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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.
1

The initial phase of the sodium bisulfite pulping of softwood dissolving pulp

Deshpande, Raghu January 2015 (has links)
The sulfite pulping process is today practised in only a small number of pulp mills around the globe and the number of sulfite mills that use sodium as the base (cation) is less than five. However, due to the increasing interest in the wood based biorefinery concept, the benefits of sulfite pulping and especially the sodium based variety, has recently gained a lot of interest. It was therefore considered to be of high importance to further study the sodium based sulfite process to investigate if its benefits could be better utilized in the future in the production of dissolving pulps. Of specific interest was to investigate how the pulping conditions in the initial part of the cook (≥ 60 % pulp yield) should be performed in the best way. Thus, this thesis is focused on the initial phase of single stage sodium bisulfite cooking of either 100 % spruce or 100 % pine wood chips. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and cooking time were varied. Activation energies for different wood components were investigated as well as side reactions concerning the formation of thiosulfate and sulfate. / Single stage sodium bisulfite cooking was carried out on either spruce or pine wood chips to investigate the influence of several process parameters in the initial phase of such a cook i.e. between 100 % and 60 % pulp yield. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and time in the initial stage were varied. The influence of dissolved organics and inorganics components in the cooking liquor on the final pulp properties and side reactions were investigated. The impact of temperature and time on the pulp components were analyzed with respect to carbohydrates, lignin, extractives and thiosulfate. Kinetic equations were developed and the activation energies for delignification and carbohydrate dissolution were calculated using the Arrhenius equation. It was found that if using a mill prepared cooking acid, this had a beneficial effect with respect to side reactions, better extractives removal and higher pH stability during the cook, compared to a corresponding cook with a lab prepared cooking acid. Cooking with mill prepared and lab prepared cooking acids showed the same behaviour with respect to delignification and carbohydrate degradation, but the lab acid experiments resulted in a higher thiosulfate formation during the cook. The cellulose yield was not affected at all during the initial phase of the sulfite cook verifying earlier results by other researchers. The temperature had an influence on both the delignification rate and the rate of hemicelluloses removal.  The corresponding activation energies were found to increase in the following order; cellulose, xylan, glucomannan and lignin. / <p>Artikel 1: "The Initial Phase of Sodium Bisulfite Pulping of Spruce: Part 1" ingick i avhandlingen som manuskript. Nu publicerad.</p>
2

USE OF MTB-100TM, PROVIDED THROUGH A MINERAL MIX, TO REDUCE TOXICITY WHEN LACTATING BEEF COWS GRAZE ENDOPHYTE-INFECTED TALL FESCUE

Hoar, Melanie E 01 January 2013 (has links)
Two experiments were conducted at the University of Kentucky, Eden Shale Farm, Owenton, KY to evaluate the use of MTB-100TM (Alltech, Inc., Nicholasville, KY) to alleviate the symptoms of fescue toxicity when lactating Angus x Beefmaster cows and their calves grazed endophyte-infected KY-31 tall fescue. Experiment 1 provided a carbohydrate based toxin adsorbent, MTB-100TM, ad libitum in a commercial mineral supplement to project a daily consumption rate of 0, 20 or 40 g of MTB-100TM per cow. Cows were weighed, assigned a body condition score (BCS) and hair coat score (HC), rectal temperatures were recorded and fecal grab samples were taken for ergovaline (EV) and lysergic acid (LA) analysis every 35 days for three grazing seasons (May to September). Calves were also weighed and assigned a HC score. Although MTB-100TM did not improve cow or calf performance, cows older than 4 years and those with greater Beefmaster breeding exhibited a higher tolerance to fescue toxicity than 2 and 3-yr-olds and cows with greater Angus breeding. Experiment 2 was conducted to evaluate the response of lactating beef cows and their calves to strategic supplementation with MTB-100TM. MTB-100TM was mixed with a complete mineral so daily intake was projected to be 0 or 20 g/cow. The experimental period extended from May 5 to October 2 and was divided into 3 strategic periods: P1 = May 5 to July 5; P2 = July 5 to August 31; P3 = August 31 to October 2. Treatments were either 0 or 20 g•cow-1•d-1 MTB-100TM within a period (Treatment 1 = 0, 0, 0; Treatment 2 = 20, 0, 20; Treatment 3 = 0, 20, 0; Treatment 4 = 20, 20, 0; and Treatment 5 = 20, 20, 20). Cow and calf performance was measured the same as Exp. 1, but every 21 days. Supplementation early in the grazing season tended to improve cow weight gain and body condition; however, there was no effect on calf performance. Fecal output of EV and LA did not increase in either experiment with supplementation. In conclusion, strategically invoked MTB-100TM consumption can increase performance of cows grazing endophyte-infected tall fescue forage.
3

