1 |
Uso de compostos extraÃdos da manga (Mangifera indicus) no controle da oxidaÃÃo lipÃdica na carne de frango, em produto cÃrneo tipo mortadela e ovos de consumo / Use of compounds extracted of manga (Mangifera indicus L.) in the control of the lipidic oxidation in chicken meat, meat product type bologna and eggs for consumptionÃngela da Silva Borges 16 November 2009 (has links)
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / O presente trabalho teve como objetivos avaliar o efeito da inclusÃo de antioxidantes naturais da manga na raÃÃo de frangos de corte e de poedeiras comerciais sobre a estabilidade oxidativa da carne de frango, produto cÃrneo tipo mortadela, bem como dos ovos de consumo. Foram preparados dois extratos etanÃlicos com a casca (E1) e o caroÃo (E2) da manga. Os extratos desidratados foram utilizados em dois ensaios biolÃgicos: um com frangos de corte e outro com poedeiras comercias. Em ambos os ensaios os tratamentos alimentares das aves consistiram no controle, T1, raÃÃo sem adiÃÃo de extratos; T2 raÃÃo com adiÃÃo de 200ppm de butilato de hidroxitolueno (BHT); T3 e T4, raÃÃes com 200 e 400ppm de extrato da casca da manga, respectivamente; e T5 e T6, raÃÃes com 200 e 400ppm de extrato do caroÃo da manga, respectivamente. No ensaio com frangos foram utilizados 360 pintos de um dia, da linhagem Ross, distribuÃdos ao acaso entre os seis tratamentos com seis repetiÃÃes de 10 aves. No ensaio com poedeiras foram utilizadas 180 aves da linhagem Hisex x Whitw, com 40 semanas de idade, distribuÃdas ao acaso entre os seis tratamentos com cinco repetiÃÃes de seis aves. A carne dos frangos de corte foi utilizada para os Experimentos 1 e 2 e os ovos das poedeiras para o Experimento 3. No Experimento 1, quatro aves com 42 dias de idade, foram selecionadas e apÃs o abate, foram coletados os peitos desossados, divididos ao meio e embalados a vÃcuo. Os peitos esquerdos foram armazenados em refrigeraÃÃo (4ÂC) e os peitos direitos em congelamento (-20ÂC). Foram realizadas anÃlises de cor e da oxidaÃÃo lipÃdica da carne nos tempos 0, 5, 10 e 15 dias, nas amostras refrigeradas, e nos tempos 0, 30, 60 e 90 dias nas amostras congeladas. No Experimento 2, foram utilizados os mesmos frangos do Experimento 1, sendo que os cortes da coxa e sobre coxa foram coletados e apÃs a desossa e retirada da pele a carne foi utilizada na formulaÃÃo de mortadelas que foram armazenadas em refrigeraÃÃo (4C) por 90 dias. Durante o armazenamento foram realizadas anÃlises de cor e estabilidade lipÃdica (TBARS) do produto cÃrneo com 0, 30, 60 e 90 dias. No Experimento 3, foram selecionados 25 ovos de cada repetiÃÃo os quais foram armazenados em refrigeraÃÃo (4C) e as anÃlises da cor (leque colorimÃtrico e sistema CIE Lab) e da oxidaÃÃo lipÃdica da gema realizadas nos tempos 0, 15, 30, 45 e 60 dias. No Experimento 1, foi observada uma reduÃÃo dos valores do componente de cor L* (luminosidade) durante o armazenamento da carne de peito de frango em congelamento, e um aumento do componente a* (intensidade de vermelho) durante o armazenamento em refrigeraÃÃo. Os valores de TBARS sofreram aumento considerÃvel na carne de peito proveniente de todos os tratamentos durante o armazenamento sob refrigeraÃÃo e sob congelamento. Comparando com o tratamento controle (T1), os tratamentos contendo BHT ou os extratos E1 e E2 nas concentraÃÃes de 200 e 400 ppm (T2, T3, T4, T5 e T6) foram eficientes no controle da oxidaÃÃo lipÃdica da carne do peito de frango em refrigeraÃÃo por 5 dias ou em congelamento por 3 meses. No Experimento 2, de uma forma geral o armazenamento das mortadelas por 90 dias provocou reduÃÃo nos valores do componente de cor L* e aumentos nos valores dos componentes de cor a* e b*. Os produtos formulados com a carne proveniente de frangos em todos os tratamentos sofreram aumentos nos valores de TBARS com o tempo de armazenamento. Durante a estocagem em refrigeraÃÃo os tratamentos T2 e T6 foram os mais eficientes no controle da oxidaÃÃo lipÃdica nas mortadelas. No experimento 3, nÃo houve variaÃÃo significativa do componente de cor L* na gema dos ovos provenientes dos tratamentos alimentares T2, T3, T4, T5 e T6, em relaÃÃo ao tratamento controle (T1), durante todo o perÃodo de