High Pressure Speed of Sound and Related Thermodynamic Properties of 1-Alkyl-3-methylimidazolium Bis[(trifluoromethyl)sulfonyl]imides (from 1-Propyl- to 1-Hexyl-)

The knowledge of thermodynamic high-pressure speed of sound in ionic liquids (ILs) is a crucial way either to study the nature of the molecular interactions, structure and packing effects or to determine other key thermodynamic properties of ILs essential for their applications in any chemical and industrial processes. Herein, we report the speed of sound as a function temperature at pressures up to 101 MPa in four ultrapure ILs: 1-propyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, 1-pentyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, and 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, taking into consideration their relaxation behavior. Additionally, to further improve the reliability of the speed of sound results, the density, isentropic compressibility, and isobaric heat capacity as a function of temperature and pressure are calculated using an acoustic method.

Examination of stress and strain in glass structures during pressure treatment using FEM simulation and experimental tests

Otto-von-Guericke-Universität Magdeburg, Fakultät für Maschinenbau, Dissertation, 2016

Experimental viscosity measurements of biodiesels at high pressure

The viscosity of biodiesels of soybean and rapeseed biodiesels blended with mineral diesel fuel were measured at pressures of up to 200 MPa. Using a falling sinker-type viscometer reproducible viscosity data were obtained based on the time taken for a sinker to descend a fixed distance down an enclosed tube under the influence of gravity. Measurements were taken using pressures which correspond to those of interest in automotive common rail diesel engines, and at temperatures of between 25oC and 80oC. In all cases, the viscosity of the biodiesel blends were found to increase exponentially for which the blends were noted as being more viscous than pure mineral fuels. A pressure-freezing effect was not observed for the blends.

Flame-propagation rates in ammonia-air combustion at high pressure

The reluctance of ammonia to be ignited easily and the necessity to advance the spark for optimum performance in combustion engines led to this investigation. Ionization gap techniques showed that long induction times and slow flame speed were both contributors to the observed phenomena. The most important factor in determining combustion characteristics of ammonia was found to be the extent of predissociation prior to attempted ignition. There was evidence from combustion gas analysis that NO + was the probable most abundant ion contributing to succesful application of the ionization gap techniques, and that the NO + was probably produced in the pyrolysis of ammonia rather than by equilibrium reactions. © 1967 Combustion Institute.

Limitations of high pressure sputtering for amorphous silicon deposition

Amorphous silicon thin films were deposited using the high pressure sputtering (HPS) technique to study the influence of deposition parameters on film composition, presence of impurities, atomic bonding characteristics and optical properties. An optical emission spectroscopy (OES) system has been used to identify the different species present in the plasma in order to obtain appropriate conditions to deposit high purity films. Composition measurements in agreement with the OES information showed impurities which critically depend on the deposition rate and on the gas pressure. We prove that films deposited at the highest RF power and 3.4 × 10^−2 mbar, exhibit properties as good as the ones of the films deposited by other more standard techniques.

Applications of synchrotron x-ray powder diffraction in hydrated cements: high-resolution and high-pressure studies

The main aim of this study is to apply synchrotron radiation techniques for the study of hydrated cement pastes. In particular, the tetracalcium aluminoferrite phase, C4AF in cement nomenclature, is the major iron-containing phase in Ordinary Portland Cement (OPC) and in iron rich belite calcium sulfoaluminate cements. In a first study, the hydration mechanism of pure tetracalcium aluminoferrite phase with water-to-solid ratio of 1.0 has been investigated by HR-SXRPD (high resolution synchrotron X-ray powder diffraction). C4AF in the presence of water hydrates to form mainly an iron-containing hydrogarnet-type (katoite) phase, C3A0.84F0.16H6, as single crystalline phase. Its crystal structure and stoichiometry were determined by the Rietveld method and the final disagreement factors were RWP=8.1% and RF=4.8% [1]. As the iron content in the product is lower than that in C4AF, it is assumed that part of the iron also goes to an amorphous iron rich gel, like the hydrated alumina-type gel, as hydration proceeds. Further results from the high-resolution study will be discussed. In a second study, the behavior of pure and iron-containing katoites (C3AH6 and C3A0.84F0.16H6) under pressure have been analyzed by SXRPD using a diamond anvil cell (DAC) and then their bulk moduli were determined. The role of the pressure transmitting medium (PTM) has also been studied. In this case, silicone oil as well as methanol/ethanol mixtures have been used as PTM. Some “new peaks” were detected in the pattern for C3A0.84F0.16H6 as pressure increases, when using ethanol/methanol as PTM. These new peaks were still present at ambient pressure after releasing the applied pressure. They may correspond to crystalline nordstrandite or doyleite from the crystallization of amorphous aluminium hydroxide. The results from the high-pressure study will also be discussed.