Carbohydrate degradation and dissolution during Kraft cooking : Modelling of kinetic results

Johansson, Dan January 2008 (has links)
<p>Chemical pulp fibres from wood are commonly used in products associated with packaging as well as with printing and writing. The prevalent way of liberating fibres is by subjecting wood chips to Kraft cooking. This process has a history of almost 130 years and should be both well described and well established. However, new products and new applications that use fibres as an important renewable resource make it all the more important that the properties of fibres be controllable. The properties of wood fibres are influenced by their carbohydrate composition which, in turn, is dependent on the cooking conditions used. This thesis studies the degradation and dissolution of the different carbohydrates during Kraft cooking and summarizes the results in kinetic expressions.</p><p>Industrial wood chips from Norway spruce (Picea abies) were cooked at a high liquor-to-wood ratio in an autoclave digester at varying concentrations of hydroxide ions, hydrogen sulphide ions and sodium ions as well as varying temperatures. The pulps were analysed for carbohydrate composition, kappa number, content of hexenuronic acid and the pure cellulose viscosity, i.e. only the cellulose content in the pulp sample was used for calculating the viscosity. Kraft cooking of Eucalyptus urophylla and Eucalyptus grandis was also studied, using industrial liquor-to-wood ratios, to examine the relationship between hexenuronic acids and the amount of xylan in the pulp samples.</p><p>For Kraft cooking of Norway spruce it was found that an increase in the concentration of hydroxide ions increased the rate of dissolution of the carbohydrates and the degradation of the cellulose degree of polymerization (DP). However, measured at a kappa number of 30, it is seen that a low hydroxide ion concentration can lower the carbohydrate yield and the pure cellulose viscosity dramatically. The hydroxide ion concentration not only affects the rate of dissolution but also the amount of xylan that reacts in the slower, final phase. Both cellulose and hemicelluloses were found to be affected by the hydrogen sulphide ion concentration. The dissolution of cellulose and hemicelluloses at varying sodium ion concentrations was found to be affected in different directions. The effect of sodium ion concentration on the DP was found to be dependent on the method of evaluation. The pulp viscosity was found to be affected twice as much by the sodium ion concentration than the pure cellulose viscosity was. For Kraft cooking of hardwood it was found that a high xylan yield not always is synonymous with a high hexenuronic acids content.</p>
4

Carbohydrate degradation and dissolution during Kraft cooking : Modelling of kinetic results

