Toxicidade da mistura formulada de imazethapyr e imazapic sobre o azevém em função do teor de umidade do solo

Herbicidas do grupo das imidazolinonas têm, em geral, fraca adsorção ao solo e alta solubilidade em água, e, por isso, os níveis de umidade do solo podem alterar a disponibilidade desses herbicidas e seu efeito sobre culturas suscetíveis. Com o objetivo de comparar o efeito de doses da mistura formulada de imazethapyr + imazapic (75 + 25 g i.a. L-1) sobre plantas de azevém, cultivadas em solo com três níveis de umidade, foi realizado um experimento em casa de vegetação, no delineamento em blocos ao acaso com quatro repetições. Os tratamentos foram constituídos pela combinação de sete níveis do fator dose (0, 100, 200, 300, 400, 600 e 800 mL ha-1 do produto formulado), combinados com três níveis do fator umidade do solo (0, -10 e -100 kPa). Houve aumento na toxicidade e na taxa de redução da massa da matéria seca das plantas com o aumento nas doses do herbicida, sendo esses efeitos menores em solo com teor de água de -100 kPa. O teor de água no solo altera a toxicidade da mistura formulada de imazethapyr + imazapic sobre o azevém, sendo a cultura mais afetada em solos com maiores níveis de umidade.

Espectro de gotas de pontas de pulverização com adjuvantes de uso agrícola

O sucesso de uma boa aplicação de produtos fitossanitários depende da sinergia entre fatores como tamanho de gota, tipo de ponta, pressão, volume e composição da calda e características do alvo. Assim, o objetivo deste trabalho foi avaliar o espectro de gotas produzidas por pontas de jato plano defletor (TT 11002) e jato plano defletor com indução de ar (TTI 11002), com diferentes adjuvantes adicionados à calda de pulverização, pela técnica de difração de raio laser. O experimento foi conduzido em delineamento inteiramente casualizado, com quatro repetições, em esquema fatorial 2 x 5, ou seja, duas pontas de aplicação (jato plano defletor e jato plano defletor com indução de ar) e cinco composições de calda (água e água mais quatro adjuvantes: fosfatidilcoline+ácido propiônico, éter poliglicólico de monilfenol, ésteres de ácidos graxos e nonil-fenol etoxilado+óxido de etileno). Em ambiente controlado, avaliou-se o espectro de gotas, por meio de um analisador a laser de gotas em tempo real, na pressão de 276 kPa. O efeito dos adjuvantes no espectro de gotas mostrou-se dependente da ponta de pulverização empregada. A adição dos adjuvantes à calda não alterou o risco potencial de deriva, expresso pela porcentagem do volume em gotas com diâmetro inferior a 100 µm, porém o adjuvante fosfatidilcoline+ácido propiônico reduziu o diâmetro da mediana volumétrica das gotas produzidas pela ponta de jato plano defletor com indução de ar, em relação à avaliação feita somente com água.

Influência da pressão, temperatura e pré-tratamentos na secagem a vácuo de cenoura e abóbora

O presente trabalho visou estudar experimentalmente a cinética de secagem a vácuo de cenoura e abóbora "in natura" e pré-tratadas por branqueamento e congelamento. Os ensaios experimentais foram conduzidos em um secador a vácuo, nas pressões de 5, 15 e 25 kPa e temperaturas de 50, 60 e 70°C. Estudou-se a influência da pressão e temperatura assim como os pré-tratamentos adotados sobre a cinética de secagem. A análise do efeito dos pré-tratamentos e dos parâmetros pressão e temperatura sobre a velocidade de secagem revelou que os melhores valores foram obtidos com a temperatura de 70°C e pressão de 5 kPa para as amostras prétratadas por congelamento. Quanto ao tipo de matéria-prima utilizado, a abóbora apresentou maiores velocidades de secagem que a cenoura, independentemente do tratamento recebido e da condição de secagem utilizada. As curvas experimentais de secagem foram ajustadas ao modelo difusional de Fick para uma placa plana infinita.

