Rozprawy doktorskie: „High-pressure Techniques”

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Allan, David Robert. "Crystal-structure studies and techniques at high pressure". Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/17021.

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This thesis is concerned with the application of high-pressure diffraction techniques - involving both x-rays and neutrons, single crystal and powder samples - to the study of crystal-structures at high pressure and to the development of such techniques for the determination of crystal-structures with greater accuracy and more reliability. The current state-of-the-art high-pressure diffraction techniques are reviewed and applied to the study of a number of interesting materials. The crystal structure of KTiOPO₄(KTP) has been determined as a function of pressure as its phase transition at 5.5 GPa is approached, using single-crystal x-ray diffraction techniques. The principal changes with pressure are in the co-ordination environments of the potassium atoms and in the linking angles of the TiO₆-PO₄ structural framework. In general the distortions of the TiO₆ octahedra, which have been linked to the second harmonic generating properties of KTP, are retained although there are some small changes in the Ti-O bond lengths. The structure of the high-pressure phase of KTP has also been determined, using single-crystal x-ray diffraction, and it appears that, although the phase transition is strongly first-order and involves a 4.2% reduction of the unit-cell volume, the Pna2₁ space-group symmetry of the low-pressure phase is retained. The main structural changes at the phase transition involve tilting of the PO₄ tetrahedra relative to the TiO₆ octahedra, while both units remain relatively unchanged in size and shape. In particular, the TiO₆ octahedra remain highly distorted and retain their anomalously short Ti-OT bonds. The potassium atoms are also observed to undergo relatively large movements of about 0.5 AA along the polar c-axis at the transition. The crystal structure of KH₂PO₄ (KDP) has been determined at 2.9 GPa, a pressure just below that of its high-pressure ambient-temperature phase transition, using single-crystal neutron diffraction. It appears that the oxygen-oxygen distance, 2R, undergoes a uniform compression to 2.9 GPa which is moderated by the rotation of the essentially rigid PO₄ tetrahedra around their =4-axes.

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Ridley, Christopher James Taylor. "Development of high pressure and cryogenic techniques, and their application to neutron diffraction". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28890.

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Neutron diffraction is an extremely powerful technique in condensed matter research; it can be used to measure crystallographic structures, including some of those undeterminable using X-rays. It is also perhaps the most powerful technique for determining magnetic structures, and for probing the strength of magnetic interactions, revealing information beyond that extractable from a magnetometer. High pressure is used by many condensed matter researchers as an additional thermodynamic variable, or tool to perturb otherwise stable systems, and has been used with neutron diffraction for many years. When coupled with low temperatures, this has led to the discovery of an enormous range of non-ambient phases of matter, with a range of exotic properties, some of which are discussed in this thesis. Pressure has a very strong effect on the magnetic properties of a material, with many of the most unusual magnetic phases existing only at extremely low temperatures, or pressures which can only be reached on very small samples. The main topic for this thesis is the study, development, and implementation of new techniques to combine low temperatures, high pressures, and neutron diffraction measurements from micro sized samples. A new pressure cell has been designed, tested, and commissioned with neutron beam time on the WISH diffractometer at the ISIS neutron facility. The cell is compact, with a total mass of approximately 5 kg, and is capable of generating large loads in excess of 4.5 tonnes force. Depending on the sample size used with the cell, the opposed anvil system is capable of generating a range of different pressures beyond what is widely available for low temperature neutron diffraction measurements. To save wasted experimental time in cooling and warming the device, the cell is capable of varying the applied load continuously down to 5 K, whilst the sample pressure can also be measured in-situ using a compact spectrometer system. Obtaining refineable neutron diffraction data from the small samples (< 1mm3) possible in an opposed anvil pressure cell is challenging due to extremely low ratios of signal-to-background when compared with large volume pressure cells. Finite element analysis (FEA) was performed to minimise the mass of the cell, whilst also minimising the amount of supporting material in the beam. Despite this, the signal from the sample is typically very weak; to overcome this, a novel 3D printed device has been designed and tested to collimate extremely small samples, removing much of the background signal from the surrounding material. It has enabled neutron data to be collected from samples an order of magnitude smaller than previously measurable in the cell. To maximise the pressures achievable in the pressure cell, for a given sample volume, an extended FEA study was performed to understand the evolutions of stresses in the cell, and understand the limitations of using sapphire as an anvil material. To complement this work, a compact piston cylinder cell has also been designed for a combination of different measurements. One of the key challenges in high pressure research is in knowing, or ensuring, that the conditions the sample is under are approximately the same for a variety of different measurements. Since different instruments, and techniques, may not allow for the same apparatus to be used between them, this is not always possible. A compact clamped piston cylinder cell has been designed, suitable for in-situ electrical measurements, with additional potential for simultaneous neutron diffraction measurements. The device is demonstrated through an ultrasonic characterisation of the compound UGe2. In addition to the information obtainable from neutron diffraction, much can be learnt from studying the transport properties of a material. This information can be used alongside neutron data to provide a full understanding of how a material behaves. One technique of interest measures how the electrical properties of a material changes under applied magnetic field. This is difficult to achieve under pressure due to the often anisotropic construction of the pressure cell affecting the magnetic field on the sample in different orientations, and the challenge in getting wires to the sample under pressure. This thesis presents the design, and preliminary testing, of an ultra compact high symmetry piston cylinder cell designed to be taken to sub-Kelvin temperatures and rotationally oriented in applied magnetic field. The spherical construction of the cell means that the field on the sample position is, to a very close approximation, identical in all orientations. Finally, this thesis presents a study of the binary alloy Pd3Fe under pressure. Pd3Fe was recently reported to undergo a large-volume collapse under high pressure at room temperature, resulting in near zero thermal expansion]. There are several competing theories on the mechanism behind this process. To investigate further, a series of single crystal Pd3Fe samples were grown, cut, prepared, and extensively analysed. The results of this study suggest that the cause for the large volume collapse may not be magnetic in nature, as previously expected.

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Kepa, Michal Wawrzyniec. "Probing the phase diagram of the ferromagnetic superconductor UGe2 using high pressure ultrasonic techniques". Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/15955.

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The main goal of the project was to develop new experimental techniques to further investigate the phase diagram of the ferromagnetic superconductor UGe2 at high pressures. Of particular interest is the metamagnetic transition (FM1-FM2) which is thought to play the key role in the unconventional superconductivity in UGe2. The project attempted to detect experimentally the critical ferromagnetic fluctuations associated with the FM1-FM2 transition. The development of the experimental equipment constitutes a substantial part of the project and includes: (1) a 2-axis Rotation Stage for High Pressures, (2) an Ultrasonic Sapphire Anvil Cell and (3) a High Pressure Pulse Echo Setup. (1) allows transport measurement on single crystal samples with simultaneous two-axis rotation at temperatures down to 2 K, magnetic fields up to 9T and pressures up to 5GPa to be made. (2) employs Resonant Ultrasound Spectroscopy on a sample in the anvil type cell with an optical access at cryogenic temperatures. (3) uses the Pulse Echo Technique inside a cylinder type cell allowing for ultrasonic measurements on samples with a well-defined orientation. The design, technical challenges and tests results are presented and discussed. The existing techniques, used in the project, included Inelastic Neutron Scattering. A single crystal of UGe2 was studied at 12 kbar with a large volume two-layered piston-cylinder cell. No critical fluctuations were detected at Tx associated with the FM1-FM2 transition. Instead, a small inelastic signal below this transition temperature was observed at the threshold of the instrument sensitivity. The fluctuations at TC associated with the paramagnetic-to-ferromagnetic transition (PM-FM) were detected and the energy scale of these fluctuations was found to have decreased, as compared to the ambient pressure case, in proportion to the resistivity - a result supporting recent theory. The elastic constant c11 of a single crystal of UGe2 was measured as a function of temperature using (3) at ambient pressure as well as pressures up to 11 kbar. The elastic constant exhibits clear features associated with the two transitions, PM-FM and FM1-FM2. The temperature dependence of the elastic constant at ambient pressure was modelled with two main contributions (Schottky-like and Wiess-like) to the magnetic heat capacity coming from the two energy scales, Tx and TC, as well as two corresponding Gruneisen parameters, Ωx and ΩC. The values of Gruneisen parameters obtained from the data fitting were in good agreement with the values determined from the slope of the phase transition lines on the phase diagram. The temperature dependence of the elastic constant at high pressures was modelled according to the two-component system with coupled moments. The behaviour of the fitting parameters (including the Ωx and ΩT ) was consistent with the phase diagram of UGe2 and captured important features of c11 temperature evolution. The way forward would be to continue the measurements of c11 at higher pressures but also to repeat the measurements at different ultrasonic frequencies in order to obtain the temperature dependence of the ultrasonic attenuation which will provide more insight on the FM1-FM2 transition.

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Leonard, Simon. "Solid-state structural chemistry at high pressure using X-ray synchrotron radiation diffraction techniques". Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/33783.

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Energy dispersive X-ray diffraction with synchrotron radiation has been used to probe the room temperature, high pressure phase diagrams of several inorganic compounds. A review of the publications for high pressure X-ray diffraction at synchrotron sources is given. The techniques, theory, apparatus and errors of high pressure X-ray diffraction are discussed. A spectroscopic system used to enable pressure calibration is refined and its merits discussed. The calibration of this instrument against an NaC1 standard is presented. CuGeO3 undergoes two phase transitions at 73 kbar and 110 kbar respectively. The effect of pressure on the Jahn-Teller distortion around copper is discussed. The first high pressure polymorph of hafnia (beginning at 26 kbar) is shown to be iso-structural with that of zirconia. A mechanism for the transition is offered. The effect of pressure on the series of iso-structural vanadates MVO3 (M = K, Rb, Cs, NH4) reveals phase transitions in KVO3 and RbVO3 at 27 and 40 kbar respectively. Models for the transitions are offered. Intuitive expectations of an increase in compressibilities with an increase in cation size are not realised. NH4VO3 transforms to an amorphous phase at 47 kbar. A full structural model for (COD)PtNPhS(O)2NPh is offered with an R- factor of 2.54%. A discussion of ring-puckering in this and similar systems is given. An improved structural model for powdered hafnia is offered. High resolution synchrotron techniques are used in combination with Rietveld refinement methods. A discussion of the structure is given.

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Edwards, Clare M. "Applications of high-pressure spectroscopic and powder x-ray diffraction techniques to inorganic materials". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0005/NQ44419.pdf.

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Edwards, Clare M. "Application of high-pressure spectroscopic and powder X-ray diffraction techniques to inorganic materials". Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37544.

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The vibrational spectra (IR, Raman) of (eta6-C 6H5CO2CH3)Cr(CO)3, (eta 6-C6H5CO2CH3)Cr(CO) 2(CS), [Pt(NH3)4][PtCl4] (MGS), [Pt(ND 3)4] [PtCl4] (MGS-D), [Pt(NH 3)4][PtBr4] (MGS-Br), ReH7(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane) and CpCo(C64H4) (Cp = cyclopentadiene) have been studied under pressures up to ∼45 kbar. The magnitude and direction of the pressure-induced shift of the Raman-active nu(CO) and nu(CS) vibrational modes of (eta6-C6H 5CO2CH3)Cr(CO)3 and (eta6 -C6H5CO2CH3)Cr(CO) 2(CS) indicate an increase in the amount of pi-backbonding to the CO and CS ligands, under pressure, the increase being greater to the CO ligand than to the CS ligand. Wavenumber vs. pressure plots revealed a phase transition in both the tricarbonyl and thiocarbonyl complexes between 10--15 kbar. For CpCo(C64H4), discontinuities in the wavenumber vs. pressure plots at 10 kbar indicate a phase transition at this pressure, most likely involving rotation of the Cp ring. Insertion of the Co atom into the cage does not occur under compression; a shift to higher wavenumbers was observed for all the Raman and IR vibrational modes of CpCo(C64H4) and the parent fulleride, C 64H4. Phenyl ring rotation is thought to occur in ReH 7(dppe) under compression. Three pressure regions, from ambient pressure to ∼16 kbar, between 16 and 29 kbar and above 29 kbar, were identified from the wavenumber vs. pressure plots. A broad, weak feature in the ER spectrum appears from 5 kbar, increasing in intensity with increasing pressure. This peak has been assigned to the nu(HH) mode of a coordinated dihydrogen ligand, Re(eta2-H2). Ring rotation may assist the pressure-induced dihydride-dihydrogen interconversion. The pressure-tuning IR study of MGS and its derivatives probed the intermolecular interactions, in particular the interactions of the NH3 groups and investigated the hypothesis that hydrogen bonding of the type N- H&cdots;Cl exists in MGS. Splitting of the IR bands at ambient pressure, and

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Che, Idris Azam. "Characterization of high speed inlets using global measurement techniques". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/characterization-of-high-speed-inlets-using-global-measurement-techniques(ca8b687b-aff0-4b50-892f-897a962e22ba).html.

