Critical care patients are often connected to ventilators, to support or replace their breathing. The ventilators deliver a mixture of gas to the patient by applying a specific volume or pressure, and then the patient exhales passively. This thesis is based of the hypothesis that a slower reduction of the expiration pressure could benefit intensive care patients connected to a ventilator. To enable research within the area, a device which can control the expiration is needed. In this thesis project, an expiration valve was controlled to create different pressure patterns during expiration. To facilitate the research and the usage of the expiration control, an application software was created with the purpose to simulate relevant pressure, flow and volume curves. The prototype is an expiration cassette created for the ventilator Servo-i by Maquet Getinge Group. To enable flexibility, the prototype is external and no information is transmitted from or to the ventilator. The prototype has its own flow and pressure sensors. The different pressure patterns which the prototype uses are designed as a linear decrease and as if a constant resistance was added to the system. The user can also create their own pressure pattern, by deciding 20 pressure points in the duration of two seconds. The simulation application was designed with the ability to simulate the same pressure patterns available with the prototype. By using a lung model, it is possible to simulate the ideal pressure, flow and volume in the lungs which can be expected from the chosen expiration control. During the implementation, two different types of lung models were evaluated in order to determine the specificity required. The prototype was tested with settings which were chosen to challenge the performance of the control. Some problematic areas were detected, such as high pressures or large volumes. However, the prototype was judged to perform well enough to be used in animal trials. The lung model used for the simulation application was a simple model of the lung, consisting of a resistor and a capacitor in series. The simulations were compared with the real system with the purpose to get an indication on the difference between theory and reality. The application presents the expected behavior when using the expiration control. However, it should be kept in mind by the user that the application represents a theoretical model.

No description available.

A numerical approach to including electromagnetism with general relativity is developed using GRAXI as a starting point. We develop a mathematical model describing electromagnetism coupled to a scalar field in an evolving axisymmetric spacetime. As there are numerous formulations of electromagnetism, we evalute different formulations in a limited flat space case. The full curved space system is then developed, using the flat case as a guide to implementing electromagnetism. This model is then implemented using GRAXI as a code base.

We investigate spherically-symmetric gravitational collapse in the presence of a single "large" extra dimension through the use of analytical and numerical techniques. This has bearing on higher-dimensional ideas concerning hypothetical objects called "black strings," or black holes extending into an extra circular dimension, which dimension we hereinafter label zeta. These putative objects were first seriously considered as elements of string theory but have relevance in simpler, higher-dimensional generalization of Einstein's general relativity. We assume a universe topologically consisting of a two-dimensional Lorentzian manifold crossed with the sphere, crossed again with the circle. We model the formation of a uniform black string via two modes—the collapse of a massless scalar field, and of pure gravitational waves consisting of (gaussian) distortions in the extra dimension. We report on and discuss two aspects of the nonlinear dynamics, viz., that in five dimensions larger-amplitude fields appear to collapse more slowly than their lower amplitude cousins; and that pure gravitational field collapse exhibits signs of self-similarity at the threshold between black string formation and dispersal of the collapsing field.

No description available.

No description available.