Frutas estruturadas de umidade intermediária obtidas de polpas concentradas de abacaxi, manga e mamão

O objetivo deste trabalho foi estabelecer procedimento tecnológico para produção de fruta estruturada com elevados teores (450 a 700 g/kg) de polpas concentradas de abacaxi (39ºBrix), manga (35ºBrix) e mamão (16ºBrix), e quantidade mínima de sacarose, utilizando alginato ou pectina baixamente metoxilada. Glicose ou glicerol foi utilizado como supressor de atividade de água. Valores de firmeza de 240 g para géis de alginato e 1300 g para géis de pectina, determinados em Analisador de Textura TA.XT2, podem ser utilizados como indicadores para a estruturação, baseando-se nas propriedades de corte das frutas estruturadas. O processo de estruturação compreende a mistura sob vácuo (88 kPa) da polpa concentrada previamente aquecida a 60ºC e o hidrocolóide disperso em açúcar. Soluções de CaHPO e Glucona-Delta-Lactona foram adicionadas à mistura para favorecer a formação do gel. Os resultados mostraram a importância de elevar o pH de polpas de abacaxi e manga para 4,00 com NaOH. O alginato produziu 4 géis mais firmes e o glicerol foi o supressor de atividade de água mais eficiente. As frutas estruturadas de mamão com alginato apresentaram maior firmeza (acima de 3 kg). Os géis de abacaxi com alginato não puderam ser cortados com a faca, embora os géis de manga puderam ser cortados, eles aderiram à faca.

Filmes e coberturas comestíveis compostas à base de amidos nativos e gelatina na conservação e aceitação sensorial de uvas Crimson

Filmes compostos de gelatina com amidos nativos de trigo, sorgo, batata e arroz foram produzidos separadamente e caracterizados quanto às propriedades físico-químicas (solubilidade em água e barreira ao vapor de água), físicas (espessura e opacidade) e mecânicas (resistência à tração e porcentagem de elongação na ruptura). As mesmas soluções filmogênicas foram preparadas e aplicadas em uvas Crimson para avaliação sensorial e acompanhamento da perda de massa durante 22 dias. As coberturas de sorgo e arroz foram as mais eficientes na extensão da vida útil (aumento de 10 dias). Entretanto, em relação aos atributos sensoriais, as uvas com cobertura de arroz não diferiram estatisticamente do controle, que apresentou as menores notas para os parâmetros de aparência global e intenção de compra. O filme de sorgo apresentou uma permeabilidade ao vapor de água de 5,40 g.mm.m-2.d.kPa, resistência à tração de 85,89 MPa, elongação de 6,61% e opacidade de 40%. Mesmo não apresentando os melhores valores de caracterização, como filme, tornou-se a melhor opção como cobertura. Na avaliação sensorial, as uvas cobertas obtiveram aceitação igual ou maior que o controle quanto à aparência global, brilho, cor e intenção de compra. Na degustação das uvas, nenhuma das coberturas exerceu influência significativa no aroma, sabor e textura, sendo aceitas pelo consumidor em todos os parâmetros.

Pre-treatment of thermoduric spores in CO2 modified atmosphere and their survivability during food extrusion

The aim of this experiment was to evaluate how susceptible spores become to mechanical damage during food extrusion after being submitted to CO2. B. stearothermophilus spores sowed to corn and soy mix were submitted to 99% CO2 for 10 days and extruded in a single-screw extruder. The treatments were: T1 - spore-containing samples, extruded at screw rotational speed of 65 rpm and barrel wall temperature of 80 °C; T2 - as T1, except for screw rotational speed of 150 rpm; and T3 - as T2, except that samples were submitted to the modified atmosphere. The results for cell viability, minimum and maximum residence times, and static pressure were T1 - 19.90 ± 3.24%, 123.3 ± 14.50 seconds; 203.3 ± 14.05 seconds; 2.217 ± 62 kPa; T2 - 21.42 ± 8.24%, 70.00 ± 5.77 seconds; 170.00 ± 4.67 seconds; 2.310 ± 107 kPa; and T3 - 11.06 ± 2.46%, 86.00 ± 7.23 seconds; 186.00 ± 7.50 seconds; 2.403 ± 93 kPa, respectively. It was concluded that the extrusion process did reduce the cell count. However, screw rotational speed variation or CO2 pre-treatment did not affect cell viability.

