In gas-condensate reservoirs, production rate starts to decrease when retrograde condensation occurs. As the bottomhole pressure drops below the dewpoint, gascondensate and water buildup impede flow of gas to the surface. To stop the impairment of the well, many publications suggest wettability alteration to gas-wetting as a permanent solution to the problem. Previous simulation work suggests an "optimum wetting state" to exist where maximum gas condensate well productivity is reached. This work has direct application in gas-condensate reservoirs, especially in identifying the most effective stimulation treatment which can be designed to provide the optimum wetting conditions in the near-wellbore region. This thesis presents an extensive experimental study on Berea sandstone rocks treated with a fluorinated polymer. Various concentrations of the polymer are investigated to obtain the optimum alteration in wettability to intermediate gas-wet. This wetting condition is achieved with an 8% polymer solution treatment, which yields maximum gas mobility, ultimately increasing the relative permeability curves and allowing enhanced recovery from gas-condensate wells. The treatments are performed mainly at room conditions, and also under high pressure and high temperature, simulating the natural environment of a reservoir. Several experimental techniques are implemented to examine the effect of treatments on wettability. These include flow displacement tests and oil imbibitions. The experimental work took place in the Wettability Research Lab in Texas A&M University at Qatar in Doha, Qatar. The studies in this area are important to improve the productivity of gas-condensate reservoirs where liquid accumulates, decreasing production of the well. Efficiency in the extraction of natural gas is important for the economic and environmental considerations of the oil and gas industry. Wettability alteration is one of the newest stimulation methods proposed by researchers, and shows great potential for future research and field applications.

Student Number : 0107553H - MSc research report - School of Science Education - Faculty of Science / One of the most important challenges of the secondary school science teacher is to help learners to obtain, analyze and evaluate evidence using experimental and investigative methods. The understanding and application of concepts of evidence play a central role in setting up valid experiment and is usually ignored in the secondary school science curriculum. Recognizing the significance and value of an understanding of evidence in developing learners’ ability to carry out appropriate experimental work in science, the question arises of learners’ understanding of ‘concepts of evidence’ in experimental design. In this study the researcher endeavored to answer some of the questions concerning learners’ understanding of evidence: What understanding do learners entering the Further Education and Training (FET) band have of the concepts of validity in experimental design? What is the effect of an intervention on their understanding of concepts of validity? How well do learners show their ability to apply concepts of evidence to an assessment task? The study investigated the ability of a sample of grade 10 Physical Science learners, in one Gauteng Province secondary school to use and understand the concepts of evidence before and after an intervention, and their ability apply these ideas about evidence in an assessment sheet task. First, a survey of learners’ understanding of the concepts of validity was conducted using a written diagnostic test, consisting of three probes that had been previously used to diagnose learners’ understanding of validity in experimental design. Second, an evaluation of changes in such understanding due to a specific teaching intervention was completed using the same diagnostic test. Finally, the 2004 Grade 9 Common Tasks for Assessment (CTA) investigation task was administered to the same subjects in order to investigate whether or not their understanding of concepts of evidence would be apparent in this CTA investigation task. Several key findings emerged from the data. The major findings of this study were that the sample investigated began the study with a level of understanding equal to a group of Foundation University students tested in a previous study and that their understanding did not change much during the intervention. In fact, analysis of the results from the probes in the diagnostic test revealed that learners had little problem choosing the independent variable and controlling variables. However, the findings from the probes indicated that the intervention did not seem to have had a major effect since the difference in the number of responses between the pre-test and post- test was relatively small. Moreover, the results also revealed that it was possible to analyze learners’ responses using the existing model of learners’ understanding of validity, and that the majority of learners fell into Level C in the model which refers to the application of previous understanding in a new situation. The results from the CTA investigation task revealed that learners’ understanding of concepts of evidence could be demonstrated in new science context. In fact, the results revealed that learners showed ability to apply their understanding of concepts of evidence in experimental design to the assessment task. Moreover, the CTA results indicated that the understanding of identifying variables, constructing graphs; describing the relationship between variables in a graph; formulating the investigative questions were the most applied concepts of evidence by learners. Finally, the results of this study highlight the need for providing secondary science learners with opportunities to practice and develop concepts of evidence. In the light of these findings it is recommended that children need to be explicitly taught about the purpose of science investigations and introduced to important ideas about evidence if their ability to perform investigation tasks is to be improved.

