Дисертації: "High and Ultra High Molecular Weight DNA"

1

Roukema, Mees. "High-speed spinning of ultra-high molecular weight polyethylene fibres." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 1991. http://irs.ub.rug.nl/ppn/291241077.

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2

Karanfilov, Christopher. "ION IMPLANTATION OF ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243981285.

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3

Burger, Nicolaas Daniel Lombard. "Failure analysis of ultra-high molecular weight polyethyelene acetabular cups." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-12142006-134036.

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4

Zhang, Zhijie. "A study of ultra-high-molecular-weight polyethylene, UHMWPE, foams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60758.pdf.

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5

Boontongkong, Yot. "Orientation of channel die-compressed ultra-high molecular weight polyethylene." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46093.

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6

Burger, N. D. L. (Nicolaas Daniel Lombard). "Failure analysis of ultra-high molecular weight polyethyelene acetabular cups." Thesis, University of Pretoria, 2005. http://hdl.handle.net/2263/30360.

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Анотація:

Owing to the crippling nature of arthritis, surgeons have been trying for well over a century to successfully treat this debilitating disease particularly when attacking the hip joint. In the early 1970s, Sir John Charnley started with total hip replacement as a solution to this ever-increasing problem. Many different designs were developed but all the designs revolved around a femoral stem, femoral head and acetabular component. Independent of the design, longevity of the implant remains a problem. The major cause of replacements, according to various hip registers, is due to aseptic loosening resulting from osteolysis. According to these registers, the average in-vivo life of a hip replacement is approximately 12 years. The main aim of this study was to determine the root cause of mechanical failure of the acetabular cups and to determine the origin of the excessive amount of ultra-high molecular weight polyethylene (UHMWPE) wear debris floating in the joint resulting in osteolysis. During the study, various techniques were used to investigate the acetabular components to try to establish the root cause of mechanical failure. These techniques included: 1. Visual inspection 2. Investigation making use of dye penetrant spray 3. Investigation under stereo microscope 4. Investigation making use of a scanning electron microscope 5. Electrophoresis 6. Mass-spectrometric analysis 7. Analysis of the synovial fluid on high-frequency linear-oscillation machine (SRV). The wear debris retrieved from the scar tissue surrounding the joints of a number of patients was also analysed. Apart from the obvious defects such as mechanical damage due to impingement, the main defect on which this study focuses is the wear patches found on the inside of the acetabular components. The wear areas were presented as areas where the surface layer of the UHMWPE was ripped off by adhering to the rotating femoral head. This type of failure is possible if localised overheating takes place resulting in the material either adhering to the rotating femoral head or the material being squeezed out under the prevailing pressure. Both these mechanisms were confirmed by the wear debris retrieved from the scar tissue, being either droplets of UHMWPE or whisker-like wear products. To confirm the existence of elevated temperatures the brown discolouring on the inside of the acetabular cups was analysed, making use of electrophoresis, mass-spectrometric analysis and scanning electron microscope recordings. In this part of the study, it was confirmed that localised temperatures on the bearing surface had reached at least 60°C during in-vivo service. This temperature was confirmed by inserting a thermocouple just under the surface of an acetabular cup and then measuring the temperature while in-vitro testing was taking place on a hip simulator. The wear debris as retrieved was also duplicated in laboratory experiments while the temperature on the surface of an acetabular cup was monitored. It was established that wear particles similar in shape and size were formed at temperatures in excess of 90°C. At temperatures above 50°C the UHMWPE had visually shown extensive increase in creep, indicating that at these temperatures the material softens sufficiently for this type of debris to be generated The overheating as described can also only occur if there is a lack of lubrication in the bearing couple. The synovial fluid from 12 patients was retrieved during revision surgery. This synovial fluid was then tested on a high-frequency linear-oscillation machine (Optimol SRV test machine) to determine the lubricity characteristics of the synovial fluid as retrieved. It was discovered that the load-carrying capability of the synovial fluid did not comply with the minimum requirements for a fluid to function as a lubricant. The final conclusion of this study is that excessive amounts of wear debris are generated due to the localised overheating of the bearing couple as a result of insufficient lubrication. The localised heat build-up results in excessive amounts of wear debris being generated and deposited in the joint area resulting in osteolysis.
Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2005.
Mechanical and Aeronautical Engineering
unrestricted

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7

Wernle, James David. "Micron-scale wear mechanisms in ultra high molecular weight polyethylene." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.

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8

Titone, John Carlos. "Supercritical carbon dioxide sterilization of ultra-high molecular weight polyethylene." Connect to resource, 2009. http://hdl.handle.net/1811/37004.

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9

Ruan, Shilun. "Multi-walled carbon nanotube reinforced ultra-high molecular weight polyethylene composites /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20RUAN.

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10

Ma, Yue. "Polymer grafted carbon nanotube reinforced ultra high molecular weight polyethylene fibre." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/45828.

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In this research, a series of experiments have been conducted to develop a high performance ultra-high molecular weight polyethylene (UHMWPE) fibre with improved mechanical properties. A novel process was developed whereby polyethylene grafted multi-walled carbon nanotubes (PE-g-MWCNTs) were used to reinforce UHMWPE fibre. PE-g-MWCNT/UHMWPE fibres with remarkable modulus and tensile strength of 125.5 GPa and 4.0 GPa, respectively, were successfully fabricated and showed definite potential for reducing the weight of body armour. A systematic study was carried out to investigate the effects of gel spinning conditions on tensile properties and morphologies of UHMWPE fibre. Spinning parameters, including polymer concentration, spinning temperature and winding-up speed, were selected and studied systematically and the spinning condition of UHMWPE fibre was optimized by design of experiment. Intensive experiments were conducted to investigate the feasibility of reinforcing UHMWPE fibre with pristine multi-walled carbon nanotubes (MWCNTs). Various mechanical methods include ultra-sonication, ball milling, microfluidizing, etc. were applied for dispersing pristine MWCNTs. Studies on tensile properties and morphologies of formed MWCNT/ UHMWPE fibre demonstrated that pristine MWCNTs tend to exist in micro-meter size agglomerations and no improvement in tensile properties of the MWCNT/UHMWPE fibres was found. Finally, chemical functionalization of MWCNTs using a coupling agent and polymer grafting technology was studied. The effective modulus and strength of MWCNTs were calculated based on the ‘rule of mixture’. Compared to coupling agent functionalization, polymer grafting has been found to be more effective in improving reinforcement of MWCNTs in UHMWPE fibre due to a stronger load transfer on the interface. The reinforcement mechanism of polymer grafted MWCNTs was analyzed based on experimental observations.

