Les protéines [Fe-S] sont des enzymes ubiquitaires, assurant des fonctions clés au sein des organismes vivants. La biosynthèse des centres [Fe-S], à savoir les processus permettant un assemblage correct des atomes de fer et de soufre au sein des protéines cibles, requièrent la participation de machineries protéiques complexes. Parmi elles se trouve la machinerie SUF qui intervient dans des conditions de stress oxydant et de carence en fer. Elle est composée de six gènes sufABCDSE. La protéine SufA est proposée comme étant une protéine scaffold ayant pour rôle de préassembler transitoirement des centres [Fe-S] et de les transférer à des protéines cibles. Elle possède trois résidus cystéines conservés proposés comme étant les ligands des centres [Fe-S].<br />SufA est obtenue principalement sous forme apo après purification. Le centre [Fe-S] peut être reconstitué chimiquement in vitro. Dans ces conditions, SufA contient un mélange de centres [2Fe-2S] et [4Fe-4S]. Nous avons alors isolé SufA native métallée après purification à partir de tout l'opéron suf en anaérobiose, et montré qu'elle contient un centre [Fe-S], plutôt de type [2Fe-2S], transférable efficacement à la ferrédoxine. Nous avons également étudié les mécanismes moléculaires de formation du cluster dans SufA. SufA est capable de fixer à la fois du soufre, au niveau de ses trois cystéines conservées, et du fer, majoritairement au niveau d'atomes d'azote et d'oxygène. Ces éléments sont mobilisables pour la formation d'un centre [Fe-S] en milieu réducteur. Enfin, des expériences préliminaires réalisées in vitro avec des mutants dirigés n'ont pas permis d'identifier la nature exacte des ligands du centre [Fe-S] dans SufA.

Le phenomène de transition de spin correspond au changement d'état de spin d'un ion de transition sous l'action d'une perturbation extérieur (T, P, B, hv). Cette commutation ouvre de réelles perspectives dans le domaine de l'affichage et du stockage d'information. Ce travail présente, tout d'abord, l'étude d'un complexe macrocyclique heptacoordiné à transition de spin, noté {Fe(L222(N3O2)(CN)2}.H2O avec une sphère de coordination FeN3O2C2. L'examen attentif des propriétés magnétiques et structurales a permis de proposer un diagramme de phase ewpliquant la nature multi-métastable de ce système. Nous analysons et discutons l'influence de la température, des aspects cinétiques et de la photo-excitation sur les phases mises en jeu. Nous avons ensuite synthétisé divers analogues en tentant d'influer sur la géométrie du macrocycle (forme ouverte, accroissement de la rigidité), sur la nature de la sphère de coordiantion (substitution des atomes d'oxygène par des atomes de soufre et azote). Deux résultats majeurs ont été obtenus : une température limite record d'effet de trempe T(TIESST) de 171 K et une stabilité d'un étét photo-induit avec un T(LIESST) de 110 K pour un composé totalement bas spin jusqu'à 440 K.

Background: Most traffic safety research projects require accurate real world data which is collected in different databases around the world. This is especially important since the results of these projects form the basis for new crash test procedures and standards. In many of these databases the involvement of the frontal structures of the car in frontal crashes is coded by using the SAE J224 practice (Society of Automobile Engineers). There were indications that by using this practice the database would contain an overestimate of the car frontal structure involvement in real world crashes. One purpose of this thesis is therefore to develop a new method for real world crash investigations to better address this issue. One purpose was also to adopt this method in a data collection of fatal crashes in Sweden and examine injury causation mechanisms. Studies shows that the commonly used Hybrid III dummy is not fully reproducing the kinematical behavior observed in frontal sled test with belted PMHS (Post Mortem Human Subject). A human FE-model (Finite Element) might be able to reproduce the behavior evidenced with the PMHS in order to study upper body kinematics in certain types of frontal collision events. Method: A new data collection method was developed with the purpose to examine actual load paths active in the car front during a frontal crash. An important purpose was to examine if there was a relation between these load paths and injury producing mechanisms. This was done in an examination and analysis of 61 fatally injured occupants in 53 car frontal crashes in a sample area covering 40 % of the population of Sweden. Sample period was one year (1st October 2000 to 30th September 2001). An existing human FE-model was developed and validated with respect to upper body kinematics by using existing frontal belted PMHS tests. This was done by building a FE-model of the seat and seat belt used in the PMHS tests. Results: A generic car structure was developed which was used in the data collection methodology. By adopting this new method, Small Overlap (SO) crashes emerged as the most common crash configuration (48 %) among belted frontal fatalities. The injury producing mechanism in SO crashes is characterized by occupant upper body impacts in the side structure (door, a-pillar) of the car. This upper body kinematics is induced by both the crash pulse and the asymmetrical three point belt system. Current crash test procedures are not designed to fully estimate the performance of neither car structures nor restraints in SO crashes. In order to develop a better tool for reproducing this kinematical behavior a FE-model of a human body was refined and validated for belted conditions. This validation was performed with satisfying result. Conclusions: This study showed that by adopting new methods of data collecting new areas of traffic safety could be considered. In this study SO (48 %) crashes emerged as the most common crash configuration for belted frontal fatalities. Approximately ¼ of the fatalities occurred in a crash configuration comparable to current barrier crash test procedures. The body kinematics of PMHS in the SO crashes can be replicated and studied by using a FE-model of a human body in the collision load case model. With this tool possible collision counter measures could be evaluated for the SO crash configuration.