armazenamento. Os valores do componente de cor a* sofreram aumentos com o tempo de armazenamento em todos os tratamentos, enquanto que para os valores do componente de cor b* nÃo houve diferenÃa significativa entre os tratamentos. Quanto à cor medida pelo leque colorimÃtrico, os tratamentos nÃo tiveram efeito significativo em relaÃÃo ao tratamento controle (T1), ao longo de todo o perÃodo de armazenamento. A oxidaÃÃo lipÃdica da gema dos ovos dos tratamentos com adiÃÃo de antioxidante (T2, T3, T4, T5 e T6) foi menor que a dos ovos do tratamento controle (T1), mas aumentou durante o armazenamento dos ovos. Os ovos do T5 apresentaram a menor taxa de aumento da oxidaÃÃo lipÃdica ao final do perÃodo de armazenamento, seguido daqueles dos tratamentos T4 e T6, respectivamente. Pode ser concluÃdo que os extratos da casca e do caroÃo da manga podem ser usados na alimentaÃÃo das aves para ajudar no controle da oxidaÃÃo lipÃdica dos produtos avÃcolas carne e ovos. / The present study aimed to evaluate the effects of addition of natural antioxidants from mango in the feed of the broiler chickens and laying hens on the oxidative stability of chicken meat, a product processed from this meat (chicken mortadella) and eggs for consumption. It was prepared two ethanolic extracts from the peel (E1) and (E2) mango seed. The dried extracts were used in two bioassays, one with chickens and one with laying hens. In both trials, the alimentary treatments consisted in control, T1, feed without addition of extracts, T2, feed with addition of 200 ppm of butylated hydroxytoluene (BHT), T3 and T4, feed with 200 and 400ppm of extract of the mango peel, respectively, and T5 and T6, feed with 200 and 400ppm extract of the mango seed, respectively. In the trial with chickens, 360 chicks in a day, from Ross line were used, which were distributed randomly among the six treatments with six replicates of 10 poultry. In the trial with laying hens, 180 poultry from Hisex x Whitwam line, with 40 weeks of age were used, which were randomly distributed among six treatments with five replicates of six poultry. The meat of the broiler chickens was used for the Experiments 1 and 2 and the eggs of the laying hens for the Experiment 3. In Experiment 1, four poultry with 42 days of age, were selected and after slaughter, the boneless breasts were collected, split in half and vacuum packed. The samples of left breasts were stored under refrigeration (4 oC) and the rights breasts under freezing (~20 oC). The analyses of color and lipid oxidation of the meat were performed at 0, 5, 10 and 15 days in the refrigerated samples, and at 0, 30, 60 and 90 days in the frozen samples. In Experiment 2, the same chickens from Experiment 1 were used, whose the sections of the leg and thigh were collected and after boning and skinning the meat was used in the formulation of mortadella which were stored under refrigeration (4 oC) for 90 days. During the storage of meat product were carried out color (CIE Lab system) and lipid stability (TBARS) analysis at 0, 30, 60 and 90 days. In Experiment 3, it was selected 25 eggs from each replicate which were stored under refrigeration (4 oC) and analysis of color (color fan and the CIE Lab) and lipid oxidation (TBARS) of yolk were realized at 0, 15 , 30, 45 and 60 days. In Experiment 1, it was observed a reduction of L * values (brightness) in chicken breast during storage under freezing, and an increase in a* value (redness) during storage under refrigeration. The values of TBARS suffered considerable increase in all treatments during storage under refrigeration or freezing. Compared with the control treatment (T1), treatments containing BHT (T2) or extracts E1 and E2 at concentrations of 200 and 400 ppm (T3, T4, T5 and T6) were effective in controlling lipid oxidation of breast meat chicken chilled for 5 days or frozen for 3 months. In Experiment 2, the storage of the mortadella for 90 days resulted in reduction of the L* value and increases of the a* and b* values. The chicken meat products in all treatments had elevated values of TBARS with increase in storage time. During storage under refrigeration, T2 and T6 treatments were the most effective in controlling lipid oxidation in