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After the end of the NASA space shuttle programme, there has been resurgence of interest in developing a single stage-to-orbit spacecraft. The key technology to realize this dream is the airbreathing scramjet engine. The scramjet concept has been around for decades, but much work is still needed in order to eliminate the remaining obstacles to develop a practical working prototype of the engine. Many such obstacles are related to the inlet which functions as the main compression unit for the engine. Typically, a high speed inlet is designed to function properly in a single flight condition. Such an inlet would experience adverse flow conditions related to various shock-shock interactions, viscous effects, shock-boundary layer interactions, and many other flow phenomena at off-design conditions. The traditional mechanism to mitigate the adverse flow conditions is by varying the inlet geometry at off-design conditions. There are still gaps in understanding the behaviour of inlets at off-design conditions and the effectiveness of variable geometry as inlet flow control. This is partly due to complex flow diagnostics setup, which limits the type, quantity and quality of information that can be extracted from the inlet flow. The first objective of this thesis was to develop a global inlet measurement system that can provide an abundance of information on inlet flow. The pressure sensitive paint method was employed together with other methods to provide comprehensive understanding on inlet flow characteristics. Calculation of Mach number at the isolator exit using the isolator sidewall pressure map was successfully demonstrated. The measurement of Mach number at the isolator exit has allowed for performance of the inlet to be calculated without the need for intrusive flow diagnostics tools used by previous researchers. The global measurement system was then employed to investigate the characteristics of the scramjet inlet operating at various off-design conditions. Complex shock structures were observed at the inlet cowl entrance as the angle-of-attack was increased. The relationship of flow quality and inlet performance was examined and discussed. General improvements on the inlet performance were obtained if the size of separation on the compression ramp was reduced. The inlet was also observed to perform poorly when compression shocks impinged on the inner cowl surface. Cowl deflections were demonstrated to be effective in controlling the internal flow of the inlet and improving its performance. An exploratory study on the role of micro-vortex generators to control boundary layer separation on scramjet inlets has been included as well. Strategies for optimizing an inlet at off-design conditions were analysed, and it was found that any variable geometry combination must maintain high throat-to-freestream Mach number ratio in order to preserve high inlet performance.

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Ferguson, Derek. "The development of air-cooling techniques for fast response pressure transducers in high temperature environments". Thesis, Cranfield University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387639.

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Facy, Olivier. "Optimisation des techniques de chimiothérapie intracavitaire". Thesis, Dijon, 2013. http://www.theses.fr/2013DIJOMU07/document.

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Introduction. L’efficacité de la chimiothérapie intracavitaire dépend de la pénétration du produit au sein du péritoine (CHIP) ou de la plèvre. L’hyperthermie et l’hyperpression peuvent augmenter cette pénétration. Ce travail étudie leur effet intrapéritonéal, puis établit la méthode optimale pour les délivrer. L’étude de la faisabilité et de la tolérance d’une hyperpression intrapleurale est essentielle pour transposer ces bénéfices à la cavité thoracique. Méthodes. Quatre groupes de porcs ont reçu une CHIP ouverte avec de l’oxaliplatine à une concentration constante (150 mg/l) pendant 30 minutes en normothermie ou hyperthermie (42-43°C) ; et en pression atmosphérique ou hyperpression (25 cmH2O). Deux groupes ont reçu une procédure fermée en hyperthermie et hyperpression ou forte hyperpression (40 cmH2O). L’absorption systémique et tissulaire d’oxaliplatine a été étudiée. La tolérance d’une perfusion pleurale a été étudiée chez 21 porcs avec ou sans résection associée, avec ou sans chimiothérapie (cisplatine + gemcitabine), à divers niveaux de pression de 15 à 25 cmH2O. Résultats. L’hyperthermie augmente les concentrations de platine dans les surfaces viscérales (p=0.0014), alors que l’hyperpression l’augmente dans les surfaces viscérales et pariétales (respectivement p= 0.0058 et p= 0.0044). L’association des deux facteurs permet d’obtenir les concentrations les plus importantes dans le péritoine viscéral (p= 0.00001) et pariétal (p= 0.0003). Les concentrations obtenues lors des procédures fermées sont inférieures à celles obtenues en ouvert, même lorsque la pression atteint 40 cmH2O. Une chimiothérapie intrapleurale à 20 cmH2O sans résection associée est le niveau maximal toléré durant 60 minutes. Conclusion. Au cours d’une CHIP, l’hyperthermie augmente la pénétration d’oxaliplatine dans le péritoine viscéral, alors que l’hyperpression est efficace dans le péritoine viscéral et pariétal. Leur association est synergique et la procédure ouverte semble la meilleure pour la délivrer. Une chimiothérapie intrapleurale est faisable à 20 cmH2O dans ce modèle
Introduction. In order to achieve a good effect, chemotherapy drugs need to penetrate into the peritoneal (HIPEC) or pleural tissue. Hyperthermia and high-pressure may enhance this penetration. The aim of this study was to evaluate their peritoneal effect and to establish the best technique to it. A feasibility study of an intrapleural high-pressure was an essential step to export these effects to the thoracic space. Methods. Four groups of pigs underwent an open HIPEC with a constant concentration (150 mg/l) of oxaliplatin during 30 minutes either in normothermia, or in hyperthermia (42-43°C); and either with atmospheric pressure or with high-pressure (25 cmH2O). Two more groups underwent a closed procedure with hyperthermia and either high-pressure or very high-pressure (40 cmH2O). The systemic and tissue absorption of oxaliplatin were studied. The haemodynamic and respiratory tolerance of a pleural infusion was also tested in 21 pigs with and without associated resection; with and without chemotherapy infusion (cisplatin + gemcitabin) and at various levels of pressure (from 15 to 25 cmH2O). Results. Hyperthermia enhances the concentrations of platinum in visceral surfaces (p=0.0014), whereas high-pressure enhances it both in visceral and in parietal surfaces (p= 0.0058 and p= 0.0044, respectively). Their association obtains the highest concentrations both in the visceral (p= 0.00001) and the parietal peritoneum (p= 0.0003). The concentrations obtained during closed procedure are lower than those achieved with the open technique, even with 40 cmH2O of pressure. A 60-minutes intrapleural chemotherapy perfusion with 20 cmH2O of pressure without any lung resection was the maximal tolerated level. Conclusion. During HIPEC, hyperthermia improves the penetration of oxaliplatin in the visceral peritoneum, whereas high-pressure is effective in both peritoneal surfaces. Their association is synergic and the open technique seems to be the best one to deliver it. An intrapleural chemotherapy with a 20 cmH2O pressure is feasible in this model

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Kirollos, Benjamin William Mounir. "Aerothermal optimisation of novel cooling schemes for high pressure components using combined theoretical, numerical and experimental techniques". Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:72168abd-48f7-49c6-a6ef-3d4a9f6cc6e9.

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The continuing maturation of metal laser-sintering technology has presented the opportunity to de-risk the engine design process by experimentally down-selecting high pressure nozzle guide vane (HPNGV) cooling designs using laboratory tests of laser-sintered - instead of cast - parts to assess thermal performance. Such tests are very promising as a reliable predictor of the thermal-paint-engine-test, which is used during certification to validate cooling system designs. In this thesis, conventionally cast and laser-sintered parts are compared in back-to-back experimental tests at engine-representative conditions over a range of coolant mass flow rates. Tests were performed in the University of Oxford Annular Sector Heat Transfer Facility. The aerothermal performance of the cast and laser-sintered parts is shown to be very similar, demonstrating the utility of laser-sintered parts for preliminary engine thermal assessments. It can be shown that in most situations counter-current heat exchanger arrangements outperform co-current arrangements. This concept, though familiar in the heat exchanger community, has not yet been applied to hot-section gas turbine cooling. In this thesis, the performance benefit of novel reverse-pass cooling systems - that is, systems in which the internal coolant flows substantially in the opposite direction to the mainstream flow - is demonstrated numerically and experimentally in film-cooled HPNGVs. It is shown numerically that reverse-pass cooling systems always act to flatten lateral wall temperature variation and to reduce peak metal temperature by maximising internal convective cooling at the point of minimum film cooling effectiveness. Reverse-pass cooling systems therefore require less coolant than other internal flow arrangements to maintain acceptable metal temperatures. The benefits of reverse-pass cooling can be fully realised in systems with long, undisturbed surface length, such as the suction-side (SS) of a HPNGV, afterburner liners, HPNGV platforms, and combustor liners. Three engine-scale HPNGVs with SS reverse-pass cooling systems were subsequently designed using bespoke numerical conjugate heat transfer and aerodynamic models to satisfy engine-realistic aerothermal and manufacturing constraints. The reverse-pass HPNGVs were metal laser-sintered and tested in back-to-back experiments with conventionally cooled HPNGVs in the Annular Sector Heat Transfer Facility. The reverse-pass HPNGVs are shown to reduce peak engine metal temperature by 30 K and reduce mean SS engine metal temperature by 60 K compared to conventionally cooled HPNGVs with the same cooling mass flow. A physically-based infra-red thermography procedure was implemented which takes into account the transmittance of the external optics, the surface emissivity of the object, the black-body temperature-radiometric characteristics of the camera, and the time-varying surrounding radiance. Failure to account for surrounding radiance is shown to result in an absolute error in overall cooling effectiveness of 0.05. A new experimental facility - the Coolant Capacity Rig - was developed in order to measure row-by-row, compartmental and total coolant capacity of HPNGVs to a precision of 0.03%, over a large range of pressure ratios and mass flows using a differential mass flow measurement technique, bypass system, and calibrated mass flow orifice. A novel method for estimating internal loss coefficients from the coolant capacity measurements has been devised which, uniquely, does not require internal pressure measurement.

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O'Dowd, Devin Owen. "Aero-thermal performance of transonic high-pressure turbine blade tips". Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:e7b8e7d0-4973-4757-b4df-415723e7562f.

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Watson, Robert. "New numerical techniques to quantify and predict the effect of entrainment defects, applied to high pressure die casting". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7153/.

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High Pressure Die Casting (HPDC) is an attractive option for automotive manufacturers, as it has a number of advantages over wrought process routes. An improved understanding of the defects which may result from the process could allow castings to deliver lighter vehicle structures. A novel algorithm was developed to predict the formation of entrainment defects, which may limit the strength of castings. This model was integrated into FLOW-3D, a fluid dynamics solver. Theoretical advances were made, which offer a means of extrapolating a spatial distribution of damage to location specific statistical distributions, an improved way of characterising the contribution of each defect type to strength, and a means of correlating parameters for statistical distributions, allowing the variation in strength may be predicted at arbitrary locations within a casting. Casting and numerical experiments were performed, to evaluate these algorithms and underlying fluid flow solution, and to test the influence of entrainment defects on the strength of HPDC parts. Defects formed by air entrainment were found to significantly limit the strength of the studied castings. The methods and techniques explored in this work showed promise, but further advances would be needed, before ab intio strength prediction for HPDC parts can be realised.

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Pereira, M. F. V. T., M. Williams i R. Bruwer. "Rapid die manufacturing using direct laser metal deposition". Journal for New Generation Sciences, Vol 7, Issue 3: Central University of Technology, Free State, Bloemfontein, 2009. http://hdl.handle.net/11462/542.

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Published Article
Global issues such as energy and climate changes have impacted on both the automotive and aerospace industries, forcing them to adopt measures to produce products that consume fewer combustibles and emit less carbon dioxide. Making vehicles lighter is one of the logical ways of reducing fuel consumption. The need for light components, able to fulfil technical and quality specifications, led to market growth for tooling that is able to mass produce parts using manufacturing processes such as high pressure die casting. Competitive pressures to reduce the lead time required for tooling-up has also increased dramatically. For this reason research into various methods, techniques and approaches to tool manufacture is being undertaken globally. This paper highlights the work undertaken at the CSIR on the issue of rapid die manufacturing through the application and evaluation of a rapid prototyping technique and coating technologies applied to die components of a high pressure casting die for the production of aluminium components. Criteria for determining suitability were developed against which the technique was evaluated that included time, cost and life-expectancy. Results of accelerated testing procedures to evaluate the die material produced by the rapid prototyping technique and surface coatings and treatments of die materials for their resistance to washout, erosion, heat checking and corrosion in a high pressure die casting environment, are presented. The outcomes of this research will be used for further development and application of specific techniques, design principles and criteria for this approach.

