Polymers in concrete have received considerable attention over the past 30 years. Superplasticizers are one of the admixtures which have polymeric structure. In this study, polycarboxylate type slump-releasing dispersant, which is a copolymer of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and methacrylic acid (MAA), was synthesized in different feed compositions. The synthesis procedure of this copolymer was retrieved from literature. The derivatives of this water-soluble copolymer (AMPS-MAA) were synthesized by a macromonomer which was synthesized by the esterification of poly(ethylene glycol) methyl ether (PEG) with MAA (PEGMA) and then copolymerizing this macromonomer with AMPS monomer, the resulting copolymer is AMPS-PEGMA. In order to study the methyl group effect on fluidity, the other type of macromonomer (PEGA), composed of PEG and acrylic acid (AA), was synthesized and copolymerized with AMPS monomer, giving AMPS-PEGA. The structures of synthesized polymers were verified by NMR and FT-IR analysis. The slump-releasing effect of the synthesized copolymers was studied in terms of reaction pH, composition, molecular weight, amount of PEG side chains, and molecular weight of PEG side chains. The AMPS-MAA copolymer with 40% AMPS content was the most effective in promoting the fluidity of cement pastes. In scope of reaction pH, the AMPS-MAA copolymer, synthesized at a pH of 11, gave the most effective result on fluidity of the cement pastes. In copolymers of PEG acrylate macromonomers and AMPS monomers, copolymers with 5% PEG acrylate content showed the highest fluidity both in copolymers of PEGA and PEGMA. In copolymers with PEG side chains, the 15% AMPS-PEGA copolymer synthesized at pH of 6 gave the most effective result on fluidity of cement pastes. In the study of mechanical properties of the mortar samples prepared by the copolymers selected, AMPS-PEGA copolymer with 25% PEG content showed the highest flexural strength, and AMPS-MAA copolymer with 60% AMPS content and a reaction pH of 11 gave the highest compressive strength. In this study, zeta potential measurements were also performed to analyze the fluidity behavior of the copolymers.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Materials Science and Engineering." Includes bibliographical references.

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Methyl bromide fumigation, a common method used to combat soil borne pathogens in commercial tomato cultivation, was to be limited by the Montreal Protocol due to concerns of ozone depletion. Alternative methods to protect tomatoes against diseases include grafting. However, short grafted transplants may expose the scion to the soil. To avoid scion exposure, hypocotyl elongation of two tomato rootstocks 'Maxifort' and 'Aloha' via end-of-day far-red (EOD-FR) was examined in terms of light quality (red to far-red ratio, or R/FR) and dose (product of far-red intensity and duration). In EOD-FR light quality experiments, 'Aloha' seedlings were exposed to unfiltered and filtered incandescent light with an R/FR of 0.5 and 0.05 respectively. The resulting hypocotyl elongation was higher in filtered light than either the unfiltered light or the untreated control. Hypocotyl elongation response to EOD-FR dose in 'Aloha' and 'Maxifort' was affected by both far-red intensity and treatment duration. A saturating response was also found within a far-red dose between 0–8 mmol•m⁻²•d⁻¹ and modeled using non-linear regression with a three parameter Michaelis-Menten equation to estimate the far-red dose required to obtain near-maximum hypocotyl elongation for 'Aloha' and 'Maxifort'. The far-red dose required was affected by cultivar and experimental period. None of the EOD-FR treatments affected plant mass or stem diameter. To conclude, for maximum hypocotyl elongation using EOD-FR, the lower R/FR would increase the effectiveness of the treatment. The far-red dose should preferably be at 4–8 mmol• m⁻²•d⁻¹.