mortadella. In experiment 3, there was no significant variation in the color component L * of the eggs yolk from the T2, T3, T4, T5 and T6 treatments compared to the control treatment (T1), throughout the storage period. The a* values was increased with the storage time for all treatments, while for the b* values there was no significant difference between treatments. In relation to the color measured by yolk color fan, the treatments had no significant effect in comparison to control treatment (T1), throughout the storage period. The lipid oxidation of egg yolk from added-antioxidant treatments (T2, T3, T4, T5 and T6) was smaller than the eggs from the control treatment (T1), but increased during storage of eggs. The eggs from T5 treatment had the lowest rate of increase in lipid oxidation at the end of the storage period, followed by those of T4 and T6 treatments, respectively. It was concluded that the extracts of peels and seed of mango can be used in poultry feed to help control lipid oxidation poultry products and eggs.
|
2 |
Efeito da adição de butil-hidroxitolueno nos meios de refrigeração e congelação sobre a viabilidade espermática de equinos / Effect of the addition of butylated hydroxytoluene into cooling and freezing extenders on the viability of equine spermAraujo, Endrigo Adonis Braga de [UNESP] 26 February 2016 (has links)
Submitted by ENDRIGO ADONIS BRAGA DE ARAUJO null (adonis.tecvet@yahoo.com.br) on 2016-04-27T02:07:05Z
No. of bitstreams: 1
DISSERTAÇÃO_BHT_Araujo, EAB.pdf: 638286 bytes, checksum: 01feb4c9fddef023795b0f62318b20f2 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-04-28T16:16:58Z (GMT) No. of bitstreams: 1
araujo_eab_me_bot.pdf: 638286 bytes, checksum: 01feb4c9fddef023795b0f62318b20f2 (MD5) / Made available in DSpace on 2016-04-28T16:16:58Z (GMT). No. of bitstreams: 1
araujo_eab_me_bot.pdf: 638286 bytes, checksum: 01feb4c9fddef023795b0f62318b20f2 (MD5)
Previous issue date: 2016-02-26 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O processo de criopreservação acarreta estresse oxidativo à célula espermática e a adição de antioxidantes aos meios de refrigeração e congelação de sêmen pode auxiliar na proteção dos espermatozoides contra o dano induzido pelas espécies reativas de oxigênio (ERO), incluindo perda da motilidade de forma irreversível, peroxidação lipídica e fragmentação do DNA, interferindo na capacidade de fertilização do espermatozoide. Dentre os diferentes antioxidantes, o Butil-hidroxitolueno (BHT) é um análogo sintético da vitamina E, cujo efeito protetor é atribuído a dois mecanismos: o aumento da fluidez da membrana plasmática após a incorporação do antioxidante, e o segundo por conter a cascata de peroxidação lipídica pela conversão de peroxil em hidroperóxido lipídico. O BHT foi testado em diversas espécies demonstrando melhora na motilidade, integridade de membrana plasmática e viabilidade espermática; porém, na espécie equina, a inclusão de BHT em diluentes para criopreservação de sêmen necessita ser melhor avaliada. Deste modo, o objetivo deste trabalho foi avaliar a influência do BHT nas células espermáticas de equinos submetidas à criopreservação e sua capacidade de conter a peroxidação lipídica e produção de espécies reativas de oxigênio quando os espermatozoides foram submetidos a estresse. / The process of cryopreservation brings out oxidative stress to spermatic cell and the addition antioxidant of into cooling and freezing semen extenders could assist in protection of spermatozoa against the damage induced by reactive oxygen species (ROS), including irreversible loss in motility, lipid peroxidation and DNA fragmentation, interfering with the fertilizing capacity of sperm. Among different antioxidants, the butylated hydroxytoluene (BHT) is a synthetic analogue of vitamin E, whose protective effect is attributed to two mechanisms: the increase in sperm membrane fluidity after the addition of antioxidant, and the lipid peroxidation cascade for converting peroxy radicals into lipid hydroperoxides. BHT was tested in different species and the results include improvement in motility, spermatic membrane integrity and sperm viability. However, the addition of BHT in horse semen extenders for cryopreservation purposes demands further research. Thereby, the aims of this study were (1) to evaluate the influence of BHT on equine spermatic cells submitted to cryopreservation and (2) the capacity of BHT to contain the lipid peroxidation and the production of reactive species of oxygen when sperm cells were submitted to stress. / FAPESP: 2014/00175-8