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Pereira, M. F. V. T., M. Williams i Preez W. B. Du. "Characterization of metal powder based rapid prototyping components with respect to aluminium high pressure die casting process conditions". Journal for New Generation Sciences, Vol 8, Issue 2: Central University of Technology, Free State, Bloemfontein, 2010. http://hdl.handle.net/11462/563.

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Published Article
This paper is based on tests performed on die component specimens manufactured by EOS-DMLS (direct metal laser sintering) and LENS (laser engineered net shape) RP (rapid prototyping) technology platforms, as well as manufactured specimens machined out of preferred standard hot work steel DIN 1.2344. These specimens resemble typical components used in metal high pressure die casting tool sets. The specimens were subjected to a programme of cyclic immersion in molten aluminium alloy and cooling in water-based die release medium. The heat checking and soldering phenomena were analyzed through periodic inspections, monitoring crack formation and evidence of surface washout. At the end of the thermal tests, mechanical strength and hardness tests were performed to assess toughness and core resistance variations in relation to the initial conditions. Finally metallographic investigations were performed through optical microscopy on all the specimens considered. The outcomes of this research will be presented and used by the CSIR for further development and application of the assessed EOS-DMLS and LENS rapid prototyping technologies in rapid die manufacturing techniques and die design principles, including time and economic feasibility criteria to be applied when considering rapid die manufacture.

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Bogdanov, Bogdan. "Structures, thermochemistry, and dynamics of negative gas phase cluster ions studied by pulsed-ionization high pressure mass spectrometry and computational quantum chemistry techniques". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ65224.pdf.

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ZHANG, TANTAN. "Design of innovative solutions for high-pressure fuel injection systems, optimization of measuring techniques for injected flow-rate and modeling of 1D flows". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2843978.

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Pilsl, Ludwig K. A. [Verfasser], i Oliver [Akademischer Betreuer] Reiser. "Enantioselective cyclopropanation of heterocycles and the use of high-pressure techniques for the conformational analysis of peptide foldamers / Ludwig K. A. Pilsl. Betreuer: Oliver Reiser". Regensburg : Universitätsbibliothek Regensburg, 2014. http://d-nb.info/1070996041/34.

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Navare, Arti T. "Development of high-sensitivity atmospheric pressure (ap) matrix-assisted laser desorption/ionization (maldi) and open air ionization techniques for the analysis of biomolecules by mass spectrometry". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33942.

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Matrix-assisted laser desorption/ionization (MALDI) has been celebrated as a soft ionization method for analyzing very diverse biological species including large proteins, peptides, carbohydrates, lipids and metabolites. The fact that MALDI is tolerant to salts and buffers and that it mostly produces singly charged ions from intact biomolecules is considered highly advantageous over electrospray ionization (ESI). Almost two decades after the introduction of vacuum MALDI, the technique was successfully implemented under atmospheric pressure (AP) conditions by Laiko and co-workers. Some of the most salient advantages of AP-MALDI over vacuum MALDI are its ability to generate intact ions from labile species with minimal fragmentation due to collisional cooling under AP, the ability of performing MSn experiments, and its exchangeability with other ion sources. However, AP-MALDI suffers from limited sensitivity due to low ion transmission efficiency under AP conditions. Because sensitivity is a function of the sample pretreatment method of choice, both preconcentration and selective sample fractionation can be used during the initial stages of the analytical pipeline to improve detectability. To that end, the first part of the work presented in this thesis is aimed at investigating various approaches to improve the sensitivity of AP-MALDI for mass spectrometric analysis of biomolecules. Chapter 1 reviews the history of laser desorption ionization (LDI), presenting salient features of vacuum MALDI and AP-MALDI, and concludes with a brief overview of leading ambient ionization techniques, such as Direct Analysis in Real Time (DART) ionization. Chapter 2 presents an investigation of an on chip sample preconcentration approach coupled to AP-MALDI for high-sensitivity analysis of neuropeptides extracted from Aedes aegypti mosquito heads. The theme of exploring efficient and reproducible purification methods for complex biosamples is continued in Chapter 3, where an evaluation of new on-tip solid-phase extraction (SPE) micro columns with various functional groups is presented. A second approach for enhancing AP-MALDI sensitivity by constructing a new pneumatically-assisted (PA) AP-MALDI ion source is presented in Chapter 4, where various factors affecting the performance of this device are investigated. Chapter 5 describes work involving the evaluation of DART ionization as a high-throughput method for the detection and identification of small terpene molecules central to the Aedes aegypti mosquito lifecycle.

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Pu, Yongjia. "AN ASSOCIATION STUDY BETWEEN ADULT BLOOD PRESSURE AND TIME TO FIRST CARDIOVASCULAR DISEASE". VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3857.

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BACKGROUND: Several studies have demonstrated the association between the time to hypertension event and multiple baseline measurements for adults, yet other survival cardiovascular disease (CVD) outcomes such as high cholesterol and heart attack have been somewhat less considered. The Fels Longitudinal Study (FLS) provides us an opportunity to connect adult blood pressure (BP) at certain ages to the time to first CVD outcomes. The availability of long-term serial BP measurements from FLS also potentially allows us to evaluate if the trend of the measured BP biomarkers over time predicts survival outcomes in adulthood through statistical modeling. METHODS: When the reference standard is right-censored time-to-event (survival) outcome, the C index or concordance C, is commonly used as a summary measure of discrimination between a survival outcome that is possibly right censored and a predictive-score variable, say, a measured biomarker or a composite-score output from a statistical model that combines multiple biomarkers. When we have subjects longitudinally followed up, it is of primary interest to assess if some baseline measurements predict the time-to-event outcome. Specifically, in this study, systolic blood pressure, diastolic blood pressure, as well as their variation over time, are considered predictive biomarkers, and we assess their predictive ability for certain time-to-event outcomes in terms of the C index. RESULTS: There are a few summary C index differences that are statistically significant in predicting and discriminating certain CVD metric at certain age stage, though some of these differences are altered in the presence of medicine treatment and lifestyle characteristics. The variation of systolic BP measures over time has a significantly different predicting ability comparing with systolic BP measures at certain given time point, for predicting certain survival outcome such as high cholesterol level. CONCLUSIONS: Adult systolic and diastolic BP measurements may have significantly different ability in predicting time to first CVD events. The fluctuation of BP measurements over time may have better association than BP measurement at a single baseline time point, with the time to first CVD events.

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20

Blackmore, Paul David. "Degradation of polymeric outdoor high voltage insulation : surface discharge phenomena and condition assessment techniques". Thesis, Queensland University of Technology, 1997.

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Saouane, Sofiane [Verfasser], Francesca [Akademischer Betreuer] [Gutachter] Fabbiani, Werner F. [Gutachter] Kuhs, Ralf [Gutachter] Ficner, Heidrun [Gutachter] Sowa, Dietmar [Gutachter] Stalke i Kai [Gutachter] Tittmann. "Extending the Search Space for Novel Physical Forms of Pharmaceuticals and Biomolecules using High-Pressure Techniques / Sofiane Saouane. Betreuer: Francesca Fabbiani. Gutachter: Francesca Fabbiani ; Werner F. Kuhs ; Ralf Ficner ; Heidrun Sowa ; Dietmar Stalke ; Kai Tittmann". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://d-nb.info/110448045X/34.

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Saouane, Sofiane Verfasser], Francesca [Akademischer Betreuer] [Gutachter] Fabbiani, Werner F. [Gutachter] Kuhs, Ralf [Gutachter] Ficner, Heidrun [Gutachter] [Sowa, Dietmar [Gutachter] Stalke i Kai [Gutachter] Tittmann. "Extending the Search Space for Novel Physical Forms of Pharmaceuticals and Biomolecules using High-Pressure Techniques / Sofiane Saouane. Betreuer: Francesca Fabbiani. Gutachter: Francesca Fabbiani ; Werner F. Kuhs ; Ralf Ficner ; Heidrun Sowa ; Dietmar Stalke ; Kai Tittmann". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://nbn-resolving.de/urn:nbn:de:gbv:7-11858/00-1735-0000-0028-878A-D-4.

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Charnay, Romain. "Experimental study of flow boiling in horizontal minichannels at high saturation temperature". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0047/document.

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La valorisation de l'énergie thermique contenue dans des gaz chauds pour produire de l'électricité est possible grâce à l'utilisation de cycles thermodynamiques, parmi lesquels le cycle de Rankine mérite d'être considéré. Cependant, l'industrialisation d'un tel système passe par une connaissance approfondie du comportement thermohydraulique du fluide actif. Ceci permettra d'améliorer le design des principaux composants du système, spécialement les échangeurs de chaleur. Dans le cas du cycle organique de Rankine, les conditions thermodynamiques du fluide sont éloignées des conditions usuelles rencontrées dans les domaines de la climatisation ou de la réfrigération. En effet, le fluide est mis en œuvre dans des conditions proches de son point critique. La température des gaz d'échappement varie entre 400°C et 900°C et l'évaporation se produit à une température de saturation supérieure à 100°C. En ce qui concerne les caractéristiques des écoulements diphasiques (chute de pression, coefficient de transferts thermiques, régimes d'écoulement), la quasi-totalité des méthodes de prédiction a été développée pour des températures comprises entre -20°C et 40°C correspondantes aux domaines de la climatisation ou de la réfrigération. C'est pourquoi la fiabilité de ces modèles reste incertaine dans les conditions d'évaporation du cycle de Rankine, car leur utilisation est limitée par la base de données à partir de laquelle ils ont été établis et ne peuvent être extrapolés avec précision. Cette thèse vise à étudier les caractéristiques thermohydrauliques du R-245fa en ébullition convective dans les conditions du cycle de Rankine. Dans un premier temps, un banc expérimental a été conçu et construit afin de réaliser des tests en ébullition convective dans un minicanal de 3.00 mm de diamètre. Ce banc expérimental permet de faire des mesures sur les régimes d'écoulement, les coefficients de transfert de chaleur et les pertes de charge par frottement. Dans un second temps, une méthode de traitement d'image a été développée afin de caractériser différents régimes d'écoulement. Cette méthode couplée à une analyse des transferts thermiques a permis d'identifier quatre principaux régimes d'écoulement. L'influence de la température de saturation sur les régimes d'écoulement et leurs transitions a été soulignée et discutée. Les caractéristiques des bulles ont également été étudiées à l'aide de cette méthode. Dans un troisième temps, une base de données expérimentale sur les coefficients de transfert de chaleur a été créée. L'influence de la température de saturation sur les mécanismes de transfert thermique a été étudiée dans ces conditions originales. Afin de tester la fiabilité des méthodes de prédiction, les résultats expérimentaux ont été confrontés à différentes méthodes. Finalement, les chutes de pressions ont été mesurées et une analyse paramétrique a été menée. Les mesures ont été confrontées aux principales méthodes disponibles dans la littérature
Because of current environmental issues, some technologies are being developed to reduce the fuel consumption and to reduce the emissions of CO2. Energy recovery by means of Organic Rankine Cycles or Hirn Cycles recovery is one investigated track to answer these issues. At present, some systems based on Organic Rankine Cycle (ORC) are available in industry but advanced studies are needed to allow their application in the road transport industry. A better understanding of the two-phase fluid behaviour is necessary to optimize the design models of the components containing a two-phase refrigerant. For the Organic Rankine Cycle system, the thermodynamic conditions are different to standards relevant to refrigeration or air-conditioning systems. Indeed, the key characteristic of the ORC system is the evaporation saturation temperature. Exhaust gases temperature ranges from 400°C to 900°C and the refrigerant evaporation occurs at temperatures higher than 100°C. Almost all the flow boiling heat transfer models or correlations have been obtained for saturation temperatures ranging from -20°C to 40°C which correspond to standards relevant to refrigeration or air conditioning systems. The empirical models for boiling in such conditions are limited by the experimental data on which they are based, whereas analytical and theoretical approaches are needed to advanced knowledge on the behaviour of thermohydraulic two-phase refrigerant. This PhD thesis aims at studying the flow boiling characteristics of R-245fa in a 3.00 inner diameter channel in the thermodynamic conditions of the ORC system. Therefore, the saturation temperature ranged from 60°C to 120°C. To achieve this goal, an experimental test facility was designed and built to conduct refrigerant evaporation experiments. This test facility allowed to perform flow regime visualizations, pressure drop and heat transfer measurements in minichannel. First, an image processing method for two phase flow pattern characterization was developed. Based on this method and with the help of an adequate analysis of the heat transfer coefficient, the main flow regimes have been identified. The influence of saturation temperature on the flow patterns and their transitions has been highlighted. The second objective was to provide new experimental data concerning flow boiling heat transfer in minichannel. Flow boiling heat transfer coefficients at such high temperature have, so to say, almost never been reported in the open literature so far. The influence of saturation temperature on the heat transfer mechanisms has been discussed. In order to evaluate the capability of the current flow boiling prediction methods to predict the heat transfer coefficient, the comparison between experimental results and theoretical results predicted with the commonly used correlations and models were made. Lastly, pressure drop databases are presented. Experimental values of pressure drops were compared against several methods

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GIKUNDA, MILLICENT NKIROTE. "An improved sample loading technique for cellular metabolic response monitoring under pressure". Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470194454.

