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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Synthesis, characterization and properties of rigid macromolecules with extended conjugation, using palladium-catalyzed alkynylated polyhaloarenes.

Akintomide, Temiloluwa 12 1900 (has links)
A synthetic approach to macromolecules of acetylenic arrays and luminescent properties is proposed and the execution of initial steps is described. Palladium-catalyzed coupling of 1,3,5-triiodobenzene with trimethylsilylbuta-1,3-diyne, trimethylsilylocta-1,3,5,7-tetrayne, and trimethylsilylhexadeca-1,3,5,7,9,11,13,15-octayne to yield the new 1,3,5-tris(trimethylsilylbuta-1,3-diynyl)benzene and the proposed 1,3,5-tris(8-(trimethylsilyl)octa-1,3,5,7-tetraynyl)benzene and 1,3,5-tris(trimethylsilyl)hexadeca-1,3,5,7,9,11,13,15-octaynyl)benzene respectively. The proposed three-coordinate Au (I) complexed macromolecules will be derived from the metallation of the aforementioned alkynylated arenes.
82

Studies on the secretion of macromolecules by the mammalianepididymis, their interaction with spermatozoa and their roles insperm maturation

曾潤福, Tsang, Yun-fuk, Angus. January 1983 (has links)
published_or_final_version / Physiology / Doctoral / Doctor of Philosophy
83

Toward the synthesis of organic moieties for use in luminescent lanthanide materials: from benzodithiophene based linkers to a series of 2,3 pyridinedicarboxylate coordination polymers

Unknown Date (has links)
The main focus of this thesis is to present the structural and photophysical characteristics of the coordination polymers [Ln(C7H3NO4)(C7H4NO4)(H2O)]n (Ln is Pr, Nd, Sm, Eu, and Tb), as well as attempting to synthesize the novel organic linker 4,4'(4,8-Dihydrobenzo[1,2-b:4,5-b']dithiophene-4,8-diyl)dibenzoic acid (BDTDC). Various lanthanide salts were coordinated with 2,3-pyridinecarboxylate (2,3- pydc) via hydrothermal synthesis. ... Progress was made toward the synthesis of a novel metal-organic framework linker BDTDC. Synthesis of the intermediate benzo[1,2-b:4,5-b']dithiophene as well as the determination of the crystal structure, were performed successfully and are reported herein. / by Amanda Lyn Staggeer Ramirez. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
84

Electrostatic effects on the restricted diffusion of macromolecules

Smith, Frank Glenroy January 1981 (has links)
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Frank Glenroy Smith, III. / Sc.D.
85

Characterisation and extrusion of Metroxylon sago starch

Ansharullah, University of Western Sydney, Hawkesbury, Faculty of Environmental Management and Agriculture, School of Food Science January 1997 (has links)
The study presented here was firstly to investigate the physiochemical properties of native sago starch (obtained from Metroxylon sp. and designated as sago INA), in comparison with those of Metroxylon sago starch obtained from a different source, sago starch derived from Arenga sp. palms, wheat, corn, and tapioca starches. The properties analysed were chemical composition, total starch content, apparent amylose content, pasting properties, endothermic thermal behaviour, starch paste clarity, freeze-thaw stability, hardness of gel, and microscopic structure of the granules. The results obtained indicated that sago INA starch sample contained less fat and protein, compared to cereal starches. The sago starch sample had larger sized granules and had a more transparent paste. The gels of the starch were harder, and showed a relatively better stability to freeze-thaw treatment. The other part of the study was extrusion of sago INA starch both in the absence and presence of enzyme by utilising a response surface design. In the absence of the enzyme, the experiment was conducted to establish the extrusion process conditions including moisture contents, melt temperature, and screw speed. The extruded products were then analysed for degree of molecular degradation, light microscopic structure, reducing sugars of the water soluble materials, water absorption index, water solubility index, enzyme susceptibility, and gelatinisation endothermic energy. Increased mechanical and thermal energy input received by the products in the extruder resulted in a significant degradation of the molecular weight of the macromolecules. Light photomicrographs also suggested that the granule structures of the extrudates have been reshaped. All extrudate samples had a very low gelatinisation endothermic energy compared to its native starch. The specific mechanical energy received by the products in the extruder was calculated and related to the process variables. The possibility of using the products in food application was also discussed. / Doctor of Philosophy (PhD)
86

Molecular interactions of latent transforming growth Factor-β binding Protein-2 (LTBP-2) with fibrillins and other extracellular matrix macromolecules [electronic resource]: LTBP-2 competes with LTBP-1 for binding to Fibrillin-1 suggesting that LTBP-2 may modulate latent TGF-β storage