|
3 |
Efeito da adição de butil-hidroxitolueno nos meios de refrigeração e congelação sobre a viabilidade espermática de equinosAraujo, Endrigo Adonis Braga de. January 2016 (has links)
Orientador: Frederico Ozanam Papa / Resumo: O processo de criopreservação acarreta estresse oxidativo à célula espermática e a adição de antioxidantes aos meios de refrigeração e congelação de sêmen pode auxiliar na proteção dos espermatozoides contra o dano induzido pelas espécies reativas de oxigênio (ERO), incluindo perda da motilidade de forma irreversível, peroxidação lipídica e fragmentação do DNA, interferindo na capacidade de fertilização do espermatozoide. Dentre os diferentes antioxidantes, o Butil-hidroxitolueno (BHT) é um análogo sintético da vitamina E, cujo efeito protetor é atribuído a dois mecanismos: o aumento da fluidez da membrana plasmática após a incorporação do antioxidante, e o segundo por conter a cascata de peroxidação lipídica pela conversão de peroxil em hidroperóxido lipídico. O BHT foi testado em diversas espécies demonstrando melhora na motilidade, integridade de membrana plasmática e viabilidade espermática; porém, na espécie equina, a inclusão de BHT em diluentes para criopreservação de sêmen necessita ser melhor avaliada. Deste modo, o objetivo deste trabalho foi avaliar a influência do BHT nas células espermáticas de equinos submetidas à criopreservação e sua capacidade de conter a peroxidação lipídica e produção de espécies reativas de oxigênio quando os espermatozoides foram submetidos a estresse. / Abstract: The process of cryopreservation brings out oxidative stress to spermatic cell and the addition antioxidant of into cooling and freezing semen extenders could assist in protection of spermatozoa against the damage induced by reactive oxygen species (ROS), including irreversible loss in motility, lipid peroxidation and DNA fragmentation, interfering with the fertilizing capacity of sperm. Among different antioxidants, the butylated hydroxytoluene (BHT) is a synthetic analogue of vitamin E, whose protective effect is attributed to two mechanisms: the increase in sperm membrane fluidity after the addition of antioxidant, and the lipid peroxidation cascade for converting peroxy radicals into lipid hydroperoxides. BHT was tested in different species and the results include improvement in motility, spermatic membrane integrity and sperm viability. However, the addition of BHT in horse semen extenders for cryopreservation purposes demands further research. Thereby, the aims of this study were (1) to evaluate the influence of BHT on equine spermatic cells submitted to cryopreservation and (2) the capacity of BHT to contain the lipid peroxidation and the production of reactive species of oxygen when sperm cells were submitted to stress. / Mestre
|
4 |
Influence of catalytic systems on the synthesis of (dis)entangled UHMWPE and its implications on mechanical propertiesRomano, Dario January 2014 (has links)
Two different catalysts (bis[N-(3-tert-butylsalicylidene)-pentafluoroanilinato] titanium (IV) dichloride and [1-(8-quinolyl)indenyl] chromium (III) dichloride catalysts) activated with aluminoxane based co-catalysts (MAO, PMAO, MMAO12 and MMAO3A) have been evaluated in the polymerisation of ethylene leading to UHMWPE having a reduced number of entanglements between the chains. The effect of a co-catalyst modifier (BHT) on the catalytic systems and the resulting polymers is also addressed. Both catalysts are capable to promote the synthesis of UHMWPE having a reduced amount of entanglements in the conditions used. Uniaxial solid-state deformation of UHMWPE samples of different molar masses have been evaluated and related with the entanglement state of the polymers synthesised. A clear relationship between some mechanical properties and the molar mass/entanglement density of the polymers synthesised has been found.