Johansson, Dan January 2008 (has links)
Chemical pulp fibres from wood are commonly used in products associated with packaging as well as with printing and writing. The prevalent way of liberating fibres is by subjecting wood chips to Kraft cooking. This process has a history of almost 130 years and should be both well described and well established. However, new products and new applications that use fibres as an important renewable resource make it all the more important that the properties of fibres be controllable. The properties of wood fibres are influenced by their carbohydrate composition which, in turn, is dependent on the cooking conditions used. This thesis studies the degradation and dissolution of the different carbohydrates during Kraft cooking and summarizes the results in kinetic expressions. Industrial wood chips from Norway spruce (Picea abies) were cooked at a high liquor-to-wood ratio in an autoclave digester at varying concentrations of hydroxide ions, hydrogen sulphide ions and sodium ions as well as varying temperatures. The pulps were analysed for carbohydrate composition, kappa number, content of hexenuronic acid and the pure cellulose viscosity, i.e. only the cellulose content in the pulp sample was used for calculating the viscosity. Kraft cooking of Eucalyptus urophylla and Eucalyptus grandis was also studied, using industrial liquor-to-wood ratios, to examine the relationship between hexenuronic acids and the amount of xylan in the pulp samples. For Kraft cooking of Norway spruce it was found that an increase in the concentration of hydroxide ions increased the rate of dissolution of the carbohydrates and the degradation of the cellulose degree of polymerization (DP). However, measured at a kappa number of 30, it is seen that a low hydroxide ion concentration can lower the carbohydrate yield and the pure cellulose viscosity dramatically. The hydroxide ion concentration not only affects the rate of dissolution but also the amount of xylan that reacts in the slower, final phase. Both cellulose and hemicelluloses were found to be affected by the hydrogen sulphide ion concentration. The dissolution of cellulose and hemicelluloses at varying sodium ion concentrations was found to be affected in different directions. The effect of sodium ion concentration on the DP was found to be dependent on the method of evaluation. The pulp viscosity was found to be affected twice as much by the sodium ion concentration than the pure cellulose viscosity was. For Kraft cooking of hardwood it was found that a high xylan yield not always is synonymous with a high hexenuronic acids content.
5

The location and significance of the O-acetyl groups in a glucomannan from Parana pine

Katz, Gerald 01 January 1964 (has links)
see pdf
6

The Effect of Different Xylan Contents on the Strength Properties of Softwood Kraft pulp

Svedinger Andersson, Maria January 2013 (has links)
The aim of this Master thesis was to investigate if the xylan content had any influence on the physical properties of softwood kraft pulps. To achieve pulps with different xylan content different kraft cooking conditions were used; two different temperatures and two different effective alkali levels. The cooking conditions used were 160°C with 30% effective alkali (EA) referred to as reference cook and 145°C with 17% effective alkali (EA) referred to as the mild cook. The first step in this study was to determine the cooking time needed for reaching a certain kappa number, i.e.30. It was also determined whether the difference in xylan content between the pulp samples was sufficient when these cooking conditions were used. When the correct cooking time and cooking conditions had been found new cooks were made using these conditions. All cooks were made at a liqour to wood ratio of 4:1.   The difference in xylan content between the corresponding pulp samples was found to be 3%. The physical testing showed no significant difference in the tensile strength between the two pulps after beating. There was a difference in tear index however and the pulp with the highest content of xylan had the lowest tear index. Zero-span index was the same for the two pulps when unbeaten. After beating the zero-span index decreased for the pulp with highest xylan content but stayed unchanged for the pulp with the lower amount of xylan. These results can be explained by the results from the fibre analysis which showed that the fibres with high xylan content were longer, thicker and had a higher coarseness. Thicker fibres are probably stiffer than thinner fibres which gives the paper fewer bonding points and a lower strength. The result from the zero-span test indicated that the fibres with higher xylan content are affected more by beating than fibres with the lower xylan content. / Målet med examensarbetet var att undersöka om och hur mycket xylaneti pappersmassan påverkar fiberns och därmed papperets fysikaliska egenskaper. Egenskaperna som undersöktes var drag- och rivstyrka samt zero-spanstyrka. Xylaninnehållet skulle varieras genom att kokförhållandena förändrades dels genom olika koktemperaturer dels olika satsningar av effektivt alkali vid given sulfiditet. Dessa var 160ºC med 30% effektivt alkali(EA) hädanefter benämnd referenskoket och 145ºC med 17% effektivt alkali(EA) som benämns det milda koket i fortsättningen.En bestämning av koktiden gjordes för att nå 30 i kappatal och två provkok, ett vid varje temperatur behövde göras.Skillnaden i xylanhalt mellan de slutliga massaproverna låg på c:a 3% enheter.   Styrkeproverna gav inga entydiga svar på om skillnaden i xylanhalt gav någon effekt på massastyrkan. Dragproverna visade att för omald massa var massan från referenskoket starkast men att massan från det mildare koket reagerade kraftigare på malningen. Redan vid 1000 varv hade den i princip samma dragindex som referensmassan vid samma malgrad. Zero-span mätningarna visade att fibrerna hade samma styrka när de var omalda.   Resultaten från fiberanalysenverifierade resultaten från styrketesterna eftersom en tjockare fiber bör ge en styvare fiber och därmed erhålls färre bindningspunkter.  Färre bindningspunkter ger en lägre dragstyrka och det krävs mindre energi för att bryta bindningarna. Efter malningen kan man se att zero-span styrkan har minskat betydligt för massan med högre xylanhalt medan referensmassan behöll styrkan. Dessutom har dragstyrkan ökat för båda massorna men mest för massan med högre xylanhalt. Det kan förklaras med att malningen ger små fibriller på ytan av fibern och en mjukare och böjligare fiber. Därmed ökar bindningsstyrkan då bindningsarean ökar och fibern blir mjukare och böjligare. Den ökade bindningsgraden samt den minskade fiberstyrkan kan förklara varför rivindex fortfarande var lägre för massan med högre xylanhalt trots att dragindex ökade med ökad malning.En annan förklaring kan vara att vid ett långt kok med låg temperatur är det troligt att lignin adsorberas på fibrerna.Ligninet på ytan ger en sämre bindningsförmåga vilket leder till att de är lättare att dra ur nätverket med lägre energiåtgång som följd.
7

