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Assembly of macromolecular complexes examined by electrospray ionisation mass spectrometryTito, Mark Anthony January 2000 (has links)
No description available.
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Effects of Deletions of High Molecular Weight Glutenin Subunit Alleles on Dough Properties and Wheat Flour Tortilla QualityTuncil, Yunus 2012 August 1900 (has links)
In wheat (Triticum aestivum L), high molecular weight glutenin subunits (HMW -GS) are synthesized by the loci Glu-A1, Glu-B1, and Glu-D1 on the long arm of group 1 chromosome, and their variants play a significant role in the functional properties of flour; hence dough properties and tortilla quality. This study was conducted to understand the effects of HMW-GS on dough properties and tortilla quality using 40 different wheat lines from two different locations; Texas Agrilife Experiment Station at McGregor, and at Castroville, Texas, in 2010.
Wheat lines in which one or more of these loci were absent (deletion lines) and non-deletion lines were used. Flours were evaluated for insoluble polymeric protein (IPP) content and mixograph properties. Dough properties; compression force, stress relaxation test, and dough extensibility, were determined using a texture analyzer. Tortillas were produced by hot-pressed method and evaluated for physical properties and textural change during 16 days of storage.
Flour from deletion lines had lower average IPP content (38.4%) than non-deletion lines (41.9%). Dough from deletion lines were more extensible (44.8 mm) and required lower equilibrium force from stress relaxation test (4.91 N) compared to non-deletion lines (34.2 mm, and 6.56 N, respectively). Deletion lines produced larger diameter tortillas (177 mm) than non-deletion lines (165 mm) and had lighter color (L* = 82.3) than tortillas from non-deletion lines (L* = 81.0). Most of the deletion lines interestingly produced tortillas with acceptable flexibility scores on day 16 of storage (>= 3.0). Flour IPP content (r = -0.57) and equilibrium force (r = -0.80) were negatively correlated with tortilla diameter, but positively correlated with 16 day flexibility scores (r = 0.72, and r = 0.68, respectively). In general, deletion at Glu-A1 or Glu-D1 or presence of 2+12 instead of 5+10 allelic pair at Glu-D1 locus produced large diameter tortillas, but with poor day 16 flexibility. However, combination of 7+9 at Glu-B1 locus with deletions at Glu-A1 or Glu-D1 or 2+12 at Glu-D1 consistently produced tortillas that had large diameter and retained good flexibility scores during 16 days of storage. The results indicate the presence of 7+9 at Glu-B1 may play a crucial role in selection of wheat varieties for tortilla making.
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Studies of polymer thin films using atomic force microscopyPeng, Dongdong 22 January 2016 (has links)
This thesis focuses on how the properties of polymer thin films depend on the film thickness and molecular weight (Mw). Previous studies of polystyrene (PS) films coated on silica with Mw of 2.4 and 212 kg/mol found that the viscosity of the films decreases with decreasing film thickness. A two-layer model assuming a 3 nm thick
mobile layer situated at the top surface of the film and hydrodynamically coupled to a bulklike inner layer is able to describe the viscosity of the films. To better understand the dynamics exhibited by the surface mobile layer, this work extends the measurement to various other Mw up to 2316 kg/mol.
The result shows that the viscosity of the films also decreases with decreasing film thickness and can be described by the same two-layer model. But there are exceptional findings as well. Specifically, the viscosity of the high-Mw films (> 60 kg/mol) exhibit a Mw^0 dependence, distinctly different from the Mw^3.4 dependence exhibited by the viscosity of the bulk polymer. Moreover, the surface chains in the high-Mw films, as inferred from the two-layer model, are in an unphysically stretched
state. These observations led to the conjecture that the viscosity reduction in the high-Mw films is due to a different mechanism from that in the lower Mw films which is directly tied to the surface mobile layer as in the two-layer model.
To scrutinize this conjecture, viscosity measurement is extended to PS films doped with Dioctyl phthalate (DOP). A previous experiment showed that the influence of the surface on the overall dynamics in this system is likely to be much smaller than in the undoped films. The measurement results are examined to determine, among other things, whether the viscosity reduction relative to that in the undoped films is weaker in the low-Mw than in the high-Mw regime.
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SYNTHESIS OF ULTRAHIGH MOLECULAR WEIGHT POLY(METHYL METHACRYLATE) FOR SINGLE POLYMER STUDIESRen, Kehao 28 April 2021 (has links)
No description available.
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Mechanical Properties of Very High Molecular Weight PolyisobutyleneWeidknecht, Marcia E. 15 September 2014 (has links)
No description available.
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Synthesis of High Molecular Weight Poly (methyl methacrylate) by ARGET ATRPQiu, Jialin 15 September 2015 (has links)
No description available.
