• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 17
  • 5
  • 1
  • Tagged with
  • 30
  • 20
  • 9
  • 7
  • 7
  • 7
  • 6
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 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

Lyotropic discotic dye/water systems

Turner, J. E. January 1988 (has links)
No description available.
2

A study of the passivity produced by chromic acid on 18 per cent chromium 8 per cent nickel alloy ...

Kenny, Frederic Joseph, January 1931 (has links)
Thesis (Ph. D.)--Columbia University, 1931. / Vita. Bibliography: p. 53.
3

Relationship between digestibility index marker and dietary characteristics in the determination of energy and nutrient utilization for pigs and broiler chickens

Tingting Wang (5930387) 17 January 2019 (has links)
<div><p>The objective of this study was to investigate the effect of type and level of digestibility index marker (DIM) and dietary characteristics including dietary fiber type, dietary protein sources, and inclusion of xylanase in pigs and broiler chickens.</p><p> An experiment was conducted to investigate if (i) the apparent digestibility of gross energy (GE) and nitrogen (N) were influenced by the type of DIM and dietary fiber; (ii) the concentration pattern of DIM was influenced by dietary fiber, ileal digesta collection day (Day), and time period (TP). Eighteen barrows (initial BW = 24.2 ± 0.3 kg) fitted with a T-cannula at the end of the ileum were used in a 2-period study. Three corn-soybean meal-based diets were formulated with corn starch, corn bran or oat bran at 100 g/kg. Acid insoluble ash (AIA), chromic oxide (Cr<sub>2</sub>O<sub>3</sub>), and titanium dioxide (TiO<sub>2</sub>) were included as DIM in each diet. Each period consisted of a 7-d adjustment period followed by a 3-d total fecal collection period and a 3-d ileal digesta collection period, where ileal digesta was collected every 3 h between 09:00 to 21:00 h with 4 TP on each of the 3 day. The DIM had similar effect on apparent ileal digestibility (AID) of GE and N within each diet, but different effects among the 3 diets. However, the apparent total tract digestibility (ATTD) of GE or N of corn starch and the ATTD of N of corn bran determined by the 3 DIM were not different. The recovery of TiO<sub>2</sub>in feces of pigs fed the oat bran was 78.3%, which was the least among the 3 diets (<i>P</i>< 0.05). The distribution of Cr concentration in ileal digesta of pigs fed cornstarch, corn bran, and oat bran was similar to that of Tiand AIA irrespective of TP. In conclusion, the AID of GE or N was more influenced by the choice of DIM compared with ATTD; the recovery of TiO<sub>2</sub>in pigs fed oat bran was less than corn starch or corn bran; the Day had limited effect on DIM concentration; and the three DIM moved synchronously in diets irrespective of TP.</p><p> Another study was conducted to investigate if the AID of GE or N was influenced by inclusion level and type of DIM and inclusion level of OB, and if the ATTD of GE or DIM recovery was influenced by the three aforementioned factors and duration of feces collection. Six diets were formulated as a 2 ´3 factorial arrangement with two levels of OB (0 or 100 g/kg) and three levels of DIM (2.5, 5.0, or 7.5 g/kg). BothCr<sub>2</sub>O<sub>3</sub>and TiO<sub>2</sub>were added to the same diet as DIM and their inclusion levels were consistent in each experimental diet.<b></b>In Exp. 1, eighteen barrows (initial BW = 24.2 ± 0.3 kg) fitted with T-cannulas at the distal ileum were used in a triplicate 6 × 2 incomplete Latin Square design with 6 dietary treatments and 2 periods. The ileal digesta were collected for 3 d after 5-d adaptation. In Exp. 2, a total of 72 barrows (initial BW = 26.9 ± 0.5 kg) were used in a randomized complete block design, and the feces were collected for either 3 or 5 d after a 7-d adaptation according to the assignment. Experimental diets were same as Exp. 1. The AID of GE and N determined by TiO<sub>2</sub>were greater (<i>P</i>< 0.05) than Cr<sub>2</sub>O<sub>3</sub>regardless of the OB level and DIM level. Neither the OB level nor the DIM level affected the AID of GE or N. The DIM level and duration of feces collection had no effect on ATTD of GE and DIM recovery. The ATTD of GE were greater (<i>P</i>< 0.05) determined by TiO<sub>2</sub>than that determined by Cr<sub>2</sub>O<sub>3</sub>. Similarly, the recovery of TiO<sub>2</sub>was greater (<i>P</i>= 0.007) than Cr<sub>2</sub>O<sub>3</sub>. Inclusion of 100 g/kg OB did not affect the recovery of DIM. In conclusion, the AID of GE and N, the ATTD of GE, and the recovery of Cr<sub>2</sub>O<sub>3</sub>or TiO<sub>2</sub>were affected by DIM type, but not DIM level; the inclusion of OB had no effect on AID of GE and N, and DIM recovery; and the duration of feces collection had no effect on ATTD of GE, and DIM recovery.