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11

Webber, Robert Stephen. "The strain dependent behaviour of microporous ultra-high molecular weight polyethylene." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263897.

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12

Chang, Natasha Anna 1974. "The effect of molecular orientation on the wear of ultra-high molecular weight polyethylene." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/46240.

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13

Elmkharram, Hesham Moh A. "Mechanically Processed Alumina Reinforced Ultra-high Molecular Weight Polyethylene (UHMWPE) Matrix Composites." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/31522.

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Alumina particles filled Ultra-high Molecular Weight Polyethylene (UHMWPE), with Al2O3 contents 0, 1, and 2.5 wt% were milled for up to 10 hours by the mechanical alloying (MA) process performed at room temperature to produce composite powders. Compression molding was utilized to produce sheets out of the milled powders. A partial phase transformation from orthorhombic and amorphous phases to monoclinic phase was observed to occur for both the un-reinforced and reinforced UHMWPE in the solid state, which disappeared after using compression molding to produce composite sheets. The volume fraction of the monoclinic phase increased with milling time, mostly at the expense of the amorphous phase. The melting temperature decreased as a function of milling time as a result of modifications in the UHMWPE molecular structure caused by the milling. At the same time, for a given alumina composition the activation energy of melting increased with milling time. Generally, the crystallinity of the molded sheets increased with milling time, and this caused the yield strength and elastic modulus to increase with milling time for a given alumina composition. However, the tensile strength and ductility remained about the same.
Master of Science

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14

Tam, Yee Kam. "Mechanism study of carbon nanotube reinforced ultra-high molecular weight polyethylene fibers /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CBME%202008%20TAM.

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15

Lau, Kwan Yee. "An environmentally friendly process for the preparation of high performance ultra-high molecular weight polyethylene thin films /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CENG%202002%20LAU.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 106-111). Also available in electronic version. Access restricted to campus users.

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16

Bartsch, Ingo. "Zytokinprofil einer humanen Knochenmarkszellkultur nach Exposition mit Ultra-high-molecular-weight-Polyethylen-Abriebpartikeln." [S.l.] : [s.n.], 2005. http://archiv.ub.uni-marburg.de/diss/z2005/0355/.

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17

Goktepe, Canan. "Water Soluble Monomer Grafting On Thin Films Of Ultra High Molecular Weight Polyethylene." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1081546/index.pdf.

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This study covers grafting of Acrylic Acid (AA) and Methacrylic Acid (MAA) on Ultrahigh Molecular Weight Polyethylene (UHMWPE) thin films by surface grafting and xylene-swollen grafting methods with Co-60 &
#947
-ray in air. Also characterizations of pure, irradiated and grafted films were made by applying gravimetric, spectroscopic, thermal and mechanic tests. The thin films of UHMWPE were prepared by using compression molding. AA and MAA grafting on thin UHMWPE films were carried out by surface grafting and xylene-swollen grafting methods. During grafting processes, homopolymerization of monomers was avoided by using Fe2+ and Cu2+ ions. Grafting degree of AA and MAA were calculated for the samples irradiated at different doses. To verify grafting of AA and MAA on UHMWPE films, FTIR spectra of grafted films were used. Metal-uptake capacity is important property of grafted polyethylene for environmental applications. Thus, we examined metal-uptake capacities of AA and MAA grafted films for Fe(III) and Ni (II) and it was found that AA and MAA grafted UHMWPE films showed good affinity towards Fe(III) and Ni(II) metals. Thermal behavior of films were examined by DSC analysis. First run and second run DSC thermograms showed the thermal stability of films under heat. Mechanical properties of UHMWPE decrease with irradiation and grafting. However stress at break values of xylene-swollen grafted samples tend to increase with irradiation dose. In conclusion, water soluble monomers were successfully grafted on UHMWPE and these AA and MAA grafted UHMWPE films can be used in biomedical, environmental applications and other related areas.

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18

Yu, Jie. "Oxidation of ultra high molecular weight polyethylene, UHMWPE, containing traces of cobalt ion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/MQ53349.pdf.

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19

Bruton, Allison Renee. "Manufacturing and performance of titanium dioxide-ultra high molecular weight polyethylene nanocomposite materials." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 175 p, 2007. http://proquest.umi.com/pqdweb?did=1251905071&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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20

Wu, Jun Jie. "The integrity of moulded ultra-high molecular weight polyethylene for joint replacement prostheses." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325574.

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21

Bell, Carol Jane. "Variability, oxidation resistance and wear of 'medical grade' ultra-high molecular weight polyethylene." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394335.