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ION IMPLANTATION OF ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENEKaranfilov, Christopher 08 September 2009 (has links)
No description available.
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South African experience with cross-linked ultrahigh molecular weight polyethylene in total hip arthroplastyCakic, Josip Nenad 21 October 2009 (has links)
Ph.D.,Dept. of Orthopaedic Surgery, Faculty of Health Sciences, University of the Witwatersrand, 2009. / Total hip replacement (THR) is an effective method of treatment for patients with hip
disability. The procedure is capable of providing long-term functional improvement
with excellent control of pain and restoration of function. Sir J Charnley developed a
concept of low friction arthroplasty, which was based on use of ultra-high molecular
weight polyethylene acetabular and stainless steel femoral components. The
components were attached to bone with the use of polymethylmethacrylate (PMMA)
bone cement. This concept has been very successful, and is considered the gold
standard of THR.
Aseptic loosening of the prosthetic components remains the single most important
reason for failure of THRs. Wear to the ultra high molecular weight polyethylene
(UHMWPE) acetabular cup is a well-known cause of osteolysis and aseptic loosening
of the components. Thus, substantial improvement to the wear resistance of
UHMWPE could extend the clinical life span of total hip replacements. In an attempt
to reduce polyethylene wear and subsequent osteolysis, a method was developed in
the early seventies in South Africa to improve polyethylene quality by means of
gamma ray cross-linking. The acetabular cup was irradiated with 100 Kilogray in an
acetylene environment, which was used as a cross-linking gas material, resulting in
improvement of UHMWPE wear resistance.
Influenced by the world trend and with the advent of a ceramic bearing surface, the
Project of cross-linking was, to a certain extent, forgotten. Patients followed up in the
late 1990s, showed minimal or total absence of wear after 15 years or longer.
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Based on my preliminary studies, and anticipating the world trend of acceptance of
cross- link UHMWPE, the aim of this research is to consolidate the results from the
largest long term group of patients with acetylene cross-link UHMWPE, to study
polyethylene gamma irradiated in the presence of a cross-linking acetiylene gas and
the effects of it, in vitro, using a hip simulator. I was planning to communicate with as
many patients as possible from the group operated on from 1977 until 1983 in whom
cross-link UHMWPE was used. This group of over thousand patients represents the
largest group of patients with cross-linked UHMWPE acetabular components in the
world, with the longest clinical follow up of over 20 years on average.
The first part of the research is a retrospective study:
The goal was to contact as many patients as possible who were operated on during the
period 1977 to 1983 when cross-linked polyethylene was used. To qualified for the
study each patient had to have an early postoperative and the latest follow up
radiograph.
The radiological study consisted of the radiological measurement of wear. For this
purpose the Hip Analysis Suite program was used. This is a software program
designed by Dr John M. Martell from the University of Chicago, which is widely used
and internationally accepted for
that purpose. Image analysis offers significant improvements in reproducibility and
accuracy when compared to manual analysis.
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The final results were compared with results of polyethylene wear in patients in
whom conventional UHMWPE was used. For this comparison only patients with
acetabular components made from the same UHMWPE material and from the same
supplier were used. The conventional UHMWPE is a component of the gold standard
of hip replacement surgery. World-wide published follow up studies of 15 years and
longer using conventional UHMWPE were compared to the cross-link UHMWPE
group.
If revision surgery was indicated for whatever reason in patients in with cross-linked
UHMWPE acetabular components, the retrieved prosthesis was analyzed. The
analysis consisted of examination of the articular surface of the cross-linked
acetabular component for micro wear phenomena using a Scanning Electron
Microscope (SEM). In order to perform an objective analysis of the retrieved
components, two independent laboratories were used, namely:
Peterson Tribology Laboratory, Loma Linda University, California, and
Biomechanical Laboratory, Faculty of Engineering, University of Pretoria.
The analyses were possible thanks to collaboration with Dr Ian Clark from Peterson
Tribology Laboratory and Dr NDL Burger in charge of the Biomechanical Laboratory
at the Department of Engineering, University of Pretoria
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"Estudo do efeito da radiação ionizante por feixe de elétrons sobre o polietileno de ultra alto peso molecular virgem e reciclado industrial" / IONIZING RADIATION EFFECT STUDY BY ELECTRON BEAM ON ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE VIRGIN AND RECYCLED INDUSTRIALRosário, Salmo Cordeiro do 15 September 2006 (has links)
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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"Estudo do efeito da radiação ionizante por feixe de elétrons sobre o polietileno de ultra alto peso molecular virgem e reciclado industrial" / IONIZING RADIATION EFFECT STUDY BY ELECTRON BEAM ON ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE VIRGIN AND RECYCLED INDUSTRIALSalmo Cordeiro do Rosário 15 September 2006 (has links)
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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