<b></b></p><p> The additivity of AID and standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA) in mixed diets containing wheat, canola meal (CM), meat and bone meal (MBM), and sorghum distillers’ dried grains with solubles (DDGS) fed to pigs with Cr<sub>2</sub>O<sub>3</sub>and TiO<sub>2</sub>as DIM was investigated in the third study. Four diets were prepared to contain wheat, CM, MBM, or DDGS as a sole source of N; three mixed diets were prepared to contain wheat, CM, and MBM; wheat, MBM, and DDGS; or wheat, CM, MBM, and DDGS; and a N-free diet was prepared to estimate the BEL of CP and AA. Both Cr<sub>2</sub>O<sub>3</sub>and TiO<sub>2</sub>, each at 5 g/kg were incorporated into each diet. Sixteen barrows (initial BW = 34.7 ± 0.6 kg) surgically fitted with T-cannulas at the distal ileum were allotted to a duplicate 8 × 4 incomplete Latin square design with 8 experimental diets and 4 periods. Chromic oxide and TiO<sub>2</sub>determined similar BEL, AID, and SID of CP and AA. In wheat-CM-MBM diet, the measured AID of CP and most AA determined with Cr<sub>2</sub>O<sub>3</sub>or TiO<sub>2</sub>were not different from the predicted values. The results indicated that the determination of BEL, AID, and SID of CP and AA were not affected by DIM type;the additivity of AID and SID of CP and most indispensable AA in mixed diets was not affected by DIM type; and more accurate prediction of ileal digestibility of AA was achieved using SID rather than AID in mixed diets containing wheat, CM, MBM, and DDGS.</p><p> The aim of the last study was to investigate the growth performance and nutrient utilization responses of broiler chickens and the nutrient utilization of pigs to xylanase, experimental diet formulation method for energy (FME), and DIM. In Exp. 1, a total of 448 male broiler chickens were used in a randomized complete block design with BW as a blocking factor. Seven dietary treatments were prepared in a 3 × 2 + 1 factorial arrangement with inclusion of sand, diatomaceous earth (DAE), or wheat bran (WB) as FME and without or with xylanase (26,400 unit/kg of diet) plus positive control, which contained sufficient energy content for animals. Each of Cr<sub>2</sub>O<sub>3</sub>and TiO<sub>2</sub>were incorporated at 5 g/kg in diets. In Exp. 2, twenty-one barrows (initial BW = 33.0 ± 0.3 kg), fitted with simple T-cannulas at the distal ileum, were used in a triplicate 7 × 2 incomplete Latin Square design with 7 dietary treatments, which were prepared by the same arrangement as in broilers. In Exp. 1, the growth performance of birds was not affected by xylanase, but was affected by the choice of FME. There were interactions (<i>P</i>< 0.05) between xylanase and FME for AID of CP, His, Met, Thr, and Trp. In Exp. 2, there were interactions (<i>P</i>< 0.05) between xylanase and FME for AID of dry matter, GE, Arg, and Lys. The DIM type had no effect on responses in pigs. In conclusion, the efficacy of xylanase on ileal energy and AA digestibility depends on the choice of FME in broilers and pigs, and DIM affects ileal digestibility in broilers.</p><p> In summary, the AID of GE or N was more influenced by the DIM type compared with ATTD, and the three DIM moved synchronously in diets irrespective of TP. The AID of GE and N, the ATTD of GE, and the recovery of Cr<sub>2</sub>O<sub>3</sub>or TiO<sub>2</sub>were affected by DIM type, but not DIM level. However, the choice of DIM had no effect on the determination of BEL, AID, and SID of CP and AA, and additivity of AID and SID of CP and most indispensable AA in mixed diets. In addition, more accurate prediction of ileal digestibility of AA was achieved using SID rather than AID in mixed diets containing wheat, CM, MBM, and DDGS. Finally, the efficacy of xylanase on ileal energy and AA digestibility depends on the choice of FME in broilers and pigs, and DIM affects ileal digestibility in broilers.</p></div><p></p>
4