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Lu, Yubin. "The dynamic behaviour of hydrostatic-pressure-sensitive materials at high strain-rates based on split hopkinson pressure bar technique". Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515096.

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Johnson, Timothy Paul Mahal. "High strain rate mechanical characterization of trabecular bone utilizing the split-Hopkinson pressure bar technique". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/38294.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 185-188).
The split-Hopkinson pressure bar (SHPB) technique has been in use in one form or another for more than fifty years and has recently gained a great deal of attention for its ability to characterize materials such as metals, plastics, and even stiff foams at strain rates of up to 105 sec-1. Historically, however, numerous obstacles have stood in the way of applying this technique to softer biological tissues. This study is aimed at bridging this gap by employing various innovations in the field of split-Hopkinson pressure bar techniques (including hollow aluminum and solid polymeric pressure bars) to the characterization of trabecular bone. A preliminary study is conducted on a polyurea (PU) blend to assess the advantages and shortcomings of these approaches, as well as to validate the results obtained with each. Bovine trabecular bone with marrow in-situ, which was chosen for its ability to be tested with a wide spectrum of techniques, is then characterized with the selected techniques at rates of up to 1300 s-1 and strains of 0.07. The results are presented for each technique in the form of engineering stress vs. engineering strain curves.
(cont.) Average trend curves are also provided. Unfortunately, many of the samples were too damaged to allow for accurate measurement of apparent density. Consequently, a study into the effect of density on high strain rate responses is left as future work. Recommendations are made for increasing the strain imposed on the samples and suggestions for future studies on both trabecular bone and softer biological tissues are put forward.
by Timothy Paul Mahal Johnson.
S.M.

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De, Villiers A. J. (Andre Joubert). "Evaluation of pressure- and electrodriven separation techniques for the determination of phenolic compounds in wine". Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51753.

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Thesis (MSc)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: The phenolic content of wine is responsible for determining characteristics such as the organoleptic qualities, colour stability, ageing properties and health-beneficial effects associated with wine. The aim ofthis study was to investigate the possibilities offered by capillary electrophoresis (CE) as an alternative separation technique to high performance liquid chromatography (HPLC) for the analysis of polyphenols in wine. The complexity of wine samples was the cause that neither technique was capable of a satisfactory singlestep analysis of wine. Suitable sample preparation techniques such as Sephadex- and Sep- Pak fractionation and ether extraction of wine polyphenols were investigated. These techniques did not, however, prove to be universal. A novel form of sample preparation namely a process analogous to lyophylization used to separate wine volatiles from nonvolatiles was introduced. The versatility of CE was further investigated in an attempt to eliminate the need for sample preparation. The use of polyvinylalcohol (PVA) coated capillaries, micellar electrokinetic chromatography (MEKC) and capillary gel electrophoresis (CGE) were investigated in this regard. Although none of these techniques could offer conclusive results, useful applications were forthcoming and routes for further investigation were outlined. Liquid chromatography coupled to electro spray ionisation mass spectroscopy (LC-ESI-MS) and capillary electrophoresis coupled to electro spray ionisation mass spectroscopy (CE-ESI-MS) were compared for the analysis of polyphenols in wine. While the latter technique could not produce sufficient separation compared to the former, future development ofCE-ESI-MS should make it a powerful technique for these analyses.
AFRIKAANSE OPSOMMING: Die fenoliese komponente in wyn speel 'n bepalende rol by eienskappe soos die organoleptiese karakter, kleur stabiliteit, verouderingspotensiaal en gesondheids-voordele wat met wyn geassosieër word. Die doel van hierdie projek was om ondersoek in te stel na die potensiaal wat kapillêre elektroforese (CE, "capillary electrophoresis") as 'n alternatiewe skeidingstegniek teenoor hoë druk vloeistof chromatografie (HDVC) vir die analise van die polifenole in wyn bied. Die kompleksiteit van wyn monsters is van so 'n aard dat 'n bevredigend enkelstap analise met geeneen van die tegnieke moontlik is nie. Gepaste monster-voorbereidingstappe soos Sephadex- en Sep-Pak fraksionering asook eter ekstraksie van die polifenole in wyn is ondersoek. Geeneen van die tegnieke was egter universeel toepaslik nie. 'n Nuwe metode van monster-voorbereiding, naamlik 'n proses analoog aan liofilisasie wat gebruik word om die wyn te skei in vlugtige en nievlugtige komponente is gedemonstreer. Die veelsydigheid van CE was gevolglik ondersoek in 'n poging om monstervoorbereiding uit te skakel. Die gebruik van polyvinielalkohol-(pVA) bedekte kapillêre, missellêre elektrokinetiese chromatografie (MEKC) en kapillêre gel elektroforese (CGE, "capillary gel electrophoresis) is in hierdie verband ondersoek. Alhoewel geeneen van hierdie tegnieke onweerlegbare resultate gelewer het nie, het bruikbare toepassings hieruit voortgespruit en is die grondslag vir verdere navorsing gelê. Vloeistof chromatografie gekoppel aan eIektrosproei ionisasie massaspektroskopie (LCESI- MS) en kapillêre elektroforese gekoppel aan elektrosproei ionisasie massaspektroskopie (CE-ESI-MS) is vergelyk vir die analise van polifenole in wyn. Alhoewel laasgenoemde tegniek onvoldoende skeiding lewer vergeleke met eersgenoemde, behoort toekomstige ontwikkelinge op die gebied van CE-ESI-MS dit 'n kragtige tegniek vir die analise van hierdie monsters te maak.

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Balugani, Sofia. "Experimental protocol for the determination of elastic properties at ambient and high pressure by picosecond acoustics technique". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22350/.

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This thesis work focused on establishing an experimental protocol for the determination of the materials’ elastic constants at ambient pressure and at high pressure by picosecond acoustics. Picosecond acoustics is a pump-probe experimental technique that allows to measure the travel times of the acoustic waves that propagate across the sample. The acoustic waves’ velocities are derived from the travel times and from the sample thickness. An inversion program developed within the research group allows to extract the elastic constants from the measured sound velocities by inverting the Christoffel equation that relates them to the elastic tensor. The high pressure is generated by the diamond anvil cell (DAC) technology. The investigated samples are magnesium oxide (MgO), a transparent insulator, oriented along the [001] direction, and ruthenium (Ru), an opaque metal, oriented along the [0001] direction. The first was studied at ambient pressure, while the second was studied at both ambient and high pressure. The elastic constants of MgO were extracted with the inversion program and the results obtained agree with the values found in the literature. The values obtained are: C11= (296.96± 0.19) GPa, C44= (153.60 ± 0.10) GPa, C12= (98.78 ± 0.11) Gpa. The elastic constants at ambient pressure of Ru agree with the data in the literature and are: C11= (564± 6) GPa, C33= (626 ± 8) GPa, C44= (182.2 ± 0.5) GPa and C12= (175 ±7) Gpa. The measurements at high pressure on ruthenium did not allow to derive the elastic constants as from the data analysis it emerged that the sample had been damaged during the pressure increase. Probably this was due to the selected pressure transmitting medium of the DAC, that did not guarantee completely the pressure hydrostaticity.

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Al, Hinai Nasser Mohammed Saba. "A Novel Mobility Control Technique in Miscible Gas Injection Using Direct Gas Thickening in High Pressure and Temperature Reservoir". Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/75655.

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This thesis presents for the first time, the details of extensive numerical and experimental evaluations of effectiveness of thickened associate gas injectionat high temperature for miscible gas floodingwith specific focus on FieldAlocated in southern Oman. The study has identified commercialand safe gas thickeners capable of increasing viscosity of injected gas. It hasalso proposedanovel alternating injection technique that canlower the volume of thickeners usedduringfield-scale applications.

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Arnaud, Cécilia. "Elaboration d’aliments nouveaux par hautes pressions : étude technique et juridique". Electronic Thesis or Diss., Nantes, Ecole nationale vétérinaire, 2017. http://www.theses.fr/2017ONIR103F.

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Le traitement par hautes pressions est une technologie innovante de conservation des aliments qui consiste en la pressurisation uniforme d’un produit emballé sous vide. Ensuite, le secteur des produits de la mer, en pleine expansion, doit répondre aux demandes des consommateurs de produits plus sains et moins transformés. Ces travaux avaient pour objectif d’évaluer l’impact de la pressurisation sur les propriétés technologiques, organoleptiques et nutritionnelles du muscle d’un poisson maigre, le cabillaud, d’un poisson gras, le saumon et d’un coquillage, la noix de Saint-Jacques, à la suite d’un stockage réfrigéré. Les produits obtenus correspondent à des tranches de produits de la mer crus en marinade Ready-To-Eat. Les échantillons ont subi un traitement de 150, 300 ou 450 MPa et ont été conservés à 4 °C pendant 21 jours. La pressurisation impacte les constituants du poisson (protéines et lipides), modifiant ainsi les propriétés physiques des produits (couleur et texture). Une pression de 450 MPa est nécessaire pour conserver le cabillaud et le saumon jusqu’à 11 jours et la noix de Saint-Jacques jusqu’à 19 jours. Avec ce barème de pression, les produits de la mer sont acceptables pour une consommation crue. De plus, une marinade pour accompagner ces produits a été formulée sous forme d’organogels pour obtenir des propriétés innovantes. Une étude sur l’aspect législatif et la perception des consommateurs de la technologie des hautes pressions a été menée. Les hautes pressions sont régulées par le règlement Novel Food de 1997 qui a été révisé en 2015. Les consommateurs sont réceptifs aux avantages du traitement par hautes pressions
High pressure processing is an innovative technology for food preservation which consists in the uniform pressurization of a vacuum packed product. Moreover, eafood sector, in a huge expansion, must answer the consumers’ demands for healthier and less transformed food items. This research study reports on the evaluation of the pressurization impact on technological, organoleptic and nutritional characteristics of the muscle of a lean fish, cod, a fatty fish, salmon and a shellfish,Pecten maximus scallop following a cold storage. This innovative product correspond to Ready-to-Eat marinated and raw slices of seafood. The samples were subjected to a high pressure treatment of 150, 300 or 450 MPa and stored at 4 °C for 21 days. The pressurization impacts fish constituents (proteins and lipids), thus modifying the products physical properties (color and texture). A 450 MPa treatment is necessary to preserve cod and salmon until 11 days and scallop until 19 days. With this pressure level, the seafood product is acceptable for a crude consumption. Moreover, the marinade to go along with those products was formulated as an organogel to obtain innovative properties. In addition, a study of the legal aspect and the consumer’s perception of the high pressure technology was carried out. High pressure processing is regulated under the regulation Novel Food of 1997 which was revised in 2015. Consumers are receptive to the benefits of high pressure processing

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Salama, Fawzi. "Electrostatic Charge Generation and Wall Fouling in a High-Pressure Gas-Solid Fluidized Bed: Implementation and Preliminary Testing of a Measurement Technique". Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26123.

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Due to the nature of gas-solid fluidized beds, providing continuous contacts between fluidizing particles and between particles and the reactor wall, the occurrence of electrostatic charges is unavoidable. In the polyethylene industry, electrostatics is a major problem. Large amounts of electrostatic charges are generated causing polyethylene and catalyst particles to adhere to the reactor wall, forming sheets. Particle sheets can break off and block the distributor plate, causing long shutdown periods for clean-up which result in economic loss due to decreased production and higher maintenance costs. The overall purpose of the project of which this thesis is part of is to help industry in minimizing this problem by examining the mechanisms underlying this phenomenon. Towards this goal, an experimental technique for the measurement of the degree of wall fouling and its charge distribution was previously developed and implemented in an atmospheric system with a column of 0.102 m in diameter. This technique was extended in this thesis to a pilot-scale unit (0.154 m in diameter) designed to be capable of operating at pressures and temperatures up to 2 600 kPa and 100°C respectively and gas velocities up to 1 m/s, which are operating conditions of industrial polyethylene reactors. Preliminary experiments showed that increasing the operating pressure from 101 kPa to 401 kPa almost doubled the amount of polyethylene wall fouling due to the higher bubble rise velocity at this pressure, enhancing charge generation within the fluidized bed. Changing the particle size distribution by removing particles smaller than 250 μm had no significant effect on the extent of the wall fouling. Increasing the column diameter from 0.102 m to 0.154 m decreased wall fouling due to the lower column wall area per mass of particles. Overall, particle-particle contacts generated positively and negatively charged particles, but did not produce a net charge in the bed due to the negligible elutriation. However, particle-wall contacts produced a net charge. The formation of the wall layer was due to the image force created by the net charge and the layering effect created by the attraction between oppositely charged particles.