Hirani, Rena M January 2006 (has links)
Elastic fibres, a major component of many connective tissues, are composed of an amorphous elastin core surrounded by fibrillin - containing microfibrils. The function of these microfibrils appears to require the co - ordinated interactions of fibrillins with a range of extracellular matrix ( ECM ) macromolecules including, latent transforming growth factor - β ( TGF - β ) binding proteins ( LTBPs ). LTBPs share a high degree of structural similarity to fibrillins, since they both contain unique 8 - cysteine motifs. Of the four members of the LTBP family, LTBPs - 1, - 3 and - 4 covalently bind to latent forms of TGF - β. LTBP - 1 has been shown to interact with the N - terminal domains of fibrillin - 1 and - 2 and LTBP - 4 interacts with the N - terminal domains of fibrillin - 1, suggesting that fibrillin - containing microfibrils may act as TGF - β stores and localise latent TGF - β complexes to the ECM. LTBP - 2 differs from other members of the LTBP family since it does not covalently bind latent TGF - β. However, LTBP - 2 strongly co - localises with fibrillin - containing microfibrils in a number of tissues suggesting that LTBP - 2 could have a structural role associated with these elements presumably independent of TGF - β storage, or could act to mediate specific microfibril - ECM interactions. To understand more about the function of LTBP - 2, this study involved screening for potentially important molecular interactions of LTBP - 2 with fibrillins and a variety of ECM proteins. Human recombinant LTBP - 2 ( r - LTBP - 2 ) was cloned, expressed and purified using a mammalian cell culture system. Solid phase binding assays were used to screen for interactions between r - LTBP - 2 and continguous fragments of fibrillin - 1 and - 2 as well as MAGPs, tropoelastin, collagens and proteoglycans. A cation dependant interaction was found between the C - terminal domains of LTBP - 2 and the N - terminal domains of fibrillin - 1, but not with the analogous region of fibrillin - 2. Thus, LTBP - 2 seems to have an exclusive role associated with fibrillin - 1 - containing microfibrils. Further studies found that the C - terminal region of LTBP - 2 competes with LTBP - 1 for binding to fibrillin - 1, suggesting that the binding site for LTBP - 2 on fibrillin - 1 is the same or in close proximity to that for LTBP - 1. Immunohistochemical analysis of LTBP - 1 and - 2 within developing human aorta indicated that both LTBPs co - localised with fibrillin - 1. However, the two LTBPs did have distinct distribution patterns in relation to each other, in that LTBP - 2 was found throughout the medial layer whereas LTBP - 1 was mainly located in patches of the outer medial layer. No regions of strong co - localisation of the two LTBPs were found. Thus, these findings suggest that LTBP - 2 could indirectly modulate the presence of TGF - β upon the fibrillin - containing microfibrils by competing for binding with the LTBP- 1 / TGF - β complex to these structures. Other binding studies showed a cation independent interaction between r - LTBP - 2 and an as yet unidentified component of a crude bovine collagen - IV extract. Since collagen - IV is a major component of basement membranes, an interaction between r - LTBP - 2 and a protein within this bovine collagen - IV preparation suggests LTBP - 2 may have a further function involving a basement membrane component. It will be interesting to determine if LTBP - 2 acts as a bridging molecule between basement membrane structures and fibrillin - containing microfibrils or if it has another function independent of these microfibrils. / Thesis (Ph.D.)--School of Medical Sciences, 2006.
87

Stabilization of Z-DNA by demethylation of thymine bases : a crystallization and thermo-dynamic study of d(m⁵CGUAm⁵CG)

Zhou, Guangwen 16 September 1991 (has links)
Graduation date: 1992
88

A Selectivity Study on the Use of Caffeine and Theobromine Imprinted Polypyrrole Surface Electrodes

