Desiccation-induced soil cracking is of significant interest in several engineering disciplines, which include geotechnical and geoenvironmental engineering, mining engineering, and agriculture engineering. The hydraulic, mechanical, thermal and other physico-chemical properties of unsaturated soils can be predominantly influenced due to cracks. Reliable information of these properties is required for the rational design and maintenance of earth structures taking account of the influence the soil-atmosphere interactions (e.g., for expansive soil slopes, earth dams, and embankments). In spite of significant research studies published in the literature on the desiccation-induced cracks during the past century, the fundamental mechanism of crack initiation and propagation of soils induced by drying and shrinkage is still elusive. For this reason, the focus of this thesis is directed towards understanding the tensile strength of unsaturated soils which is associated with soil crack initiation criterion (i.e. maximum tensile stress criterion). Tensile strength is the key property of soils for interpreting the initiation of soil cracking from a macroscopic point of view. A semi-empirical model is proposed for predicting the tensile strength of unsaturated cohesionless soils taking into account the effect of both the negative pore-water pressure in saturated pores and the air-water interfacial surface tension in unsaturated pores. The proposed model is calibrated and validated by providing comparisons between the model predictions and the experimental measurements on 10 cohesionless soils (i.e. five sandy soils and five silty soils) published in the literature. The proposed model is simple and requires only the information of Soil-Water Characteristic Curve (SWCC) and Grain Size Distribution curve (GSD), which can be obtained from conventional laboratory tests. To investigate the influence of microstructure, a practical and reliable estimation approach for predicting the evolution of the microstructural void ratio of compacted clayey soils subjected to wetting and drying paths is proposed. The microstructural evolution of 13 examined soils were investigated quantitatively using the mercury intrusion porosimetry (MIP) results. The investigated soils include four high-plasticity clays, eight low-plasticity clays and a glacial till which is a relatively coarse-grained soil with some fines. Based on this study, a novel criterion has been developed for identifying different pore populations of compacted clayey soils. The “as-compacted state line” (ACSL) was proposed to estimate the initial microstructural void ratio based on the compaction water ratio. A constitutive stress is derived to interpret and predict the volumetric deformation of compacted clay aggregates. The linear elastic constitutive model is used for predicting the microstructural void ratio of the examined compacted soils following monotonic wetting and drying paths. The developed approach (i.e. the ACSL and the linear elastic constitutive model) is validated by providing comparisons between the predicted and interpreted microstructural void ratios for all the examined soils. In addition to the matric suction and microstructure, the confining pressure also influences the tensile strength of unsaturated compacted clayey soils. The tensile strength tests on a compacted clayey soil by both the direct method (i.e. triaxial tensile test) and the indirect method (i.e. Brazilian split test) were performed. It is found that the tensile strength increases as the compaction water content decreases for the range investigated in this study, which could be explained by the variation of the inter-aggregated capillary bonding force and the change in microstructure. The increase in the confining pressure has been found to induce the change in failure mode (i.e. from pure tensile failure mode to combined tensile-shear failure mode). In spite of limitations associated with the Brazilian split test, tensile strength is widely determined using this test due to the simple procedure of specimen preparation and wide availability of test equipment in conventional laboratories. However, the Brazilian tensile strength is found to overestimate the tensile strength of compacted specimens with water content greater than the plastic limit. This is due to the considerable plastic deformation associated with the ductile failure instead of brittle failure. In summary, this thesis is devoted to providing insight into the fundamental mechanisms associated with the desiccation-induced crack initiation by quantitatively investigating the various factors that influence the tensile strength of unsaturated soils, which include the matric suction, the microstructure, and the confining pressure from theoretical studies and laboratory investigations.

M. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / The developed oil-water separation membranes used in membrane technology are currently inefficient due to their poor morphological and topographical properties during nanoparticle coating. Researchers have developed different wettable membrane surfaces using jet spray coating. Most of these developed membranes are inadequate due to poor morphological and topographical properties normally observed as clusters, creating a rougher membrane surface that hinders wettability. This has resulted in the existing membrane fouling and degradation during the oil/water separation process and again due to different responses to corrosion and rusting. In the current study, membrane clusters were minimised on the ceramic membranes to create a smoother surface, improving membrane wettability. These clusters were minmised at optimal coating force, optimal coating distance and optimal coating angle. Part one of the study was to model and simulate different parameters that decreased clusters using the jet-spray coating. A theoretical model was derived from the first principles and all the external and internal forces that impact membrane clusters were considered during the model derivation. These forces are the force due to applied pressure from the spray gun, the force of nano-particles, the force of viscosity, the upward force on solid wall due to nanoparticles, the downward force on solid wall due to nanoparticles and the reaction force on the solid wall due to nanoparticles. The tools of stochastic theory and the concept of fluid dynamics were used in the modelling process. The total coating force from the jet spray gun nozzle was increased from 0,2x107 kN to 2,4x107 kN, which gave optimal coating force. The coating distance from the jet spray gun nozzle to the membrane surface was increased from 10 mm to 24 mm, which gave optimal coating distance. The jet spray angle in the spray region was also increased from 1⁰ to 9⁰ with reference from the vertical axis to the membrane surface, which gave optimal coating angle. This lead to optimal spread of nanoparticles on the membrane surface thus resulting to optimal cluster minimisation during the coating process. This decreased cluster sizes during nanoparticle coating, resulting in a smooth membrane surface, thus leading to lowered surface energy on the membrane. Part two of the study was to fabricate the ceramic membrane with fewer clusters on the surface for improved wettability using the jet-spray coating. It was important to produce the ceramic membrane surfaces with minimised membrane clusters by considering the optimal parameters revealed to minimise these membrane clusters during coating. Nanoparticle coating was performed under a controlled laboratory environment, and the optimal parameters that were studied to minimise membrane clusters were revealed. These parameters are coating force, coating distance and coating angle. More coating rounds were applied on ceramic samples and clusters were minimised during these coating rounds. The coated samples were analyzed by a scanning electron microscope and the nanoparticles on the membrane surfaces were characterised for optimal performance during oil-water separation. The scattering, orientation, morphology, spatial distribution, surface roughness, surface smoothness, contact angles, surface density of the particles, pore size network, mean size of the coated nanoparticle on the membrane surface after different coating rounds were characterised and analysed to minimise membrane cluster during nanoparticle coating. It was shown that more clusters were observed in 1st LP, 2nd LP, 3rd LP and 4th LP coating rounds when compared to 1st HP, 2nd HP, 3rd HP and 4th HP coating rounds. It was also shown that material surface roughness increased the formation of clusters in membrane surface as more clusters were observed in rough membrane surface when compared to the smooth membrane surface. The microstructure revealed a smoother membrane surface where membrane clusters were minimised. Part three of the study was to compare the newly designed ceramic membrane with the previously designed ceramic membrane from previous the literature. The correlation was done on the experimental results obtained in this study with the experimental results obtained from the previous literature. Different coating rounds were performed from the current study and the previous literature to design nanostructured ceramic membranes with fewer clusters on the surface. The results in the last coating round in this study, revealed a smooth membrane with a homogeneous substrate with fewer clusters and small sizes compared to other coating rounds.

No description available.

