation of CaCO3-all aromatic polyamide composites. The alternate soaking process induced the formation of plate-like calcite mesocrystals at the hydrogel/solution interface, and cubic mesocrystals in the inner space of the hydrogel. The obtained composites are the first example that CaCO3-all aromatic polyamide composites with ordered structures of LC matrix and CaCO3 were prepared through in situ mineralization. In Part 2 (Chapter 2 & Chapter 3), a photoinduced crystallization of CaCO3, which takes advantage of the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphenyl)propionic acid) in the homogeneous precursor solutions, in which a partially hydrolyzed poly(vinyl alcohol) maintained the homogeneity of the solution by preventing the salt formation of Ca2+ and KP, was investigated. The fundamental concept behind this study concerns the development of the technique controlling the transportation of CO32?. This is the first example of the application of KP in the control crystallization of CaCO3. In Chapter 2, the UV irradiated samples under the alkaline condition at pH 10 were lyophilized. Ca2+ were completely converted to nanometer-to-micron sized calcite in the PVAPS matrix by photodecarboxylation of KP under UV irradiation for 50 min. The present results demonstrate a possibility for the photoinitiated site-selective crystallization of CaCO3 in a polymer matrix to fabricate designable composite materials. In Chapter 3, the UV irradiated samples under alkaline conditions (pH 8.4 and 10) were centrifuged for the preparation of CaCO3 composite particle in single digit micrometer sizes. As the result, spheroidal calcite composites, which contained organic components of about 10 wt%, were obtained at pH 8.4. The comparison of the characteristics of CaCO3 composites obtained at the different alkaline conditions suggests that the aggregation-based crystal growth in the presence of PVAPS seemed to enable the formation of the spheroidal composites of calcite in single digit micrometer sizes
高機能有機・無機コーティングの特性と耐久性に関する研究
Get PDF京都工芸繊維大学博士（工学）第１章の「緒論」では本論文の研究分野である、フッ素樹脂コーティング、シリコーン樹脂コーティング、有機無機ハイブリッドコーティング、色素増感太陽電池の概要、これまでの研究例、現在の動向について述べた。 第２章「低温焼成フッ素樹脂コーティング膜の物性と耐摩耗性に及ぼす焼成温度の影響」では、低温焼成フッ素樹脂塗料を用いて焼成温度を変えたコーティング膜を作製し、コーティング膜の物性と耐摩耗性についてまとめた。焼成温度が高いほど、コーティング膜の鉛筆硬度、非粘着性、耐摩耗性が良好であることを明らかにした。全反射フーリエ変換赤外分光とX線光電子分光分析により、耐摩耗試験における未摺動部と摺動部を分析した結果、摺動部ではフッ素樹脂の減少を確認し、コーティング膜の劣化メカニズムを明確にした。 第３章の「有機・無機ハイブリッドコーティングの特性に及ぼす焼成温度の影響」では、メチルトリメトキシシランの加水分解と縮合反応により得られる有機・無機ハイブリッドコーティング膜を作製し、コーティング膜の物性と耐摩耗性における焼成温度の影響についてまとめた。コーティング膜の鉛筆硬度、水の接触角及びテープ剥離荷重は80,150,200,250℃の各焼成温度においてほぼ同じ値となったが、耐摩耗性については焼成温度が高いほど良好な結果となることを明らかにした。全反射フーリエ変換赤外分光により、耐摩耗試験における未摺動部と摺動部を分析した結果、摺動部ではSi-CH3の減少を確認し、コーティング膜の劣化メカニズムを明確にした。 第４章の「有機・無機ポリマーハイブリッドコーティング膜の作製と特性評価」では、メチルトリメトキシシランを出発原料としたセラミックコーティング塗料にポリ（N-ビニルピロリドン）を添加して、有機－無機ポリマーハイブリッドコーティング膜を作製した。表面粗さ分析と表面観察より、表面に凹凸の多い特異的な形状になることがわかり、撥水性が向上することを明らかにした。全反射フーリエ変換赤外分光とX線光電子分光にてコーティング膜を分析した結果、メチル基を含むシロキサン（Si-O-Si）とポリ（N-ビニルピロリドン）がハイブリッド化して有機・無機ポリマーハイブリッドコーティング膜になっていることを確認し、コーティング膜の設計指針を得た。 第５章の「色素増感太陽電池色素の共吸着剤の物質と効果」では、D908色素を用いた色素増感太陽電池の光起電力性能において、共吸着剤としてのマロン酸誘導体と酢酸誘導体の効果を調べた。フェニルマロン酸(PMA)またはシクロペンチル酢酸(CPEAA)を共吸着させると、色素の吸着量は減少したが、太陽電池の光電流と光電圧が向上すること明確にした。全反射フーリエ変換赤外分光スペクトルよりPMAまたはCPEAAの共吸着がチタニア表面に結合した色素の量を増加させること、電気化学インピーダンスよりPMAまたはCPEAAの共吸着が逆電子移動抵抗R2を増加させ、電解液の拡散抵抗R3を減少させることを確認し、共吸着剤の分子設計指針を得た。 第６章の「色素増感太陽電池電解液の高性能化」では、色素増感太陽電池のチタニア負極と界面を接する電解液の電解質と溶媒の高性能化について述べた。