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Tupper, Heather Suzanne. "The effects of divalent cations on the dynamics of sulfogalactosylceramide and sulfogalactosylacylalkylglycerol multilayers: A study using the technique of high pressure Fourier-transform infrared spectroscopy". Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10063.

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Sulfogalactosylacylalkylglycerol (SGG) and sulfogalactosylceramide (SGC) are structurally related sulfatides that are found ubiquitously in the plasma membrane of male germ cells. Since Ca$\sp{2+}$ is a cation that plays important roles in many fertilization related events (Yanagimachi, 1988), we have been interested in determining whether Ca$\sp{2+}$ interacts with the negatively charged SGG/SGC and whether this interaction results in changes to the lipid dynamics. In this study, we used high pressure Fourier-transform infrared spectroscopy, a powerful technique that reveals information on different structural regions of the lipid molecule based on their specific infrared vibrational absorption modes. The study was performed using multilayer suspensions of the sulfatides. Our results showed that all three divalent cations electrostatically interacted with the sulfate moiety of hydrated SGG, although with varying degrees of strength. Similarly Ca$\sp{2+}$ bound to the sulfate moiety of solid SGC. It was found that hydrated SGG-Na$\sp+$ was interdigitated whereas hydrated SGC-Na$\sp+$ was not. The divalent cations presumably crosslinked the sulfate groups of neighbouring lipid molecules. In the case of SGG, this crosslinking removed the interdigitation. With SGC, the crosslinking by Ca$\sp{2+}$ weakened the hydrogen bonding of the interfacial region and the hydrocarbon chains became more disordered. Similar lipid dynamic effects of divalent cations were found in the SGG studies, with Mg$\sp{2+}$ inducing the greatest chain disorder followed by Ca$\sp{2+}$ then Sr$\sp{2+}$. An increase in chain disorder would increase the bilayer fluidity. Such a phenomenon may prove relevant to the changes of the sperm plasma membrane during fertilization-related event. (Abstract shortened by UMI.)

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Giraudet, Cédric Michel Marius. "Contributions à l’étude de la thermo diffusion de mélanges binaires en conditions de réservoirs". Thesis, Pau, 2015. http://www.theses.fr/2015PAUU3003/document.

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La thermodiffusion, également appelé effet Soret, décrit le couplage entre les gradients de température et les flux massiques qui en résultent. Ce phénomène intervient dans de nombreux processus naturels et applications industrielles. En particulier, les réservoirs pétroliers sont sujets à ce phénomène impliquant des fluides multi constituants confinés dans une matrice poreuse et soumis à un gradient de température. Néanmoins, malgré beaucoup des progrès, il existe relativement peu de mesures fiables de ce phénomène et sa modélisation reste largement un problème ouvert. L’objectif principal de cette thèse s’inscrit dans ce cadre, à savoir développer une approche expérimental permettant de fournir des données de références sur la thermodiffusion notamment dans l’optique de quantifier l’effet de la pression sur cette dernière. Ainsi, durant cette thèse, nous avons développé une cellule de thermodiffusion en milieu libre qui permet d’étudier par shadowgraphie les fluctuations de non équilibre induites par effet Soret. L’appareil de mesure a ensuite été utilisé pour étudier deux mélanges binaires représentatifs de fluides pétroliers, à savoir le mélange équimassique tétraline/dodécane (en phase liquide) et le mélange dioxyde de carbone/méthane (en phases gaz et supercritique). En complément, des simulations de dynamique moléculaire ont été réalisées sur le mélange dioxyde de carbone/méthane. Par analyse dynamique des images de shadowgraphie nous avons pu déterminer les coefficients de diffusion et Soret en fonction de la pression pour le mélange tétraline/dodécane. Aux incertitudes près, nous observons une décroissance linéaire avec la pression pour ces coefficients. De plus nous avons observé l’effet du confinement de la cellule sur les fluctuations en très bon accord avec la théorie et les simulations. Pour le mélange dioxyde de carbone/méthane l’analyse dynamique a montré une cinétique difficilement accessible de par les limites physiques et informatiques du dispositif expérimental utilisé. L’analyse statique montre, quant à lui, une croissance rapide de l’amplitude des fluctuations avec la pression jusqu’à un seuil au-delà duquel elle décroît. Sur ce mélange les simulations de dynamique moléculaire ont montré un bon accord avec les prédictions théoriques
Thermodiffusion, also called the Soret effect, describes the coupling between temperature gradient and resulting fluxes. This phenomenon is involved in a number of natural and industrial processes. In particular, multi components fluids in petroleum reservoirs are subjected to this phenomenon because of the geo-thermal gradient. Nevertheless, in spite of a lot of advances, there are few available data of this phenomenon and the establishment of a theoretical model, able to give a quantitative estimation of these transport coefficients whatever molecules in presence, is still an open question. The principal aim of this thesis is to develop an experimental approach allowing providing reference data on thermodiffusion as a function of the pressure. During this thesis, we developed a high pressure thermodiffusion cell in free medium, enabling us to study concentration non-equilibrium fluctuations induced by the Soret effect by means of shadowgraph optical technique. With this setup we investigated two binary mixtures representatives of petroleum fluids; namely the equimassic tetralin/dodecane mixture in liquid phase and the carbon dioxide/methane mixture in gaseous and super critical state. Furthermore, molecular dynamic simulations on the second mixture were performed. Using a dynamic image analysis, we have measured molecular diffusion and Soret coefficient for the tetralin/dodecane mixture. Within experimental uncertainties, we observed a linear decrease of these coefficients with the pressure. Furthermore, we were able to observe the effect of confinement (finite size effect induced by cell vertical boundary conditions) on fluctuation dynamics, in good agreement with calculations and simulations based on hydrodynamic fluctuation theory on similar solutal Rayleigh number. Concerning the carbon dioxide/methane mixture, the dynamic analysis revealed a kinetic too fast for our experimental apparatus. Conversely, static analysis revealed a rapid increase of the non-equilibrium fluctuation magnitude as a function of the pressure up to a threshold beyond which it decreases. On this mixture, performed molecular dynamic simulations provided results in good agreement with expected theoretical behaviour

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Diegor, Wilfredo G. "Development of a high pressure digestion technique and a data acquisition/reduction procedure and their application to the ICP-MS analysis of urban sediments and soils from Cebu, Philippines". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/MQ42368.pdf.

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Dunja, Jakovljević. "Biološko dejstvo vodenog ekstrakta ploda štavelja (Rumex crispus L., Polygonaceae)". Phd thesis, Univerzitet u Novom Sadu, Medicinski fakultet u Novom Sadu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=110304&source=NDLTD&language=en.

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Štavelj (Rumex crispus, Polygonaceae) je višegodišnja zeljasta biljka, koja predstavlja bogat izvor fenolnih komponenti. Iako se smatra invazivnim korovom, mlado lišće štavelja je jestivo i često se koristi kao salata. Dalje, upotreba plodova štavelja opisana je u srpskoj i turskoj narodnoj medicini u lečenju gastrointestinalnih tegoba. Cilj ovog rada bio je procena in vitro i in vivo antioksidantne/prooksidantne i citotoksične aktivnosti, i određivanje eventualnog in vitro antiinflamatornog efekta vodenog ekstrakta ploda Rumex crispus. Ukupan sadržaj flavonoida određen je spektrofotometrijskom metodom. Kvalifikacija i kvantifikacija flavonoida potvrđena je visokoefikasnom tečnom hromatografijom (HPLC). Antioksidantna aktivnost vodenog ekstrakta ploda štavelja procenjena je na osnovu in vitro testova: Ferric-reducing antioxidant power (FRAP), sposobnosti ekstrakta da neutrališe slobodne radikale NO•, OH• i DPPH• i uticaja na lipidnu peroksidaciju u lipozomima. Citotoksičnost ispitivanog ekstrakta je određena in vitro na tumorskim ćelijskim linijama: humani karcinom cerviksa (HeLa), adenokarcinom (HT-29) i adenokarcinom dojke (MCF7). Takođe, moguća in vivo hepatoprotektivna i antioksidantna svojstva ekstrakta određena su kod oksidativnog stresa izazvanog CCl4 kod eksperimentalnih životinja. Pored toga, proverena je hipoteza u kojoj testiran ekstrakt pokazuje in vivo antiproliferativnu aktivnost kod Ehrlich-ovih (EAC) i Hepatoma AS30D ćelija, merenjem zapremine ascitesa, procenta vijabilnih ćelija i nivoa nekoliko antioksidantnih enzima. Optimizovan in vitro test za određivanje potencijala inhibicije ciklooksigenaze-1 (COX-1) i 12-lipooksigenaze (12-LOX) preduzet je u svrhu procene antiinflamatornog efekta vodenog ekstrakta ploda R. crispus. HPLC analiza otkrila je da je mikvelianin najdominantniji flavonoidni konstituent ekstrakta. Testirani ekstrakt pokazao je potencijalnu antioksidantnu aktivnost rezultujući velikom moći u neutralizaciji slobodnih radikala, i sposobnošću da smanji lipidnu peroksidaciju u lipozomima. Rezultati su ukazali na tkivno-selektivnu citotoksičnost ekstrakta ploda R. crispus in vitro. Najizraženija antitumorska aktivnost primećena je prema HeLa i MCF7 ćelijskim linijama. Podaci sugerišu da bi se ispitivani ekstrakt mogao smatrati potencijalnim in vivo hepatoprotektivnim i antioksidantnim agensom, sprečavajući oksidativna oštećenja jetre. S druge strane, pomenuti ekstrakt može pokazati in vivo prooksidantna svojstva, uzrokujući oksidativni stres u maligno transformisanim EAC i AS30D ćelijama i smanjujući zapreminu ascitesa i udeo vijabilnih ćelija, u poređenju sa kontrolnom grupom. Promene u aktivnosti antioksidantnih enzima su verovatno posledica indukovanog oksidativnog stresa u EAC i AS30D ćelijama, naročito kod pretretiranih životinja. Vodeni ekstrakt ploda štavelja pokazao je COX-1, kao i 12-LOX inhibitornu aktivnost, navodeći da bi ispitivani ekstrakt mogao biti antiinflamatorni agens. Vodeni ekstrakt ploda R. crispus ima potencijalnu antioksidantnu, citotoksičnu i antiinflamatornu aktivnost. Ispoljavanje prooksidantnih svojstava predstavlja mogući mehanizam antiproliferativnog efekta ekstrakta.
Curly dock (Rumex crispus, Polygonaceae) is a wild perennial herbaceous plant, which products are described as a rich source of phenolic compounds. Apart from being considered a seriously invasive weed, young leaves of curly dock are edible and often used as salad. Furthermore, the use of its fruits has been described in Serbian and Turkish traditional medicine against stomach complaints. The objectives of this study were to evaluate in vitro and in vivo antioxidant/prooxidant and cytotoxic activities, and to determine an eventual in vitro anti-inflammatory effect of the aqueous extract of Rumex crispus fruits. Total flavonoid content was determined by spectrophotometric method. Qualification and quantification of flavonoids were confirmed using High performance liquid chromatography (HPLC). The aqueous extract of curly dock fruits was evaluated for its antioxidant activity by in vitro assays for Ferric-reducing antioxidant power (FRAP), NO•, OH• and DPPH•-free radical scavenging activities and the influence on lipid peroxidation in liposomes. The cytotoxicity of tested extract was examined in vitro in human cervix carcinoma (HeLa), colon adenocarcinoma (HT-29) and breast adenocarcinoma (MCF7). Also, the potential in vivo hepatoprotective and antioxidant properties of investigated extract were determined on CCl4-induced oxidative stress in experimental animals. Furthermore, the hypothesis that the examined extract might show in vivo antiproliferative activity in Ehrlich carcinoma (EAC) and Hepatoma AS30D cells was tested by measuring volume of ascites, percentage of viable cells and level of several antioxidant enzymes. The optimized in vitro test for determination of cyclooxygenase-1 (COX-1) and 12-lipoxygenase (12-LOX) inhibition potency was undertaken in order to estimate an anti-inflammatory effect of aqueous extract of R. crispus fruits. HPLC analysis revealed miquelianin as the most abundant flavonoid constituent of the extract. The tested extract might have an antioxidant activity resulting in scavenging of free radicals and ability to decrease lipid peroxidation in liposomes. The results could indicate tissue-selective cytotoxicity of R. crispus fruit extract in vitro. The most prominent antitumor activity was observed towards HeLa and MCF7 cell lines. The data suggested that investigated extract may be considered as potential in vivo hepatoprotective and antioxidant agent due to prevention of the liver injuries induced by oxidative damage. On the other hand, mentioned extract could exhibit in vivo prooxidant property, causing the oxidative stress in malignant transformed EAC and AS30D cells and reducing volume of ascites and percentage of viable cells, in comparison with control group. Changes in activities of antioxidant enzymes might be the results of induced oxidative stress in EAC and AS30D cells, especially in the pretreated animals. The aqueous extract of curly dock fruits showed COX-1, as well as 12-LOX inhibitory activity, suggesting that tested extract might be an anti-inflammatory agent. It could be concluded that aqueous fruit extract of R. crispus might have antioxidant, cytotoxic and anti-inflammatory activities. The prooxidant properties of examined extract could be the mechanism of potential antiproliferative effect of extract.