Baigiamajame darbe pateikta: detergentų paplitimas, jų fizikinės, cheminės savybės, klasifikacija ir daroma žala aplinkai. Analizuojami detergentais užterštų nuotekų valymo metodai. Analizuojami dujų burbuliukų susidarymo detergentų tirpaluose ypatumai, aprašomos dinaminės ir statiškai stabilios putos, pateikiama putų aparatų charakteristika. Pateikiamos suspenduoto sluoksnio charakteristikos ir jo galimybės detergentams iš nuotekų valyti. Darbo tikslas – ištirti suspenduoto sluoksnio įtaką valant detergentus iš nuotekų. Darbą sudaro 7 dalys: įvadas; tyrimo objektas ir problemos aprašymas; detergentais užterštų nuotekų valymas, putų burbuliukų ir putų susidarymo ypatumai, putų aparatai; suspenduoto sluoksnio charakteristikos ir jo galimybės panaudojant detergentams iš nuotekų valyti; eksperimentinė dalis; išvados; literatūros sąrašas. Eksperimentinėje dalyje teoriškai apskaičiuoti suspenduoto sluoksnio parametrai, aprašomas eksperimentinis stendas, jo veikimo principas, naudotos matavimo priemonės, pateikta eksperimento atlikimo metodika, pagal gautus eksperimentinius duomenis apskaičiuoti kintamieji suspenduoto sluoksnio parametrai. Darbo pabaigoje analizuojami gauti rezultatai ir pateikiamos darbo išvados. Darbo apimtis – 67 p. teksto be priedų, 21 iliustracija, 4 lentelės, 24 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai. / Thesis submits the spread of detergents, their physical, chemical properties, classification and environmental damage. There are analyzed various waste water cleaning methods of detergents. Froth formation in detergent leaches, dynamic and static stability of foams and basic information about froth devices are given. The characteristics of the suspended layer and its use in water treatment of detergents are given. The aim of this work – is to explore the suspended layer in cleaning waste water of detergents. Final work consists of seven parts: introduction; the subject matter and the problem description; water purification of synthetic detergents, characteristics of froth bubbles and froth formation, froth machines; suspended layer characteristics and the possibility of using it in waste water cleaning of detergents; experimental part; conclusions and references. Experimental part includes theoretically calculated suspended layer parameters, description of the experimental stand, its operating principle, instruments used during the experimental procedures, calculations of suspended layer variable settings according to the experimental data. In the end the results are analyzed and the conclusions are included. Thesis consists of: 67 p. text without appendixes, 21 picture, 4 tables, 24 bibliographical entries. Appendixes included.

Vid framställning av papper och pappersmassa krävs en stor mängd energi och även stora mängder vatten som med fördel tas från en närliggande sjö eller vattendrag. Avloppsvattnet passerar flera olika reningssteg såsom mekanisk, kemisk och biologisk rening innan det återinförs till recipienten. Vid aerob biologisk rening sker en nedbrytning och oxidation av det organiska materialet som utförs av mikroorganismer. Aeroba mikroorganismer kräver närvaro av syre varvid luft tillsätts till dammen. Luftningen utgör drygt hälften av det externa reningsverkets totala energibehov och försvåras av extraktivämnen som finns i träden. Vid Stora Enso Skoghalls bruk används en luftad damm som biologisk rening. Det finns problem med att få syret att räcka till i hela dammen. Om ett försteg placeras innan dammen skulle detta kunna bryta ned en del av de syreförbrukande ämnena. Förstegets utformning skulle vara en MBBR (Moving Bed Biofilm Reactor) innehållande bärare där termofila bakterier bildar biofilm. Två olika försöksuppställningar byggdes upp i ett laboratorium på Karlstads Universitet innehållande MBBR och luftade dammar. De luftade dammarna skulle likna Skoghalls bruks luftade damm med samma uppehållstid och innehålla samma sorts mikroorganismer. Processvattnet hämtades från Skoghalls bruk och pumpades kontinuerligt in till försöksuppställningarna. Vattnet togs från två olika ställen på bruket och innehöll dels CTMP och dels CTMP blandat med vatten från blekeriet och indunstningen. För utvärderingar av försöken utfördes analyser av COD, TOC, SÄ, SVI, ytspänning, extraktivämnen samt mikroskopering. Resultatet uppvisade en relativt jämn COD-och TOC-reduktion för de luftade dammarna på runt 70 %, vilket är jämförbara värden med Skoghalls bruks luftade damm. För det termofila MBBR-försteget med temperaturen 45 °C uppvisades en reduktionskapacitet på 30 – 40 %. Resultatet vid körning med vatten innehållande endast CTMP påvisades en reduktion på 30 %. Mätning av ytspänning och extraktivämnen ger en indikation på om syresättningen av avloppsvattnet kan bli effektivare. Det visade sig att biofilmen i de termofila stegen är mycket känslig och relativt enkel att slå ut om förhållandena för de termofila bakterierna inte är optimala eller om inkommande vatten innehåller någon giftig substans. Bioslammet i samtliga luftade dammar bestod av både bakterier, protozoer och metazoer. I referensdammen uppvisades stora och kompakta flockar medan det för dammarna som föregicks av termofila MBBR påvisade mindre