第１節では、電解液中の1,3-アルキルイミダゾリウムヨージドの効果について調べた。ヨウ化リチウムと1-エチル-3-メチルイミダゾリウムヨージドの組み合わせで、光電変換効率は8.6％と、1-メチル-3プロピルイミダゾリウムヨージドと1-ブチル-2-メチルイミダゾリウムヨージドを使用した電解液よりも高い値になることを見出し、インピーダンス測定により、1-エチル-3-メチルイミダゾリウムヨージドは逆電子移動抵抗を増加させ、チタニアからのリーク電流を抑制することを明確にした。第２節では、電解液の溶媒として大気圧での沸点が200℃以上である5種類の含窒素ヘテロ環化合物を選択して性能を調べた。沸点270℃の3-メチル-2-オキサゾリドンを用いた場合に光電変換効率は7.0%と最も高い値を示すことを明らかにした。また、-24.4℃と低い融点を有するN-メチルピロリドンに高い比誘電率を有するN-メチルホルムアミドを容量比1:1で添加した場合、光電変換効率は5.0％から6.5％まで向上することを確認し、実用可能性を示唆した。 第７章の「色素増感太陽電池負極材料の高性能化」では、カーボンナノチューブをテンプレートとして合成した、新しい材料であるチタニアナノチューブを合成し、チタニアナノ粒子に2重量％添加した負極を用いることにより、5mm角の小型セルで変換効率10.4％を達成した。チタニアナノチューブの添加により、チタニア負極内の電子の移動を促進して電子の漏れを防止し、電解液のイオン移動を促進して電子の受け渡しをしやすくし、短絡電流密度とフィルファクターを向上させることを考察し、チタニア負極材料の設計指針を得た。 第８章では結言として、本論文の総括を述べた。 以上、有機・無機コーティングの応用分野である、フッ素樹脂コーティング、有機・無機ハイブリッドコーティング、色素増感太陽電池の３つの分野について、製造プロセスの最適化や添加材よる性能向上の指針と、耐久性評価による劣化メカニズムを明らかにした
Structure and properties of short fiber reinforced polymer composite and hybrid composite fabricated by injection molding process
Get PDF京都工芸繊維大学博士（学術）Short fiber reinforced polymer composites have found extensive applications in many fields due to their low cost, easy processing and superior mechanical properties over the neat thermoplastics. For interpreting the mechanical properties of composite by several variable parameters, additional measurements are required when changes occur in the composite system variables. Thus, experiments may be time consuming and cost prohibitive. Therefore, theoretical models of determining composite properties should use to predict the effects of a large number of parameters on the properties of composites. Prediction of the performance of injection molded short fiber reinforced polymer composites is desirable from the design standpoint. The using of appropriated models and suitable variables can predict the mechanical properties of short fiber composites and hybrid composites with good agreement with the experimental results. The rising concern towards environmental issues has led to increasing interest in fully green composites. Polylactic acid (PLA) based biocomposite reinforced with different natural reinforcement were prepared. The addition of natural reinforcements improved the stiffness of PLA as the result of addition of high stiffness material. However, the tensile, flexural and Izod impact strength of PLA biocomposites decreased when the reinforcement content increases. The application of flexible epoxy surface treatment improved mechanical properties of PLA biocomposites by improving the bonding between natural fiber and PLA matrix. However, it can be seen that the effectiveness of flexible epoxy treatment depended on the types of reinforcements. As the major drawback of using bio-based polymer matrices is their high cost, which makes them unaffordable even for large-scale productions. Some other drawbacks of bio-based composites include brittleness and low heat distortion temperature, which restrict their use in a wide-range of applications. The concept of hybrid systems for improved material performance is well known in engineering design. Hybrid green composites can be designed by the combination of synthetic fiber and natural fiber in a matrix. The development of the fabrication of long natural fiber reinforced thermoplastic through long fiber thermoplastic (LFT) technology provided natural fiber reinforced thermoplastic pellets with very high fiber concentration. The effects of twisted and un-twisted