Valor nutritivo da silagem de grãos úmidos de milho na alimentação de vacas da raça holandesa

Persichetti Junior, Pedro [UNESP] 06 August 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:27:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-06Bitstream added on 2014-06-13T20:16:57Z : No. of bitstreams: 1 persichettijunior_p_me_botfmvz.pdf: 249687 bytes, checksum: 19c41163201cd31693703836f8a81764 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / Cinco vacas primíparas da raça Holandesa Preto e Branca – PO foram distribuídas em quadrado latino 5x5 com o objetivo de avaliar o efeito de níveis de substituição do grão seco de milho (GSM) pela silagem de grãos úmidos de milho (SGUM) sobre o consumo, digestibilidade total dos nutrientes e glicose plasmática. As dietas foram compostas por silagem de canadeaçúcar e feno de gramínea como volumosos e rações concentradas com farelo de soja como fonte protéica e milho seco e/ou silagem de grãos úmidos de milho como fontes energéticas, constituindo os seguintes tratamentos: 1) 100% GSM; 2) 75% GSM e 25% SGUM; 3) 50% GSM e 50% SGUM; 4) 25% GSM e 75% SGUM; 5) 100% SGUM. O período experimental foi de 70 dias, divididos em cinco fases de 14 dias cada, onde os 10 primeiros dias foram de adaptação e os quatro últimos dias de coleta de dados e amostragens. Os animais foram submetidos a duas ordenhas diárias e a alimentação foi ad libitum, três vezes por dia. A digestibilidade foi obtida por método indireto utilizando o óxido crômico (Cr2O3) como indicador. Amostras de fezes foram colhidas duas vezes por dia após a ordenha, diretamente do reto do animal e amostras de sangue foram coletadas apenas no último dia de cada período antes do fornecimento da primeira refeição (0h) e 2h, 4h, 6h e 12h após a refeição. Não houve efeito (P>0,05) sobre o consumo de matéria seca (MS), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA) e amido. A digestibilidade aparente total da MS, proteína bruta (PB), FDN e FDA não foram afetadas (P>0,05) pelos tratamentos, assim como a concentração de glicose plasmática. Todavia, houve efeito linear decrescente (P<0,05) para o consumo de PB e efeito linear crescente (P<0,05) para a digestibilidade do amido, à medida que se aumentou o nível de SGUM... / Five primiparous Black and White Holstein cows were distributed in a 5x5 Latin square design to evaluate substitution levels of drygrounded corn grain (DGCG) by high moisture corn grain silage (HMCGS) on intake, total nutrients digestibility and plasma glucose. Diets were composed by sugarcane silage and grass hay as forage and the concentrate contained soybean meal as protein source and drygrounded corn grain and/or high moisture corn grain silage as energetic source in the following treatments: 1) 100% DGCG; 2) 75% DGCG and 25% HMCGS; 3) 50% DGCG and 50% HMCGS; 4) 25% DGCG and 75% HMCGS; 5) 100% HMCGS. The experimental period lasted 70 days, divided in five phases of 14 days each, where the first 10 days were for adaptation and the four last days for sampling collection. The animals were milked twice a day and, the cows were fed ad libitum three times a day. Digestibility was obtained by indirect method using chromic oxide (Cr2O3) as the marker. Feces samples were collected twice a day after milking, directly from the rectum and blood samples were collected only at the last day of each period before the first meal (0 h) and 2, 4, 6 and 12 h after meal. Intake of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF) and starch were not affected (P>0.05) by treatments. Total apparent digestibility of DM, crude protein (CP), NDF and ADF were not affected (P>0.05) by treatments, as well as plasma glucose. However, there was decreasing linear effect (P<0.05) for CP intake and increasing linear effect (P<0.05) for starch digestibility as the level of HMCGS increased in the diets.
5

Determination of chromic acid and sodium dichromate in a concentrated electrolytic solution with the aid of Artificial Neural Networks