slam och mindre kompakta flockar. För dammen innehållande endast CTMP påvisades förutom att flockarna var små även flytslam och skumproblem. / The production of pulp and paper requires a large amount of energy and also large amounts of water which, by advantage, can be taken from a nearby lake or river. The wastewater passes through several different purification steps, such as mechanical, chemical and biological treatment before being reintroduced to the recipient. During aerobic biological treatment, a degradation and oxidation of the organic material occurs and is performed by microorganisms which require oxygen. Aeration consumes about half of the external plant's total energy and is aggravated by extractives present in the trees. At Stora Enso Skoghall mill an aerated pond is used as biological treatment, but there are troubles to get the oxygen to last for the entire pond. If a pre-treatment is placed before the pond this would be able to reduce the substances which demands oxygen. The implementation of the pre-treatment would be a MBBR (Moving Bed Biofilm Reactor) containing carriers and where thermophilic bacteria form biofilms. The experimental setups were built up in a laboratory at the University of Karlstad. The aerated ponds would resemble the aerated pond at Skoghall mill, with an identical retention time and contain equivalent microorganisms. The wastewater was continuously pumped into the experimental setups and was received from Skoghall mill and contained only CTMP water and CTMP mixed with water from the bleach plant and evaporation plant. As evaluation of the experiments analyzes of COD, TOC, SS, SVI, surface tension, extractives and microscopy were done. The results showed a relatively uniform COD and TOC reduction for the aerated ponds at around 70 %, which is comparable with the real pond at Skoghall mill. For the thermophilic MBBR with a temperature of 45° C and with probe 10-water, a capacity of reduction at 30 - 40% was noticed. The result with water containing only CTMP showed a reduction of 30%. Measurements of surface tension and extractives show if the concentration of extractives is decreasing in the thermophilic pre-treatments and also in the aerated ponds, which indicates a more effective oxygenation of the water. It was also found that the biofilm in the thermophilic stages are very sensitive and relatively easy to decimate if the conditions for the thermophilic bacteria are not optimal or if the incoming water contains any toxic substance. The sludge in all aerated ponds consisted of bacteria, protozoa and metazoa. The reference pond showed large and dense flocks while for the ponds that were preceded by thermophilic MBBR indicated less sludge and less dense flocks. For pond containing CTMP-water the flocks were small, but in addition, floating sludge was detected and foam problems arose.

Master of Science / Department of Mechanical and Nuclear Engineering / Steven J. Eckels / Membrane dehumidification and evaporative cooling applications have the potential to significantly improve the energy efficiency of air conditioning equipment. The use of wire mesh media in such membrane applications is feasible but has not been studied extensively. Therefore, the aim of this work is to investigate the heat and mass transfer performance of several different wire mesh media in membrane based dehumidification and evaporative cooling. There were six wire mesh membranes tested in an experimental facility. The wire mesh membranes vary with respect to percent open area, wire diameter, pore size and material. Two non-permeable, solid membranes were also tested in the facility and compared with the wire mesh membranes. The test section of the experimental facility consists of a narrow air duct and a plate apparatus. The membrane samples were fashioned into rectangular plates and installed into the test section. The plate membranes separate liquid water and air flow streams. The inlet air temperature and humidity are altered to produce condensation or evaporation at the membrane surface. The average convective heat and mass transfer coefficient of the air boundary layer is measured for each of the experimental plates. Membrane based dehumidification and evaporative cooling were accomplished using the wire mesh media. However, the wire mesh membranes did not exhibit any significant differences in their performance. The mesh plates were compared with the solid plate membranes and it was discovered that the solid plates exhibited significantly higher heat transfer coefficients during condensation conditions. This result most likely is due to the formation of large water droplets on the solid plates during condensation. The experimental data is then compared to analytical predictions of the heat and mass transfer coefficients developed from several heat transfer correlations and by invoking the heat and mass transfer analogy. The experimental data is also compared directly with the heat and mass transfer analogy. It was found that the data did not compare well with the heat and mass transfer analogy. This result is attributed to the fact that the membrane surface limits the amount of direct exposure to the gas-liquid interface.