jute yarn during LFT pellet preparation and re-compounding on mechanical properties of jute fiber/polypropylene (JF/PP) and glass fiber/jute fiber/polypropylene (GF/JF/PP) hybrid composites were evaluated. Mechanical properties of JF/PP composites are mainly depended on the fiber aspect ratio, fiber orientation and the distribution of jute fibers. The incorporation of glass fibers is found to improve mechanical properties of jute fiber reinforced polypropylene composites. The increasing of mechanical properties of hybrid composites was depended on type of JF/PP pellets. In order to maximize the effectiveness of glass fiber hybridization, the fiber distribution and fiber orientation of jute fiber might be seriously considered. Sandwich injection molding is an extension of the conventional injection molding technology which two different materials are either simultaneously or in rapid sequence injected through the same gate. The fabrication of GF/JF/PP hybrid sandwich composites through the combination of two different materials several benefits can be obtained. Regards the effect of glass fiber hybridization on the jute/PP sandwich structure composite, the addition of glass fiber in the core layer or skin layer can significantly improve both tensile and flexural modulus of sandwich composite. By using the concept of hybridization and sandwich structure, several combinations of sandwich hybrid composites can be designed. This design`s flexibility is very useful in engineering design to achieve the optimum properties for appropriate application. The extrusion compounding for preparing fiber filled polymer pellets, has a practical processing limit on the fiber attrition problem, which decreases the reinforcement efficiency of the fibers. In this study, the novel processing technique for the fabrication of short fiber reinforced composite is introduced as the direct fiber feeding injection molding (DFFIM) process. This process reduces the fiber breakage during conventional screw compounding and results in longer length of retained fiber. The fiber in composites fabricated with DFFIM process show poor quality of fiber distribution when compared with the compounded composite. The new parameter called fiber distribution index is introduced and this parameter can be used as the indicator for the quality control of fiber distribution in short fiber reinforced composites. The modification of interfacial property of composites fabricated by DFFIM process was evaluated through the hybrid glass fiber/carbon fiber and glass fiber/jute fiber reinforced polypropylene composites. The effects of addition of coupling agent and carbon fiber surface treatment on interfacial bonding between carbon fiber, glass fiber, jute fiber and polypropylene were discussed. The using of polyamide 6 (PA6) and maleic anhydride grafted polypropylene (MAPP) as co-coupling agent significantly improved the interfacial bonding between carbon fiber and polypropylene. In addition, the amino silane sized carbon fibers further improved the bonding between carbon fiber and the co-coupling agent as compared to the as-received carbon fiber. The using of MAPP as coupling agent improves the interfacial bonding between both glass fiber and jute fiber with PP matrix. The new injection molding technology is a simple process without the requirement of extrusion compounding step and it can be easily adapted to existing injection molding equipment. This technology provides a unique route and high processing flexibility to market for injection molders to incorporate cost reduction into their business strategy