|
5 |
An assesssment of non-conventional measures of lung function and the effedt of a herbal extract on mild-moderate childhood asthmaMaxwell, Sheena, sheenamax@optusnet.com.au January 2007 (has links)
Background: Respiratory conditions are prevalent and cause an enormous burden on society. In recent decades, there has been a global increase in asthma in children and adults, yet the diagnosis of asthma must be made on clinical grounds as the diagnostic use of pharmacological reversibility of airway obstruction remains controversial. It is possible however that tools exist from different medical paradigms that may assist in the clinical diagnosis of asthma. Tools such as Traditional Chinese Medicine (TCM) enquiry, Breath Holding Time (BHT) or Electro-Dermal Screening Test (EDST) may provide useful clinical information, yet their use has not been widely explored or validated. Integrative medicine may be considered to represent a new frontier in medicine where each therapy and diagnostic method is seen to have its own advantages and limitations and where an integration of both diagnostic and therapeutic techniques from conventional and complementary medicine is seen to produce the best results. However, while there is a high community use of complementary therapies for conditions such as asthma, there is also a need to maintain accepted standards of medical and scientific principles and foster high quality research into complementary therapies. Objectives: The current study sought to determine: If there is a correlation between conventional measures of lung function such as Forced Expiratory Volume in one second (FEV1) and less conventional measures such as airways expired NO level (eNO), electrodermal measures, TCM enquiry and BHT. If any of the lung function measures are able to distinguish between asthmatic and healthy subjects. If the use of a rye grass extract is better than placebo in improving requirements for bronchodilator medication, peak flow, forced expiratory volume in one second or quality of life in mild to moderate childhood asthma. Rational for carrying out two separate studies as one study; The author was interested on both the integration of diagnostic techniques as well as the effect of the herbal extract on asthma so it was decided to use the opportunity and put both in one study. Method: A range of conventional and non-conventional measures were conducted in healthy and asthmatic children including demographic details, quality of life data, spirometry measures, airway nitric oxide levels, electro-dermal measures, TCM history enquiries, breath holding time, and skin prick tests. The data were analysed to determine any significant correlations between these measures. A double blind randomized controlled pilot clinical trial was also performed to assess the effect of using rye grass extract in asthmatic children aged 8 to 16 years. Results: There were significant correlations between forced expiratory volume in one second and active quality of life, TCM spleen score and fraction of exhaled nitric oxide measurements. There were also statistically significant differences between asthmatic and healthy subjects in TCM history, breath holding time and exhaled nitric oxide. The use of rye grass extract did not produce any significant improvement over placebo in any of the asthma outcome measures. Conclusions: The use of inexpensive measures such as BHT and TCM enquiry may provide useful clinical information when assessing respiratory conditions such as asthma. However, further research is required in larger populations to confirm their use. The use of the rye grass extract at the dose given in this study did not provide any clinical benefit for the asthmatic children in this study.
|
6 |
The design and synthesis of potential dual action cardioprotective agents acting at adenosine receptorsGregg, Alison Dianne January 2006 (has links)
Adenosine and adenosine analogues are recognised as cardioprotective agents due to the responses that they induce through the activation of myocardial adenosine receptors. Antioxidants such as nitroxide radicals have also been found to possess cardioprotective properties in biological systems, namely through their ability to scavenge the oxygen-based free radicals that are potentially damaging to tissues and cells. It was envisaged that the linking of an antioxidant moiety to adenosine would produce an adenosine analogue that activates adenosine receptors and also scavenges oxygen-derived free radicals in the body. Consequently, one aim of this project was to synthesise a series of adenosine analogues that possessed a nitroxide or a phenolic antioxidant at the N6 position of the adenosine skeleton.