Le devenir des hydrocarbures (HC) dans les environnements hypersalins constitue une problématique environnementale majeure. Ce travail pour objectifs (1) d’évaluer l’impact d’une pollution pétrolière sur les communautés microbiennes d’un milieu hypersalin, (2) de déterminer comment les archées hydrocarbonoclastes accèdent aux HC et, (3) de déterminer si la biodégradation est possible en conditions anaérobies dans ces environnements hypersalés. Nous avons démontré qu’une biodégradation modérée du pétrole est possible en milieu hypersalin environ 10 % de la fraction aliphatique du pétrole sont biodégradé. Une disparition progressive des composés aromatiques les plus légers est également observée, liée aux processus abiotiques. La dynamique des communautés procaryotiques montre un changement dans la structure de la communauté bactérienne autochtone des saumures. Une résistance à la contamination pétrolière a en revanche été observée pour les communautés archéennes des saumures. Dans une deuxième partie du travail, nous avons pu montrer, à l’aide d’une souche d’archée hyperhalophile modèle (Haloferax volcanii MSCN14), que les archées hydrocarbonoclastes de ces environnements mettent en oeuvre plusieurs mécanismes leur permettant d’augmenter la biodisponibilité des HC. Dans une dernière partie des travaux, nous avons testé les capacités d’une souche modèle (Hfx. volcanii MSNC 16) à dégrader les HC en anaérobiose. Si Hfx. volcanii MSNC16 est bien capable d’utiliser le fumarate comme accepteur terminal d’électrons, elle n’est en revanche pas capable de dégrader l’alcane testé (heptadécane) en absence d’oxygène. / The fate of hydrocarbons (HC) in hypersaline environments is an important environmental issue. This work aimed to (1) assess the impact of oil pollution on microbial communities of a hypersaline environment, (2) determine how hydrocarbonoclastic archaea can access to HC and (3) whether biodegradation is possible in these hypersaline environments in the absence of oxygen. We have shown that moderate oil biodegradation is possible under hypersaline conditions. In these conditions close to natural ones, about 10% of the aliphatic hydrocarbons were biodegrade. A gradual disappearance of the lighter aromatic compounds was also observed, but these losses were mainly due to abiotic processes. The monitoring of prokaryotic communities based on molecular fingerprints showed a change in the structure of the indigenous bacterial community. On the contrary, resistance to oil contamination was observed among the indigenous archaeal communities of brines. In the second part of this work, laboratory cultures of a hyperhalophilic archaeal strain (Haloferax volcanii MSCN14), allowed to demonstrate that, in hypersaline environments, hydrocarbonoclastic archaea use several strategies to increase the bioavailability of HC. Indeed, strain MSCN14 was capable of producing one or several biosurfactants during growth on different HC, and was adhering to the surface of the HC. In the last part of this work, we tested the capacities of a model archaeal strain (Hfx. volcanii MSNC 16) to degrade HC anaerobically. If Hfx. volcanii MSNC16 was able to use fumarate as a terminal electron acceptor, it was, however, not capable of degrading heptadecane in the absence of oxygen.