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Pioche, Mathieu. "Optimisation de la technique de dissection sous muqueuse à l’aide d’un bistouri à jet d’eau haute-pression pulsée pour le traitement endoscopique des tumeurs superficielles du tube digestif". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10166/document.

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Dans cette thèse, nous avons travaillé sur les différents versants de la technique de dissection sous-muqueuse et les problèmes que pose ce geste quasi chirurgical dans des unités d'endoscopie initialement médicales. Tout d'abord, nous avons travaillé sur la formation à la technique en développant un modèle d'apprentissage sur colon de bovin plus adapté à la situation européenne où les lésions colo-rectales sont les plus fréquentes. Ce modèle de rectum de bovin, simple à trouver et à préparer permet une formation dans des conditions plus proches de la paroi colique humaine que celles offertes par l'estomac de cochon. Un travail à plus grande échelle évaluant les bénéfices d'une aide à l'apprentissage par un logiciel interactif dédié mené sur ce modèle avec 37 étudiants français et japonais est en cours d'analyse et sera publié prochainement. Ensuite, nous avons réfléchi à la stratégie de la procédure pour la rendre plus simple en évaluant précocement la technique du tunnel pour la dissection des lésions œsophagiennes. Cette stratégie permet de maintenir une traction sur les bords lésionnels et nous offrent une sorte de triangulation en élargissant physiquement la zone de travail. Cette stratégie est devenue un standard pour les résections œsophagiennes dans de nombreuses équipes. Enfin, nous avons travaillé conjointement avec la société Nestis® au développement d'un outil permettant d'optimiser la procédure de dissection sous-muqueuse en associant les bénéfices des bistouris bi fonction (injectant et coupant avec le même outil}, de la haute pression pulsée et des solutions macromoléculaires visqueuses. Le système Nestis® permet pour la première fois cette association et a démontré son intérêt en termes de sécurité et de performance par rapport à la méthode classique utilisant l'aiguille et un bistouri électrique conventionnel. Avec cet outil bi fonction, il n'est plus nécessaire de changer d'instrument puisque toutes les étapes de la procédure sont désormais réalisées avec un seul et même outil. D'autres projets sont déjà prévus avec ce matériel pour étudier ses bénéfices et sa sécurité en dissection colique humaine qui est réputée comme la plus difficile compte tenu de la finesse de la paroi. Enfin, ce matériel offre la possibilité d'injecter sous pression des principes actifs qui pourrait dans le futur permettre de prévenir la survenue de sténoses œsophagiennes ou diriger la cicatrisation. Nous avons ainsi travailler avec la pharmacie de l'hôpital Edouard Herriot pour stabiliser la solution macromoléculaires de mélange de glycérol pour permettre son utilisation en pratique quotidienne
First of all, we worked on the training for unexperienced operators by developing a bovine colon model more adapted to the European situation where colo-rectal lesions are the most common. This model of rectum from bovine, easy to find and to prepare allows training in conditions most close to the human colonic wall than those offered by the pig stomach. Furthermore, such models allows to teach the initial skills but avoiding the risk of adverse events for the first procedures in humans. A future work evaluating the benefits of a learning support by a dedicated interactive software on this model with 37 french and Japanese students is now being analyzed and will be reported soon. Then we thought about the strategy of the procedure in order to make it more simple using the tunnel technique to perform ESD for the esophageal lesions. This strategy helps to maintain traction on the edges and offers a sort of triangulation physically expanding the working space. This strategy has become a standard for esophageal resections in many teams and we still work to improve its efficacy. Finally, we worked jointly with Nestis® Company to develop a tool to optimize the submucosal dissection procedure by combining the benefits of the catheters bi function (injecting and cutting with the same tool), but adding high pulsed pressure and capability to inject viscous macromolecular solutions. The Nestis® system allows for the first time this association and demonstrated his interest in terms of security and performance compared with the conventional method using the needle and a conventional electrocautery device. With this bi function tool, it is not necessary to change instrument frequently since all stages of the procedure are now done with a single device. Other projects are already included with this material to explore its benefits and its safety in human colonic dissection that is deemed as the most difficult due to the thinner wall. Finally, this material offers the possibility to inject pressurized active drugs which could be used in the future to prevent the occurrence of esophageal strictures or to direct healing. We also worked with the hospital Edouard Herriot pharmacy to stabilize the solution glycerol mix to allow its use in daily practice in our unit

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Zauer, Mario, Frank Meissner, Rudolf Plagge i André Wagenführ. "Capillary pore-size distribution and equilibrium moisture content of wood determined by means of pressure plate technique". De Gruyter, 2016. https://tud.qucosa.de/id/qucosa%3A38475.

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This paper deals with the determination of the capillary pore-size distribution (CPSD) and equilibrium moisture content (EMC) of untreated and thermally modified (TM) Norway spruce [Picea abies (L.) Karst.] by means of the pressure plate technique (PPT). Desorption experiments were conducted at very high values of relative humidity (RH) in the range between 99.2% and 100%. The thermal modification of spruce results in an alteration of the CPSD, owing to the formation of intercellular cracks in the middle lamella, as a result of cell-wall compression. The desorption curves for both untreated and TM spruce show an extremely upward bend at 99.97% RH. This step reflects an EMC of 38.1% for untreated spruce and 33.8% for TM spruce. None of the samples shrunk during the PPT measurements. Following desorption experiments at 97.4% RH, all samples shrunk. This step reflects an EMC of 27.9% for untreated spruce and 21.7% for TM spruce.

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Patout, Maxime. "Evaluation des techniques pour la prise en charge diagnostique et thérapeutique de l'insuffisance respiratoire chronique A Randomized controlled trial on the effect of needle gauge on the pain and anxiety experienced during radial arterial puncture Long term survival following initiation of home non-invasive ventilation : a European study Neural respiratory drive predicts long-term outcome following admission for exacerbation of COPD : a post hoc analysis Neural respiratory drive and cardiac function in patients with obesity hypoventilation syndrome following initiation of non-invasive ventilation Polysomnography versus limited respiratory monitoring and nurse-led titration to optimise non-invasive ventilation set-up a pilot randomised clinical trial Chronic ventilator service Step-down from non-invasive ventilation to continuous positive airway pressure : a better phenotyping is required AVAPS-AE versus ST mode : a randomized controlled trial in patients with obesity hypoventilation syndrome Technological advances in home non-invasive ventilation monitoring : reliability of data and effect on patient outcomes Efficacy of a home discharge care bundle after acute exacerbation of COPD Prediction of severe acute exacerbation using changes in breathing pattern of COPD patients on home noninvasive ventilation Charasteristics and outcome of patients set up on high-flow oxygen therapy at home Trial of portable continuous positive airway pressure for the management of tracheobronchomalacia". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR115.

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L’insuffisance respiratoire chronique est un syndrome défini par une défaillance monoviscéralerespiratoire. Sa principale origine est aujourd’hui le syndrome obésité-hypoventilation qui concerne 4 à 5% des patients obèses. L’IRC est aussi le stade évolutif terminal de la bronchopneumopathie chronique obstructive qui touche 6 à 8% de la population adulte. L’incidence de ces pathologies et donc de l’insuffisance respiratoire est en augmentation constante. Dans cette thèse, nous avons évalué les nouvelles modalités diagnostiques et thérapeutiques qui pourraient améliorer la prise en charge des patients atteints d’insuffisance respiratoire chronique.Concernant la prise en charge diagnostique, nous avons montré que les données fournies par l’électromyographie de surface des muscles intercostaux, outil qui évalue le travail respiratoire, constituent un marqueur pronostique indépendant chez les patients atteints de bronchopneumopathie chronique obstructive. Nous avons également montré leur pertinence pour prédire l’efficacité clinique et l’observance à la ventilation non-invasive à domicile.Concernant la prise en charge thérapeutique, nous avons montré que l’utilisation d’un mode semi-automatisé de ventilation non-invasive a la même efficacité que celle de modes classiques en permettant une mise en place plus rapide du traitement. Nous avons également rapporté l’intérêt de l’oxygénothérapie à haut débit au domicile alors que ce traitement était utilisé jusque-là dans le seul cadre des soins intensifs. Enfin, nous avons rapporté les bénéfices de la pression positive continue au cours de l’effort chez les patients ayant une trachéobronchomalacie. Concernant le suivi des patients, nous avons montré que les données des logiciels de ventilation non invasive permettent de prédire la survenue d’une exacerbation sévère de BPCO mais que l’utilisation de la télémédecine chez les patients insuffisants respiratoires chroniques ne peut être encore pleinement intégrée dans la pratique clinique. Au cours de cette thèse, nous avons identifié de nouveaux outils physiologiques, de nouvelles modalités d’administration des traitements et de nouveaux outils de suivi à domicile, à même d’améliorer la prise en charge des patients insuffisants respiratoires chroniques
Single-organ respiratory failure defines chronic respiratory failure. Obesity hypoventilation syndrome is the main cause of chronic respiratory failure and occurs in 4 to 5% of obese patients. Chronic respiratory failure is also the end-stage evolution of chronic obstructive pulmonary disease that has a prevalence of 6 to 8% in the adult population. The incidence of these diseases increases so does the incidence of chronic respiratory failure. In this thesis, we will evaluate novel diagnostic and therapeutic modalities that could improve the care of patients with chronic respiratory failure. Regarding diagnostic modalities, we have seen that evaluating the work of breathing with surface parasternal electromyography was an independent prognostic marker in patients with chronic obstructive pulmonary disease. We have also seen that it was a relevant tool to predict the clinicalefficacy and compliance to home non-invasive ventilation. Regarding therapeutic modalities, we have shown that the use of a semi-automatic mode of non-invasive ventilation had the same efficacy of a standard mode with a shorter length of stay for its setup. We have shown the relevance and feasibility of the use of high-flow oxygen therapy in the home setting whilst it was only used in intensive care units. Finally, we have shown the benefits of continuous positive airway pressure during exertion in patients with tracheobronchomalacia. Regarding patients’ follow-up, we have shown that the use of data from built-in software could predict the onset of a severe exacerbation of chronic obstructive pulmonary disease. However, we also show that the implementation of tele-medicine in patients with chronic respiratory failure cannot be included in daily clinical practice yet. In this thesis, we have identified novel physiological tools, novel ways to administer treatments and novel follow-up tools that can improve the management of patients with chronic respiratory failure

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Clariana, Orduña Maria. "Efecto de la aplicación de altas presiones hidrostáticas en un producto de origen animal, el jamón curado y en un producto vegetal, el nabo". Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/53634.

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High pressure processing is a food preservation technique which can be an alternative to heat treatment. Pressurization, in theory, produces changes in organoleptic properties and antioxidant compounds to a lesser extent. The objective of the present dissertation has been to study the effect of high pressure processing on oxidative processes and their relation to the organoleptic qualities of diced swede and packaged sliced ham. The results have pointed to pressurization at 600 MPa, and produce an effective decontamination is that which causes less loss of compounds or antioxidant properties. For swede, this pressure level also caused a minor modification of the organoleptic qualities. This dissertation has also shown that depending on feed composition, the effect of pressurization on the organoleptic qualities can be diametrically opposite.
La aplicación de altas presiones hidrostáticas es una técnica de conservación de alimentos que puede ser una alternativa al tratamiento térmico. La presurización, en teoría, produce una menor modificación de las propiedades organolépticas y de los compuestos antioxidantes. En el presente trabajo se ha estudiado el efecto de las altas presiones hidrostáticas en los procesos oxidativos y su relación con las cualidades organolépticas del nabo troceado y del jamón curado empaquetado loncheado. Los resultados obtenidos han apuntado a que la presurización a 600 MPa, además de producir una descontaminación efectiva, es la que causa una menor pérdida de compuestos o propiedades antioxidantes. En el caso del nabo, esta presión también es la que ocasiona una menor modificación de las cualidades organolépticas. En el presente trabajo también se ha observado que en función de la composición del alimento, el efecto de la presurización en las cualidades organolépticas puede ser diametralmente opuesto.

