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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Fresh and fresh-cut tomatoes have been associated with numerous outbreaks of salmonellosis in recent years. While the exact routes of contamination are unknown, high pressure processing (HPP) is being evaluated as a post harvest treatment to eliminate Salmonella enterica from tomatoes. The objectives of the study were to determine the potential for of HPP to reduce S. enterica serovars Newport, Javiana, Braenderup and Anatum (clinical isolates from tomato outbreaks) in tryptic soy broth (TSB) and to determine the effect of HPP to reduce the most pressure resistant S. enterica serovar from fresh diced and whole tomatoes. Five ml portions of broth containing 8 log CFU/ml of one of the four serovars (nalidixic acid resistant) were packaged in sterile stomacher bags and subjected to one of three different pressures (350, 450, or 550 MPa) for 120s. Samples were enumerated by surface plating onto tryptic soy agar supplemented with 50 ppm nalidixic acid (TSAN) and incubated at 35°C for 48 hours. The most pressure resistant S. enterica serovar evaluated was Braenderup. Subjecting the broth culture to 350, 450 and 550 MPa resulted in a 4.53, 5.74 and 7.09 log reduction in S. Braenderup, respectively. Diced tomatoes (150g) and whole red round tomatoes (150g; packaged in 350ml of 1% CaCl2) were inoculated with S. Braenderup, to obtain 6 log CFU/g throughout the sample and subjected to the same pressure treatments as described above. After HPP, diced tomatoes were homogenized for 1 minute and then plated on TSAN. Whole tomatoes were surface sampled, and then homogenized for 1 minute. Surface and homogenate samples were plated on TSAN supplemented with 1% pyruvic acid (TSANP). Significant reductions of S. Braenderup concentrations in diced tomatoes (P < 0.05) were seen after processing at 350 (0.46 CFU/g), 450 (1.44 log CFU/g), and 550 MPa (3.67 log CFU/g). In whole tomatoes, significant reductions (P < 0.05) were also seen at 350 (1.41 log CFU/g), 450 (2.25 log CFU/g) and 550 MPa (3.35 log CFU/g). There were no differences in visual appearance between fresh and HPP diced and whole tomatoes. HPP may be an effective post harvest strategy to reduce low levels of S. enterica contamination in diced tomatoes. / Master of Science in Life Sciences

Topic of master´s thesis is design of pressure washer trailer system which is independent of external sources of energy and water. Its compact dimensions and relatively low weight can provide use with standard car. Design must respect main requirements of ergonomic, technology and esthetic aspects.

Master of Science / Food Science Institute / James L. Marsden / Consumers demand for high quality, natural and fresh tasting food, free from preservatives and additives, with a clean label and an extended shelf life has increased. High pressure processing (HPP), also known as high hydrostatic pressure, is a non-thermal food preservation technique that has the potential to meet these demands. It is an opportunity to preserve food, by applying intensive pressure in the range of 300-900 MPa, without adversely affecting organoleptic, textural and nutritional qualities as thermal processing like pasteurization and sterilization may do. In a typical high pressure batch cycle, the food prepackaged in a high-barrier flexible pouch or a plastic container is loaded into a perforated basket that goes into the pressure vessel; the pressure is then increased to the processing target pressure (come-up time); the product is held at the desired pressure for 3 to 10 minutes (pressure holding time); after which the pressure is released in usually few seconds (decompression time) and the product can be unloaded at this point. The pressure is applied uniformly in all directions simultaneously and this is known as isostatic pressure. Pressurization is usually accompanied by a moderate and uniform temperature increase called adiabatic heating. However, the food product usually rapidly returns to its initial temperature at decompression. With the recent shift in consumer lifestyle toward healthy living and healthier food, the consumption of raw fruits and vegetables has increased in popularity. However, as per the Centers of Disease Control and Prevention, fruits and vegetables have recently been associated with multiple foodborne disease outbreaks; the effect of high pressure processing on microbial safety, quality and sensory characteristics of fruits and vegetables has therefore been widely investigated as an alternative to traditional food processing and preservation methods. HPP inactivates microorganisms and quality-deteriorating enzymes and has limited effects on covalent bonds resulting in minimal modifications of food-quality attributes such as color, flavor and nutritional values. However, depending on the fruit or vegetable, high pressure could induce chemical or biochemical reactions that can affect their quality attributes.

A growing field of research has evolved around the design and synthesis of a variety of porous metal-organic framework (MOF) materials. Some of the most promising areas for which these materials are potentially useful candidates include gas-separation, heterogeneous catalysis, and gas-storage, and all of these applications involve placing the MOF under pressure. There is clearly a need to understand the structural response of MOFs to applied pressure. Nevertheless, hitherto there are very few published investigations dedicated to determining the behaviour of porous hybrid materials under pressure. Through the use of high-pressure single-crystal X-ray diffraction studies, a series of MOF materials have been studied. Here we present the effect of pressure on a series of MOFs. In chapter 2, the effect of pressure on the prototypical MOF called MOF-5 was studied experimentally from ambient pressure to 3.2 GPa. Here, application of pressure was driven by the hydrostatic medium being forced into the pores of the MOF, which altered the mechanical properties of MOF-5, in particular, medium inclusion delayed the onset of amorphization. Complementary computational analysis was also performed to elucidate further the effect of medium inclusion on compressive behaviour. Detailed structural data was also collected as a function of pressure on the MOF Cu-btc. Application of pressure caused solvent to be squeezed into the pores (like MOF-5) until a phase transition occurred, driven by the sudden compression and expansion of equatorial and axial Cu–O bonds. High-pressure post-synthetic modification of a MOF is reported for the first time. On application of pressure of 0.2 GPa to the Cu-based MOF called STAM-1, a ligand exchange reaction takes place resulting in a change in pore size, shape, and hydrophilicity of the resulting pores. Here, we also demonstrate the ability to force hydrophilic molecules into hydrophobic pores using pressure, counteracting the hydrophobic effect. A high-pressure combined experimental and computational study has been carried to probe the effect of pressure on ‘breathing’ mechanisms in a zeolitic imidazolate framework (or ZIF) called ZIF-8. The penetration of guest molecules and the accommodation of pressure are shown to be inextricably linked to the rotation of methylimidazolate groups in the structure. Finally, the application of pressure to the MOF Sc₂BDC₃ and the nitro functionalized derivative Sc₂(NO₂-BDC)₃ was also studied. Here, the effect of chemical modification of the organic ligand, whilst maintaining framework topology, has been investigated as it pertains to compressibility. Directionality of compression is observed and this is rationalized with respect to the framework topology and medium inclusion/exclusion.

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