Allosteric ligands have several advantages over orthosteric ligands as potential therapeutic agents, and research into the allosteric enhancement of adenosine receptors is a burgeoning field. It was envisaged that the linking of an antioxidant moiety to an allosteric enhancer would produce a compound that enhances the response of endogenous activation of adenosine receptors and also scavenges oxygen-based free radicals in the body. Consequently, a second aim of this project was to synthesise a series of allosteric enhancers of the A1 adenosine receptor that possessed antioxidant capability endowed by a nitroxide or a phenolic antioxidant functionality.
This project has resulted in the synthesis and characterisation of 19 novel N6 substituted adenosine analogues, and additionally 12 novel derivatised thiophenes. Each of the target compounds was tested for its ability to bind to each of the adenosine receptor subtypes and some analogues were found to be potent and selective adenosine receptor agonists.
|
7 |
Développement d'un matériau piézoélectrique sans plomb pour la réalisation de sondes ultrasonores haute fréquence / Development of lead free materials for high resolution ultrasonographyRichardot, Thomas 01 March 2016 (has links)
L’échographie haute résolution est une technique d’imagerie médicale permettant une observation du corps de très bonne définition, à faible profondeur (quelques micromètres). Pour réaliser cela, des ondes ultrasonores sont utilisées (quelques dizaines de mégahertz), produites par l’élément actif de la sonde: un film piézoélectrique. Pour atteindre de telles fréquences, cet élément doit être d’une épaisseur déterminée: de l’ordre de la dizaine de micromètres. Aujourd’hui, le PZT, zirconotitanate de plomb, est le matériau piézoélectrique démontrant les meilleures propriétés pour de telles applications. Mais des évolutions législatives sont en cours pour restreindre son utilisation, du fait des risques que représente le plomb pour la santé et l’environnement. Le défi actuel dans le domaine des matériaux piézoélectriques est de trouver un matériau de substitution. C’est l’objectif de cette étude. Un matériau piézoélectrique sans-plomb choisi dans la littérature, le BHT, ou titanate de baryum dopé à l’hafnium, est étudié, dans le but de remplacer le PZT dans les appareils échographiques. Le procédé sol-gel composite est ensuite utilisé pour sa mise en œuvre sous forme de films épais piézoélectriques. / Ultrasonography is a medical imaging technique that allows exploring, with high resolution, a body in a few micrometers depth. For this purpose, ultrasonic waves , produced with a piezoelectric film, are used. This film must have a thickness of at least few micrometers to yield megahertz waves. Nowadays , PZT , lead zirconate titanate, is the key material for such applications. But since recently, a change has come in lead exploitation. It is recommended by the authorities to use another material when it is possible, which became a big challenge in piezoelectric material researches . Therefore, the aim of this study is to investigate a lead-free piezoelectric material in the purpose to use it in ultrasound echography. The selected material is BHT, barium hafnate titanate, and it is shaped as a thick film using sol-gel composite proceed.