Vinjamuri, Anil Kiran Kumar 01 August 2008 (has links)
Molecularly imprinted polymers (MIPs) are proving to be very effective in development of synthetic recognition systems and are of great interest to those interested in the field of sensor technology. The use of MIPs is receiving considerable interest due to the ability to prepare recognition matrices that possess high substrate selectivity and specificity. Conducting polymers (CP) have proved to be an excellent tool for the preparation of nano-structured biologically selective systems. Polypyrrole (Ppy) is one such CP that is extensively used for the construction of bioanalytical sensors. Ppy has shown great promise primarily due to its biocompatibility and thermal stability under a variety of environmental conditions. In this study, caffeine imprinted electrodes (CIE) and theobromine imprinted electrodes (TIE) were prepared. This research project subsequently focused on three main aspects: 1) to determine the selectivity of a caffeine and theobromine imprinted MIP using Ppy as the conducting polymer matrix, 2) comparing pulsed amperometric detection (PAD) and electrical impedance spectroscopy (EIS), for their value as potential detection schemes and 3) to determined the applicability of the molecularly imprinted polypyrrole by analyzing commercial samples of instant coffee and tea and comparing results to that obtained from established HPLC procedures. In summary, the following conclusions are stated: - Both PAD and EIS measurements taken from CIE and TIE MIPs showed no statistical difference in response at the 95% confidence level using a standard paired t-test. - Reproducibility for both MIPs was estimated by calculating an average percent relative standard deviation (%RSD) for the corresponding MIPs and was determined to be less than 3%. - The degree of selectivity was estimated by calculating a % relative error for the CIE and TIE electrodes using both PAD and EIS analysis. These results revealed percent relative errors typically less than 5% for equimolar amounts of “interfering” analyte. - A ruggedness revealed that over the concentration range and time interval tested (1-20 mM and 5 days), the average percent relative standard deviation was determined to be less that 7%. - The caffeine content in the coffee sample analyzed, as determined by PAD and EIS, was consistent with results obtained by HPLC analysis however, the theobromine content determined in tea using PAD and EIS was significantly different from that determined by HPLC at the 95% confidence level.
89

Effect Of Ionizing Radiation On Different Polymers And Possible Use Of Polymers In Radioactive (nuclear) Waste Management

Ozdemir, Tonguc 01 May 2006 (has links) (PDF)
In this study three polymers, namely poly(carbonate urethane), poly(bisphenol-a-epichlorohydrin) and poly(methyl methacrylate), were selected and change of properties with gamma treatment were studied. Two different dose rates were used for irradiations and the properties of the irradiated polymers exposed to same total absorbed dose were compared. In addition, long irradiations of up to about six months with high dose rate were done in order to understand the radiation stability of the polymers, which may be possible candidates for embedding media for low and intermediate level radioactive (nuclear) waste before their final disposal. Tensile, DSC, DMA, TGA, FTIR-ATR, FTIR tests were completed to understand the degradation of the polymers as a function of dose rate and total absorbed dose. The DSC and FTIR results showed that there was not much structural chemical changes in polymer chains with irradiation. However, the changes in mechanical properties were recorded. It was concluded that poly(carbonate urethane) and poly(bisphenol-aepichlorohydrin) can possibly be used in conditioning of radioactive waste, as they are radiation stable polymers. However, due to the moderate resistance of poly(methyl methacrylate) to ionizing radiation, it can be used for low level radioactive waste conditioning.
90

Preparation And Characterization Of Chitosanpolyethylene Glycol Microspheres And Films For Biomedical Applications

Gunbas, Ismail Dogan 01 April 2003 (has links) (PDF)
In recent years, biodegradable polymeric systems have gained importance for design of surgical devices, artificial organs, drug delivery systems with different routes of administration, carriers of immobilized enzymes and cells, biosensors, ocular inserts, and materials for orthopedic applications. Polysaccharide-based polymers represent a major class of biomaterials, which includes agarose, alginate, dextran, and chitosan. Chitosan has found many biomedical applications, including tissue engineering, owing to its biocompatibility, low toxicity, and degradation in the body, which has opened up avenues for modulating drug release in vivo in the treatment of various diseases. These chitosan-based delivery systems range from microparticles to nanoparticles and from gels to films. In this study, chitosan (CH) and chitosan-polyethylene glycol (CH-PEG) microspheres with different compositions were prepared by oil/water emulsion method and crosslinked with gluteraldehyde. Some microspheres were loaded with a model chemotherapeutic drug, methotrexate (MTX). SEM, particle size and in vitro release analysis were performed. In vitro drug release studies showed that the release of MTX from CH-PEG microspheres was faster compared to CH microspheres. In the second part, CH-PEG microspheres were conjugated with a monoclonal antibody which is immunoglobulin G (IgG). The cytotoxicity efficiencies of entrapped drug were determined by using MCF-7 and MCF-7/MDA-MB breast cancer cell lines. In the third part, CHF-PEG films with the same compositions as in microspheres were prepared by solvent casting method. IR, DSC, mechanical and surface analysis were performed. The mechanical properties of films were improved by the presence of proper amount of PEG but higher amounts of PEG caused the deteriotion in the properties.

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