Abbreviations ADP – autodermoplastics. CUL – chronic ulcers of legs. CVUL – chronic venous ulcers of legs. DGP – a doctor of general practice. KMU – Kaunas Medicine University. KMUH –Kaunas Medicine University Hospital. CSVD – Clinic of Skin and Venereal diseases. 1. Introduction The pathology of chronic ulcers of legs is quite often and it makes a huge influence on the daily life of a patient. According to the literature, ulcers open to 1,5 from 1000 people who are under the age of 65, and if we take into account healed up ulcers of legs, there are 36 people from 1000 to whom ulcers of legs have ever been opened. The reason of ulcers up to 80% of all cases is chronic insufficiency of veins. In Lithuania there are about 150 000 patients suffering from the chronic insufficiency of leg vein blood circulation, and about 30 000 of which are venous ulcers of legs. As in Lithuania in some of the medical institutions the treatment and the prophylaxis of chronic venous blood circulation and ulcers is insufficient, the above mentioned numbers of patients may be even higher. All the authors have noted that the oftenest reason of CUL is the insufficiency of venous blood circulation. In this case, CUL open due to the increased pressure in leg veins. The main reason for that is the insufficiency of surface and deep veins and the perforating vein valves. The good functioning of mentioned veins and their valves is necessary so that the blood could come back to the heart during each... [to full text]

This thesis described the modification of glassy carbon (GC) electrodes with aminophenyl (AP) films via in situ reduction of aminobenzene diazonium ions. The characterisation of the AP modified GC was conducted electrochemically by oxidation of the AP functionalities in acidic aqueous conditions. Ferricyanide and ruthenium hexamine redox probes were also used to investigate the blocking properties of the AP films. Before electrochemical oxidation of the AP functionalities, AP films were shown to have a nett positive charge at pH 7. After electrochemical oxidation in protic conditions, the film was either neutral or negatively charged. The preparation of diazonium cation terminated surface, which is termed 'sticky surface', by reaction of the AP modified electrodes with NaNO₂ in acidic condition, was investigated and the sticky surface was electrochemically characterised. More than one species was formed in the reaction of the AP film with NaNO₂. The reactions of sticky surface with aniline, citrate- and thiol-capped gold nanoparticles (Au-nps) were also studied. Spontaneous reaction of sticky surface with thiol-capped Au-nps had been achieved, and suggested that the reaction leads to the formation of Au–C bonds, via the loss of nitrogen. However, for the reaction of the sticky surface with citrate-capped Au-nps, it was unclear whether covalent bonding had been achieved. The reason for this was due to the possibility of an electrostatic interaction between the negatively charged citrate-capped Au-nps and the positively charged sticky surface. The stability of the sticky surface in acidic aqueous conditions was studied electrochemically and by reaction with thiol-capped Au-nps. It was found that the diazonium cations on the sticky surface are not stable over one hour in aqueous acidic conditions, or even in low temperature. The electro-catalytic activity of the thiol-capped Au-nps attached to the GC electrode via sticky surface towards the oxidation of ascorbic acid was briefly examined, and the surface was found to catalyse the oxidation reaction.

Polymeric surface modification has become an important technique over the last few decades in many areas, including medicine. It provides improved surface properties for specific applications without altering the bulk of the material. Graft copolymerisation is one technique which allows an existing polymer to covalently immobilise different monomers with or without new functional groups. Some polymeric implants are used as hard tissue substitutes for bone. However, the surface of the implant is often deficient in binding with hard tissue. Since phosphates are one of the building blocks of hydroxyapatite [Ca10(PO4)6(OH)2] or HAP, which is the main inorganic composition of bone, phosphate groups may be utilised on the surface of polymeric implants. This has the possible effect of directing bone formation at the material/tissue interface. The radiation-induced grafting of MOEP (methacryloyloxyethyl phosphate) onto ePTFE (expanded PTFE) has been carried out by a simultaneous irradiation technique in the presence of solvents. Two solvents and one mixed solvent system (in this study: methanol, MEK and a mixture of methanol, water and DCM) were used to dilute MOEP under various monomer concentrations and experiments were carried out using two different dose rates. The modified surfaces were characterised using the weight increase, XPS, FTIR-ATR, SEM, and contact angle measurement. The degree of grafting was found to be proportional to the monomer concentration but did not depend on the dose rates used. However, the grafting yield was strongly dependent upon the type of solvent used. The grafting decreased in the order: mixed solvent system » MEK > methanol. In addition, different morphologies of grafting were observed from SEM images depending on the solvent used. The samples prepared in methanol had a smooth morphology, whereas the samples obtained in MEK with a monomer concentration of greater than or equal to 10% w/v and with a mixed solvent system, had globular morphologies. A combination of in vitro tests onto three types of grafted membranes was performed (in this study: simulated body fluid (SBF), protein and cell attachment tests). Structure, composition and morphology of the calcium phosphate growth on the samples after 7 days of immersion in SBF were studied by SEM/EDX and FTIR-ATR. It was found that the growth of CaP onto the sample with low surface grafting (24%) and with a smooth morphology, was carbonated HAP. With the samples with higher grafting and globular morphologies, the inorganic minerals formed were less and had not HAP stoichiometric composition but were presumably Brushite and Octacalcium phosphate (OCP). The amount of protein adhesion in BSA solution (with 24 hours of immersion) and serum solution (with 1 hour of immersion) were determined gravimetrically and by XPS. In addition, the protein layer was investigated using FTIR-ATR. It was found that protein adsorption was highest on the surface with high grafting (100%) possibly due to the electrostatic interaction. Human osteoblast-like cell attachment and cell morphology (both after 3 hours) were examined by cellular protein synthesis assays and SEM. Cell attachment and morphology were also better on the samples with high grafting yield compared to that of low grafting, which follows the results of protein adsorption. The different in vitro tests do not agree, however, in all cases better bioactivity was found for grafted samples than that for untreated samples. This research emphasises the importance of using a series of in vitro tests to evaluate the bioactivity of materials. Although it is not clear as to what the optimum grafting conditions are at this stage, grafting of phosphate-containing monomer onto ePTFE has significantly improved the bioactivity in vitro.