Elementbyggnad medför ofta problem, dels på grund av avsaknaden av naturliga kopplingar mellan dess element, dels kring hur konstruktionen i dess utformning ska motstå fortskridande ras. Med fortskridande ras avses det förlopp som uppstår då kollaps av en enskild bärverksdelsprids till intilliggande konstruktion. En konstruktion som har tillräcklig förmåga att motstå detta förlopp benämns robust.Bo G. Hellers, professor emeritus i konstruktionslära vid Kungliga tekniska högskolan, beskriver i en debattartikel att många byggnader uppförda med prefabricerade betongelement från miljonprogrammet inte uppnår tillräcklig robusthet.Syftet med denna studie baseras på Bo G. Hellers uttalande och har varit att undersöka om en befintlig byggnad uppförd under miljonprogrammet är utformad på ett sådant sätt att tillräcklig robusthet uppnås. Om otillräcklig robusthet påvisas tas även åtgärdsförlag fram för att öka byggnadens robusthet enligt dagens norm.De frågor som studien besvarar är: Hur är undersökt byggnad konstruerad i avseende på robusthet? Kan det med någon av dagens dimensioneringsmetoder påvisas att byggnaden är robust? Hur kan eventuella åtgärder utformas för att uppnå tillräcklig robusthet?För att besvara den aktuella frågeställningen har en litteraturstudie av de metoder som finns för dimensionering i avseende på robusthet genomförts, liksom av material som rör miljonprogrammet och dess områden. Dessutom har ritningar av en aktuell byggnad samlats inoch analyserats. Vidare har även diskussioner med professionella aktörer med kompetens inom området genomförts.För att uppfylla de normkrav som ställs krävs att det finns horisontella och vertikala dragband, alternativt att konstruktionen utformas med horisontella dragband och att alternativa lastvägar kan påvisas vid fiktivt avlägsnande av en bärverksdel. Kan inte alternativa lastvägar påvisasska avlägsnad bärverksdel dimensioneras som en väsentlig bärverksdel. Konstruktionen ska även innehålla tillräcklig sammanhållningsarmering mellan fasad och bjälklag.Vid analys av ritningar över den befintliga byggnaden konstateras att de kopplingar som finns mellan bjälklagselementen, tillsammans med bjälklagens böjarmering, samt mellan bjälklag och gavelelement kan utgöra horisontella dragband respektive sammanhållningsarmering. Eftervidare undersökning påvisas dock att de horisontella kopplingarnas kapacitet inte är tillräcklig för att överföra de krafter som erfordras och kräver därav åtgärd.De vertikala kopplingar som finns mellan gavelelementen bedöms inte kunna vara verksamma som vertikala dragband då dessa kopplingars förankringslängd är bristande. För innerväggar saknas helt kopplingar i vertikalled vilket omöjliggör ett uppfyllande av kraven.Ett alternativ för att uppfylla normen är att möjliggöra alternativa lastvägar. Vid fiktiv borttagning av ett gavelelement betraktas fallet som en flaggkonstruktion. Här krävs att en skjuvkraft ska vara överförbar mellan kvarstående gavelelement och ovanpåliggande bjälklag. Vid undersökning av kapacitet hos de befintliga kopplingarna mellan elementen visar sig denna vara bristande och kraftöverföringen är inte möjlig. Samma fall kan tillämpas vid fiktiv borttagning av en innervägg men då denna helt saknar kopplingar är inte någon kraftöverföring möjlig. Innerväggen kan även betraktas som en fritt upplagd balk där dragkapaciteten i underkant ska vara tillräcklig, vilket den efter undersökning inte kan påvisas vara. Inga bärverksdelar uppfyller heller kraven för väsentliga bärverksdelar.För att uppnå tillräcklig kapacitet och möjliggöra erforderliga kraftöverföringar används i samtliga fall plattstål samt L-stål som förankras i betongen med expander. För att möjliggöra inre dragband monteras plattstål mellan bjälklagen och då böjarmeringens kapacitet är tillräcklig i samtliga