漆工芸における職人の特徴認識と材料特性に関する研究
Get PDF京都工芸繊維大学博士（学術）漆工芸の作品・製品は修理・修復を繰り返すことで、長い年月の使用が可能である。修理・修復の際、職人は作品・製品の状態、技法、材料を判断する必要がある。これには“見立て”と呼ばれる観察技能による“見極め”が必要となってくる。しかしながら、非熟練者にとって見立て技能を直接学ぶ機会は少なく、またどのような修練を積めばよいのかも判然としない。そこで本論文では、見立ての際、熟練者がどのように作品・製品の特徴や情報を認識しているかを明らかにすること、また、熟練者の特徴認識に影響を与えている材料特性について明らかにすることを目的とした。 本論文は、第1章の緒論から第7章の結論までの7章構成である。以下に、第2章以降の目的と内容について簡潔に記述する。 第2章では、見立て時の作品・製品の観察動作の違い、および見立て技能の評価方法について検討することを目的に、職人や学生を被験者として見立てを行ない、観察動作の分類やクラスター分析を行なった。その結果、熟練者は作品を細かくあおる動作を中心に見立てを行なっていたことが明らかとなった。変数間クラスター分析では、作品あおりと見立ての発言時間の類似度が高かったことから、見立てでは作品を細かくあおる動作が発言につながることが指摘できた。また被験者間クラスター分析では、熟練者と他の被験者との類似度が明らかとなり、クラスター分析の見立て技能の評価への可能性が示唆された。 第3章では、熟練者が作品・製品をどのように動かし、特徴を認識しているのかを検討することを目的に、異なる粗さの金粉で作製した蒔絵試験片を複数用意し、その見立てを行なう際の試験片の動きについて動作解析を行なった。その結果、熟練者は見立ての際、金粉の粗さに応じて試験片の動かし方を変えている可能性が指摘でき、非熟練者は最適な動かし方がわからず、どの試験片も大きく動かすことで、外観変化を大まかに捉えていたことが推測された。 第4章では、漆工芸の熟練者における見立て時の眼の使い方を明らかにすることを目的に職人らの眼球運動測定を行ない、それとともに、熟練者における見立て時の着眼点を明らかにすることを目的に職人らの発言についてテキストマイニングを実施した。その結果、以下の点について明らかとなった。見立ての所要時間および発言時間と経験年数には強い相関関係は認められなかったが、作品の特徴指摘数と経験年数には強い相関関係が認められた。眼球運動測定では、視点移動速度の最頻値が4～6deg/sec近傍の被験者と10deg/secよりも大きい被験者の存在が認められ、特に視点移動速度の最頻値が4～6deg/sec近傍の被験者は瞳孔径のゆらぎ（標準偏差）と経験年数および蒔絵の特徴指摘数に強い相関関係が認められた。さらに視点移動速度の最頻値が4～6deg/sec近傍の被験者は注視時間が長い傾向にあり、視点往復移動回数と蒔絵の特徴指摘数の間に強い相関関係が認められたことから、熟練者は注視と比較を組み合わせ、特徴認識を行なっていたことが示唆された。テキストマイニングの結果、視点移動速度の最頻値が4～6deg/sec近傍の被験者では、カテゴリ数、共通する語句ともに多かった。つまり、見立てにおける着眼点が多く、かつ着眼点間の関連性を考慮し見立てを行なっていたことが示された。 第5章では、見立てが目視で行なわれることから、目視での特徴認識に影響を与えていると考えられる蒔絵の光学特性について解明することを目的に、蒔絵の表面観察と分光測色計による蒔絵の測色を行なった。その結果、粗い粉や細かい粉は中間的な大きさの粉よりも色がくすみ、粗い粉は最もくすんでいた。蒔絵は赤色がかった黄色をしていることが明らかとなり、粗い粉で最も黄色味が強く、中間的な大きさの粉で最も赤色味が強かった。このような蒔絵の彩度および色相の違いは、金粉の占有率や加工工程の違いにより生じたことが示唆された。 第6章では、熟練者の炭研ぎ完了の見極めに及ぼす材料の状態、および身体の使い方とそれが炭研ぎ作業に及ぼす影響を検討することを目的に、炭研ぎ後の蒔絵の被研ぎ面の物性評価および炭研ぎ作業時の職人の筋電図測定を行なった。その結果、熟練者は非熟練者に比べ、研ぎをしっかり行ない、多くの金粉を蒔絵表面に露出させたことで、明るく黄色味の強い、かつムラの少ない仕上げとしていた。熟練者は1回の炭研ぎ時間および炭の面直し時間が一定であることからリズム感を持って研ぐことができており、また1回の炭の回転数および炭の面直し回数が一定であること、研ぐ箇所を決めていたこと、炭の回転に合わせた力の入れ方をしていたことからムラの少ない、一定の研ぎ下ろしにつながったものと考えられた。熟練者はムラの少ない均一な被研ぎ面により、作業をしながらの金粉露出の見極めを行なうことができ、非熟練者はムラのある被研ぎ面のため、炭の面直し時に時間を掛けて見極めを行なう必要があった。 第7章では、各章で得られた知見をまとめ、今後の展望について述べた
New Material Design of Polylactides by Controlled Stereocomplexation and Hybridization
Get PDF京都工芸繊維大学博士（工学）Stereocomplexation of PLA has been studied in various ways for creating high-performance PLA materials. However, concomitant formation of hc and sc crystals reduces the performances of the final stereo mixture of PLLA and PDLA. Therefore, in this study, sc crystallization is manipulated on sub-micron or nano-meter level by using hybridization and composite techniques in order to obtain high-performance PLAs. In the first trial, the author used hydrolytic polycondensation of silyl-terminated PLA for hyper-conjugation and hybridization of PLA. Silane coupling reaction has been often used to provide a stable bond between organic and inorganic moieties and to convert the incorporated heterogeneous phase into a uniform composite structure. The general reaction of the silane coupling agents consists of two steps. The siloxyl groups are usually protected by alkoxyl, halo, or amino groups which are readily hydrolyzed in contact with water. Following their hydrolysis, reactive silanol groups are generated