|
8 |
AvaliaÃÃo de antioxidantes aplicados à produÃÃo de biodiesel. / Evaluation of Applied Antioxidants to Biodiesel ProductionFrancisco Francielle Pinheiro dos Santos 23 July 2013 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Este trabalho apresenta um estudo do comportamento e eficÃcia de antioxidantes aditivados ao biodiesel do Ãleo de soja. Os antioxidantes mais utilizados sÃo de estrutura fenÃlica, deste modo, sintetizar, comparar e estudar a aÃÃo destes antioxidantes avaliando as possÃveis causas que os levam a serem mais eficazes traz-nos informaÃÃes para a sÃntese de compostos com melhor atuaÃÃo antioxidante. Para uso como substrato orgÃnico, foi sintetizado o biodiesel a partir do Ãleo de soja, uma vez que à a partir deste, a produÃÃo de 81 % do biodiesel produzido no Brasil. Outro fator para o uso do Ãleo de soja à que este possui majoritariamente em sua composiÃÃo Ãcido linolÃico e olÃico, Ãcidos insaturados, altamente suscetÃveis à oxidaÃÃo. O biodiesel foi sintetizado atravÃs da reaÃÃo de transesterificaÃÃo com Ãlcool metÃlico, razÃo molar Ãlcool/Ãleo de 1:6 e hidrÃxido de sÃdio 0,5 % (m/m). As amostras de biodiesel foram aditivadas com os antioxidantes comerciais (BHT e ionol) e da biomassa (cardanol hidrogenado e cardanol alquilado) nas concentraÃÃes de 300, 600, 900, 1200, 1500, 2000, 3000 e 4000 mg/kg e armazenadas em frasco Ãmbar em uma temperatura de 22,  3 ÂC. Todas as amostras foram analisadas em teste de oxidaÃÃo acelerada (Rancimat), no tempo zero (momento logo apÃs a aditivaÃÃo) e apÃs 2, 4, 6, 9 e 12 meses de armazenamento. Durante o monitoramento observou-se a variaÃÃo do tempo de induÃÃo via rancimat em funÃÃo do tempo de armazenamento das amostras. As anÃlises tÃrmicas foram realizadas com o biodiesel do Ãleo de soja, BHT, ionol, cardanol hidrogenado, cardanol alquilado, e do biodiesel aditivado com estes antioxidantes nas concentraÃÃes de 300, 900, 1500, 3000 e 4000 mg/kg, na taxa de aquecimento de 10 ÂC/min, em atmosfera de nitrogÃnio, com faixa de aquecimento de 30 ÂC â 600 ÂC. AtravÃs da anÃlise tÃrmica verificaram-se o comportamento das amostras quando submetidas a temperaturas elevadas. As anÃlises por UV-vis foram realizadas com o intuito de avaliar o processo de autoxidaÃÃo das amostras apÃs 12 meses de armazenamento. Os experimentos via rancimat revelaram que os antioxidantes comerciais sÃo melhores que os da biomassa, os experimentos termogravimÃtricos e via UV-vis auxiliaram na constataÃÃo de que para otimizar antioxidantes fenÃlicos deve-se adicionar substituintes de baixo peso molecular nas posiÃÃes orto e para. AtravÃs dos resultados via Rancimat foi desenvolvido um software para a prediÃÃo do tempo de estabilidade oxidativa em funÃÃo do antioxidante utilizado, quantidade adicionada deste, tempo de armazenamento, bem como, realizar uma anÃlise econÃmica do custo de utilizaÃÃo de cada antioxidante. / This paper presents a study of the behavior and effectiveness of antioxidants additives for biodiesel from soybean oil. The most commonly used antioxidants are ofphenolic structure, thereby synthesizing, examining and comparing the antioxidant action for evaluating possible causes for a structure to be more effective when compared to another, brings forth necessary tools in the search for better performance antioxidant compounds. For use as an organic substrate, it was synthesized biodiesel from soybean oil, since this oil is from producing about 81 % of biodiesel produced in Brazil. Another factor for the use of soybean oil is that it has in its composition mainly oleic and linoleic acids, unsaturated acids highly susceptible to oxidation. The biodiesel was synthesized by the transesterification reaction with methyl alcohol, the molar ratio alcohol / oil of 1:6 and sodium hydroxide 0.5% (m / m). The biodiesel samples were doped with antioxidants (BHT and ionol), and biomass (hydrogenated cardanol and cardanol alkylated) at concentrations of 300, 600, 900, 1200, 1500, 2000, 3000 and 4000 mg.kg-1 and stored in an amber vial at a temperature of 22,  3  C. All samples were analyzed in an accelerated oxidation test (Rancimat), at the beginning (immediately after the moment additives) and after 2, 4, 6, 9 and 12 months storage. During monitoring the observed variation via Rancimat induction time as a function of storage time of the samples. The thermal analyzes were performed with biodiesel from soybean oil, BHT, ionol, hydrogenated cardanol, cardanolalkylated, and biodiesel doped antioxidants at concentrations of 300, 900, 1500, 3000 and 4000 mg.kg-1 rate heating to 10  C / min in a nitrogen atmosphere with heating range of 30  C - 600  C.Through thermal analysis verified the behavior of the samples when exposed to elevated temperatures. The analysis by UV-vis were conducted in order to evaluate the process of autoxidation of the samples after12 months of storage. The experiments via rancimat revealed that the commercial antioxidants are better than those of biomass, and to the thermogravimetric experiments via UV-vis the finding that helped to optimize phenolic antioxidants should be added low molecular weight substituent at the ortho and para positions. Through the results via Rancimat software was developed to predict the time depending on the oxidative stability of the antioxidant used, this added amount, time of storage and, perform an economic analysis cost of use of each antioxidant.