Seepe, Alfred Hlabana 29 November 2009 (has links)
The aim of this work is to quantify the concentration of chromic acid (CA) in a saturated solution of chromium trioxide and sodium dichromate using Artificial Neural Networks (ANNs). A set of titration curves was obtained by automated acid-base titration according to a factorial experimental design that was developed for this purpose. These titration curves were divided into three subsets, a learning, training and test set for use by ANNs. Once trained, ANNs have the ability to recognize, generalize and relate the input to a particular output. Concentration of chromic acid (CA), total chromium(VI) and/or dichromate was used as the outputs and titration curves as the inputs to ANNs. Our aim here was to establish whether ANNs would be able to predict the concentration of chromic acid with an absolute error below 1%. For real world problem, the neural networks are only given the inputs and are expected to produce reasonable outputs corresponding to that inputs without any prior ‘knowledge’ about theory involved – here, no interpretation of titration curves was performed by ANNs. The test set of data that was not used for learning process, was used to validate the performance of the neural networks, to verify whether the ANNs learned the input-output patterns properly and how well trained ANNs were able to predict the concentrations of chromic acid, dichromate and total chromium. A number of ANNs models have been considered by varying the number of neurons in the hidden layer and parameters related to the learning process. It has been shown that ANNs can predict the concentration of chromic acid with required accuracy. A number of factors that affect the performance of the neural networks, such as the number of points in a titration curve, number of test points and their distribution within the training set, has been investigated. This work demonstrates that ANNs can be used for online monitoring of an electrolytic industrial process to manufacture chromic acid. / Dissertation (MSc)--University of Pretoria, 2009. / Chemistry / unrestricted
6

Textile Influence : exploring the relationship between textiles and products in the design process

Nilsson, Linnéa January 2015 (has links)
Textile materials and textile design are a part of countless products in our surroundings,as well as diverse design fields and industries, each of which has very different materialtraditions and working methods. The aim of this thesis is to add to our understandingof the relationship between textiles and products in the design process, and to explorehow textiles enter and influence product design processes and how products functionin textile design processes. A further aim is to examine the effect of new textiletechnology, such as smart textiles and 3D printed textiles, on this dynamic. This thesis is the result of an interplay between theoretical work, experimentalpractice-based projects, and observation of design practice, and it presents two typesof results: Firstly, descriptions of how the relationship can manifest itself in the designprocess, which give a broad picture of the relationship between textile and productand in so doing add to our understanding of textiles as design materials and highlightsome of the additional complexities and possibilities for the design process that comewith new forms of textiles. Secondly, this thesis presents ways of describing thedynamics between textiles and products in the design process, with the intention ofopening up for reflection on how we design, and can design, with textiles. Here, themain outcome is a theoretical framework which examines the relationship from botha product design and a textile design perspective, and includes methods and questionsthat can be used to explore and define how textiles and products meet in the designprocess.
7

Evaluation of internal and external markers for estimating dry matter intake and digestibility in cattle / Avaliação de marcadores internos e externos para estimar o consumo e a digestibilidade da matéria seca em bovinos