Peptides are considered as drugs of the future because of their advantageous features of high specificity and low toxicity. However, the complete therapeutic potential of peptides has not yet been realized because of the in vivo instability displayed by most potential peptides. In this thesis, two naturally derived cyclic peptides, cyclotides and sunflower trypsin inhibitor 1 (SFTI-1), were utilized to impart stability to linear bioactive epitopes and enhance their therapeutic potential in a biological environment. Cyclotides are plant derived mini-proteins with compact folded structures and exceptional stability. Their stability derives from a head-to-tail cyclised backbone coupled with a cystine knot arrangement of three-conserved disulfide bonds. Sunflower typsin inhibitor 1 (SFTI-1) is a stable cyclic peptide containing a single disulfide bond. Taking advantage of these stable cyclic peptide frameworks, novel drug leads to inhibit/stimulate angiogenesis were developed by using the approach of ‘epitope grafting’ in which linear epitopes were grafted onto the cyclic peptide frameworks. Angiogenesis is a physiological condition that is unregulated in the progression of many diseases, including cancers and cardiovascular diseases. Thus the drug leads designed in the current project have potential therapeutic applications to combat cancers and cardiovascular diseases. To fully exploit cyclotides as drug scaffolds, it is imperative to understand their folding. Two main subfamilies, referred to as the Möbius and bracelet cyclotides have been identified and interestingly, they require dramatically different in vitro folding conditions to achieve formation of the conserved cyclic cystine knot motif. To determine the underlying structural elements that influence cyclotide folding, the in vitro folding of a suite of hybrid cyclotides based on combination of the Möbius cyclotide kalata B1 and the bracelet cyclotide cycloviolacin O1 was examined in this thesis. The pathways of folding of the two cyclotide subfamilies were found to be different and primarily dictated by specific residues harboured within inter-cysteine loops 2 and 6. Two changes in these loops, an amino acid substitution in loop 2 and an amino acid addition in loop 6 enabled the folding of cycloviolacin O1 under conditions where folding does not occur in vitro for the native peptide. Thus, the study identified key residues that are not in close proximity in the primary sequence or three-dimensional structure which assist folding in cyclotides. A key intermediate species in the folding pathway was isolated and characterised, and found to contain a native-like hairpin structure that appears to be a nucleation locus early in the folding process. The intermediate does not have native disulfide connectivities, but disulfide shuffling processes ultimately lead to a rearrangement to the native form. Overall these mechanistic findings on the folding of cyclotides are potentially valuable for protein engineering applications that utilize cystine-rich peptides as scaffolds in the design of new drug leads. The current study has also enabled the extention of the grafting studies to the bracelet cyclotide subfamily, which was intractable to grafting prior to this work. Cyclotides are gene encoded macrocyclic proteins and another way to exploit their potential as drug scaffolds, would be to develop combinatorial cyclotide libraries. The most efficient way to generate engineered cyclotides would be via recombinant expression, which currently remains unsuccessful, partly due to lack of understanding of the mechanism of cyclotide backbone cyclization. Understanding how the cyclotide precursor folds may provide clues to how cyliclization occurs. A conserved region known as the N-terminal repeat (NTR) region in the cyclotide precursor has been speculated to play an important role in precursor folding. In this thesis, the function of the NTR in the folding of the cyclotide precursor in vitro was examined via the design of a series of constructs for the precursor protein for the prototypic kalata B1 cyclotide, with incremental additions of the NTR region. Analysis of the constructs by NMR spectroscopy for evidence of secondary structure revealed that the NTR does not assist folding of the cyclotide precursor in vitro. Using diffusion NMR, the unstructured nature of the constructs was localized to the NTR region. In a complementary study, structural analysis of the full length cyclotide precursor was carried out by expressing the precursor gene for kalata B1 in a bacterial expression system. The full-length precursor was found to be unstructured in solution despite approximately half of the precursor comprising the mature domain and NTR, both of which are structured in isolation. The unstructured nature of the cyclotide precursor suggested that a different environment, or indeed interaction of the NTR with a particular enzyme involved in processing, is necessary for it to adopt a well-defined conformation and allow processing to produce the mature circular protein. The information that NTR alone may not assist folding of the cyclotide precursors has provided new impetus to examine the role of other potential folding auxiliaries such as protein disulfide isomerase in cyclotide folding and has indirectly advanced the production of cyclotides via transgenic means. In summary, this thesis has provided a fundamental insight into the folding of cyclotides, both when expressed as part of a precursor protein and in isolation via solid phase chemical synthesis, and has exploited the potential of cyclic peptide scaffolds in drug design applications.