and spontaneously, which can condense with each other to form siloxane bonds. These processes are repeated until a hyper-conjugated configuration is formed. Although the general hyper-conjugated polymers are formed through core-to-branch propagation, the author demonstrates a branch-to-core propagation mechanism for the hyper-conjugation in solution-cast films. The first approach for their trial is to modify PLA by using PDLA and PLLA prepolymers having a trimethoxysilyl terminal group (mSi-PLA) for which hydrolytic polycondensation affords hyper-conjugated PLLA (mH-PLLA) and PDLA (mH-PDLA). Here, both mSi-PLA and mH-PLA are bleneded with PLLA by solution casting method. The resultant films are then analyzed to reveal the properties and specific morphologies related to stereocomplex crystallization and hybridization. In the second trial, triethoxysilyl-terminated PDLA (eSi-PDLA) is synthesized and blended with PLLA to compare its effects on the morphology change with that of mSi-PDLA. Since the rate of hydrolytic polycondensation is changed with the alkoxyl chain groups, the competitive hydrolytic polycondesation and stereocomplexation gives profound difference in morphology. In the third trial, direct synthesis of trialkoxysilyl PDLA polymers is examined by one-step ROP of D-lactide in order to make them in larger scale. In this new method, it is important how to control the ROP without chain transfer reactions taking place between the propagation hydroxyls and terminal siloxane groups. In the final trial, the author tries to fabricate sc-PLA fibers by using a mixture of two stereo di-block type PLAs (di-sb-PLA) having complementary PLLA/PDLA block ratios. The obtained sb-PLA fibers are allowed to form preferential sc crystallization with regularity of sc lamellae growth. These studies reveal that phase transition in PLA matrix is very important to control the properties and morphology of the sc-PLA materials in which modified PLAs play key role and effect
Silicon Nitride: A Unique Bioceramic for Total Joint Arthroplasty
Get PDF京都工芸繊維大学博士（工学）Advanced bioceramics currently play important curative roles for various orthopaedic morbidities, including their use as bearing surfaces in total hip arthroplasty (THA). Introduced during the latter half of the 20th century, these materials rapidly evolved from monolithic alumina (Al2O3) and yttria-stabilized zirconia (Y-TZP) to alumina-zirconia composites (ZTA). While their use in THA has proliferated because of their perceived bioinertness, they have yet to deliver the promised objective of being “lifetime” devices; which, in fact, brings into question the very definition of bioinertness. However, only recently have investigative tools been developed which allow examination of the surface chemistry and mechanical properties of these materials at the molecular level. In this thesis, Raman and cathodoluminescence spectroscopy coupled with traditional micromechanical methods were employed to evaluate the surface chemistry and fracture toughness of three bioceramics: Al2O3, ZTA, and a promising alternative non-oxide material, silicon nitride (Si3N4). Contrary to conventional wisdom, oxide-based ceramics were not bioinert. Indeed, bio-tribological interactions resulted in the release of oxygen from Al2O3, and mechanical instability in ZTA, which in turn, may accelerate oxidative degradation in polyethylene and increased wear of self-mated