Iron oxyhrdroxide exist in a range of crystallinities and subsequent bioavailabilities with the poorly crystalline Fe oxyhrdroxide, ferrihydrite, considered the most bioavailable. Yet, as a result of the instability ferrihydrite it quickly ripens and/or transforms to more thermodynamically stable end-members bringing into question its importance in supporting long-term Fe(III)-reducing microbial communities. Furthermore, while a wide phylogenetic diversity of microorganisms capable of reducing ferrihydrite have been isolated, these organisms show diminished abilities to reduce more stable and dominant crystalline Fe phases. Therefore to address the questions of which microorganisms and what microbial processes are responsible for controlling the reduction of diverse Fe(III) minerals phases, cultivation based approaches using both batch and column-type reactors were employed. Using geochemical and phylogenetic analysis it was revealed that the Fe oxide substrate was important in dictating the mechanisms of Fe(III) reduction, and the structure of the microbial communities. While model dissimilartory Fe reducing microorganisms were capable of reducing ferrihydrite when acetate was provided as a carbon source these organisms did not enrich and were incapable of reducing crystalline Fe(III) oxides. Instead, in enrichments where crystalline Fe(III) oxides were reduced, organisms associated with fermentation and sulfate respiration dominated, this despite using freshwater media low in sulfate (less than 200 µM). In addition, these non-model Fe reducers dominated in ferrihydrite enrichments when carbon compounds other than acetate were given. Interestingly, a strong negative correlation between Fe(III) and sulfate respiration was observed with the canonical thermodynamic view that ferrihydrite should precede sulfate as a terminal electron acceptor being challenged. Further experiments with pure cultures of Desulfovibrio putealis indicated that a catalytic sulfur cycle may be responsible for greater than expected Fe(II) values under low sulfur conditions. These findings, have broad implications in predicting microbially mediated electron flow to oxidized substrates which will dictate the pathways and degree of carbon mineralization and subsequent carbon sequestration within sediments and soils. Further, given the importance of Fe(III)-reducing communities and Fe(II) in the sequestration of both inorganic and organic contaminants, these findings will have direct bearing on contaminant mitigation and remediation. / Engineering and Applied Sciences

Avsikten med denna avhandling är att utvärdera den FE-modell som använts i modalanalyser av komponenten fan booster spool, framtagen och tillverkad av Volvo Aero Corporation, Trollhättan. Detaljen ingår i den civila flygplansmotorn GEnx som är utvecklad för flygplanet Boeing 787 Dreamliner. Inledande tester av spolen påvisade en mycket god korrelation mellan analys och test men när spolen senare provkördes i en komplett monterad motor noterades en uppenbar skillnad i resultat. Den andra noddiameterns egenfrekvenser indikerade att spolen i test hade ett något styvare beteende än vad som beräknats i analys. En teori utvecklades som byggde på att en initiell kontakt mellan rotor och ett slitskikt på statorn kunde framkalla en förstyvande effekt på spolen när rotorn på grund av rotationslaster expanderar radiellt. Detta examensarbete initierades då för att undersöka om denna kontakt kunde inkluderas i FE-modellen och för att utreda om kontakten har en möjlighet att förstyva spolen. Avhandlingen utvärderar FE-modellen med avseende på randvillkor, laster och modelleringsteknik i FE-programmet Ansys 10.0. En grundlig kartläggning av spolens känslighet påvisar en robust komponent med hög motståndskraft mot yttre och inre störningar. En förstyvande effekt relaterad till en initiell kontakt mellan slitskikt och spole bekräftas i denna avhandling. Kontakten har visat sig ha särskild inverkan på den andra noddiametern och dess egenfrekvenser. Ett förslag på modelleringsteknik där den förstyvande effekten inkluderas har däremot inte föreslagits i detta arbete då effekten enligt uppgift går förlorad efter en inkörningsperiod. Det har i detta arbete visats att det kommando som i Ansys tidigare använts för att kompensera för så kallade spin softening-effekter, kspin, resulterar i konservativa värden för spolens egenfrekvenser. En rekommendation baserad på de resultat som framkommit är därför att utesluta funktionen kspin i modalanalyser för denna komponent. Valet av sektorstorlek och kopplingsmetod mellan masselement och spole har också visats ha en tydlig inverkan på de beräknade egenfrekvenserna. Spolens radiella förskjutningar har analyserats som funktion av rotationshastigheten. Resultatet visar att den hastighet då kontakt mellan tätningständer och spole etableras är nästintill identisk med den hastighet då töjningar först börjar uppträda i spolen enligt testdata från töjningsgivarprov.