Microstructural changes of frozen strawberries submitted to pre-treatments with additives and vacuum impregnation

Strawberries were submitted to freezing after pre-treatments with hydrocolloid and calcium salts (pectin and calcium chloride) at different concentrations, in the attempt to establish a correlation of the effects of these substances and their processing, on the physical and microstructural characteristics of fruits after thawing. Strawberry halves were submitted to impregnation with controlled vacuum pressure of 84.4, 50.5 and 16.6 kPa; comprising pectin at concentrations of 0, 1.5 and 3%; with the addition of calcium chloride at concentrations of 0, 3 and 6%; and glucose at 20%, for 4 hours. Measurements were made of the total soluble solid contents, cellular fluid loss, texture and viscosity of the solution, before and after the freezing/thawing. Images of the tissue cuts during the freezing, in function of time, were taken in an optic microscope coupled to a cold-stage and controlled temperature system, where the reduction of the cellular area was quantified using an image analyzing software. The pectin concentration had an influence on and demonstrated a potential for protection of the frozen tissue samples. The photomicrographs showed that the loss of cellular fluid occurs during the growth of ice formed in the intercellular spaces and it is retarded through treatments with high pectin concentrations.

Mechanical and water vapor permeability properties of biodegradables films based on methylcellulose, glucomannan, pectin and gelatin

Mimic biological structures such as the cell wall of plant tissues may be an alternative to obtain biodegradable films with improved mechanical and water vapor barrier properties. This study aims to evaluate the mechanical properties and water vapor permeability (WVP) of films produced by using the solvent-casting technique from blended methylcellulose, glucomannan, pectin and gelatin. First, films from polysaccharides at pH 4 were produced. The film with the best mechanical performance (tensile strength = 72.63 MPa; elongation = 9.85%) was obtained from methylcellulose-glucomannan-pectin at ratio 1:4:1, respectively. Then, gelatin was added to this polysaccharide blend and the pH was adjusted to 4, 5 and 6. Results showed significant improvement in WVP when films were made at pH 5 and at polysaccharides/gelatin ratio of 90/10 and 10/90, reaching 0.094 and 0.118 g.mm/h.m².kPa as values, respectively. Films with the best mechanical properties were obtained from the blend of polysaccharides, whereas WVP was improved from the blend of polysaccharides and gelatin at pH 5.

Convective, vacuum and microwave drying kinetics of mallow leaves and comparison of color and ascorbic acid values of three drying methods

Mallow leaves (Malva sylvestris L.) with initial moisture of 5.02±0.003 on dry basis (82.5% on wet basis) were dried using three different drying methods, microwave, convective and vacuum. The leaves that weigh 75 g each were dried until their moisture fell down to 0.10±0.005 on dry basis (approximately 9% on wet basis). The following drying levels were used in each of the drying processes: 6.67, 8.67, 10, 11.33 W g-1 microwave power density; 50, 75, 100 and 125 °C for convective drying; and 3, 7 kPa at 50 and 75 °C for vacuum drying. Drying periods ranged from 6-10, 26-150 and 38-130 min. for microwave, convective and vacuum drying, respectively. Effective moisture diffisuvities ranged from 2.04403 10-10-3.63996 10-12 m2 s-1, 1.70182 10-11-1.10084 10-10 m2 s-1 and 1.85599 10-11-5.94559 10-10 m2 s-1 for microwave, convective and vacuum drying, respectively. According to ascorbic acid content and color parameters, the best microwave power density was found 10 W g-1 with a drying period of 6.5 min.

Energy evaluation of an evaporative cooling system using water driven ejector

The search for efficient and accessible cooling systems has increased worldwide. This study aims to build and evaluate an evaporative cooling system using a water driven ejector, allowing it to be installed in places with plenty of water. The system was investigated varying the flow rate and temperature of the circulating water, temperature of the replacement water, and coefficient of performance. The best vacuum obtained was 8.5 kPa at nominal operating conditions of 4.1 ± 0.1 m³/h and 5 ± 0.5 ºC for the circulating water reaching the temperature of 9.7 ± 0.5 ºC. The pulse-like disturbance generated by replacing the cooling water at different periods of times did not result in significant affect vacuum destabilization and the temperature rise in the cooling tank. The coefficient of performance of the system at the highest thermal power of 92.27 W was 0.077, which was underestimated due to possible problems related to pump efficiency. The system evaluated under the conditions proposed can be very efficient for cooling fluids at higher temperatures, and it can be complementary to main refrigeration systems.