bearings, respectively. On the other hand, Si3N4 was also not bioinert; but uniquely, it possesses positive non-bioinertness. It scavenges oxygen from the tribolayer instead of releasing it, thereby providing a protective benefit to polyethylene; and its surface toughness is immune to even severe hydrothermal conditions. Nevertheless, wear studies using self-mated Si3N4 bearings exhibited fluctuating friction (i.e., slip-stick behavior), which was also attributable to chemical interactions with the biologic environment. Overcoming this limitation represents a key challenge and recommendation for this novel biomaterial. Lastly, it was also discovered that Si3N4’s tribochemical wear products (i.e., predominately silicic acid, Si(OH)4, and ammonia, NH3) are soluble, resorbable, and can potentially buffer the local pH within the joint capsule. As such, Si3N4 may yet prove to be beneficial for arthritic patients whose diseased joints have degeneratively low pH values. While additional research is required, particularly to overcome the unfavorable frictional behavior for self-mated bearings, Si3N4’s performance as an articulation device appears particularly promising
Cell biological and genetical studies on Drosophila myeloid leukemia factor (dMLF) and DRE/DREF transcriptional regulatory pathway
Get PDF京都工芸繊維大学博士（学術）Drosophila myelodysplasia/myeloid leukemia factor (dMLF), a homolog of human MLF1, oncogene was first identified by yeast two-hybrid screen using the DNA replication-related element-binding factor (DREF) as a bait. DREF is a transcription factor that regulates proliferation-related genes in Drosophila. It is known that overexpression of dMLF in the wing imaginal discs through the engrailed-GAL4 driver causes an atrophied wing phenotype associated with the induction of apoptosis. However, the precise mechanisms involved have yet to be clarified. Here, I found the atrophied phenotype to be suppressed by loss-of-function mutation of Drosophila Jun N-terminal kinase (JNK), basket (bsk). Overexpression of dMLF induced ectopic JNK activation in the wing disc monitored with the puckered-lacZ reporter line, resulting in induction of apoptosis. The DREF-binding consensus DRE sequence could be shown to exist in the bsk promoter. Chromatin immunoprecipitation assays in S2 cells with anti-dMLF IgG and quantitative real-time PCR revealed that dMLF binds specifically to the bsk promoter region containing the DRE sequence. Furthermore, using a transient luciferase expression assay, I provide evidence that knockdown of dMLF reduced bsk gene promoter activity in S2 cells. Finally, I show that dMLF interacts with DREF in vivo. Together, these data indicate that dMLF acts with DREF to stimulate the bsk promoter and consequently activates the JNK pathway to promote apoptosis. In addition, the DRE/DREF transcriptional regulatory system has been demonstrated to activate a wide variety of genes with various functions. In Drosophila, the Hippo (Hpo) pathway is known to suppress cell proliferation by inducing apoptosis and cell cycle arrest through inactivation of Yorkie, a transcription co-activator. Here, I also carried out analyses of transcriptional regulation of the hippo (hpo) gene in Drosophila. By this analysis, I revealed that DREF is required for transcriptional activation of the hpo gene to positively control the Hippo pathway. Altogether, the DRE/DREF pathway is involved in both the JNK and the Hpo pathway, and appears to play an important role in induction of apoptosis