Le dimensionnement des digues paravalanches s’appuie sur la connaissance des processus physiques liés au ressaut, qui se forme lorsqu’un écoulement fin et rapide rencontre un obstacle suffisamment haut pour ralentir et épaissir l’écoulement incident. La hauteur du ressaut est aujourd’hui calculée à partir d’équations strictement valides pour des écoulements de matériaux non frictionnels et non compressibles tels que l’eau, sur fond plat et lisse. Or, les avalanches de neige dense sont des écoulements compressibles qui ne peuvent avoir lieu qu’en pente, et au sein desquels se produit de la dissipation d’énergie par friction et collisions entre les grains. Il est donc essentiel de mieux connaître le comportement des ressauts dans les écoulements granulaires en pente. Pour cela, la thèse s’appuie sur plusieurs approches. Les ressauts granulaires stationnaires sont d’abord étudiés de manière purement théorique, à l’aide des équations de conservation de la masse et de la quantité de mouvement moyennées dans l’épaisseur, afin de trouver une relation générale pour prédire la hauteur des ressauts quelques soient les conditions d’entrée. Nous simulons ensuite numériquement un grand nombre de ressauts granulaires en faisant varier plusieurs paramètres (la pente du plan incliné, le débit, le diamètre des grains, la friction entre les grains) à l’aide de la méthode aux éléments discrets. Cette méthode permet d’accéder à la structure interne des ressauts, et notamment à la mesure des champs de vitesse, de fraction volumique, ou encore de la dissipation d’énergie. Les simulations sont réalisées en deux dimensions. Enfin, un dispositif de mesure innovant, qui utilise la radiographie à rayons X dynamique, a été adapté à une expérience de laboratoire existante pour créer des ressauts granulaires stationnaires. Cette technique de mesure permet, en particulier, de mesurer la distribution spatiale moyennée dans la largeur de l’écoulement de la fraction volumique avant, à l’intérieur et après le ressaut granulaire. La comparaison du nouveau cadre théorique proposé avec les résultats expérimentaux et numériques nous permet de mettre en évidence une grande diversité des types de ressauts granulaires en fonction des conditions initiales. Pour chaque type de ressaut, les lacunes du cadre théorique classique, qui ne tient pas compte des forces mises en jeu dans le ressaut ni de la compressibilité, sont clairement établies. / The design of avalanche protection dams relies on the understanding and modelling of physical processes related to the formation of jumps that form when a thin and fast flow meets an obstacle high enough to slow down and thicken the incoming flow. The jump height is nowadays calculated through equations that are strictly valid for non-frictional incompressible flows on a horizontal and smooth bottom. However, dense-snow avalanches are compressible granular flows taking place on a slope, and inside which energy is dissipated through enduring frictional contacts and collisions between grains. It is then essential to decipher the behaviour of jumps formed during granular flows down inclines. To this extent, the thesis relies on several approaches. Standing granular jumps are first studied in a purely theoretical way, with the help of depth-averaged mass and momentum conservation equations, in order to find a relation to predict the height of the jumps regardless of the input conditions. A great number of granular jumps are then simulated by varying several parameters (the slope angle of the incline, the discharge, the grain diameter, the grain-grain friction) thanks to the discrete element method. This method allows us to access to the internal structure of the jumps, and in particular to the spatial distributions of velocity, volume fraction and energy dissipation. Those simulations are done in two dimensions. Finally, an innovative measurement technique using dynamic X-ray radiography was adapted to an existing small-scale laboratory device to produce standing granular jumps. This technique allows in particular the measurement of the width-averaged spatial distribution of volume fraction before, inside and after the granular jumps. The comparison between the new theoretical framework proposed and both the experimental and numerical data, allows us to evidence a rich variety of granular jump patterns as a function of the input conditions. For each type of jump pattern, the shortcomings of the classical theoretical framework, which does not account for the forces at stake within the jump volume nor the compressibility, are well established.