Use Of Whey-Based Edible Coatings as Antioxidative and Antimicrobial Agents

Weerasinghe, Sashie 11 August 2012 (has links)
Edam and Cheddar whey were thermized (T) for different time periods (5–30 min) at 70 degrees Celsius, vacuum evaporated, and spray dried to obtain whey powders (WP). Native and thermized WP were evaluated for antioxidative properties. Edam and Cheddar WP significantly reduced thiobarbituric acid-reactive substances (TBARS) and peroxide value (PV) in ferric-catalyzed soybean oil emulsions. Thermization significantly improved antioxidative properties of WP with 5T, 10T, and 15T treatments showing better protective effects compared to 20T and 30T treatments. Based on these results, native (0T) and thermized (5T, 10T, and 15T) Edam and Cheddar WP coatings, with and without enzymatically hydrolyzed casein (CH), were used to reduce oxidative degradation and moisture loss of cubed beef steak and pork loin. Thermized treatments significantly reduced TBARS and PV in both types of meat, with CH containing treatments showing enhanced antioxidative properties. Protein oxidation as reflected by carbonyl formation and a decrease in sulfhydryls was also reduced by thermization. Treated and native WP coatings significantly reduced moisture loss of meat samples. Cubed beef steak treated with Cheddar WP coatings were evaluated for microbiological quality and basic sensory attributes. Although not statistically significant, 5T, 10T, and 10TCH treatments numerically showed potential for microbial reduction up to 4 days of storage. Sensory evaluation showed significant protection of key sensory attributes by treatments throughout the storage period when compared to controls with the 5 min thermization showing the best effect on lowering offlavor development based on sensory scores. The effect of pH and glucomannan (GM) on antioxidative properties of thermized (5T) Cheddar WP coatings applied to catfish fillets was also investigated. Coatings at pH 7.0, 7.5, and 8.0 (with GM) showed markedly greater protection against oxidative degradation compared to coatings without GM, as reflected by TBARS values and PV after 7 days of storage. Carbonyl formation and oxidation of sulfhydryl groups were also significantly reduced by coatings containing GM. Cheddar WP-based edible coatings (pH 7.0–8.0) with GM markedly reduced lipid oxidation and protein oxidation of fresh catfish fillets.
8