Le procédé du rotomoulage réactif est une technologie de fabrication de pièces creuses de taille et géométrie très variés. Une compréhension et une modélisation des phénomènes physiques qui interviennent dans les différentes étapes de la fabrication apportent une contribution importante à la maîtrise de ce procédé. Les travaux abordés dans cette thèse se situent dans le cadre d'un programme plus général visant le contrôle et le pilotage du rotomoulage réactif.Tout d'abord, une caractérisation et modélisation de la cinétique du polyuréthane thermodurcissable en mode dynamique est réalisé suivie par des mesures rhéologiques afin d'établir des lois rhéocinétique ainsi que des lois du comportement viscoélastiques du système réactionnel. Ces lois de comportement sont établies conformément aux conditions réelles de la mise en œuvre du matériau.Ensuite, nous simulons le procédé du rotomoulage en utilisant un code de calcul basé sur la méthode « Smoothed Particle Hydrodynamics » (SPH), développé par notre équipe, en implémentant des nouveaux paramètres physiques: le caractère non-newtonien du mélange réactionnel et les effets de tension superficielle.Le modèle de tension de surface en 2 et 3D développé dans cette thèse permet la détection explicite de l'interface séparant le fluide réactif de l'air. Puis, nous utilisons l'interpolation lagrangienne ou la régression circulaire pour construire la courbe d'interface en 2D et la surface d'interface en 3D sera reconstruite via la régression sphérique. Quant à la modélisation de l'écoulement du fluide non-newtonien, une loi de puissance décrivant l'évolution de la viscosité en fonction du taux de cisaillement a été intégrée dans le solveur pour décrire le caractère non-newtonien du mélange réactionnel durant sa mise en œuvre. Ces paramètres physiques implémentés dans le code ont été validé par une série de cas de tests en 2 et 3D.L'intégration des effets de tension de surface et la prise en compte du caractère non-newtonien du fluide réactif nous ont permis de mieux présenter la mouillabilité de la surface interne du moule et l'étalement des différentes couches du polymères.Mots clés : rotomoulage réactif, polyuréthane thermodurcissable, rhéocinétique, Smoothed Particle Hydrodynamics, tension de surface, fluide non-newtonien, simulation. / Reactive Rotational molding (RRM) is a process for manufacturing hollow plastic products with no weld lines, in virtually any shape, size, color and configuration, using biaxial rotation and high temperature. Understanding and modelling of physical phenomena provide a great contribution for process control that is the purpose of a more general program.Firstly, a characterization and the kinetic modeling of the thermoset polyurethane are performed in anisothermal conditions followed by rheological measurements in order to establish rheokinetik model and the the viscoelastic behavior of the reactive system according with RRM conditions.Afterwards, to simulate the RRM, Smoothed Particles Hydrodynamics (SPH) method is applied which is suited method to simulate the fluid flow with free surface such as occurs at RRM. This solver is developed by our team. Modelling and simulating reactive system flow depend on different parameters; the physical phenomena involved are: surface tension force and non-newtonian fluid behavior.The surface tension method has been successfully applied to simulate RRM using SPH solver taking into account free surface tension force. Surface tension force is given explicitly in the current model. After detecting the boundary particles, the interface is locally fitted by using Lagrangian interpolation polynomial or fitting circle in 2D and by using fitting sphere in 3D, respectively. To study the non-newtonian fluid flow during RRM, a power law describes the evolution of the viscosity versus shear rate was adopted to describe the viscoelastic nature of the reactive fluid during its shaping.The implementation of surface tension and viscoelasticity allows us to present the wettability of internal surface of the mold and the spreading of different polymers layers.Keywords : Reactive rotational molding, thermoset polyurethane, rheokinetik, Smoothed Particle Hydrodynamics, surface tension, non-newtonian fluid, simulation.