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22

Miler, Josef L. "Methods for increasing the thermal conductivity of ultra-high molecular weight polyethylene (UHMWPE)." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36291.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
"June 2006."
Includes bibliographical references (p. 31-33).
A two-part study was conducted to determine methods for producing ultra-high molecular weight polyethylene with high thermal conductivity by way of polymer chain orientation. The first portion of this report surveys current research involving polyethylene chain orientation and manufacturing. This section includes analysis of shish-kebab morphology, past polymer thermal studies, self-reinforcement studies, manufacturing techniques, and experimental techniques for low thermal conductivity materials. The second portion reviews the results of an experiment conducted to test the feasibility of stretched thermoforming of UHMW-polyethylene. Sheets of UHMWPE were stretched and tested for anisotropy in thermal conductivity. For samples with draw ratios of X 10, anisotropy in thermal conductivity was observed to increase. These results show potential for future development of this proposed methodology.
by Josef L. Miler.
S.B.

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23

Medhekar, Vinay Shantaram. "Modeling and simulation of oxidative degradation of Ultra-High Molecular Weight Polyethylene (UHMWPE)." Link to electronic thesis, 2001. http://www.wpi.edu/Pubs/ETD/Available/etd-0828101-135959.

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24

Camacho, Nayeli. "Wear analysis on retrieved ultra-high-molecular weight polyethylene tibial components from total knee replacements." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

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25

Turell, Mary Elizabeth. "Effect of Counterfaceroughness on the Cross-Path Wear of Ultra-High Molecular Weight Polyethylene." Yale University, 2006. http://ymtdl.med.yale.edu/theses/available/etd-06282006-145406/.

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Ultra-high molecular weight polyethylene (UHMWPE) is used worldwide as a bearing material in total joint replacement prostheses. Despite its excellent biocompatibility and high wear resistance, wear of UHMWPE components continues to be a major problem limiting the clinical lifespan of UHMWPE-containing orthopaedic implant devices. Multi-directional motion or cross-path motion is known to affect wear rates of UHMWPE in total knee and hip replacement prostheses. The purpose of this study was to quantify the effect of counterface roughness on the cross-path wear of UHMWPE and to determine if the previously established unified theory of wear model could accurately predict wear rates in an abrasive wear environment. UHMWPE pins were articulated against both smooth (centerline roughness, Ra, of 0.015 µm) and rough (Ra = 0.450µm) cobalt-chromium counterfaces in a series of six rectangular wear paths (width = A, length = B) with systematically increasing aspect ratios (B/A) and linear tracking (A = 0), all with identical path lengths (20mm) per cycle. Gravimetric weight loss was converted into volumetric wear rates and wear factors, k. The results showed that for both smooth and rough-counterface tests, wear reached a maximum when a 3mmx7mm wear path was employed. The unified theory of wear was generally accurate in predicting wear rates; however, for rough-counterface tests there was a larger increase in the wear factor for higher aspect ratio rectangular wear paths. The ratio [k rough/ k smooth] decreased monotonically as a function of increasing width of rectangles, normalized by total path length, or A/(A +B). This study showed that wear of UHMWPE articulating in a rectangular motion path likely occurs via a two-step mechanism beginning with molecular orientation followed by material fracture from the UHMWPE surface. The models inability to accurately predict UHMWPE wear for rectangular paths with lower aspect ratios suggests that there may be other operative wear mechanisms including significant re-orientation in the perpendicular sliding direction. In conclusion, it is possible to predict the wear behavior of UHMWPE using mathematical models. A robust model would have an important role in characterizing and predicting performance of currently used and potential future orthopaedic implant materials.

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26

Ophir, Amos. "Toughness enhancement of poly(ethylene terephthalate) with chemically modified ultra high molecular weight polyethylene." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/13881.

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The present work was concentrated on exploring and developing a toughening material system to be used in engineering products made of high crystalline PET [poly(ethylene terephthalate)]. The work addressed some fundamental objectives in the technology. of crystallised PET (CPET) related to toughness and thermoforming. PET is widely used in fibres and oriented films but is also an attractive material for moulded products, owing to its high melting point and solvent resistance. Crystalline PET, however, is brittle and susceptible to hydrolytic degradation through water absorption. The polymeric toughening system was based on suitably modified UHMWPE (ultra high molecular weight polyethylene) a crystalline polymer with very high fracture toughness under plane strain conditions, low water absorption, but with a relatively low melting point. Being a thermoplastic it has a modulus about 1,000 times higher than the equivalent hydrocarbon elastomer usually used to toughen PET and polyamides. Hence, deterioration of strength and stiffness is minimized. Blending PET with UHMWPE produces coarse microstructures and poor mechanical properties due to lack of compatibility of the two polymers. Compatibility is expected to be improved by reducing the interfacial tension and increasing the adhesion between the two phases; the first will reduce the size of the dispersed phase, while the latter would improve the mechanical properties. Compatibilisation of a pair of immiscible polymers, like in blend of PET with UHMWPE, can be achieved by incorporation of reactive units along the main chains of the UHMWPE, which are capable of strong interactions with the matrix component (PET). The methods used in this investigation involved smface grafting and irradiation treatment to produce chemically active groups on the UHMWPE polymer chain to achieve the required level of interfacial adhesion assisting the agglomerate particle breakdown into small size and to develop strong bonding to the PET when the two polymers are blended in a high shear mixing. The results obtained with several modified UHMWPE powders incorporated into PET by melt mixing showed a clear formation of small primary particles of UHMWPE strongly bonded to the matrix, thereby achieving a vast improvement in toughness while preserving other important fundamental properties related to both the end product and the material processing.

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27

DesJardins, John D. "Tribological systems for the evaluation of supercritical carbon dioxide sterilized ultra-high molecular weight polyethylene." Connect to this title online, 2006. http://etd.lib.clemson.edu/documents/1171901535/.

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28

Nguyen-Tra, Hong Phuong. "Melting behavior of strained crystals of ultra high molecular weight polyethylene with and without solvent." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74682.