Biomassakattilan simulointi

Tässä diplomityössä mallinnetaan Apros-simulointiohjelmistolla kylläistä höyryä tuottava KPA Uniconin toimittama Biograte-kattilalaitos. Työ on rajattu käsittelemään vesihöyrypiiri syöttövesisäiliöstä prosessiin lähtevään höyryyn saakka. Savukaasupuoli on mallinnettu polttoaineen ja palamisilman syötöstä savupiippuun asti, mutta savukaasujen puhdistus on jätetty pois simulaatiomallista. Työssä kerrotaan yleisesti biopolttoaineista, kattilalaitoksista ja tulipesäratkaisuista. Simuloitava kattilalaitos ja sen säätöjärjestelmä käydään läpi yksityiskohtaisemmin. Simuloinnista ja sen mahdollisuuksista kerrotaan yleisesti, jonka jälkeen esitellään tehty simulaatiomalli. Simulointituloksia verrataan kattilan mitoitusarvoihin ja tärkeimpien prosessisuureiden muutoksia tutkitaan kuormanmuutostilanteissa. Lopuksi tuloksista tehdään yhteenveto ja esitellään jatkotoimenpidesuunnitelmat. Simuloitu kattilalaitos tuottaa kylläistä höyryä halutun määrän oikeassa paineessa ja lämpötilassa. Kattilan prosessisuureet vastaavat melko hyvin mitoitusarvoja ja simulaatiomalli toimii vakaasti myös kuormanmuutostilanteissa. Suurimmat kompromissit ja yksinkertaistukset on tehty tulipesän ja polttoaineensyötön mallinnuksessa. Näitä osa-alueita kehittämällä simulaation tarkkuutta olisi mahdollista parantaa entisestään. Jatkossa simulointimallia on tarkoitus kehittää laajentamalla se kattamaan myös laitoksen sekundääripuoli kokonaisuudessaan. Tulosten perusteella simulaatiota voidaan pitää onnistuneena mallina Biograte-kattilalaitoksesta.

L’intégration de la prise de décision visuo-motrice et d’action motrice dans des conditions ambiguës

La prise de décision est un mécanisme qui fait intervenir les structures neuronales supérieures afin d’effectuer un lien entre la perception du signal et l’action. Plusieurs travaux qui cherchent à comprendre les mécanismes de la prise de décision sont menés à divers ni- veaux allant de l’analyse comportementale cognitive jusqu'à la modélisation computationnelle. Le but de ce projet a été d’évaluer d’un instant à l’autre comment la variabilité du signal observé («bruit»), influence la capacité des sujets humains à détecter la direction du mouvement dans un stimulus visuel. Dans ces travaux, nous avons éliminé l’une des sources potentielles de variabilité, la variabilité d’une image à l’autre, dans le nombre de points qui portaient les trois signaux de mouvements cohérents (gauche, droite, et aléatoire) dans les stimuli de Kinématogramme de points aléatoires (KPA), c’est-à-dire la variabilité d’origine périphérique. Les stimuli KPA de type « V6 » étaient des stimuli KPA standard avec une variabilité instantanée du signal, et par contre les stimuli KPA de type « V8 », étaient modifiés pour éliminer la variabilité stochastique due à la variabilité du nombre de pixels d’un instant à l’autre qui portent le signal cohérent. Si la performance des sujets, qui correspond à leur temps de réaction et au nombre de bonnes réponses, diffère en réponse aux stimuli dont le nombre de points en mouvement cohérent varie (V6) ou ne varie pas (V8), ceci serait une preuve que la variabilité d’origine périphérique modulerait le processus décisionnel. Par contre, si la performance des sujets ne diffère pas entre ces deux types de stimuli, ceci serait une preuve que la source majeure de variabilité de performance est d’origine centrale. Dans nos résultats nous avons constaté que le temps de réaction et le nombre de bonnes réponses sont modulés par la preuve nette du mouvement cohérent. De plus on a pu établir qu’en éliminant la variabilité d’origine périphérique définit ci-dessus, on n’observe pas réellement de modification dans les enregistrements. Ce qui nous à amené à penser qu’il n y a pas de distinction claire entre la distribution des erreurs et les bonnes réponses effectuées pour chacun des essais entre les deux stimuli que nous avons utilisé : V6 et V8. C’est donc après avoir mesuré la « quantité d’énergie » que nous avons proposé que la variabilité observée dans les résultats serait probablement d’origine centrale.