Velasquez, Alejandro Vargas 07 March 2017 (has links)
Feed intake assessment is a valuable tool for herd management decisions. The use of markers, either internal or external, is currently the most used technique for estimating feed intake in production animals. Three experiments were conducted with beef and dairy cattle. In dairy cows fed a corn silage based diet with 45% concentrate, the average fecal recovery (FR) of TiO2 was higher than FR of Cr2O3 and both FR were more than unity. The FR was unaffected by the fecal sampling procedure but, estimates for dry-matter digestibility (DMD) and fecal output (FO) were affected. The Cr2O3 + indigestible acid detergent fiber (iADF) marker pair produced accurate dry-matter intake (DMI) estimates. In steers fed diets with different forage sources FR of TiO2 was close to 1 and this marker produced adequate FO estimates. The FR was affected by the forage source that composed the diet and none of the marker pairs produced accurate DMI estimates. In young Nelore bulls fed corn silage or Tifton-85 hay based diets with varying F:C ratios, the average FR of internal markers acetyl bromide lignin (ABL), indigestible neutral detergent fiber (iNDF), iADF and cutin was different from 100%. Markers Cr2O3 and TiO2 had FR lower and higher than 100%, respectively. The combination of internal and external markers to estimate DMI produced satisfactory and accurate results, particularly Cr2O3 based pairs with iNDF and iADF. Internal markers ABL and cutin deserve more attention. The GRAB sampling procedures yielded accurate DMD, FO and DMI estimates, which were as good as or better than BULK sampling procedures. Regardless of the fecal sampling method and the composition of the diet, it is necessary to establish the FR of the markers to be used in each experiment, in order to obtain correct estimates. None of the markers had complete FR consistent throughout the 3 experiments. Cutin and ABL had lower than unity FR on all diets and failed to produce accurate DMD estimates. When either one was paired with Cr2O3 or TiO2, DMI estimates were also not accurate. Of the indigestible fibers, iNDF and iADF, the later was more accurate in estimating DMI when paired with Cr2O3. Consistently throughout the experiments, FR was lower than and higher than unity for internal and external markers, respectively. Corrected FO estimates were accurate for Cr2O3 on various diets under GRAB sampling. The same was not true for TiO2, which even after FR correction was applied failed to produce accurate FO estimates consistently. The method of dosing the external markers is extremely important and greatly affects and determines results. Whichever the method, it must allow the animals to display normal feeding behavior and not affect performance. The GRAB sampling procedures can replace TFC (once FR is established) which may open new possibilities for pasture based or collectively housed animals. / A determinação do consumo de alimentos é uma valiosa ferramenta na hora da tomada de decisões de manejo do rebanho. O uso de marcadores, sejam internos ou externos, é atualmente a técnica mais utilizada para estimar o consumo em animais de produção. Três experimentos foram conduzidos. Em vacas de leite alimentadas com silagem de milho com 45% de concentrado, a recuperação fecal (RF) média de TiO2 foi maior do que a RF de Cr2O3 e ambas foram maiores do que a unidade. A RF não foi afetada pelo método de coleta de fezes, mas, as estimativas de digestibilidade da matéria seca e produção fecal (PF) foram. A dupla de marcadores Cr2O3+i fibra detergente ácido indigestível (iADF) produziu estimativas de consumo de matéria seca (CMS) acuradas. Em novilhos alimentados com diferentes fontes de forragem, a RF do TiO2 foi próxima a 1 e este marcador produziu estimativas de PF adequadas. A RF foi afetada pela fonte de forragem que compunha a dieta e nenhum dos marcadores produziu estimativas de CMS acuradas. Em tourinhos Nelore alimentados com dietas compostas de silagem de milho ou feno de Tifton-85 e diferentes relações de volumoso:concentrado, a RF média dos marcadores internos lignina brometo de acetila (LBA), fibra detergente ácido indigestível (iFDN), (iFDA) e cutina foi diferente de 100%. Os marcadores Cr2O3 e TiO2 tiveram RF menor e maior que 100%, respectivamente. A combinação de marcadores internos e externos para estimar o CMS produziu resultados acurados e satisfatórios, principalmente as duplas Cr2O3 e iFDN ou iFDA. Os marcadores internos LBA e cutina merecem mais estudos. O método de coleta GRAB produziu estimativas de DMS, PF e CMS acuradas, as quais foram iguais ou melhores que as produzidas pelo método de coleta BULK. Independentemente do método de coleta de fezes e da composição da dieta, é necessário estabelecer a RF real dos marcadores que serão usados em experimento para obter estimativas corretas. Nenhum dos marcadores teve RF completa e consistente nos 3 experimentos. A cutina e LBA tiveram RF menor do que a unidade em todas as dietas e falharam em produzir estimativas acuradas de DMS. Quando qualquer dos dois foi pareado com Cr2O3 ou TiO2 as estimativas de CMS também não foram acuradas. Das fibras indigestíveis, iFDN e iFDA, a segunda foi mais acurada em estimar o CMS quando pareada com Cr2O3. As estimativas de PF corrigida foram acuradas para Cr2O3 em diferentes dietas sob metodologia de coleta GRAB. O mesmo não foi observado para o TiO2, que produziu estimativas enviesadas inclusive após a correção. O método de dosagem dos marcadores externos é extremadamente importante já que afeta e determina em grande medida os resultados. Qualquer que seja o método, este deve permitir ao animal comportar-se e alimentar-se normalmente sem comprometer seu desempenho. Os métodos de coleta GRAB podem substituir a coleta total de fezes (CTF) (após determinação da RF) o que poderá abrir novas possibilidades para estudos com animais em pastagem ou alojados em baias coletivas.
8

Comparação de diferentes indicadores com método de coleta total para determinação da digestibilidade aparente de diferentes dietas para eqüinos / Different markers comparison with total collection method to determine the apparent digestibility in different equine diets