riktningar kan bjälklagen, efter denna åtgärd, utnyttjas som både inre och yttre dragband.Vid gavelelementen monteras plattstål på dess utsida och L-stål på dess insida. Dessa förankras med expander och möjliggör tvärkraftsöverföring och ger tillräcklig förankring på varje bjälklagsnivå. Plattstål kopplar även samman enskilda gavelelement och vertikala krafter kan därmed också överföras. För innerväggen monteras L-stål vilket möjliggör tillräcklig kraftöverföring mellan innerväggen och ovanförliggande bjälklag.Efter genomförd undersökning kan följande slutsatser dras: Byggnaden är till viss del utformad i avseende på robusthet då gavelelement är kopplade till varandra samt till bjälklagselement. Även bjälklagselementen är kopplade till varandra. Byggnaden i dess aktuella utförande kan inte påvisas vara tillräcklig robust för att uppfylla kraven som ställs i dagens gällande normer. För att uppfylla kraven på tillräcklig robusthet kan fogarna förstärkas genom att montera L-stål och plattstål förankrade med expandrar. Med föreslagen åtgärd kan tillräcklig robusthet endast uppnås vid dimensionering enligt betongnormen. / The avoidance of joints in critical locations and how to design a structure to prevent progressive collapse is often two major problems associated with the use of precast concrete structures. This is due to the lack of natural connections between the elements which is generated automatically when using structures cast in situ. A building which has a good ability to withstand a progressive collapse can be referred to as “robust”.The purpose of this study is to investigate the robustness of a building from the million program era in regards to its initial structural design. If the ability to withstand a progressive collapse is proven to be insufficient, actions based on current standards will be proposed.Questions intended to be answered by this study are: How is the examined building designed in regards to robustness? Can the building by current standards be referred to as robust? Which actions can be taken to achieve sufficient robustness?To answer these questions a survey of literature, relevant for the subject, has been conducted as well as discussions with professionals with expertise in the subject. Blueprints of a building from the million program era has also been collected and analyzed.Analysis of the blueprints show that the building was built with some regards to robustness. Horizontal ties were placed in joints to connect the floor elements and the floor elements with the wall elements. Between exterior wall elements vertical ties were also placed to handle vertical loads. However, vertical ties, that connect the inner walls to the floor elements, are none existent.Further analysis of these joints show that their capacity does not meet the requirement for them to be able to transfer the desired forces. Therefore actions have to be taken to meet current standards.The actions proposed in this study is based on placing flat steel connections and L-steel connections in the joints to increase the capacity and enable the required force transfers. The steel connections are anchored to the concrete with expansion anchors.The study leads to the following conclusions: The building is in some ways designed to withstand a progressive collapse. The wall elements are connected with horizontal and vertical ties to nearby elements. The floor elements are also connected with horizontal ties. The initial building design does not meet the requirements of the current standards in regards to robustness. To meet the current standards the joints have to be reinforced. These reinforcements are done by placing flat steel connections and L-steel connections in the joints. These actions only fulfill the requirements of the concrete structures standard.