Orientador: Odete Pacubi Baierl Teixeira / Banca: Odisséa Boaventura de Oliveira / Banca: Marco Aurélio Alvarenga Monteiro / Banca: Roberto Nardi / Banca: Renato Eugênio da Silva Diniz / Resumo: O presente trabalho aborda um estudo sobre a Resolução de Problemas baseado em atividades experimentais investigativas visando a compreensão das ações pedagógicas realizadas durante o Curso de Férias "Desvendando o Corpo dos Animais" envolvendo professores e alunos do Ensino Médio, que aconteceu no município de Oriximiná (PA). Procuramos inicialmente detalhar as características do curso para iniciar discussões sobre os conhecimentos abordados no âmbito da Biologia. No embasamento teórico da nossa pesquisa, procuramos por intermédio de trabalhos nas áreas da Argumentação e do Ensino e Aprendizagem analisar o processo comunicativo/argumentativo definindo qualificadores que ajudassem a compreender como se construíram a produção e organização de saberes durante as perguntas e respostas fornecidas pelos professores e alunos, no decorrer das socializações dos procedimentos experimentais realizados para solução do problema. Os instrumentos empregados para a composição dos dados foram oriundos de videogravações obtidas durante o período em que as experimentações foram oriundos de videogravações obtidas durante o período em que as experimentações foram socializadas para o auditório. A análise dos dados apontou descritores que definiram as diversas ações ocorridas durante o curso, bem como o encaminhamento de orientações relacionadas ao processo de ensino e de aprendizagem envolvendo a resolução de problemas por intermédio de atividades experimentais investigativas / Abstract: The current work adress a study about the resolution of problems based on investigative experimentive experimental activities, with activities, with the aim the to understand the pedagogical actions realized during the Vacation Course "Desvendando o Corpo dos Animais", that envolved teachers and student of high school, and occurred in the city of Oriximina (PA). We attempted initially to detail the characters of the characters of the course to initiate discussions about the approached knowledge in biology. For the theoretical basement of our research, we used previous work in the area of Argumentation and the Teaching of Learning to analyse the communicative/argumentative process, defining qualificators that would help to comprehend how the production and organization of the knowledge was built during the questions and answers given by the teachers and students during the socialization of the experimental proceeds realized. The instrument utilized to compose the data were obtained of videos recorded during the period in which the experimental were socialized to the public. The data analysis pointed descriptors that occurred during the course, as well as the directioning of orientations related to the process of teaching and learning envolving the solution of problems by investigative experimental activities / Doutor

Parmi les combustibles fossiles, le gaz naturel est le plus propre, en termes d'émissions de CO2, d'efficacité énergétique et de quantité de polluants atmosphériques émis. Le méthane est l'élément principal du gaz naturel; néanmoins, il contient des quantités considérables de gaz acides (CO2, H2S) qui peuvent entraîner la corrosion des équipements et des pipelines si de l'eau est présente. Les mercaptans sont d’autres composés soufrés présents dans le gaz naturel dont combustion peut produire du SO2 qui est un produit chimique indésirables causant des problèmes environnementaux. Les gaz acides et les mercaptans doivent être retirés du gaz naturel jusqu'à une norme acceptable. Le gaz naturel traité contient jusqu'à 2% de CO2, 2-4 ppm de H2S et 5-30 ppm de mercaptans. L'absorption chimique avec des solvants aqueuses comportant des alcanolamines [3] (comme la monoéthanolamine (MEA), la diéthanolamine (DEA), la méthyldiéthanolamine (MDEA)) est la méthode la plus bien malteuse pour séparer les gaz acides du gaz naturel. Les gaz acides réagissent selon une réaction acide base dans l'absorbeur pour former des espèces électrolytes. Les mercaptans et les hydrocarbures ne réagissent pas avec les molécules d'alcanolamines, et sont physiquement absorbés.Le modèle thermodynamique a une grande importance pour la conception du procédé de traitement des gaz acide, car il va permettre de déterminer l'Equilibre Liquide Vapeur et faire les bilans d’énergie. Des modèles thermodynamiques fiables peuvent permettre aux concepteurs non seulement de confirmer leurs limites réglementaires, mais aussi de minimiser la perte de composants précieux comme les hydrocarbures.Dans ce travail, un modèle thermodynamique a été développé pour prédire:•Les solubilités des alcanes (méthane, éthane, propane, n-butane, n-pentane, n-hexane), aromatiques (ethylbenzène, benzène, toluène) et mercaptans (MM, EM) dans une solution aqueuse d'alcanolamine• Les solubilités des gaz acides (CO2, H2S) dans