O presente estudo teve como objetivo avaliar a ação das soluções de quitosana, EDTA e ácido cítrico sobre a microdureza da dentina radicular. Utilizaram-se 10 incisivos centrais superiores humanos, os quais tiveram suas coroas seccionadas transversalmente e desprezadas. As raízes foram incluídas em resina acrílica de rápida polimerização e o bloco formado raiz/resina adaptado a máquina de corte. Desprezou-se o primeiro corte transversal da porção cervical e dividiu-se o segundo, em quatro quadrantes. Cada quarto foi destinado à confecção do corpo de prova obtendo-se 4 espécimes para cada raiz, um para cada solução (n=10): G1- EDTA 15%; G2- ácido cítrico; G3- quitosana 0,2% e G4- controle. Os espécimes receberam 50 &mu;L da solução por 5 minutos, sendo em seguida, lavados com água deionizada. Utilizou-se um microdurômetro (dureza Knoop) com carga de 10 g durante 15 segundos. Os resultados mostraram que todas as soluções avaliadas apresentaram capacidade de reduzir a microdureza da dentina radicular de forma semelhante entre si e estatisticamente diferente a do grupo controle (p<0,01). Concluiu-se as soluções de quitosana 0,2%, EDTA 15% e ácido cítrico 10% apresentam efeito semelhante na redução da microdureza dentinária. / The aim of this study was to evaluate the action of solutions: chitosan, EDTA and citric acid on the microhardness of the root dentin. There were used 10 human maxillary central incisors which ones had their crown cross-sectioned and discarded. The roots were embedded in acrylic resin of rapid polymerization and the block formed root/resin suitable by cutting machine. Neglecting the first cross-section of the cervical portion and the second was divided in four quadrants. Each quarter was destined to the confection of the specimen and it was got 4 specimen to each root, one for each solution (n=10): G1- EDTA 15%; G2- citric acid;G3- chitosan 0,2 % and G4- control. The specimen received 50 &mu;L of the solution for 5 minutes, and following up they were washed by deionized water. It was used a microhardness (Knoop hardness) with a load of 10g during 15 seconds. The results showed that all the solutions evaluated presented a capacity to reduce the microhardness of the root dentin in a similar way between them, and statically differ from the control group (p<0,01). It was concluded that chitosan 0,2% EDTA 15% and the citric acid 10% presented a similar effect in the reduction of the dentin microhardness.

The primary objective of this research was to determine if changes in iron availability influence the periodicity of blue-green algal growth. A secondary goal was to resolve how iron availability was related to events such as calcite (calcium carbonate) precipitation and sediment nutrient release. The biogeochemical regulation of blue-green algal succession was studied in three eutrophic hardwater lakes located upon the Thompson Plateau in south-central British Columbia. The experimental approaches included iri situ bottle and limnocorral experiments, sediment core analysis, monitoring of seasonal changes in water chemistry, and whole-lake manipulation by hypolimnetic aeration, or calcium hydroxide addition. Growth and primary production bioassays were used to evaluate iron availability. Microbial chelators were isolated from algal cultures and lake water, quantified by a chelation assay, and used to determine their in situ effects on algal productivity and bacterial heterotrophy. Microbes were able to regulate the bioavailability of iron. Algal siderophore isolates were rapidly assimilated in lake water and they were highly specific for iron chelation. Moreover, chelator concentrations in Black Lake usually exceeded the dissolved iron concentration. Algae excreted chelators that could suppress growth of some other species of algae by 90%, enhance the primary production of some other algal species by 30%, or suppress the heterotrophic activity of bacteria by 14-98%. The degree of iron limitation varied greatly during the summer. In Black Lake, iron limitation was more than ten-fold more intense in early summer than in late summer. Dense blooms of blue-green algae occurred in Black Lake only after the iron content of the lake increased from 20 to more than 100 ug/L. An increase in iron concentration in the water column of the three lakes was caused by a midsummer sediment release of iron. Although sediment pyrite formation converted available iron into refractory iron in both Chain and Frisken lakes, the degree of iron limitation varied greatly among the lakes. Unlike in Black Lake, the algae in Chain Lake were not limited by iron availability. Phosphorus solubility was a good index of iron availability. Black and Frisken lakes had too little iron for iron phosphate to precipitate, but the higher iron concentration in Chain Lake regulated phosphorus solubility. The differences among lakes was primarily a function of external iron loading, not sediment iron release. Chain Lake received 10³ more iron per m² than Frisken or Black lakes. Carbonate equilibria integrated the microbial responses to iron enrichment. When iron availability was increased in the epilimnion of Black Lake, algal productivity was enhanced which resulted in an increase in pH and the coprecipitation of more calcite and phosphorus than in control treatments. The precipitation of calcite could sediment as much as 90% of the algae and 97% of the phosphorus from the epilimnion. The hypolimnia of the iron-enriched limnocorrals had the lowest pH and highest dissolution of precipitated phosphorus. Three reactions, iron chelation, sediment iron release, and calcite precipitation, can regulate much of the periodicity of blue-green algal growth in hardwater lakes. / Science, Faculty of / Zoology, Department of / Graduate

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No description available.