This report investigates the feasibility and accuracy of determining fastener flexibility with 3D FE and representing fasteners in FE load distribution models with simple elements such as springs or beams. A detailed study of 3D models compared to experimental data is followed by a parametric study of different shell modelling techniques. These are evaluated and compared with industry semi-empirical equations. The evaluated 3D models were found to match the experimental values with good precision. Simulations based on these types of 3D models may replace experimental tests. Two different modelling techniques were also evaluated for use in load distribution models. Both were verified to work very well with representing fastener installations in lap-joints using the ABAQUS/Standard solver. Further improvement of one of the models was made through a modification scale factor. Finally, the same modelling technique was verified using the NASTRAN solver. To summarize, it is concluded that: • Detailed 3D-models with material properties defined from stress-strain curves correspond well to experiments and simulations may replace actual flexibility tests. • At mid-surface modelling of the connecting parts, beam elements with a circular cross section as a connector between shell elements is an easy and accurate modelling technique, with the only data input of bolt material and dimension. • Using connector elements is accurate only if the connecting parts are modelled in the same plane, i.e. with no offset. Secondary bending due to offset should only be accounted for once and only once throughout the analysis, and it is already included in the flexibility input.

No description available.

A new technique based on the study of the transmitted neutron beam has been developed to study the low-temperature decomposition of austenite in a 0.4 wt.% C–3 wt.% Mn–2 wt.% Si steel. Experiments were conducted in which the neutron beam continuously passed through a specially designed layered sample, the temperature of which could be controlled to allow for a high-temperature austenization treatment followed by accelerated cooling to an isothermal transformation temperature in the range of 275–450 °C. It was possible to measure the volume fraction of the face-centred cubic (fcc) and body-centred cubic (bcc) phases and the carbon concentration of the fcc phase by characterizing the neutron Bragg edges in the transmitted beam. This provides a technique for in situ continuous measurements on the decomposition of austentite. The technique has been validated by comparing the data with other experimental techniques such as dilatometry, quantitative optical metallography and room temperature X-ray diffraction.

This research investigated the tribological performance of a composite material, formed from an ultra high molecular weight polyethylene (UHMWPE) matrix and quasicrystalline Al-Cu-Fe alloy powders. An evaluation was conducted for the microstructure, material properties, and tribological performance of quasicrystalline materials formed from Al-Cu-Fe alloys. Arc melting was used as the fabrication technique for these alloys, and some samples were additionally heat treated in an argon environment. Vickers microhardness testing was done to make comparisons to wear rate behavior of the various alloys. Tribological studies were conducted using a linear pinon- desk configuration to evaluate friction and wear. Research indicated the annealed samples of Al-Cu-Fe that formed icosahedral quasicrystalline phases, where the quasicrystalline phase was most dominant of the observed alloys, displayed the greatest wear resistance and hardness. Abrasive wear was observed in each of the samples, as the brittle, hard nature of the quasicrystalline phase would not allow for the ductile adhesion. The addition of small amounts of Al-Cu-Fe quasicrystalline particles, crushed and pulverized from the arc-melted ingots, reduced the coefficient of friction and wear rate of UHMWPE, when added to the polymer.

Detoxification of chlorinated organic compound is an important and urgent issue in water remediation nowadays. Trichloroethylene (TCE), as a model compound in this study, has been proved to be degraded effectively by bimetallic nanoparticles (NPs) in solution phase. In this study, Fe/Pd bimetallic NPs were synthesized in poly (acrylic acid) (PAA) functionalized polyvinylidene fluoride (PVDF) microfiltration membranes. TCE dechlorination with these bimetallic NPs was conducted under different pH values and different metal loadings to study the role of corrosion on reaction rates. One-dimensional mathematical model with pseudo first-order reaction kinetic was introduced to discuss the TCE dechlorination profile in membrane system. Reduction reaction in pores is affected by several parameters including NP loading and size, TCE diffusivity, void volume fraction and surface-area-based reaction rates. This model result indicated that modification is needed to correct the reaction rate obtained from bulk solution in order to represent the actual efficiency of NPs on reduction reaction. In addition, TCE dechlorination mainly occurred near NPs’ surface. Second part of model indicated that reduction mechanism with TCE adsorption-desorption behavior could be used to discuss dechlorination with a high TCE concentration.