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The origin of the gel formation in dilute solutions of ultra high molecular weight polyethylene (UHMWPE) is the subject of this thesis. At low heating rates v, 0.5 12 K/h, it cannot be detected in the usual DSC runs made at v = 600 K/h or higher.
The crystallinity found including fraction (III) (0.84-0.94) upgrades the calorimetric crystallinity to the values found by techniques not involving melting. Arrested melting which occurs between fractions (II) and (III) reveals the existence of a network whose cohesive junctions are unmelted and stabilized by strain. The amount of fraction (III) which is about 20% in the nascent sample increases to about a third of all crystals in a sample submitted to cycles of slow melting and slow crystallization.
Fraction (III) is stable in the presence of a solvent. However, its concentration in the sample can be made to vary between 5 and 25% by the appropriate choice of the solvent and thermal history. The network is stabilized during the dissolution of fraction (II) in decalin while it is reduced if the solvent is trichlorobenzene. Other thermal histories minimize the effect of solvent on the partition of the crystals between fractions (II) and (III). Crystallization in a temperature gradient is effective in diminishing fraction (III) and increasing fraction (II). A hypothesis to explain the high crystallinity of gels obtained by quenching is proposed.
The metastable states obtained during dissolution do not revert to the equilibrium state when the solvent is evaporated. Mechanical properties such as drawability and also the melting trace of the dried gels are affected by the solvent-induced changes in the melting pattern. The amount of fraction (III) appears to be a good test of drawability.
The dissolution traces at low v provide a much-needed quantitative characterization of UHMWPE gels, the crystals formed on quenching having a dissolution trace distinguishable from those grown isothermally or under shear.
Since fraction (III) results from a general process of melting, its occurrence in other polymers is expected and indeed has been found in preliminary experiments on poly-4-methylpentenel (P4MP1) and polypropylene (PP). (Abstract shortened by UMI.)

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29

Rimell, James Tristan. "Selective laser sintering of ultra high molecular weight polyethylene and Rapidsteel 2.0 for biomedical applications." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246693.

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30

Shibata, Nobuyuki. "Fatigue Damage of Ultra-high Molecular Weight Polyethylene (UHMWPE) and its Control in Joint Prostheses." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149441.

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31

Dwyer, Kimberly A. "Effect of heterogeneous structure on ultra high molecular weight polyethylene, failure mechanisms in total joint arthroplasty." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20558.pdf.

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32

Lee, Angela Wai-Wai. "In vitro degradation of ultra high molecular weight polyethylene, UHMWPE, by oxidative and/or hydrolytic processes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0014/MQ34115.pdf.

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33

Kenyon, Philip [Verfasser]. "Disentangled Ultra-High Molecular Weight Polyethylene by Ni(II)-Catalysed Polymerisation in Compartmentalised Systems / Philip Kenyon." Konstanz : KOPS Universität Konstanz, 2019. http://d-nb.info/1236503058/34.

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34

Urkaç, Sokullu Şadiye Emel Tıhmınlıoğlu Funda. "Characterization of Ultra High Molecular Weight Polyethylene (Uhmwpe) Modified By Metal-Gas Hybrid Ion Implantation Technique/." [s.l.]: [s.n], 2006. http://library.iyte.edu.tr/tezlerengelli/master/malzemebilimi/T000576.pdf.

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35

Schnitte, Manuel [Verfasser]. "Catalysts and Process Design for Living Aqueous Polymerization to Ultra High Molecular Weight Polyethylene Nanocrystals / Manuel Schnitte." Konstanz : KOPS Universität Konstanz, 2021. http://d-nb.info/1229837639/34.

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36

Ravi, Kesavan. "Mechanistic understanding of high strain rate impact behavior of ultra-high molecular weight polyethylene and the mechanism of coating formation during cold spraying." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI008/document.