Glucomannan-poly(N-vinyl pyrrolidinone) bicomponent hydrogels for wound healing

Shahbuddin, M., Bullock, A.J., MacNeil, S., Rimmer, Stephen January 2014 (has links)
No / Polysaccharides interact with cells in ways that can be conducive to wound healing. We have recently reported that konjac glucomannan (KGM) which is comprised of D-mannose and D-glucose linked by beta-1,4 glycosidic chains, stimulates fibroblast proliferation. The aim of this study was to produce a range of crosslinked KGMs and bicomponent KGM containing hydrogels and to examine their potential for wound healing. Two types of KGM hydrogel were synthesized, biodegradable from crosslinked KGM and non-biodegradable by forming semi-IPNs and graft-conetworks with a second synthetic component, poly(N-vinyl pyrrolidinone-co-poly(ethyleneglycol) diacrylate) (P(NVP-co-PEGDA)), which was produced by UV initiated radical polymerization. Crosslinked KGM was formed by bimolecular termination of macro-radicals formed by oxidation with Ce(IV). Semi-IPNs were formed by copolymerization of NVP and PEGDA in the presence of KGM and in the graft-conetworks the KGM was also crosslinked using the Ce(IV) procedure. The hydrogels had different swelling properties and differences could be observed in their chemical structure using C-13 solid state NMR, DSC and FTIR. Both forms were cytocompatible but only the graft-conetworks had the ability to stimulate fibroblast metabolic activity and to stimulate the migration of both fibroblasts and keratinocytes. In conclusion a form of KGM hydrogel has been produced that could benefit wound healing.
9

NÍVEIS BAIXOS DE AFLATOXINAS DIETÉTICAS E ADSORVENTES NO DESEMPENHO DE MATRIZES DE CORTE E DE SUA PROGÊNIE / LOW LEVELS OF DIETARY AFLATOXINS AND ADSORBENTES IN THE BROILER BREEDER HENS AND PROGENY PERFORMANCE

Uttpatel, Rodrigo 19 December 2007 (has links)
This study was conducted to investigate the effect of the consumption of aflatoxins and adsorbents (esterifid glucomannan) for broiler breeders on productive and reproductive aspects addition to verify the residual effects on the progeny. Four experiments were conducted, with the first consisting of 240 broiler breeders feed with increasing levels of aflatoxins, according to the treatment: T1 free aflatoxins diet and treatments T2, T3 and T4, dies containing 0.250, 0.500 and 0.750mg the aflatoxins/kg of diet. The second experiment was composed of 300 broiler breeders submitted to diets containing aflatoxins, in the presence or not of adsorbent as treatments: T1 breeders feed free aflatoxins diets, T2 breeders feed diets containing 0.500mg of aflatoxins / kg of diet, T3 breeders submitted to the same level of aflatoxins in T2, but with 0.10% of adsorbent, T4 consists of breeders feed diets containing 0.750mg of aflatoxins/kg of diet and treatment T5 breeders submitted to the same level of aflatoxins of T4, but with 0.10% of adsorbent. The third and fourth experiments were composed of chicks from broiler breeder belonging to the first and second experiment, respectively. The parameters evaluated in the broiler breeders were: body weight, egg production, mass of eggs, egg weight, specific gravity, hatchability and chicks quality, and the study involving progeny were evaluated body weight, weight gain, feed conversion by weight gain, blood protein and albumin and liver and bursa weights in the first day of age. The performance of breoiler breeders subjected to diets containing increasing levels of aflatoxins, as well, broiler breeders subjected to diets containing levels of aflatoxins and adsorbent in the throws was not influenced. The progeny performance, in the same way, does not show the effect of the treatments applied on the broiler breeder hens. / Este estudo foi realizado para investigar o efeito do consumo de aflatoxinas e adsorventes (glucomananos esterificados) por matrizes de corte sobre aspectos produtivos e reprodutivos, além de verificar os efeitos residuais sobre a progênie. Foram realizados quatro experimentos, sendo o primeiro composto por 240 matrizes submetidas a níveis crescentes de aflatoxinas, segundo os tratamentos: T1 - dieta isenta de aflatoxinas, T2, T3 e T4, matrizes submetidas à dietas contendo 0,250, 0,500 e 0,750mg de aflatoxinas/kg de dieta. O segundo experimento foi composto por 300 matrizes submetidas à dietas contendo aflatoxinas, com presença ou não de adsorvente, conforme os tratamentos: T1 - matrizes submetidas à dietas isentas de aflatoxinas; T2 - aves alimentadas com dietas contendo 0,500mg de aflatoxinas/kg de dieta; T3 - aves submetidas ao mesmo nível de aflatoxinas do T2, porém com 0,10% de adsorvente, T4 - constituído por aves alimentadas com dietas contendo 0,750mg de aflatoxinas/kg de dieta e o tratamento e T5 - aves submetidas ao mesmo nível de aflatoxinas do T4, porém, com 0,10% de adsorvente. O terceiro e o quarto experimentos foram compostos por pintos oriundos de matrizes pertencentes ao primeiro e segundo experimento, respectivamente. Os parâmetros avaliados nas matrizes de corte foram: peso corporal, taxa de postura, massa de ovos, peso de ovos, gravidade específica, eclodibilidade e qualidade de pintos, e no estudo envolvendo a progênie foram avaliados peso corporal, ganho de peso, conversão alimentar, proteína e albumina sanguíneos e pesos de fígado e bursa ao primeiro dia de idade. O desempenho de matrizes de corte submetidas à dietas contendo níveis crescentes de aflatoxinas, bem como, de matrizes submetidas a dietas contendo níveis de aflatoxinas e adsorvente na deita não foi influenciado. Os índices zootécnicos da progênie, da mesma forma, não evidenciaram efeito dos tratamentos aplicado às matrizes de corte.
10