Cocoa (Theobroma cacao L.) is an important cash crop in the coastal areas of Papua New Guinea (PNG). In 2000, a mutant cocoa genotype MJ 12-226, with abnormal growth characteristics was identified at the Cocoa and Coconut Institute of PNG. The mutant, found among progenies of the cross Scavina 12 x Nanay 149, was characterized by dwarfing, small and narrow leaves, a small root system and strong branching habit. This study was designed to improve the understanding of the dwarf cocoa mutant and identify its relevance to future cocoa farming. The specific objectives are to investigate the feasibility of using a dwarf mutant of cocoa as a commercial rootstock for various hybrid cocoa clones, to study the genetics of this dwarf mutant and the role of plant hormones in differentiating this mutant from the normal phenotype. This study was carried out at the Cocoa and Coconut Institute of PNG, Rabaul, Papua New Guinea, and at the University of Queensland, Gatton Campus, Australia. The comparative study of mutant and normal cocoa seedlings revealed distinct vegetative differences between the two genotypes at the nursery stage. The largest effects of the mutant genotype are on stem elongation, short internodes, multiple stems, root growth and leaf growth. The agronomic results indicated that the mutant rootstock significantly reduced tree vigour at least in the early years. When used as a rootstock, the mutant had a significant dwarfing effect on scion growth of cocoa clones in the nursery and persisted in the field 12 months after planting. After that, the cocoa clones grafted on mutant rootstock reverted to normal growth. It was postulated that the accumulation of endogenous growth substances and cambial activity between the scion (normal) and the rootstock overcame the dwarfing effect of the mutant genotype. Yield and vegetative data collection from this trial ceased on May 2006 and recommenced in May 2007 to allow trees to recover from heavy canopy pruning due to cocoa pod borer attack. This resulted in one year loss of yield and vegetative data from this experiment. The first two years’ yield data indicated no significant differences between mutant, normal segregants and commercial rootstocks. However, cocoa clones bud grafted on these mutant rootstocks produced significantly greater yield at higher planting density compared with lower densities and this was sustained for two years. However, it might be expected that competition among cocoa trees would increase with increased size of trees, favouring low density planting and reducing the differential performance of the trees under high density planting with time. The major advantages of reducing tree vigour are to improve the harvest index, ease of harvesting, pruning and overall management of the trees. The continuation of this study to collect mature tree yield data (from fifth to eighth years) would confirm these results. This work has also demonstrated for the first time that cocoa clones grafted on mutant rootstock can produce similar yields to clones grafted on normal or commercial rootstocks. Moreover, this study has also established that cocoa clones derived from orthotropic scions can yield the same as plagiotropic scions when grafted on to either mutant or normal rootstocks. Therefore, it is proposed that mutant rootstocks and orthtropic scions should also be considered for future use in cocoa farming. The strong branching habit and dwarfing stature of the mutant suggested that the mutation affects the quantity or the balance of plant growth hormones, or both. The effect of exogenously applied gibberellic acid (GA3) on developmental processes in dwarf mutant and normal cocoa seedlings was studied. Both dwarf mutant and normal one month old cocoa seedlings responded to gibberellic acid (GA3) by accelerated longitudinal growth, especially seedling height. Paclobutrazol (PBZ) applied to normal cocoa seedlings altered the growth so that they almost resembled the mutant phenotype. It was postulated that PBZ prevented GA biosynthesis in the normal cocoa seedlings and therefore decreased bioactive auxin (IAA) which, in turn, then promoted lateral shoot growth; PBZ also slightly retarded plant growth. Synthetic auxin (IBA/NAA) significantly inhibited lateral bud sprouting and growth of intact, decapitated and nodal segments of mutant and normal cocoa seedlings compared with control and those treated with IAA. It appears that the mutant and normal cocoa genotypes have a similar capacity to metabolize IAA and this capacity was much greater than for synthetic auxins. The results suggested that auxin levels in the mutant seedlings were probably limiting, and therefore affected biosynthesis of gibberellic acid thus resulting in the dwarfing characteristics of the mutant cocoa genotype. However, analysis of endogenous IAA and GA1 levels at four months old did not reveal differences between the mutant and normal seedlings. The present genetic studies which included backcrossing, test crossing and selfing of F1 progenies confirmed earlier work on the mutant and showed that the mutant was probably heterozygous (Dd). The allele (DD) in mutant cocoa is probably lethal in nature because the phenotype of the homozygote was not observed amongst the mutant progenies. Mutant segregants were obtained in a 1:1 ratio only when the mutant clone was used as the female; however, when the mutant was used as male, very few mutant segregants were obtained. This suggested selective pollen viability (pollen grains carrying the D allele are nonviable) or an incompatible reaction between pollen tubes (D carrying pollen) and style or ovule. The selfing and test-crosses of F1 progenies resulted in deviation from the expected 3:1 segregation ratio to a 1:1 ratio.