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Des travaux récents ont montré que des revêtements polymères étaient réalisables par procédé connu sous le nom de Cold-Spray. Ces travaux sont particulièrement importants pour le polyéthylène de très haute masse molaire (UHMWPE) qui ne peuvent pas être mis en forme par les méthodes conventionnelles. Mais les mécanismes d'obtention des dépôts n'avaient pas été analysés. Cette thèse présente une analyse expérimentale mécanique détaillée du comportement à l'impact de particules d'UHMWPE et des mécanismes de formation du revêtement polymère sur un substrat en aluminium (Al) sous l'effet de la pulvérisation à froid de ces particules. La formation du revêtement se décompose en deux étapes : (1) se rapporte à la formation de la première couche de particules (interaction polymère-substrat), (2) à la croissance (par ajout de couches successives) du revêtement polymère (interaction polymère-polymère). La première étape de la formation du revêtement a été étudiée grâce à une technique expérimentale développée dans le cadre de cette thèse et appelée "Méthode de dépôt de particules isolées" (IPD). Il s'agit de déposer des particules isolées de UHMWPE sur un substrat en Al, en utilisant la même machine Cold-Spray, tout en contrôlant de manière précise la température du gaz et la teneur en FNA. Grâce à l'utilisation d'une caméra rapide, il a été possible de déterminer la vitesse des particules d'UHMWPE et par le calcul d'évaluer leur température avant et pendant leur impact. L'efficacité augmente avec d'une part la température et d'autre part la fraction de FNA. Cette efficacité dépend de la compétition entre l'énergie cinétique stockée sous forme d'énergie élastique Eel et l'énergie d'adhésion Ead du polymère à la surface du substrat. Pour que le film polymère se forme, il faut que Ead > Eel. Par ailleurs, Ead dépend de l'interface entre polyéthylène et aluminium, et de la présence de FNA. Les liaisons H disponibles sur la surface des FNA contribuent à l'adhésion, ce qui augmente le domaine de température favorable à la réalisation du dépôt. Concernant la croissance du revêtement, il s'agit cette fois-ci de l'adhésion polyéthylène-polyéthylène, avec toujours l'effet des nanoparticules FNA. Les études microstructurales et mécanique ont montré qu'en frittage conventionnel du UHMWPE sous forte pression, l'ajout de FNA renforce la cohésion des matériaux obtenus, mais que l'effet inverse est observé pour un frittage incomplet (sous faible pression). Enfin, afin d'explorer l'effet de vitesse de sollicitation de l'UHMWPE comparable à celles observées pour le Cold-Spray, des expériences utilisant des barres dites de Split-Hopkinson (SHPB) ont été menées. Les courbes obtenues permettent de disposer d'une cartographie complète du comportement thermo-viscoélasto-plastique de ce polymère, pur ou additionné de FNA
Recent developments showed polymer coatings to be feasible by cold spray (CS) technique on different surfaces. This is especially important for Ultra-High Molecular Weight Polyethylene (UHMWPE) which cannot be classically processed. But the mechanisms behind coating formation was not largely understood. The thesis presents a mechanistic understanding of high strain rate impact behavior of Ultra-High Molecular Weight Polyethylene and the mechanism of coating formation during CS. The coating formation is first broken down into two major categories: 1. Interaction of UHMWPE with Al substrate (impacting particle-substrate interaction) during a high-speed impact and interaction of UHMWPE with already deposited UHMWPE particles (impacting particle-deposited particles) leading to a buildup in the coating. First stage of coating formation was understood from a technique developed for this work called Isolated Particle Deposition (IPD). In the experimental IPD process, effects of gas temperature and FNA content were calibrated empirically by depositing UHMWPE particles in an isolated manner on an Al substrate. The Deposition efficiency increased with gas temperature and FNA content. The use of an ultrafast video-camera helped to determine the particle velocity, and theoretical calculations helped to evaluate the temperature of UHMWPE particles before and during the impact process. Mechanical response of UHMWPE at different temperatures were understood by calculating elastic strain energy of UHMWPE which decreased with increasing material temperature and increased with the strain rate. Rebound of UHMWPE particles on Al surface depended upon whether UHMWPE particles after impact furnished a contact area with an interfacial bond stronger than elastic strain energy of the particle. External contributions like H-bonds on the FNA surface provide sufficiently strong extra bonds at the contact surface to increase the window of deposition at higher temperatures, which was otherwise very low. Second stage of coating formation was understood from the mechanism of welding of UHMWPE grains at different interfacial loading conditions and at varying FNA contents. The morphological and mechanical characterization showed that when UHMWPE was processed under high loading conditions (using classical sintering technique), FNA particles reinforced the UHMWPE interface. On the contrary, when UHMWPE was processed under low loading conditions, FNA particles weakened the interface. Last to be discussed in the thesis is the strain rate effect of UHMWPE using Split-Hopkinson Pressure Bar (SHPB) experiments, in order to approach comparable conditions to what happens during particle impacts. This part of the study discussed in detail the effects a high strain-rate compression has on UHMWPE by analyzing its stress-strain curves, with and without FNA. Thus, the mechanical response data with the inclusion 0%, 4% and 10% FNA to UHMWPE is also presented and discussed

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Azam, Asad Muhammad. "Spectroscopic Optical Band Gap Properties and Morphological Study of Ultra-High Molecular Weight Polyethylene Nano Composites with Mg0.15Ni0.15Zn0.70Fe2O3." Thesis, Umeå universitet, Institutionen för fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-115809.

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Ultra high molecular weight polyethylene has been commonly used as a biomaterial for hip and knee implants. This thesis concerns optical and three phase morphology of nano composites of ultra high molecular weight polyethylene (UHMWPE) with Mg0.15Ni0.15Zn0.70Fe2O3 using analytical techniques such as UV-visible spectroscopy and Raman spectroscopy. Muller matrix spectro-polarimeter has been used to study the absorption behavior over the visible spectral range i.e. 400-800 nm. The results show significant changes in the absorption behavior of UHMWPE/Zn nano ferrite samples. To analyze these changes in pure and UHMWPE/Zn-nano ferrite composites, the Urbach edge method was used for the calculation of optical activation energy. Moreover, direct and indirect energy band gaps, and the number of carbon atoms in C=C unsaturation have been evaluated by using the modified Urbach formula and Tauc’s equation, respectively. The results show that the optical activation energy decreases more with the addition of 2wt% Mg0.15Ni0.15Zn0.70Fe2O3 than 1wt% of Mg0.15Ni0.15Zn0.70Fe2O3. The values of direct and indirect energy band gaps are also found to decrease more with 2wt% of Mg0.15Ni0.15Zn0.70Fe2O3. Furthermore, indirect energy gaps are found to have lower values as compared to direct energy gaps. The numbers of carbon atoms in clusters determined from modified Tauc’s equation were approximately the same for 1wt% and 2 wt% of Mg0.15Ni0.15Zn0.70Fe2O3 but differ for pure UHMWPE. The degree of crystallinity obtained from Raman spectroscopy was 42%, 43%, and 42% for UHMWPE, UHMWPE+1% of Mg0.15Ni0.15Zn0.70Fe2O3, and UHMWPE+2% of Mg0.15Ni0.15Zn0.70Fe2O3, respectively, i.e. about the same, but the relative amount of interphase and amorphous regions varied. Optical activation and sub band gap energies can be estimated for utilization of this composite in applications such as optical sensors, solar cells etc.

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Pascaud, Raphaël Stéphane. "On the influence of gamma-irradiation sterilisation and ageing on the fracture properties of ultra high molecular weight polyethylene." Thesis, University of South Wales, 1996. https://pure.southwales.ac.uk/en/studentthesis/on-the-influence-of-gammairradiation-sterilisation-and-ageing-on-the-fracture-properties-of-ultra-high-molecular-weight-polyethylene(6e08a3dc-6ee0-422e-9471-16fc1d1246f4).html.