INTRODUÇÃO: A Síndrome do Desconforto Respiratório (SDR) é uma das principais causas de morbi-mortalidade no período neonatal, acometendo predominantemente os recém-nascidos prematuros, devido a uma está deficiência de surfactante pulmonar. O Instituto Butantan desenvolveu um surfactante de origem porcina com objetivo de torná-lo disponível a todo Sistema Único de Saúde. O objetivo deste estudo foi avaliar, em um modelo experimental de SDR (coelho), a estabilidade do Surfactante Butantan (SB) um ano após sua produção e armazenamento a 2 a 8ºC.. MÉTODOS: 94 coelhos prematuros foram randomizados em dois grupos de tratamento: grupo Butantan e grupo Curosurf (controle), e foram analisados em seis momentos de avaliação: momento zero (imediatamente após a retirada do refrigerador ao final de 1 ano de armazenamento), momento 1 (24 horas após ter sido mantido a 24ºC), momento 2 (após 30 dias de armazenamento a 20º C), momento 3 (após 60 dias de armazenamento a 20º C), momento 4 (após 90 dias de armazenamento a 20º C) e momento 5 (após 180 dias de armazenamento a 20º C). Após receberem o surfactante, os animais foram ventilados por 15 minutos para avaliação da pressão ventilatória e complacência pulmonar dinâmica e curva pressão-volume pulmonar, seguindo-se à avaliação histopatológica dos pulmões. RESULTADOS: A eficácia do SB foi semelhante à do Curosurf, um ano após a sua produção e armazenamento a 2 a 8ºC. Neste momento de avaliação, não houve diferença estatisticamente significante entre os grupos de estudo quanto a: pressão ventilatória, complacência pulmonar dinâmica e curva pressão-volume pulmonar. Ao longo dos seis meses de armazenamento inadequado do SB, demonstrou-se a redução de sua eficácia durante a fase expiratória da curva pressão-volume pulmonar. No entanto, a análise histopatológica, demonstrou não haver diferença significante entre os dois grupos de estudo em nenhum dos momentos de avaliação. CONCLUSÕES: As propriedades bioquímicas do SB foram preservadas após um ano de sua produção e armazenamento em refrigeração de 2 a 8ºC. Condições inadequadas de armazenamento resultam em alterações das propriedades bioquímicas do SB e, conseqüentemente, de sua função, o que foi demonstrado por parâmetros de mecânica ventilatória, mas não pela análise histopatológica dos pulmões / INTRODUCTION: Respiratory Distress Syndrome (RDS) is one of the major causes of death among premature newborns, and its development results from surfactant deficiency. The Butantan Institute has recently produced a porcine-derived surfactant preparation in order to make it available nationwide for RDS treatment in the near future. The aim of this study was to evaluate, in an animal model of surfactant deficiency (premature rabbits), the stability of the Butantan Surfactant (SB) one year after its production and storage in the refrigerator, at 2 to 8ºC. METHODS: 94 premature newborn rabbits were randomized into two treatment groups: SB or Curosurf®(control surfactant), and were assessed in six different time-points: time-point zero (immediately after removal of surfactant from the refrigerator after one year of storage); time-point 1 (after 24h of storage at 24ºC), time-point 2 (after 30 days of storage at 20ºC), time-point 3 (after 60 days of storage at 20ºC), time-point 4 (after 90 days of storage at 20ºC) and time-point 5 (after 180 days of storage at 20ºC). The animals were artificially ventilated for 15 minutes for lung mechanics assessment (ventilatory pressure, dynamic lung compliance and pressure-lung volume curve), followed by removal of the lungs for histopathologic analysis. RESULTS: After one year of its production and storage at 2 to 8ºC, SB was as efficient as Curosurf. At this time-point, The Butantan Surfactant showed no significant differences with Curosurf® regarding the ventilatory pressure, dynamic lung compliance and pressure-lung volume curve. Throughout the six month period of warming, SB showed a decreasing efficiency, as revealed by the expiratory phase of the pressure-lung volume curve. However, the histopathologic analysis revealed no significant differences between the two groups, in any of the study time-points. CONCLUSIONS: The Butantan Surfactant preserved its biochemical properties one year after its production and storage at 2 to 8ºC. On the other hand, adverse storing conditions can lead to alterations in the SB biochemical properties that result in deterioration of its function, which was demonstrated in this study by changes in lung mechanics, but not in the histopathologic analysis

The study is focused on study of surface and interfacial properties of oil at high temperatures, to understand the mechanisms of heat transfer and oil absorption during frying