des solutions aqueuses d'alcanolamine et d'autres propriétés cruciales telles que: la concentration d'électrolyte, la composition en phase vapeur (principalement le conteneur d'eau)• Les diagrammes de phase pour les systèmes multi-composants contenant du CO2-H2S-alcanolamine-eau-hydrocabon-mercaptan.Les paramètres du model ont été déterminés avec les données expérimentales disponibles dans la littérature et les nouvelles données mesurées. / Among fossil fuels, natural gas is the cleanest, in terms of CO2 emission, burn efficiency and amount of air pollutant. Methane is the prevailing element of natural gas; therefore, there are also a variety of impurities. In fact, it contains usually considerable amounts of acid gases (CO2, H2S) which can lead to corrosion in equipments and pipelines if water is present. Mercaptans are known as toxic molecules with undesirable odor, and fuel combustion of mercaptan molecules can produce SO2 which is undesirable chemical, they can cause environmental issues. Acid gases and mercaptans are needed to be removed from natural gas until acceptable standard. The treated natural gas contains as maximum as 2% of CO2, 2–4 ppm of H2S and 5–30 ppm of total mercaptans. Chemical absorption with alkanolamines [3] (such as monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA)) is the most well-established method to separate acid gas from natural gas. Acid gases react with alkanolamines in the absorber to form electrolyte species, mercaptans and hydrocarbons do not react with alkanolamines molecules, and they are physically absorbed by aqueous alkanolamine solution. Then the loaded solution can be regenerated by heating in the stripper.Thermodynamic model is of high importance for the conception of the process, as it is linked directly to the accurate determination of the Vapor-Liquid Equilibrium and energy balances. Reliable thermodynamic models can allow designers not only to confirm their regulatory limits, but also to minimize the loss of valuable hydrocarbons components.In this work a thermodynamic model has been developed to describe:• Alkane (methane, ethane, propane, n-butane, n-pentane, n-hexane), aromatic (ethylbenzene, benzene, toluene) and mercaptans (MM,EM) in aqueous alkanolamine solution• Acid gases (CO2,H2S) solubilities in aqueous alkanolamine solutions, and other crucial properties like: electrolyte concentration, vapor phase composition(mostly water contant)• The phase diagram for multi-component system containing CO2-H2S-alkanolamine-water-hydrocabon-mercaptan.The parameters of the model were determined with the experimental data available in the literature and the new measured data.

During a period of over five years two psychiatric teams have attempted to develop a programme for cooperation between child and youth care and adult psychiatric care in common premises in a local community just outside Stockholm. The thesis docu­ments, in six parts, the experiences from these experimental working conditions and how they were used to reach the desired goals of change in the organisations and in the activities of the teams. The thesis also shows how this special situation and the circumstances which followed created obstacles to change. The research-programme was carried out by field-research me­thods, i.e. a combination of direct observation and inter-viewing. The two teams went through different phases of mutual rela­tions. Initially they had to face severe difficulties. During the first 1 1/2 years the level of conflict was high. Indivi­dual members of the staffs became more and more paralyzed. At the same time, however, they could manage to work together with client-fami1ies and with other social welfare institutions. Individuals from different teams could exchange experiences with one another but, at the same time, they were unable to genera­lize and to share these experiences consciously. In the following 1 1/2 years the teams were integrated. New ways of handling therapeutic issues were developed. There were signs of change in the therapeutic identity of the staffs. The last years of the experimental period were characterized by growing reactions against the earlier developement. The teams were again split up, both administratively and in relation to working methods, The first part of the thesis describes the developement of the experimental issue in general. It also gives a presentation of the research-programme. The working pre-conditions are examined in the second part. In the third part the cause of the paralysis of the staff's capability of action is analyzed by viewing the problem from different theoretical perspectives and as a result of a clash between the different "activity-matrices" of the teams. In the fourth part some experiences of the research-methods used are documented. Some difficulties connected with preparation, re­alization and evaluation of experimental work conditions are examined in the fifth part. The sixth part is a summing up of the earlier parts and presents an analysis of the contradictions actua­lized during the experimental period. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1985, härtill 6 uppsatser.</p> / digitalisering@umu