|
9 |
Barns rätt att bli sitt bästa jag, eller inte? : Några förskolors organisation av specialpedagogiska insatser och samverkan kring barn i behov av särskilt stödEriksson, Christina, Forslund, Sara January 2021 (has links)
Syftet med studien är att beskriva och analysera erfarenheter och upplevelser hos specialpedagoger, skolledare och pedagoger i förskolan gällande organisationen av specialpedagogiska insatser och samverkan kring barn i behov av särskilt stöd. Empirin har samlats in genom semistrukturerade intervjuer och en temaanalys visar att de centrala fynden är: Organisatoriska förutsättningar och kvalité kopplat til specialpedagogiska insatser, en önskan om specialpedagog anställd under rektor och hur stora barngrupper kan påverkar specialpedagogiska insatser. Vidare fynd är: Betydelsen av samsyn vid samverkan för barn i behov av särskilt stöd, rektors betydelse för barn i behov av särskilt stöd och önskan om samverkan med externa verksamheter. Studien diskuterar behovet av mindre barngrupper, kvalité i relation till specialpedagogiska insatser, fler specialpedagoger närmare förskolans verksamhet och en önskan om ökad samverkan med externa verksamheter. Vidare forskning behövs kring vad som kopplas till kvalité kring arbetet med barn i behov av särskilt stöd och användningen av arbetssätt samt bedömning i relation till adekvata stöd och tidiga insatser till barn i behov av särskilt stöd.
|
10 |
Fast GC: Applications and Theoretical StudiesReed, Gail L. 13 October 1999 (has links)
Experimental data are presented for the first time in support of a theoretical model of band broadening proposed by Blumberg (1997). This model addresses the effects of the compressibility of the mobile phase in gas chromatography and presents an equation derived from only two mutually independent variables. Solutions of decane and tridecane in hexane were analyzed at pressures ranging from 15 to 150 psi. Six different columns were used that varied in length, internal diameter and film thickness. Theoretical plate heights were obtained from this data and plotted versus the average linear carrier gas velocity (Golay type plots). These plots showed that at high pressures the Blumberg model fit the experimental data statistically significantly better than the earlier model proposed by Golay. The Blumberg model also accurately predicts the relationship between the optimum linear carrier gas velocity and the temperature.
The second part of this work explores the scope and limitations of fast temperature programming in the fast GC analyses of various sample types. These samples included polycyclic aromatic hydrocarbons (PAHs), hydrocarbons and food samples. Programming rates of up to 1200° C/min were used. These fast programming rates were obtained by using "flash"â ¢ temperature programming, controlled by resistive heating of a metal tube that enclosed a capillary column. The precision of peak data was found to be good, less than 5% for peak areas and 4% for retention times. However, a slight, but statistically significant decrease in peak areas was seen above programming rates of 240° C/min.
Microwave assisted extraction (MAE) was used to extract 2,6-di-(tert-butyl)-4-methylphenol, BHT, from chewing gum and breakfast cereal. The extraction was followed by a fast GC analysis (less than 4 minutes) using "flash"â ¢ temperature programming. MAE reduced the sample preparation time, from hours to minutes, and consequently reduced, the total analysis time. Extraction times longer than 5 minutes gave decreased recoveries of BHT. / Ph. D.
|
Page generated in 0.0209 seconds