Ramos, Silvio Couto 18 December 2003 (has links)
Foram utilizadas quatro eqüinos fêmeas, adultas, sem raça definida com peso médio de 450 ± 51.15kg. As foram compostas de partes iguais de feno da gramínea Tifton 85 (Cynodon sp) e concentrado contendo milho submetido a quatro processamentos diferentes (moído, laminado, floculado, extrusado). O experimento teve duração de 11 dias sendo oito de adaptação a dieta e 3 dias de coleta. O delineamento experimental utilizado foi quadrado latino 4x4 (tratamento x animal). O objetivo deste trabalho foi de comparar o indicador externo oxido crômico e os indicadores internos, lignina em detergente ácido (LDA), cinza insolúvel em detergente ácido (CIDA) com o método de coleta total (CT) para determinação da digestibilidade aparente da matéria orgânica (CDMO) A ponderação dos CDMO pelos indicadores foi efetuada através de um modelo o qual considerava a diferença entre o CDMO pelo indicador e pela CT aqui chamado de viés. A variância das respostas dos quatro indicadores são iguais, tendo assim a mesma precisão para estimar os CDMO. As médias das diferenças entre CT e os indicadores são diferentes de zero para cada indicador. Foi observada maior acurácia para a metodologia utilizando a lignina, em comparação aos demais indicadores testados (P<0,05), porem esta ainda se manteve distante dos resultados obtidos através da coleta total. O óxido crômico subestimou os coeficientes de digestibilidade, enquanto que a CIDA superestimou os valores. Entretanto, quanto à precisão, o indicador óxido crômico foi constatado ser o mais preciso em relação aos demais indicadores estudados (P<0,05). / Four adult mares, with no defined breed and an average weight of 450 ± 51.15kgwere used. The diets were composed of equal parts of Tifton 85 hay (Cynodon sp) and concentrate of corn submitted to four different processes (grinded, laminated, flocculated and extruded). The experiment lasted 11days, being 8 for diet adaptation and 3 for collection. The experimental design used was a Latin square 4x4 (treatment x animal). The objective of this experiment was to compare the external marker oxide chromic and the internal markers acid lignin detergent (ADL), Acid Detergent Insoluble Ash (ADIA) with the total collection method (TC) to determine the apparent digestibility of Organic Matter (OM). The consideration of OMDC by the by the markers was done through a model that took into account the difference between OMDC by the marker and the TC here called bias. The answer variation in the four markers is the same, this way demonstrating the same accuracy to estimate the OMDC. The average differences between TC and the markers are different from zero to each marker. It was observed a grater accuracy in the methodology using lignin, compared to the other markers tested( p<0,05). However, this one was still for from the results obtained through the total collection. The oxide chromic underestimated the digestibility coefficients, while ADIA overestimated the values. The marker oxide chromic was reported as being the most precise in relation to the others markers studied.
9

Effect of sulphate impurity in chromic acid anodizing of aluminium and aluminium alloy

Elabar, Dawod January 2016 (has links)
In this work, the nucleation and growth of pores in anodic films formed on aluminium in chromic acid and the effect of low levels of sulphate impurity in the anodizing bath on the formation of the films on aluminium and AA 2024 alloy are investigated. The sulphate concentrations considered include levels within specified limits for industrial processing. The anodizing is carried out either potentiostatically or by stepping the voltage. The films are examined by scanning electron microscopy, transmission electron microscopy and atomic force microscopy to determine the pore spacing, pore population densities, pore diameters and film thicknesses. Film compositions were determined using energy-dispersive X-ray spectroscopy, Rutherford backscattered microscopy and nuclear reaction analysis. In order to investigate the mechanism of pore formation, two tracer methods are employed. In one method, anodic films are formed first in an arsenate electrolyte in the second method, a tungsten tracer band deposited by magnetron sputtering. The behaviours of arsenic and the tungsten are investigated during the subsequent anodizing in chromic acid. The results suggest that the initiation and growth of pores in occurred as a result of electric field assisted chemical dissolution. The effect of sulphate impurity in the chromic acid is investigated using electrolytes with different sulphate content. In the initial stages of anodizing aluminium at 100 V, sulphate impurity at a level of 38 ppm in the chromic acid is shown to lead to significant incorporation of sulphate ions into the anodic film, a lower current density, a smaller cell size and less feathering of the pore walls. In addition, the efficiency of film formation is increased. In later stages of anodizing, the growth of larger pores and cells, leads to a duplex film morphology, with finer pores in the outer region. The change in pore size correlates with a reduction in the incorporation of sulphate into the film. From the results of sequential anodizing experiments, it is suggested that incorporated sulphate ions generate a space charge layer, which has an important role in determining the current density. The effects of higher sulphate concentrations up to 3000 ppm are investigated, which are shown to significantly affect the current density and the pore diameter. Anodizing of aluminium and AA 2024 alloy was also carried out according to industrial practice. The results show that there is significant effect of sulphur impurity on the film thickness. Corrosion tests in 3.5 % NaCl solution for the alloy after anodizing in low (smaller or equal to 1.5 ppm) and high (~38 ppm) sulphate-containing chromic acid electrolytes demonstrate a better corrosion resistance with films formed in the latter electrolyte.
10