Med begränsade ekonomiska resurser finns en risk att laborationsundervisningen blir lidande, t ex genom att inte tillräcklig laborationsutrustning finns tillgänglig. Med syfte att på ett djupare plan tränga in i denna frågeställning och erhålla en förståelse för vad som upplevs begränsande för dagens undervisning på skolnivå, hur undervisningen är upplagd och vad det upplevs kunna ge för konsekvenser har en exemplifierande fallstudie utförts. Studien utfördes i form av en deltagande observation i åk 7-9 vid en kommunal grundskola i en tätort med ca 70 000 invånare. Studien inkluderade intervjuer med lärare, rektor och elever samt laborationshandledningar och fältanteckningar. Vissa av kunskapskraven i styrdokumenten är direkt knutna till den laborativa verksamheten och således svåra att uppfylla utan den. Samtidigt ses i studien att både rektor, lärare och elever uppskattade laborationer, eftersom de ger möjlighet att skapa intresse, självförtroende och en lust att lära genom att lära genom att göra, att använda flera sinnen och att variera undervisningen. Därav finns det fog för att säga att laborationsundervisningen är här för att stanna. Studien visar att lärarna utförde laborationer utan kostsam utrustning. Lärarna använde vad som fanns. Undervisningen bestod främst av klassiska laborationer med enkelt material där frågeställning och metod var given och till viss del var även resultatet slutet. Rektor och lärarna var väl medvetna om att pedagogisk ämneskunskap och struktur på undervisningen påverkar lärandet. Lärarna såg förberedelsetid och trångboddhet som begränsande. Trångboddheten försvårade bl a förberedelse och materialanvändning. De uttryckte att de var glada att arbeta på en gammal skola med material från 50/60-talet och använde artefakterna i sin undervisning. De tyckte sig inte sakna artefakter, förutom en av lärarna som uttryckte att tillräcklig utrustning fanns för undervisning på den nivå som efterfrågades, men själv tyckte att nivån var för låg. Sammanfattningsvis är laborationsundervisningen under ekonomisk och pedagogisk press.

Made available in DSpace on 2014-06-11T19:31:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-06Bitstream added on 2014-06-13T20:22:43Z : No. of bitstreams: 1 malheiro_jms_dr_bauru.pdf: 2352497 bytes, checksum: ea6815ec72e6c6842b1b332b2d3107a7 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho aborda um estudo sobre a Resolução de Problemas baseado em atividades experimentais investigativas visando a compreensão das ações pedagógicas realizadas durante o Curso de Férias Desvendando o Corpo dos Animais envolvendo professores e alunos do Ensino Médio, que aconteceu no município de Oriximiná (PA). Procuramos inicialmente detalhar as características do curso para iniciar discussões sobre os conhecimentos abordados no âmbito da Biologia. No embasamento teórico da nossa pesquisa, procuramos por intermédio de trabalhos nas áreas da Argumentação e do Ensino e Aprendizagem analisar o processo comunicativo/argumentativo definindo qualificadores que ajudassem a compreender como se construíram a produção e organização de saberes durante as perguntas e respostas fornecidas pelos professores e alunos, no decorrer das socializações dos procedimentos experimentais realizados para solução do problema. Os instrumentos empregados para a composição dos dados foram oriundos de videogravações obtidas durante o período em que as experimentações foram oriundos de videogravações obtidas durante o período em que as experimentações foram socializadas para o auditório. A análise dos dados apontou descritores que definiram as diversas ações ocorridas durante o curso, bem como o encaminhamento de orientações relacionadas ao processo de ensino e de aprendizagem envolvendo a resolução de problemas por intermédio de atividades experimentais investigativas / The current work adress a study about the resolution of problems based on investigative experimentive experimental activities, with activities, with the aim the to understand the pedagogical actions realized during the Vacation Course Desvendando o Corpo dos Animais, that envolved teachers and student of high school, and occurred in the city of Oriximina (PA). We attempted initially to detail the characters of the characters of the course to initiate discussions about the approached knowledge in biology. For the theoretical basement of our research, we used previous work in the area of Argumentation and the Teaching of Learning to analyse the communicative/argumentative process, defining qualificators that would help to comprehend how the production and organization of the knowledge was built during the questions and answers given by the teachers and students during the socialization of the experimental proceeds realized. The instrument utilized to compose the data were obtained of videos recorded during the period in which the experimental were socialized to the public. The data analysis pointed descriptors that occurred during the course, as well as the directioning of orientations related to the process of teaching and learning envolving the solution of problems by investigative experimental activities