Presence of a chelating ligand in the clay structure significantly improves its ability to immobilize heavy metals from contaminated sludge or wastewater. Two-step modification procedure comprising sequential pillaring and grafting of chelating agent to the modified clay is involved. Montmorillonite and kaolin were chosen as typical examples of expandable and non-expandable clays, correspondingly. Modifications with silica and ferric oxide were targeted on development of mesoporous structure. Laboratory tests of the organoclay efficiency for purification of wastewater were conducted with the most promising sample, i.e. organoclay with the highest specific loading of chelating agent. Experiments were conducted with model wastewater containing either individual or mixed cations of heavy metals. The modified organoclay displayed a high adsorption capacity on heavy metal cations even in acidic media. The method of modification presented in this work can be used for synthesis of efficient adsorbents for applications in contaminated areas.

Effects of two types of chelating agents on proteolysis and texture properties of low fat Cheddar cheese (LFC) were analyzed and compared to full fat Cheddar (FFC) control during ripening for 120 days at 8°C. We hypothesized that chelating agents would bind calcium ions from cheese matrix to give a softer curd due to a decrease of protein-protein interactions and simultaneously increasing moisture content. Cheese milk containing (0.59% fat) was divided into three lots (A, B & C). Sodium citrate (3Na) and disodium EDTA (EDTA) were added to A & B at the rate of (0.02% and 0.2% respectively. C served as control (LFC). Cheesemilk (88°F) was preacidified to pH 6.2 prior to setting using 34 ml chymosin/454 kg and starter culture addition. After cutting, curd was cooked to 96°F for 30 min and held for 10 min. After cooking, the curd was washed, salted, hooped and pressed. FFC was made on subsequence days from same batch of milk by the stirred curd method for Cheddar cheese, cheesemaking was replicated 5 times. Significant difference in moisture content (P˂0.05) was observed between FFC and LFC. Calcium content on the EDTA and 3Na was significantly reduced (P˂0.05) compared to FFC. No significant difference (P˃0.05) in hardness was observed between FFC and LFC at day 7 and 30. After day 30, significant differences (P

Caseinate powders have been well accepted because of their foaming properties. In this study, 10% solution of reconstituted skim milk powder (SMP) chelated with sodium hexametaphosphate (SHMP) and trisodium citrate (TSC) at 1 mEq, 50 mEq, and 100 mEq were prepared to conduct a comparison with sodium caseinate, potassium caseinate, and calcium caseinate solutions. Foamability, foam stability as well as the preferential locations of αs-casein, β-casein and !-casein in their foams were analyzed. It was hypothesized that the foamability, foam stability and the preferential locations of these three caseins in the milk foams are different from treatment to treatment. Milk foam was generated with an air- injection method at a flow rate of 0.30 L/M for 18 seconds. Foam stability was measured through half-life method. The foam composition was quantified with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) method. Analysis of Variance (ANOVA) test results concluded that there were no significant differences detected in foamability (p>0.05). On the other hand, foam stability differed significantly among the treatments. Foams of reconstituted SMP-treated with 1 mEq SHMP and TSC were significantly more stable compared to other treatments (p < 0.05), β-casein (p>0.05) and !-casein (p>0.05). In conclusion, the addition of calcium chelating salts might increase the foamability to the same level as caseinate solutions. Furthermore, the study proved that the combination of calcium chelating salts and chelator levels is able to alter the foam stability.

A series of 2-substituted 8-hydroxyquinolines have been prepared and their reactions with a number of metal ions studied. Acid-dissociation constants and metal-chelate formation constants have been determined. 2-(2'-Hydroxyphenyl), 2-(2'-pyridyl) and 2-hydrazino-8-hydroxyquinoline function as terdentate ligands. The latter two ligands form a number of protonated complexes some of which are unusually stable. This stability is likely due to hydrogen bonding. / Thesis / Doctor of Philosophy (PhD)

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No description available.