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Pitting and delamination wear of ultra high molecular weight polyethylene (UHMW-PE) tibial plateaux for total joint replacements have habitually been attributed to a fatigue crack growth mechanism associated with a combination of high sub-surface cyclic shear stresses and degradation of the chemistry and structure of UHMW-PE caused by the gamma-irradiation sterilisation standard procedure. However, the exact mechanisms by which cracks initiate and grow in UHMWPE are not known and the relationships between these mechanisms and pitting and delamination are only assumptions based on qualitative observations. A fracture mechanics approach based on the J-integral concept of plane strain crack initiation toughness was therefore applied in order to firstly obtain the fracture toughness and crack growth stability of UHMW-PE and secondly to determine the mechanisms by which pitting and delamination occur in vivo. It was necessary to modify the existing standard ASTM E813-89 for the treatment of experimental J data in order to accommodate for the large crack tip plasticity and pronounced ductile tearing. This modified method was then applied to a detailed investigation of the influence of sterilisation and ageing on the chemical, physical and mechanical properties of UHMW-PE. Simulated shelf and in vivo environments enabling a rapid ageing of UHMW-PE corresponding to 10 years of natural ageing were developed. Sterilisation was either conducted by gamma-irradiation in air or nitrogen, or by gas plasma. In virgin UHMW-PE, cracks propagated by a succession of plastic deformation and craze nucleation over thin layers of material, yielding a very high value of J (90 kJ/m 2 ) at 37 : C. Gammairradiation in air followed by 10 years ageing resulted in a highly brittle material with a crack initiation fracture toughness reduced by 78% and a mechanical behaviour approaching that of a linear elastic material i.e. creation of a "cup-and-cone" in tension and formation of 45" shear lips in threepoint bending. On the other hand, gas plasma sterilised UHMW-PE could not be differentiated from unsterile UHMW-PE in either its physical nor mechanical properties. Qualitative correlations existed between the presence and location of highly oxidised regions and the crack initiation fracture toughness of the material. Quantitatively, the J-initiation toughness exhibited a hyperbolic decrease with increasing density and oxidation index while the tensile secant modulus linearly increased with density. From these empirical relationships, a model was created which described the variation of the fracture toughness with depth within a UHMW-PE sample. This model indicated that the zones of high density, oxidation and crystallinity correspond to the areas of maximum shear stress and minimum fracture toughness and that the propensity of UHMW-PE to suffer pitting, delamination and high wear rates through a fracture mechanism is significantly increased by extensive oxidative degradation.

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39

Kataoka, Akihiro. "Association of high molecular weight DNA fragmentation with apoptotic or non-apoptotic cell death induced by calcium ionophore." Kyoto University, 1997. http://hdl.handle.net/2433/202218.

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40

Varadarajan, Ravikumar. "On the Nature of Static and Cyclic Fracture Resistance of Ultra High Molecular Weight Polyethylenes Used in Total Joint Replacements." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1164903681.

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41

Shichen, Yu. "CHAIN ENTANGLEMENTS EFFECTS IN NASCENT ULTRA-HIGH MOLECULAR WEIGHT POLYPROPYLENE SYNTHESIZED BY ZIEGLER – NATTA MULTIPLE-SITES AND METALLOCENE SINGLE-SITE CATALYSTS." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1620286973657457.

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42

Sirimamilla, Pavana Abhiram. "MECHANISTIC STUDY OF CRACK INITIATION AND PROPAGATION IN CROSSLINKED ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENES (UHMWPE) SUBJECTED TO STATIC AND CYCLIC LOADING." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1345862222.

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43

Baier, Moritz C. [Verfasser]. "Living Polymerization to Ultra-High Molecular Weight and Dye-Labeled Polyethylene for Single-Molecule Fluorescence Microscopy and Reactor Blends / Moritz C. Baier." Konstanz : Bibliothek der Universität Konstanz, 2016. http://d-nb.info/1173616454/34.

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Rosário, Salmo Cordeiro do. ""Estudo do efeito da radiação ionizante por feixe de elétrons sobre o polietileno de ultra alto peso molecular virgem e reciclado industrial"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-29052007-142007/.

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O polietileno de ultra alto peso molecular (UHMWPE) é um plástico de engenharia que tem várias aplicações atualmente, mormente em áreas específicas da indústria e da medicina. O UHMWPE pode ser utilizado ainda em outras aplicações: defensas portuárias; guias de corrente; revestimentos de caçambas, silos e calhas; engrenagens; buchas; guias de correias e próteses cirúrgicas. Esta gama de aplicações se deve ao fato das excelentes características técnicas que este material possui, como: alta resistência a abrasão, elevada resistência ao impacto, anti-aderência, atóxico, excelente resistência química, baixo peso específico, fácil usinagem e alta resistência a fadiga. Os tipos de polietileno de ultra alto peso molecular (UHMWPE) utilizados neste trabalho foram o UTEC 3041 e UTEC 6541 da Braskem. A reciclabilidade do UHMWPE ganhou interesse, porque a utilização desta matéria-prima na última década cresceu mais de 600%, tornando-se um dos plásticos de engenharia mais utilizados para obtenção de peças usinadas depois da poliamida. Com o crescimento na utilização deste polímero na confecção de peças para maquinários, o seu desperdício tem sido muito grande, porque o resto deste material é desprezado, geralmente não sendo reaproveitado. Este trabalho tem como objetivo reciclar o UHMWPE UTEC 3041 e estudar as propriedades deste material virgem e reciclado e comparar os resultados entre si e com o UHMWPE UTEC 6541, e com estes materiais submetidos a diferentes doses de radiação.
Ultra High Molecular Weight Polyethylene (UHMWPE) is an engineering plastic which has several applications, chiefly, in specific areas of the industry and medicine. UHMWPE can be even for other applications such as: port fenders, current guide, bucket coating, silos and gutters, plugs, pulleys and surgical prosthesis. This range of applications is due to the excellent technical characteristics that this material owns, such as; high resistance to wear, high resistance to impact, anti-adherence, non toxic, excellent chemical resistance, low specific weight, easy mill processing, and high resistance to fatigue. The UHMWPE type used in this work were UTEC 3041 and UTEC 6541 of the Braskem. The recycling process of UHMWPE raised much interest, because the utilization of this rawmaterial grew over 600% in the last decade, becoming one of the most used engineering plastics for attainment of mill processed parts after polyamide. As the utilization of this polymer in the manufacturing of parts for machinery has grown, its waste is very big, because the rest of this material is thrown out, usually not being reused. The goal of this work is to recycle the UHMWPE UTEC 3041 and study the properties of this recycled and virgin material and compare the results between both with these materials submitted to different radiation dose.