La demande en énergies fossiles a connu une forte croissance au cours du vingtième siècle et représente aujourd'hui 80% de la consommation énergétique mondiale. Pour répondre à la demande, les industries pétrolières et gazières s'orientent vers de nouvelles sources. 40% des réserves de gaz contiennent un pourcentage important (jusqu'à 20%) de gaz acides (dioxyde de carbone et sulfure d'hydrogène). La production de ces gaz à forte teneur en gaz acides représente un défi pour les industries, étant donné la toxicité du sulfure d'hydrogène et la forte probabilité de corrosion des pipelines en présence d'eau (naturellement produite avec le gaz naturel). D'autre part, l'utilisation des énergies fossiles conduit au changement climatique avec des émissions importantes de dioxyde de carbone dans l'atmosphère. Le captage et le stockage du CO2 semble être un procédé prometteur. De l'eau est souvent présente lors du transport du gaz naturel et du CO2 capturé. Lors des étapes de production et de transport, les conditions de température et de pression sont sujettes au changement. La condensation de l'eau (à l'origine de la corrosion et donc d'une rupture possible des pipelines) et à la formation de glace et/ou d'hydrates en sont les conséquences principales. Or la formation d'hydrates est un sérieux problème avec un risque de blocage des pipelines. Pour éviter la formation des hydrates, des inhibiteurs chimiques sont utilisés. Il est donc indispensable de bien connaitre les équilibres entre phases pour les différents mélanges considérés pour un fonctionnement et une production en toute sécurité. / The twentieth century has seen an important increase of the fossil energy demand, representing today 80% of world energy consumption. To meet the request, oil and gas companies are interested in new gas fields. 40% of these reserves are acid and sour gases, i.e. the percentage of carbon dioxide and hydrogen sulphide is significant, sometimes over 20% of CO2 or H2S. Natural gas production with high content of acid gases can be a challenge, due to their corrosiveness potential in pipelines in the presence of water and H2S toxicity. On another hand, as a result of world's dependence on fossil energies, the release of carbon into atmosphere is increasing and leads to climate changes. Carbon Capture and Storage (CCS) is one of the most promising ways to reduce CO2 emissions in the atmosphere. Whether in natural gas or carbon dioxide transport, water may be present. During production, transportation and processing, changes in temperature and pressure can lead to water condensation (cause of corrosion, and consequently a possible pipeline rupture), ice and/or gas hydrates formation. Hydrates are a serious flow assurance problem and may block pipelines. To avoid hydrates formation, chemical inhibitors are used. Therefore accurate knowledge of mixtures phase equilibria are important for safe operation of pipelines and production/processing facilities.

This thesis presents the experimental work on testing the seasonal performance of a 40 kW air-to-water propane heat pump, as a part of the research project Next Heat Pump Generation working with Natural fluids (NxtHPG) that has been carried out in ‘Applied thermodynamics and refrigeration Division’ in the department of Energy Technology, KTH. The thesis work involves three parts: preparation of the HP unit test rigs, experimental campaign and the evaluation of test results. In the first part, the set-up of the measurement device and necessary modifications to the heat pump unit as well as the test rigs have been completed to create an accurate measuring environmental for the experimental campaign. During the second stage, two series of experimental campaign have been done in the heating mode of the heat pump unit, and satisfactory results have been obtained in parts of the test conditions. Finally, the evaluation on the system performance as well as the behaviors of the components is discussed. The variation between experimental results and the simulation conducted by IMST-ART model is within reasonable range, proving that the heat pump unit has been working in good conditions. The compressor is proved to have been performing as manufacturer expected. However, some further investigations on the behaviors of the heat exchangers and expansion valve, such as superheat oscillation, are recommended be carried out in the future work. The completion of the rest of tests in which minus air temperature should be maintained and the ones with the desuperheater working should be done as well. / Next generation heat pump working with natural fluids