Controlling Nano-ordered Structures by Stereocomplex Formation between Poly(L-lactide) and Poly(D-lactide) Macromolecular Chains
Get PDF京都工芸繊維大学博士（工学）Polylactides (PLAs) have been widely utilized as biomaterials for making bone implants, fixing screws, and absorbable sutures because of their excellent biocompatibility and bioabsorbability. However, their nano-order structure control is required for developing functional biomaterials that can be applied to tissue engineering and specific medical devices. Various nano-ordered morphologies have been found out thus far in various multi-component polymer blends and surface -immobilized macromolecules that are involved in phase separation and crystallization. However, little knowledge has been known on the nano-ordered morphologies that are created with enantiomeric poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), although they ought to be very important for designing PLA-based biomaterials. This study demonstrates two approaches for controlling the nano-ordered morphology by utilizing stereocomplex formation of PLLA and PDLA macromolecular chains. The first approach is based on surface immobilization of PDLA, and with which either enantiomeric PLLA homo polymer or PLLA-poly(ethylene glycol) (PEG) block copolymer is interacted to form specific morphology by stereocomplex crystallization (Chapters 1 and 2). The second is based on micelle formation of PEG-PLA block copolymers having different PLA blocks: PLLA, PDLA, and PDLA-PLLA block sequences. The crystalline structure of PLA in the core affects the nano structure of the core-shell micelles (Chapter 3). The content of each chapter is summarized as follows: Chapter 1 describes the macromolecular organization of PLA immobilized on a flat surface. Namely, a silyl-terminated PDLA oligomer was first immobilized on a silicon wafer, and both PDLA and PLLA oligomers were deposited on it. It was found out that single crystallite arrays of homochiral and stereocomplex crystals can be formed on the surface. Chapter 2 deals with nano-ordered surface morphologies by the interaction between the surface-immobilized PDLA and PEG-PLLA block copolymers. Both AB diblock and ABA triblock copolymers of PLLA (A) and PEG (B) deposited on the PDLA pre-immobilized surface were found to form characteristic particle morphologies involving the hydrophilic PEG chains near their surfaces. Chapter 3 describes stabilization of nano-structured micelles of PLA-PEG block copolymers along with the effect of sc formation of PLA blocks on the micelles. Here, a PEG-PDLA diblock copolymer, a mixture of enantiomeric diblock copolymers PEG-PDLA/PEG-PDLA, and PEG-PDLA-PLLA triblock copolymers having different block compositions were emulsified. It was found out that the triblock copolymers could form sc crystals in the core to highly stabilize the core-shell particles
Study of Design Methodology of ASIC and FPGA Considering Correlation between Process Variation and BTI-Induced Degradation