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45

Wampler, Amos. "Resolution of crystalline phases in polymorphic gel-spun ultra-high molecular weight polyethylene fibers using restrained differential scanning calorimetry and x-ray diffraction." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 70 p, 2008. http://proquest.umi.com/pqdweb?did=1597633731&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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46

Bruck, Angela Lynette. "Friction and wear behavior of ultra-high molecular weight polyethylene as a function of crystallinity and in the presence of the phospholipid DPPC (dipalmitoyl phosphatidylcholine)." [Ames, Iowa : Iowa State University], 2007.

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47

Cosentino, Emanuela. "Optimization of High and Ultra High Molecular Weight DNA purification for Third Generation Sequencing and Optical Mapping in algae." Doctoral thesis, 2020. http://hdl.handle.net/11562/1018425.

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The analysis of long DNA molecules by novel genomic technologies, such as Bionano optical mapping and Third Generation Sequencing, including PacBio Single Molecule Real Time Sequencing and Oxford Nanopore sequencing, provide the opportunity for complete genome characterization and reconstruction, allowing to identify large (balanced) structural variants, to determine the variant phasing and haplotype, to sequence full-length repeated regions and to assemble and scaffold genomes de-novo. Implementation of these technologies requires a combination of highly pure and High Molecular Weight (HMW) DNA, >10^5bp (Bionano Optical Mapping) or >10^4bp (Third Generation Sequencing) in length. However, standardized and suitable extraction methods to obtain highly pure HMW DNA are still missing for many organisms and tissues. In particular, plants and algae store a large amount of phenolic compounds, polysaccharides and a high copy number of chloroplast and mitochondrial DNA, making the extraction of both pure and HMW genomic DNA challenging. The aim of this work was the optimization of methods for the purification of highly pure and (Ultra)HMW DNA from a microalgae selected as case study, Haematococcus pluvialis (H.pluvialis), suitable for Third Generation sequencing and Bionano optical mapping. Despite H.pluvialis is unicellular green microalgae extensively studied for industrial applications, a high quality genome for its biotechnological application is still missing. Therefore, an extensive benchmarking of DNA and nuclei isolation methods was conducted to produce high-quality HMW DNA suitable to generate Third Generation sequencing and Bionano optical mapping data for the reconstruction of its genome de-novo. 4 (U)HMW DNA extraction methods and 8 nuclei isolation methods and 4 post-extraction DNA purification methods were evaluated independently or in combination. To further improve DNA purity and optimize the production of high-quality sequencing data, 4 post-extraction DNA purification methods were also tested. The methods were compared in terms of yield, length and purity of extracted DNA and its analysis by Third Generation sequencing and optical mapping. Only 3 specific combinations of these protocols yielded suitable DNA to generate successful results with PacBio (CTAB buffer+AMPureXP beads purification), Oxford Nanopore (MEB buffer+G-tip- DNA based extraction) and Bionano (MEB buffer+plug- DNA based extraction). The data produced herein can be used to obtain a highly contiguous genome for H.pluvialis with the efficient reconstruction of repetitive genomic portions (highly present in H.pluvialis genome), by eliminating ambiguity in the positions or size of genomic elements.

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48

Tang, Lei. "Enzymatic Polymerization of High Molecular Weight DNA." Diss., 2016. http://hdl.handle.net/10161/12909.

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The use of DNA as a polymeric building material transcends its function in biology and is exciting in bionanotechnology for applications ranging from biosensing, to diagnostics, and to targeted drug delivery. These applications are enabled by DNA’s unique structural and chemical properties, embodied as a directional polyanion that exhibits molecular recognition capabilities. Hence, the efficient and precise synthesis of high molecular weight DNA materials has become key to advance DNA bionanotechnology. Current synthesis methods largely rely on either solid phase chemical synthesis or template-dependent polymerase amplification. The inherent step-by-step fashion of solid phase synthesis limits the length of the resulting DNA to typically less than 150 nucleotides. In contrast, polymerase based enzymatic synthesis methods (e.g., polymerase chain reaction) are not limited by product length, but require a DNA template to guide the synthesis. Furthermore, advanced DNA bionanotechnology requires tailorable structural and self-assembly properties. Current synthesis methods, however, often involve multiple conjugating reactions and extensive purification steps.

The research described in this dissertation aims to develop a facile method to synthesize high molecular weight, single stranded DNA (or polynucleotide) with versatile functionalities. We exploit the ability of a template-independent DNA polymerase−terminal deoxynucleotidyl transferase (TdT) to catalyze the polymerization of 2’-deoxyribonucleoside 5’-triphosphates (dNTP, monomer) from the 3’-hydroxyl group of an oligodeoxyribonucleotide (initiator). We termed this enzymatic synthesis method: TdT catalyzed enzymatic polymerization, or TcEP.