Valor nutritivo da silagem de grãos úmidos de milho na alimentação de vacas da raça holandesa /

Persichetti Junior, Pedro. 1981- January 2009 (has links)
Resumo: Cinco vacas primíparas da raça Holandesa Preto e Branca - PO foram distribuídas em quadrado latino 5x5 com o objetivo de avaliar o efeito de níveis de substituição do grão seco de milho (GSM) pela silagem de grãos úmidos de milho (SGUM) sobre o consumo, digestibilidade total dos nutrientes e glicose plasmática. As dietas foram compostas por silagem de canadeaçúcar e feno de gramínea como volumosos e rações concentradas com farelo de soja como fonte protéica e milho seco e/ou silagem de grãos úmidos de milho como fontes energéticas, constituindo os seguintes tratamentos: 1) 100% GSM; 2) 75% GSM e 25% SGUM; 3) 50% GSM e 50% SGUM; 4) 25% GSM e 75% SGUM; 5) 100% SGUM. O período experimental foi de 70 dias, divididos em cinco fases de 14 dias cada, onde os 10 primeiros dias foram de adaptação e os quatro últimos dias de coleta de dados e amostragens. Os animais foram submetidos a duas ordenhas diárias e a alimentação foi ad libitum, três vezes por dia. A digestibilidade foi obtida por método indireto utilizando o óxido crômico (Cr2O3) como indicador. Amostras de fezes foram colhidas duas vezes por dia após a ordenha, diretamente do reto do animal e amostras de sangue foram coletadas apenas no último dia de cada período antes do fornecimento da primeira refeição (0h) e 2h, 4h, 6h e 12h após a refeição. Não houve efeito (P>0,05) sobre o consumo de matéria seca (MS), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA) e amido. A digestibilidade aparente total da MS, proteína bruta (PB), FDN e FDA não foram afetadas (P>0,05) pelos tratamentos, assim como a concentração de glicose plasmática. Todavia, houve efeito linear decrescente (P<0,05) para o consumo de PB e efeito linear crescente (P<0,05) para a digestibilidade do amido, à medida que se aumentou o nível de SGUM... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Five primiparous Black and White Holstein cows were distributed in a 5x5 Latin square design to evaluate substitution levels of drygrounded corn grain (DGCG) by high moisture corn grain silage (HMCGS) on intake, total nutrients digestibility and plasma glucose. Diets were composed by sugarcane silage and grass hay as forage and the concentrate contained soybean meal as protein source and drygrounded corn grain and/or high moisture corn grain silage as energetic source in the following treatments: 1) 100% DGCG; 2) 75% DGCG and 25% HMCGS; 3) 50% DGCG and 50% HMCGS; 4) 25% DGCG and 75% HMCGS; 5) 100% HMCGS. The experimental period lasted 70 days, divided in five phases of 14 days each, where the first 10 days were for adaptation and the four last days for sampling collection. The animals were milked twice a day and, the cows were fed ad libitum three times a day. Digestibility was obtained by indirect method using chromic oxide (Cr2O3) as the marker. Feces samples were collected twice a day after milking, directly from the rectum and blood samples were collected only at the last day of each period before the first meal (0 h) and 2, 4, 6 and 12 h after meal. Intake of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF) and starch were not affected (P>0.05) by treatments. Total apparent digestibility of DM, crude protein (CP), NDF and ADF were not affected (P>0.05) by treatments, as well as plasma glucose. However, there was decreasing linear effect (P<0.05) for CP intake and increasing linear effect (P<0.05) for starch digestibility as the level of HMCGS increased in the diets. / Orientador: Ciniro Costa / Coorientador: Gercílio Alves de Almeida Júnior / Banca: Paulo Rodrigues Mazza / Banca: Heraldo Cesar Gonçalves / Mestre

Page generated in 0.1179 seconds