An Inter-digital Capacitive Electrode Modified as a Pressure Sensor

Inter-digital capacitive electrodes working as electric field sensors have been developed for touch panel applications. Evaluation circuits to convert variations in electric fields in such sensors into computer compatible data are commercially available. We report development of an Interdigital capacitive electrode working as a sensitive pressure sensor in the range 0-120 kPa. Essentially it is a touch/proximity sensor converted into a pressure sensor with a suitable elastomer buffer medium acting as the pressure transmitter. The performance of the sensor has been evaluated and reported. Such sensors can be made very economical in comparison to existing pressure sensors. Moreover, they are very convenient to be fabricated into sensor arrays involving a number of sensors for distributed pressure sensing applications such as in biomedical systems.

Effect of ethanol on the micellization and gelation of Pluronic P123

In certain applications copolymer P123 (E21P67E21) is dissolved in water-ethanol mixtures, initially to form micellar solutions and eventually to gel. For P123 in 10, 20, and 30 wt % aqueous ethanol we used dynamic light scattering from dilute solutions to confirm micellization, oscillatory rheometry, and visual observation of mobility (tube inversion) to determine gel formation in concentrated solutions and small-angle X-ray scattering (SAXS) to determine gel structure. Except for solutions in 30 wt % aqueous ethanol, a clear-turbid transition was encountered on heating dilute and concentrated micellar solutions alike, and as for solutions in water alone (Chaibundit et al. Langmuir 2007, 23, 9229) this could be ascribed to formation of wormlike micelles. Dense clouding, typical of phase separation, was observed at higher temperatures. Regions of isotropic and birefringent gel were defined for concentrated solutions and shown (by SAXS) to have Cubic (fcc and hcp) and hexagonal structures, consistent with packed spherical and elongated micelles, respectively. The cubic gels (0, 10, and 20 wt % ethanol) were clear, while the hex gels were either turbid (0 and 10 wt % ethanol), turbid enclosing a clear region (20 wt % ethanol), or entirely clear (30 wt % ethanol). The SAXS profile was unchanged between turbid and clear regions of the 20 wt % ethanol gel. Temperature scans of dynamic moduli showed (as expected) a clear distinction between high-modulus cubic gels (G'(max) approximate to 20-30 kPa) and lower modulus hex gels (G'(max) < 10 kPa).

Effects of drying methods and conditions on antimicrobial activity of edible chitosan films enriched with galangal extract

The aim of this work was to study the effects of drying methods and conditions (i.e., ambient drying, hot air drying at 40 degrees C, vacuum drying and low-pressure superheated steam drying within the temperature range of 70-90 degrees C at an absolute pressure of 10 kPa) as well as the concentration of galangal extract on the antimicrobial activity of edible chitosan films against Staphylococcus aureus. Galangal extract was added to the film forming solution as a natural antimicrobial agent in the concentration range of 0.3-0.9 g/100 g. Fourier transform infrared (FTIR) spectra and swelling of the films were also evaluated to investigate interaction between chitosan and the galangal extract. The antimicrobial activity of the films was evaluated by the disc diffusion and viable cell count method, while the morphology of bacteria treated with the antimicrobial films was observed via transmission electron microscopy (TEM). The antimicrobial activity, swelling and functional group interaction of the antimicrobial films were found to be affected by the drying methods and conditions as well as the concentration of the galangal extract. The electron microscopic observations revealed that cell wall and cell membrane of S. aureus treated by the antimicrobial films were significantly damaged. (C) 2009 Elsevier Ltd. All rights reserved.