An investigation of the biology and chemistry of the Chinese medicinal plant, Amorphophallus konjac

Yee, Melinda Chua Fui January 2011 (has links)
Konjac glucomannan (KGM), the main biologically active constituent of konjac flour extracted from corms of Amorphophallus konjac (konjac), can be used to prepare functional foods and may also have potential as a pharmaceutical product to combat obesity. The current study employed three experimental approaches to study the biology and chemistry of konjac, namely (1) glasshouse experiments to study the morphogenesis, growth and productivity of konjac plants, (2) a histological and immunocytochemical investigation of the localisation and developmental regulation of the deposition and metabolism of KGM in developing corm tissues, and (3) a comparative study of methodologies for the extraction and analysis of KGM. The current data demonstrated a morphological and functional separation between the ventral and dorsal regions of corms. The ventral region appeared to function as a source during the initial period of shoot development, while the dorsal region appeared to operate as a sink after the development of mature canopy. Once the corm reached maturity, both an inflorescence and a leaf were produced within a single season. It has also been demonstrated that the age of the ‘mother’ corm is an important factor affecting the quality of offsets produced. An anti-mannan antiserum detected a temporally regulated pattern of mannan epitope production within glucomannan idioblasts in developing corm tissues, with increased expression as the corm approached maturity/dormancy. The current observations also suggest that the mobilization of KGM initiates at the periphery of the corm and proceeds inwards towards the centre of the corm. Compositional analysis showed that the purified konjac flour (PKF) produced using a modified extraction procedure contained 92% glucomannan, with a weight average molecular weight (Mw), polydispersity index (PDI) and degree of acetylation (DA) of 9.5 ± 0.6 x 105 gmol-1, 1.2 and 2.8 wt. %. These data, plus Fourier-transform infrared spectral (FTIR) and zero shear viscosity analyses of the extract (PKF) were all consistent with the literature. Comparison of three existing methodologies for the quantitative analysis of the KGM content, namely 3,5-dinitrosalicylic acid (3,5-DNS), phenol-sulphuric acid and enzymatic colorimetric assays; indicated that the 3,5-DNS colorimetric assay was the most reproducible and accurate method, with a linear correlation coefficient of 0.997 and recoveries between 97% and 103% across three spiking levels of starch. In summary, this study has provided a better understanding of aspects of the biology and cultivation of A. konjac and has also produced methodologies which can be used as the basis for an improved good laboratory practice (GLP) for the commercial extraction and analysis of this multifunctional natural polymer.

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