Get PDF京都工芸繊維大学博士（工学）We widely use LSIs (Large Scale Integrations) for many industrial products such as computers, mobile devices, automobiles, and medical instruments. LSIs are infrastructures for our current advanced information society. Hundreds of millions of transistors are integrated within a single chip through advances in the scaling. The progress of the scaling improves the economic development. LSIs play important roles in our society. LSIs must be reliable products. Reliability issues of MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), such as BTI (Bias Temperature Instability) and process variations become dominant at the highly-scaled process. BTI is one of the most significant aging-degradations on LSIs. Threshold voltages of transistors are shifted by BTI for the long-term period of use. They result in circuit delays and unstable performances because their effects are not negligible and avoidable. In this study, the design methodology considering the correlation between process variations and BTI-induced degradations is proposed. The design margins of LSIs are reduced without threatening their reliability. The frequencies of ROs (ring oscillators) on ASICs and FPGAs are measured to analyze the reliability issues. The frequencies are varied by the process variations according to locations on the test chips. They follow the Gaussian distribution. The groups of the highest, average and lowest frequencies are focused on. The aging-degradations of the three groups are measured on the accelerated test. The correlation between process variations and BTI-induced degradations are examined. The degradation at the highest frequency group is larger than one at the slowest frequency group. The appropriate design margins are defined according to this nature
ショウジョウバエのDNAグリコシレースOgg1の酸化損傷修復における役割に関する研究ならびにショウジョウバエ遺伝学の生物教育への応用
Get PDF京都工芸繊維大学博士（学術）キイロショウジョウバエ（Drosophila melanogaster ）（以下，ショウジョウバエ）は遺伝学のみならず広範囲なバイオ分野で実験材料として使われている。その理由として，ショウジョウバエには殆どの遺伝子が変化した系統が存在する，遺伝的に均一な個体を一度に多数取り扱うことができる，マウスなどの実験動物より飼育経費が少ない，世代時間が短く，結果が比較的早く得られる，さらには，遺伝子を改変することにより研究目的に最適な個体を作成することができるという点が挙げられる。本論文は５章で構成されている。第１章に緒論，第２章，第３章にショウジョウバエの特徴を生かした研究２題の成果を各々述べた。さらに本研究ではショウジョウバエの遺伝学的実験手法を高校の生物教育に応用した教材づくりも行った。その成果を第４章で述べた。最後に第５章で総合考察を行った。 第２章では，生体を用いた酸化ストレス産生物質ならびに抗酸化物質の簡易的探索システムの開発について述べた。活性酸素を生み出す化学物質ないしは抗酸化物質を，ショウジョウバエ成虫を用いて，簡便，安価に検出できる実験系を開発することをめざした。実際に，ショウジョウバエの活性酸素除去酵素Cu/Zn-SOD（superoxide dismutase）をコードする遺伝子Sod1の突然変異体成虫やSod1 をノックダウンした成虫が，体内で活性酸素を産生させる化学物質パラコート（1,1'-ジメチル-4,4'-ジピリジニウムクロリド）に高感受性であることを示した。また，試験管内で抗酸化作用を示す化学物質（アスコルビン酸，ビタミンEの水溶性誘導体であるTrolox）や同効果をもつとされている植物（茶）成分を飼料に添加して上記成虫に与えた。その生存率を調査することにより，それらの物質が消化，吸収されたのち，体内でどの程度の抗酸化作用を示すかを推定した。その結果，この方法が抗酸化作用をもつ物質の探索に有効であることがわかった。 第３章では，酸化ストレスによりDNAが酸化損傷を受けたときに，ショウジョウバエがそれをどのような酵素を使って除去し，DNA損傷を修復しているかについて，遺伝学的解析を行った結果を述べた。DNAの塩基のうち，特にグアニンが酸化されると，8-oxo-guanineがつくられ，それはアデニンと塩基を対合する。このため8-oxo-guanineの存在はDNAの塩基置換につながる。大腸菌や酵母ではこれを除去する酵素としてOgg1が報告されているが，昆虫ではその機能について知られていなかった。酵母Ogg1と相同なショウジョウバエ遺伝子CG1795が8-oxo-guanineの除去に必須な役割を果たしているか検討した。まず，Ogg1遺伝子座にトランズポゾンが挿入した変異体，その二本鎖RNAを発現できる系統，また，Ogg1遺伝子へのUAS配列挿入系統個体を用いることにより，同遺伝子の発現低下，ノックダウン，大量発現が可能なことをリアルタイムPCR法で示した。次に，酸化ストレスを発生させるパラコートを摂食させて，消化管の上皮細胞の核内に8-oxo-guanineの蓄積を確認した。同遺伝子の発現量に応じて体内の8-oxo-guanineの蓄積量が変化することを明らかにした。これらの解析によって，Ogg1 がショウジョウバエにおいて8-oxo-guanineの抑制に必須であることが証明できた。さらにOgg1遺伝子を大量発現させるだけで成虫寿命が有意に延長することをみいだした。DNAの酸化損傷の修復能が生体老化の鍵をにぎる可能性を考察した。 以上２つの研究では，化学物質の影響などを調査するために，それに対する生物応答に関与する遺伝子の発現量を変化させた。ショウジョウバエでは，遺伝子の発現量を容易に増減できる。ショウジョウバエがもつこのような利点は，生物教育においても有効なツールになるという考えに至った。例えば，劣性の突然変異がホモかヘテロかを見分けるためのマーカーの利用，特定の遺伝子の発現だけを低下させるノックダウン法や増強する過剰発現システムを使って，遺伝の「独立」「連鎖」「組換え」という一般に学生には難解な現象などを理解させるための教材を考案した。そして実際の教育現場でその効果を調査した。本論文の第４章において，ショウジョウバエの実験手法と遺伝子型の表記法を題材にした教材が，遺伝学に対する高校生の興味関心を促進し，遺伝子の独立・連鎖を意識させる教材として有効であることを示した