Specifically, this dissertation is structured to address three specific research aims. With the objective to generate high molecular weight polynucleotides, Specific Aim 1 studies the reaction kinetics of TcEP by investigating the polymerization of 2’-deoxythymidine 5’-triphosphates (monomer) from the 3’-hydroxyl group of oligodeoxyribothymidine (initiator) using in situ 1H NMR and fluorescent gel electrophoresis. We found that TcEP kinetics follows the “living” chain-growth polycondensation mechanism, and like in “living” polymerizations, the molecular weight of the final product is determined by the starting molar ratio of monomer to initiator. The distribution of the molecular weight is crucially influenced by the molar ratio of initiator to TdT. We developed a reaction kinetics model that allows us to quantitatively describe the reaction and predict the molecular weight of the reaction products.

Specific Aim 2 further explores TcEP’s ability to transcend homo-polynucleotide synthesis by varying the choices of initiators and monomers. We investigated the effects of initiator length and sequence on TcEP, and found that the minimum length of an effective initiator should be 10 nucleotides and that the formation of secondary structures close to the 3’-hydroxyl group can impede the polymerization reaction. We also demonstrated TcEP’s capacity to incorporate a wide range of unnatural dNTPs into the growing chain, such as, hydrophobic fluorescent dNTP and fluoro modified dNTP. By harnessing the encoded nucleotide sequence of an initiator and the chemical diversity of monomers, TcEP enables us to introduce molecular recognition capabilities and chemical functionalities on the 5’-terminus and 3’-terminus, respectively.

Building on TcEP’s synthesis capacities, in Specific Aim 3 we invented a two-step strategy to synthesize diblock amphiphilic polynucleotides, in which the first, hydrophilic block serves as a macro-initiator for the growth of the second block, comprised of natural and/or unnatural nucleotides. By tuning the hydrophilic length, we synthesized the amphiphilic diblock polynucleotides that can self-assemble into micellar structures ranging from star-like to crew-cut morphologies. The observed self-assembly behaviors agree with predictions from dissipative particle dynamics simulations as well as scaling law for polyelectrolyte block copolymers.

In summary, we developed an enzymatic synthesis method (i.e., TcEP) that enables the facile synthesis of high molecular weight polynucleotides with low polydispersity. Although we can control the nucleotide sequence only to a limited extent, TcEP offers a method to integrate an oligodeoxyribonucleotide with specific sequence at the 5’-terminus and to incorporate functional groups along the growing chains simultaneously. Additionally, we used TcEP to synthesize amphiphilic polynucleotides that display self-assemble ability. We anticipate that our facile synthesis method will not only advance molecular biology, but also invigorate materials science and bionanotechnology.

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49

吳朝瑞. "Synthesis of Ultra-High Molecular Weight Poly (vinyl alcohol)." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/01906606466489469257.

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碩士
逢甲大學
紡織工程研究所
83
PVA had high potential as a candidate of ultrahigh strength fibers because of its superior qualities of crystalline modulus, impact strength, weather durability, antialkaline resistance, and so on. Since Keviar was produced by Du Pont, new polymer materials which will take its place have been developed. Polyethylene gel was reported by Penning and Smith et al. PVA fiber spun from high molecular weight PVA gel is also expected to have a high modulus and high strength. 　　However, it is very difficult to obtain PVA of high molecular, because chain transfer reactions control the molecular weight of polymers in radical polymerization of vinyl acetate (VAc) which are precursors for PVA. Moreover, branched PVAc formed by chain transfer reactions. Photo-Emulsion polymerization of VAc were carried out at low temperature to obtain high molecular weight polymer after saponification of PVAc. 　　In this project, high molecular weight PVA was produced by photo-emulsion polymerization. Firstly, we discussed the variables in the polymerization process involved polymerization temperature, concentration of initiator emulsifier and monomer, and so on. The degree of polymerization of PVA, triad tacticity, 1,2-glycol sequences, degree of crystallinity, degree of saponification and physical properties were also determined. 　　The results indicated that, the concentrated emulsion had a volume fraction of vinyl acetate (VAc) of 92.2%, was irradiated with a high pressure mercury lamp in absence of initiator at 0℃ and high molecular weight poly (vinyl acetate) (PVAc) which gave poly (vinyl alcohol) (PVA) of Pn (average degree of polymerization) = 12,400 after hydrolysis was obtained. The characteristics of the typical PVA obtained as above were analyzed as following. The break strength was 0.46 GPa and initial modulus was 4.26 Gpa. The melting temperature was about 238.86℃. The degree of crystalinity was 33.21% and the degree of saponification was 99.41%. The ratios of triad tacticity were estimated as 15.32%, 40.60% and 44.47% for isotactic, heterotactic and syndiotactic triad, respectively.

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Stephens, Christopher Phillip. "Morphological Characterization of Irradiated Ultra High Molecular Weight Polyethylene (UHMWPE)." 2009. http://trace.tennessee.edu/utk_graddiss/57.

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Effects of radiation (gamma and proton) on Ultra High Molecular Weight Polyethylene (UHMWPE) is studied for prosthetic joints and for radiation shielding for manned space missions. The first section of the dissertation will cover gamma radiation effects on UHMWPE by means of solubility, hardness, three-phase model, crystallite thickness, and molecular mobility studies. The second part will cover proton radiation effects on UHMWPE by means of solubility, three-phase crystallite model, and crystallite thickness study. The combined studies of the gamma irradiated samples shows that chain scission occurs on the surface and crosslinking in the center. The combined studies of the proton irradiated samples show that crosslinking occurs in the amorphous region and breaking of the tie chains and loops causes the growth of the already existing crystals. A new method has been developed to analyze DSC data based on crystallite thickness that generates crystallite thicknesses (number-average, weight-average, and z-average) and the lamella thickness polydispersity index, PDI (lw/ln and lz/ln). This new analysis method agrees with all other experiments conducted on the samples (solubility, molecular mobility, and three-phase model analysis).

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Дисертації з теми "High and Ultra High Molecular Weight DNA"

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