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Cortez, André Filipe Ventura. "Novel Techniques for High Pressure Noble Gas Radiation Detectors". Doctoral thesis, 2018. http://hdl.handle.net/10316/83817.

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Tese de doutoramento em Engenharia Física, ramo de Instrumentacão, apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
This thesis presents the studies conducted with the objective of developing a new and ruggedized Gas Proportional Scintillation Counter (GPSC) based on high-pressure Xe (5- 20 bar) with a cylindrical geometry for the detection of hard X- and gamma-rays (100 keV to 662 keV). It is to be used in eld applications, where robustness is a requirement, for example in homeland security (detection of illegal transport of radioactive material) or for geological prospection (instrumentation for boreholes). A study of the mobility of ions in gases used in large volume detectors is also presented. In GPSCs, the detection of ionizing radiation is based on the production of scintillation photons as the ampli cation stage, followed by their detection with the help of a photosensor, typically a photomultiplier. GPSCs have an absorption/drift region where the ionizing radiation is absorbed, producing a cloud of primary electrons which is guided by a low electric eld (kept below the excitation threshold of the gas) to the scintillation region, where the electric eld is above the scintillation threshold but below the ionization threshold of the gas. In the scintillation region, they produce a large number of scintillation photons (vacuum ultra-violet photons), emitted during the deexcitation process of the gas atoms. These will eventually reach the photosensor, producing a signal proportional to the energy of the incident radiation. Conventionally, the adopted geometry is planar, since it displays the best energy resolution, but because of the photosensors usually adopted, its use in eld applications is limited. In a recent work, a prototype was developed with a planar geometry with the objective of being more ruggedized for eld applications. The main di erence consisted of the use of a deposited caesium iodide as the photosensor, with the photoelectrons produced by the VUV photons being collected at a grid close to the photocathode. However, this new detector displayed several limitations: low detection e ciency for high energy radiation (above 50 keV); small solid angle subtended by the photosensor; and the high bias voltage needed, which reduced its performance and its application scope. So, to solve these limitations a new detector for higher energies (100-662 keV) was developed using a cylindrical geometry, which is expected to display several advantages. On one hand, the cylindrical con guration allows the number of metallic grids used to be decreased, thus reducing the impact of the internal optical transmission in the detector gain. In addition, the fact that the photocathode is deposited on the inner surface of the detector walls signi cantly increases the solid angle subtended by the photosensor, improving the gain. Also because the radiation is absorbed along the cylinder axis, the detecting e ciency is improved. Moreover, this con guration will, in principle, allow the bias voltage to be minimized for the same gain when compared with the planar geometry. In this work, this new prototype was designed according to the initial performance requirements, constructed and assembled, followed by its characterization with the assessment of the prototype performance using an alpha particle source of 241Am, varying the pressure from 1 up to 3 bar. In the initial stage, the characterization of the 241Am source was performed, followed by the study of the charge collection at the anode and the characterization of the scintillation signal. In this study, it was possible to verify that increasing the E=p above the ionization threshold at the anode surface and slightly above the scintillation one in the collecting region, the energy resolution was improved. In addition, the gain and the signal-to-noise ratio (SNR) of the detector were also determined. Regarding the gain, the experimental values determined were in agreement with the theoretical ones, and at the best possible conditions we were able to reach a gain of 1.9 at 1.05 bar, which gives a good outlook for achieving gains of about 30 at 15 bar. As for the SNR, in the best possible conditions studied, the signal was 10 times greater than the noise, which allowed the minimum detectable energy to be estimated with the detector in the present operating conditions. In parallel with the development of this new detector, the transport properties of ions were also studied to provide information on ion mobility for di erent gas mixtures used or considered for several major experiments (ALICE TPC and TRD, CBM TRD, Next and the future LCTPC), as the information of the mobility of ions in gases is relevant not only for the design and modelling of gaseous radiation detectors, but also in the understanding of the signal formation. This work was developed in the scope of our participation in the NEXT Collaboration and RD51 Collaboration from CERN. The ion drift chamber used in these studies, already available in our laboratory, allows the drift time of this group of ions to be determined with precision and consequently their drift velocity and mobility. Finally, knowing the mobility of these ions and using Blanc's law with the polarization limit of the Langevin's formula, it is possible to identify most of the collected ions. In the scope of this thesis, 5 gas mixtures of interest for the above-mentioned experiments were studied: Xe-N2, Xe-CO2, Xe-CF4, Ar-C2H6 and Ar-CH4. Another interesting result coming from this work is related to the validity of the Langevin polarization formula used to predict the mobility of ions and whose limitations are related to the weak polarizability of some neutrals such as Ne, or by the numerous internal degrees of freedom, responsible for reducing the mobility in gases such as CO2 by about 10%. An alternative method to the use of the Langevin polarization limit, when it fails, is proposed, which will allow a better estimate of the mobility to be obtained.
Esta tese apresenta os estudos realizados com o objectivo de desenvolver e testar um detetor gasoso do tipo contador gasoso de cintilação proporcional (CGCP) baseado em Xe a alta pressão (5-20 bar) com geometria cilíndrica para a detecção de raios-X duros e de radiação gama (100-662 keV), para utilização em ambientes hostis em que a robustez é um requisito, por exemplo em segurança nacional (detecção de transporte ilegal de material radioativo) ou em instrumentação para prospecção geológica. Apresenta também o estudo realizado relativamente às propriedades de transporte de iões em meios gasosos de interesse para detetores de grande volume. Nos CGCPs, a detecção da radiação ionizante assenta na produção de fotões de cintilação como estágio de ampli cação e sua posterior detecção com a ajuda de um fotosensor, geralmente um fotomultiplicador. Os CGCPs são constituídos por uma região de absorção/deriva onde a radiação ionizante é absorvida dando origem a uma nuvem de electrões primários que é guiada por um campo eléctrico baixo (abaixo do limiar de excitação do gás) em direcção à região de cintilação secundária onde, devido ao campo eléctrico mantido acima do limiar de excitação e abaixo do limiar de ionização do gás, são produzidos um elevado número de fotões de cintilação (fotões de VUV). Os fotões emitidos durante o processo de desexcitação dos átomos do meio irão atingir o fotosensor originando um sinal proporcional à energia da radiação incidente. Convencionalmente, a geometria adoptada é a geometria planar por ser a que apresenta a melhor resolução em energia, mas devido à utilização de fotosensores o seu uso em ambiente de campo e limitada. Recentemente foi desenvolvido um protótipo com geometria planar, mais robusto, tendo em vista esse tipo de aplicações, uma vez que utiliza como fotosensor um depósito de iodeto de césio, sendo a carga originada no mesmo pela incidência de fotões VUV, e recolhida numa grelha colocada na sua proximidade. Contudo, este detector revelou algumas limitações: baixa eficiência de detecção para radiação de energia acima de 50 keV, baixo ângulo sólido e elevada tensão de polarização necessária, que condicionam o seu desempenho e a sua gama de aplicações. Para resolver estas limitações foi desenvolvido um novo protótipo para detecção de radiação de energia mais elevada (100-662 keV), optando-se por uma geometria cilíndrica, que apresenta inúmeras vantagens. Por um lado, a con figuração cilíndrica permite diminuir o número de grelhas metálicas utilizadas no anterior protótipo, reduzindo o impacto da transmissão óptica interna no ganho do detector, e melhora signi ficativamente o ângulo sólido. Não menos importante e a melhoria que esta con figuração permite ao nível da e ficiência de detecção, já que nesta geometria a radiação é absorvida ao longo do eixo principal do detector. Também diminui signi ficativamente a tensão de polarização quando comparado com a geometria planar. Depois de um estudo preliminar, o detector foi projetado construído e montado, tendo sido feita a caracterização preliminar do mesmo, à qual se seguiu a veri ficação do seu desempenho com o recurso a uma fonte de partículas alfa de 241Am, para pressões entre 1 a 3 bar. Numa primeira fase, foi feita a caracterização da fonte de 241Am utilizada nos testes, à qual se seguiu o estudo da carga primária recolhida no ânodo, seguindo-se a caracterização do sinal de cintilação. Com este estudo foi possível veri ficar que aumentando o E/p para valores acima do limiar de ionização à superfície do ânodo e ligeiramente acima do limiar de excitação a resolução em energia do detector na região de recolha poderia ser melhorada. Neste trabalho foram ainda estudados o ganho e a relação sinal-ruído (SNR) do detector. Em relação ao ganho, o comportamento observado era o o esperado teoricamente, sendo que nas melhores condições possíveis foi obtido um ganho de 1.9 a 1.05 bar o que nos dá boas perspectivas para alcançar ganhos na ordem de 30 para pressões de 15 bar. Já em relação à SNR, nas melhores condições possíveis, o sinal observado foi 10 vezes superior ao ruído, o que permitiu estimar a energia mínima detetável nestas condições de operação. Em paralelo com o desenvolvimento deste novo detector, foi estudada a mobilidade de iões em diferentes misturas gasosas de interesse ou utilizadas em diversas experiências de grande relevância (ALICE TPC e TRD, CBM TRD, NEXT TPC e a futura LCTPC), uma vez que a informação sobre a mobilidade de iões é relevante não só para o desenho e modelação de detectores, mas também para a compreensão da formação dos impulsos gerados. Este trabalho foi desenvolvido no âmbito da nossa participação na colaboração NEXT e RD51 do CERN. A câmara de deriva de iões positivos utilizada nestes estudos, já existente no laboratório, permite determinar com precisão o tempo de deriva deste grupo de iões e consequentemente a sua velocidade de deriva e mobilidade. Determinada a mobilidade destes iões e utilizando a Lei de Blanc e o limite de polarização de Langevin é possível efectuar a sua identi ficação. No âmbito desta tese foram feitos estudos relativos a cinco misturas com interesse para as experiências mencionadas: Xe-N2, Xe-CO2, Xe-CF4, Ar-C2H6 and Ar-CH4. Neste estudo foi também veri ficada a validade do limite de polarização de Langevin para a estimativa da mobilidade de iões, tendo-se concluído que as suas limitações estão relacionadas essencialmente com a fraca polarizabilidade dos átomos ou moléculas envolvidos como é o caso do Ne, ou pela presença de inúmeros graus de liberdade internos nas mesmas que são responsáveis por reduzir a mobilidade em cerca de 10% em casos como o do dióxido de carbono, CO2. Esta informação torna-se especialmente relevante pois a introdução de correcções permite obter melhores estimativas para a mobilidade em casos onde não existem medidas experimentais.

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41

"Studies on high-pressure magnetron sputtering plasmas using laser-aided diagnostic techniques". Thesis, 2008. http://hdl.handle.net/2237/9685.

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Bin, Nayan Nafarizal. "Studies on high-pressure magnetron sputtering plasmas using laser-aided diagnostic techniques". Thesis, 2008. http://hdl.handle.net/2237/9685.

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Novikov, Dmitri V. "Pressure treatment of polytene chromosomes and computer vision techniques for high resolution cytogenetic studies /". 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3314860.

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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.
Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 2742. Adviser: Andrew Belmont. Includes bibliographical references (leaves 42-47) Available on microfilm from Pro Quest Information and Learning.

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44

MALONE, PATRICK VERNON. "HIGH-PRESSURE/HIGH-TEMPERATURE GAS-SOLUBILITY STUDY IN HYDROGEN-PHENANTHRENE AND METHANE-PHENANTHRENE SYSTEMS USING STATIC AND CHROMATOGRAPHIC TECHNIQUES". Thesis, 1987. http://hdl.handle.net/1911/16092.