No / This article examines the role played by conflict trade in the process of state collapse. Conflict trade is defined here as the trade in non¿military goods such as diamonds, timber and drugs that finances war. Such trade includes both the export and import of goods to a war zone as well as extra¿territorial trade undertaken by supporters of a warring faction. It is argued that the decline of superpower military aid coupled with the broader effects of centre¿periphery exploitation mediated through a neo¿liberal and western imposed version of globalization has meant such trade has a particular salience both in contemporary conflict and the process of state collapse. Equally, though, the reliance of warring factions on conflict trade means they are also susceptible to changes in the market for their goods, creating a vulnerability that can (and to some extent has been) exploited to promote peace. The emerging control agenda on conflict trade is currently characterized by a number of problems ¿ most notably, the risk that the control of conflict trade might become a substitute for action on arms exports; that international action has largely been undertaken within an inappropriate statist paradigm; that control has sometimes taken second place to economic or strategic interests and that policy has become hostage to a 'drugs and thugs' agenda which risks undermining its effectiveness.

Porous polysulfone membranes prepared by phase inversion can be tailored to suit filtration requirements by the choice of solvent and coagulant. In the current research polysulfone membranes were prepared by inverting a solution in N-methyl pyrrolidinone (NMP) in isopropanol to form uniform sized pores. Phase inversion resulted in the formation of an asymmetric membrane. The membranes have a characteristic "skin" which is supported by a highly porous substructure. Water-wet membranes experience capillary force during water evaporation. Since the modulus of the membranes is lower than the capillary force, the membrane walls shrink and thicken giving rise to a condensed structure. The "skin" regulates permeation through the membranes which is essential for filtration. A change in the pore structure of the skin alters the permeability. The current research investigates the influence of amine plasma treatments on the surface pore structure of polysulfone membranes. The permeation of a rhodamine dye through the plasma treated membranes and through non-plasma treated membranes is used to examine the influence of the plasma treatment. Furthermore, the influence of plasma treatment on the loss of water from the membranes leading to pore collapse is also explored. The study revealed that a plasma ablates the skin, increasing the permeation. An ammonia plasma treatment produced more etching, and hence increased permeation compared to permeation for an aniline plasma-treated membrane. A one-minute aniline plasma treatment only caused a moderate increase in permeation. Plasma treatments introduced significant surface modification by the introduction of new functionalities. However, permeation was not influenced by the surface modification. Water trapped in the pores is essential to maintain the pore structure of the membrane. The surface treatment dictates the pore size and therefore, the convection allowing water evaporation, leading to pore collapse. Heat treating also increases the rate of water removal. Using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) the role of heat and surface treatments on the extent of pore collapse was investigated. The ammonia plasma treated samples showed maximum water loss and the control samples showed a minimum loss of water when stored at room temperature. All the samples stored at 90 °C exhibited equivalent water loss. Water loss was not affected by the plasma treatments. / Ph. D.

In this dissertation, we examine mechanics of rhythmic tracheal compression (RTC) in the darkling beetle, Zophobas morio. In Chapter 2, we studied the relationship between hemolymph pressure and tracheal collapse to test the hypothesis that pressure is a driving mechanism for RTC. We found that tracheae collapse as pressure increases, but other physiological factors in the body may be affecting tracheal compression in live beetles. Additionally, as the tracheae compress, they do so in varying spatial patterns across the insect body. In chapter 3, we examined spatial variations in the taenidial spacing, stiffness, and tracheal thickness along the length of the tracheae. We related variations in Young's modulus and taenidial spacing with measurements of collapse dimples and found that spatial patterns of Young's modulus correlate with dimensions of collapse dimples. This correlation suggests an intuitive link between tracheal stiffness variations and the unique patterns observed in compressing tracheae. Lastly, in chapter 4, we studied the non-uniform collapse patterns in 3-D. By manually pressurizing the hemocoel and imaging using synchrotron microcomputed tomography (SR-µCT), we reconstructed the tracheal system in its compressed state. While previous studies used 2-D x-ray images to examine collapse morphology, ours is the first to quantify collapse patterns in 3-D and compare with previous 2-D quantification methods. Our method is also the first to make a direct measure of tracheal volume as the tracheal system compresses, similar to the phenomenon that occurs during rhythmic tracheal compression. / Doctor of Philosophy / Insects have long been a source of curiosity and inspiration for scientists and engineers. The insect respiratory system stands as an example of a seemingly complex oxygen delivery system that operates with relative simplicity. As opposed to mammals and other vertebrates, the insect respiratory system does not deliver oxygen using blood. Instead, insects possess a massive network of hollow tracheal tubes that are distributed throughout the body. Air enters spiracular valves along the length of the insect body, travels through the tracheal tube network, and is delivered directly to the tissues. In some insects, the tracheae compress and expand, driving flow of respiratory gasses. However, unlike vertebrate lungs, there are no muscles directly associated with the tracheal system that would drive this tracheal compression, and exactly how this behavior occurs is not fully understood. In this dissertation, we examined pulsatory increases in blood pressure as a possible mechanism that underlies these tracheal compressions in the darkling beetle, Zophobas morio. Additionally, as the tracheae compress, they do so with varying spatial patterns across the insect body. Because tracheae are complex and non-uniform composite tubes, we examined spatial variations in the microstructure, stiffness, and tracheal thickness along the length of the trachea. Lastly, we visualized the variable collapse patterns in three dimensions using synchrotron micro-computed tomography combined with manual pressurization of the hemocoel. While previous studies used two-dimensional x-ray images to quantify tracheal collapse patterns, this work represents the first three-dimensional study. Understanding tracheal collapse mechanics, material properties, and their relationships with the circulatory system can help to gain an understanding of how insects create complex fluid flows within the body using relatively simple mechanisms.