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The design and discovery of sources for alternative energy such as coal liquefaction has become of major importance over the past two decades. One of the major problems in such design is the lack of available data, particularly, for gas solubility in polycyclic aromatics at high temperature and pressure. Static and gas-liquid partition chromatographic methods were used for the study of hydrogen-phenanthrene and methane-phenanthrene systems. The static data for these two binaries were taken along 398.2, 423.2, 448.2, 473.2 K isotherms up to 25.23 MPa. Pressure versus liquid mole fraction plots were presented as well as linear ln(f$\sbsp{\rm i}{\thinspace\rm g}$/x$\sb{\rm i}$) versus P-P$\sbsp{\rm s}{\rm vap}$ graphs. Using estimates of the partial molar volume in the liquid phase, V$\sbsp{\rm i}{\infty}$, the latter plots indicated both pressure and small liquid mole fraction deviations from ideal solution. Gas-liquid partition chromatography was used to study the infinite dilution behavior of methane, ethane, propane, n-butane, and carbon dioxide in the hydrogen-phenanthrene system as well as hydrogen, ethane, n-butane, and carbon dioxide in the methane-phenanthrene binary. The principle objective was to examine the role of the elution gas. Temperatures were along the same isotherms as the static data and up to 20.77 MPa. Comparison of the hydrogen and methane elution gas results indicated that the PK$\sbsp{\rm i}{\infty}$ product increases much more rapidly with pressure for the methane carrier data. However, plots of ln(PK$\sbsp{\rm i}{\infty}\phi\sbsp{\rm i}{\infty}$) versus P-P$\sbsp{\rm s}{\rm vap}$ were the same in both elution gases for ethane and n-butane. Using V$\sbsp{\rm i}{\infty}$ estimates, the plots displayed deviations from ideal solution due to pressure effects alone, with carrier gas absorption having essentially no effect. This was contrary to previous conclusions for infinitely dilute data in the hydrogen-9-methylanthracene system. Analysis of this data also indicated hydrogen solubility was not important. With the exception of carbon dioxide, Henry's constants were calculated for all systems. Expressions for the heat of solution as a function of pressure were derived for both binary and chromatographic data. Estimates of $\Delta$H$\sbsp{\rm i}{\rm sol}$ at high pressure were presented.

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45

Saouane, Sofiane. "Extending the Search Space for Novel Physical Forms of Pharmaceuticals and Biomolecules using High-Pressure Techniques". Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0028-878A-D.

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(6717671), Robert Z. Zhang. "Analysis Techniques for Characterizing High Power Turbulent Swirl Flames". Thesis, 2019.

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High speed laser diagnostics are performed in two vastly differing swirl combustors at conditions relevant for industrial gas turbines. This high quality data can not only be used to elucidate key features of the flow field but also for validation of computational models simulating turbulence, chemistry, and their interactions. The first combustor is a piloted lean premixed prevaporized arrangement common in aviation applications. Fueling parameters are varied and sensitivity towards the pilot flame is observed. Conditioning to the stagnation line demonstrates increased fluctuations of shear and rotation in the inner shear layer when the pilot fueling is reduced.

The second flame has a simpler configuration with a single swirler and combusting natural gas. Thermoacoustic instability coupled to a helical precessing vortex core is found at certain conditions. Sparse Dynamic Mode Decomposition and phase averaging is applied to the velocity fields to create a three dimensional reconstruction of the helical vortex core in a non-precessing reference frame. Heat release is found to be correlated to the interaction strength of the central recirculation bubble and the helical vortex core.

Finally, intermittent phenomena within a thermoacoustic instability are examined. The most prominent deviation is that the flame is observed to randomly lift and reattach. In addition, a convolutional neural network is employed to extract the morphology from otherwise qualitative OH species imaging. The average characteristics of the lifted and attached flame are compared and dramatic differences are found. All of the flow structures have been altered such as the precessing vortex core being greatly intensified during flame lift-off. Evaluating the average events before flame lift-off revealed the importance of conditions at the combustor inlet. However, evidence for a future reattachment event was only found with a less spatially confined perspective. In addition, transition to lift-off was very sudden while reattachment was far slower.

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"The Study on Work Pressure and Coping Strategies of Junior High School Natural Science and Life Techniques Teachers". 2005. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0021-2004200716161771.

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許總智. "The Study on Work Pressure and Coping Strategies of Junior High School Natural Science and Life Techniques Teachers". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/44463978260406976925.

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碩士
國立臺灣師範大學
工業教育學系在職進修碩士班
94
This study aims at exploring the work pressure and coping strategies of junior high school natural science and life techniques teachers particularly in the curriculum for Grades 1 to 9 and further exploring the relations between the work pressure and the coping strategies. This study adapts questionnaire survey and conducts it by taking as the population the natural science and life techniques teachers in junior high schools in the region including three counties: Hsinchu, Miaoli, and Taoyuan, and one city – Hsinchu City. 497 valid questionnaires were collected back from 800 teachers as the population thus created a valid rate of 62.1%. This study analyzes and tests the questionnaire results by making use of statistical methods such as Frequency Distribution, Percentage, Mean, Standard Deviation, Independent-Sample t Test, One-Way Analysis of Variance and Scheffé Method – Post Hoc Comparison and comes to the conclusions as the follows: 1. In terms of work pressure for the junior high school natural science and life techniques teachers from implementing the curriculum for Grades 1 to 9, the pressure value demonstrates to be moderate to high, and among others the pressure from “teaching activities” is the highest while that from “curriculum design” the lowest. 2. In terms of application frequency of coping strategies against work pressure, from implementing the curriculum for Grades 1 to 9 for the junior high school natural science and life techniques teachers, the frequency result demonstrate to be above mean value, and among all strategies “Problem-solving” strategy is of the highest frequency while “Emotion Reducing” strategy the lowest frequency. 3. In terms of perception affecting factors to the work pressure for the junior high school natural science and life techniques teachers, such as gender, post, workshop hours, teaching pattern, scale of school, school campus location, the overall measure demonstrates the female teachers perceive higher work pressure than the male teachers do; “teachers with second post in administration” perceive higher work pressure than “teachers with second post in class teacher”; teachers “with workshop hours over 40 hours” perceive apparently much higher work pressure than those “with workshop hours below 40 hours”, the main reason could be teachers’ own responsibility for class arrangement.teachers “teaching general studies” perceive higher work pressure than those “teaching specific study”; science teachers with “24 or less classes” load perceives higher work pressure than those with “61 plus classes” load; and finally teachers working in “the school in rural area” perceive higher work pressure than those working in “the school in urban area” do. 4. In terms of work pressure coping strategy, the strategies vary to the teacher’s gender, post, expertise, teaching method and school campus locations. Female teachers demonstrate a higher application frequency of coping strategies than male teachers do; “specific subject teachers” demonstrate a higher application frequency of coping strategies than “the teachers with second post in administration”; teachers teaching “biology” demonstrate a higher application frequency of coping strategies than the teachers teaching “computer science”; teachers “teaching general studies” demonstrate higher application frequency of copy strategy than those “teaching specific study”; teachers working in school located in “urban” or “township” demonstrate higher application frequency of copy strategy than those working in schools in “rural area”. 5. In terms of difference in coping strategies, the intensity of perception of work pressure or the junior high school natural science and life techniques teachers from implementing the curriculum for Grades 1 to 9, teachers under higher work pressure demon strate coping strategy more freuently then those who under lower work pressure, has resulted in obvious difference in work pressure coping strategies. At last this study tries to offer some suggestions, for reference purpose, to the educational authorities, school administration units, natural science teachers of junior high schools and the researchers interested in this domain in the coming future.

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Olsen, Lawrence Robert. "The defect chemistry and diffusion of fluoride interstitials in Eu³⁺ doped CaF₂ studied with site selective spectroscopy and high pressure techniques". 1995. http://catalog.hathitrust.org/api/volumes/oclc/34332428.html.

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Thesis (Ph. D.)--University of Wisconsin--Madison, 1995.
Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 174-176).

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AMARU', Fabio. "Multimodal techniques for biomedical image processing". Doctoral thesis, 2014. http://hdl.handle.net/11562/693559.

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Il lavoro di dottorato ha coinvolto tre principali aree di ricerca biomedica. Nella prima area, abbiamo mirato a valutare se le misure del tempo di rilassamento T1 in Risonanza Magnetica possono contribuire ad individuare dei predittori strutturali di lievi disturbi cognitivi in pazienti con forma Recidivante-Remittente di Sclerosi Multipla(RRMS). Ventinove controlli sani (HC) e quarantanove RRMS pazienti sono stati sottoposti a Risonanza magnetica a 3T per acquisire in maniera ottimale per la zona corticale e per la sostanza bianca (WML), i tempi di rilassamento T1 (rt), la conta delle lesioni e il volume. Nella WML e in quelle di tipo CL I (sostanza bianca - grigia mista), i T1 rt z-score sono risultati, significativamente, più lunghi rispetto ai tessuti dei controlli HC (p<0.001 e p<0.01, rispettivamente), indice di un’impoverimento del tessuto cerebrale. L'analisi di regressione multivariata ha rivelato che: i T1 rt z-score nelle lesioni corticali sono predittori indipendenti del recupero della memoria a lungo termine (p=0.01), i T1 z -score nella lesioni corticali della materia bianca sono predittori indipendenti del deficit relativi all’attenzione prolungata e all’elaborazione delle informazioni (p=0,02) ; Nella seconda, descriviamo un suscettometro biomagnetico a temperatura ambiente in grado di quantificare il sovraccarico di ferro nel fegato. Tramite un campo magnetico modulato elettronicamente, il sistema riesce a misurare segnali magnetici 108 volte più piccoli del campo applicato. Il rumore meccanico del suscettometro a temperatura ambiente viene minimizzato e il drift termico viene monitorato da un sistema automatico di bilanciamento. Abbiamo testato e calibrato lo strumento utilizzando un fantoccio riempito con una soluzione di esacloruro esaidrato II di ferro, ottenendo come correlazione R = 0,98 tra la massima risposta del suscettometro e la concentrazione di ferro. Queste misure indicano che per garantire una buon funzionamento dello strumento con una variabilità del segnale di uscita pari al 4-5%, eguale a circa 500ugr/gr di ferro, il tempo di acquisizione deve essere minore o uguale a 8 secondi. Nela terza area, un'analisi agli elementi finiti del modello 3D anatomicamente dettagliato del piede umano è il risultato finale della segmentazione 3D, secondo tecniche di ricostruzione applicate ad immagini standard DICOM di scansione a Tomografia Computerizzata, in congiunzione con la modellazione 3D assistita e dell’analisi agli elementi finiti (FEA). In questo modello la reale morfologia del cuscinetto adiposo plantare è stato considerata: è stato dimostrato giocare un ruolo molto importante durante il contatto con il terreno. Per ottenere i dati sperimentali da confrontare con le predizioni del modello 3D del piede, un esame posturografico statico su una pedana baropodometrica è stato effettuato. La pressione sperimentale del contatto plantare è risultata, qualitativamente, comparabile con i risultati predetti dall’analisi agli elementi finiti, principalmente, confrontando i valori sperimentali con i valori massimi delle pressioni in corrispondenza delle zona centrali del tallone e sotto le teste metatarsali.
The PhD work involved three main biomedical research areas. In the first, we aimed at assessing whether T1 relaxometry measurements may help identifying structural predictors of mild cognitive impairments in patients with relapsing-remitting multiple sclerosis. Twenty-nine healthy controls and forty-nine RRMS patients underwent at high resolution 3T magnetic resonance imaging to obtain optimal cortical and white matter lesion count/volume as well as T1 relaxation times (rt). In WML and CL type I (mixed white-gray matter), T1 rt z-scores were significantly longer than in HC tissue (p<0.001 and p<0.01 respectively), indicating loss of structure. Multivariate analysis revealed T1 rt z-scores in CL type I were independent predictors of long term retrieval (p=0.01), T1 z-score relaxation time in white matter cortical lesions were independent predictors of sustained attention and information processing (p=0.02); In the second, we describe a biomagnetic susceptometer at room-temperature to quantify liver iron overload. By electronically modulated magnetic field, the magnetic system measure magnetic signal 108 times weaker than field applied. The mechanical noise of room-temperature susceptometer is cancelled and thermal drift is monitored by an automatic balance control system. We have tested and calibrated the system using cylindrical phantom filled with hexahydrated iron II choloride solution, obtaining the correlation (R=0.98) of the maximum variation in the responses of the susceptometer. These measures indicate that the acquisition time must be less than 8 seconds to guarantee an output signal variability to about 4-5%, equal to 500ugr/grwet of iron. In the third, a 3D anatomically detailed finite element analysis human foot model is final results of density segmentation 3D reconstruction techiniques applied in Computed Tomography(CT) scan DICOM standard images in conjunctions with 3D finite element analysis(FEA) modeling. In this model the real morphology of plantar fat pad has been considered: it was shown to play a very important role during the contact with the ground. To obtain the experimental data to compare the predictions of 3D foot model, a posturography static examination test on a baropodometric platform has been carried. The experimental plantar contact pressure is, qualitatively, comparable with FEA predicted results, nominally, the peak pressure value zones at the centre heel region and beneath the metatarsal heads.

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