Estudo do processo de combustão in-situ em reservatórios maduros de óleos médios e leves (high pressure air injection)

Nearly 3 x 1011 m3 of medium and light oils will remain in reservoirs worldwide after conventional recovery methods have been exhausted and much of this volume would be recovered by Enhanced Oil Recovery (EOR) methods. The in-situ combustion (ISC) is an EOR method in which an oxygen-containing gas is injected into a reservoir where it reacts with the crude oil to create a high-temperature combustion front that is propagated through the reservoir. The High Pressure Air Injection (HPAI) method is a particular denomination of the air injection process applied in light oil reservoirs, for which the combustion reactions are dominant between 150 and 300°C and the generation of flue gas is the main factor to the oil displacement. A simulation model of a homogeneous reservoir was built to study, which was initially undergone to primary production, for 3 years, next by a waterflooding process for 21 more years. At this point, with the mature condition established into the reservoir, three variations of this model were selected, according to the recovery factors (RF) reached, for study the in-situ combustion (HPAI) technique. Next to this, a sensitivity analysis on the RF of characteristic operational parameters of the method was carried out: air injection rate per well, oxygen concentration into the injected gas, patterns of air injection and wells perforations configuration. This analysis, for 10 more years of production time, was performed with assistance of the central composite design. The reservoir behavior and the impacts of chemical reactions parameters and of reservoir particularities on the RF were also evaluated. An economic analysis and a study to maximize the RF of the process were also carried out. The simulation runs were performed in the simulator of thermal processes in reservoirs STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator) from CMG (Computer Modelling Group). The results showed the incremental RF were small and the net present value (NPV) is affected by high initial investments to compress the air. It was noticed that the adoption of high oxygen concentration into the injected gas and of the five spot pattern tends to improve the RF, and the wells perforations configuration has more influence with the increase of the oil thickness. Simulated cases relating to the reservoir particularities showed that smaller residual oil saturations to gas lead to greater RF and the presence of heterogeneities results in important variations on the RF and on the production curves

High Pressure and Low Temperature Study of Ammonia Borane and Lithium Amidoborane

Hydrogen has been considered as a potentially efficient and environmentally friendly alternative energy solution. However, one of the most important scientific and technical challenges that the “hydrogen economy” faces is the development of safe and economically viable on-board hydrogen storage for fuel cell applications, especially to the transportation sector. Ammonia borane (BH3NH3), a solid state hydrogen storage material, possesses exceptionally high hydrogen content (19.6 wt%).However, a fairly high temperature is required to release all the hydrogen atoms, along with the emission of toxic borazine. Recently research interests are focusing on the improvement of H2 discharge from ammonia borane (AB) including lowering the dehydrogenation temperature and enhancing hydrogen release rate using different techniques. Till now the detailed information about the bonding characteristics of AB is not sufficient to understand details about its phases and structures. Elemental substitution of ammonia borane produces metal amidoboranes. Introduction of metal atoms to the ammonia borane structure may alter the bonding characteristics. Lithium amidoborane is synthesized by ball milling of ammonia borane and lithium hydride. High pressure study of molecular crystal provides unique insight into the intermolecular bonding forces and phase stability. During this dissertation, Raman spectroscopic study of lithium amidoborane has been carried out at high pressure in a diamond anvil cell. It has been identified that there is no dihydrogen bond in the lithium amidoborane structure, whereas dihydrogen bond is the characteristic bond of the parent compound ammonia borane. It has also been identified that the B-H bond becomes weaker, whereas B-N and N-H bonds become stronger than those in the parent compound ammonia borane. At high pressure up to 15 GPa, Raman spectroscopic study indicates two phase transformations of lithium amidoborane, whereas synchrotron X-ray diffraction data indicates only one phase transformation of this material. Pressure and temperature has a significant effect on the structural stability of ammonia borane. This dissertation explored the phase transformation behavior of ammonia borane at high pressure and low temperature using in situ Raman spectroscopy. The P-T phase boundary between the tetragonal (I4mm) and orthorhombic (Pmn21) phases of ammonia borane has been determined. The transition has a positive Clapeyron slope which indicates the transition is of exothermic in nature. Influence of nanoconfinemment on the I4mm to Pmn21 phase transition of ammonia borane was also investigated. Mesoporus silica scaffolds SBA-15 with pore size of ~8 nm and MCM-41 with pore size of 2.1-2.7 nm, were used to nanoconfine ammonia borane. During cooling down, the I4mm to Pmn21 phase transition was not observed in MCM-41 nanoconfined ammonia borane, whereas the SBA-15 nanocondfined ammonia borane shows the phase transition at ~195 K. Four new phases of ammonia borane were also identified at high pressure up to 15 GPa and low temperature down to 90 K.

Quenching of excited states of red-pigment zinc protoporphyrin IX by hemin and natural reductors in dry-cured hams

Zinc protoporphyrin IX (ZnPP), the major red pigment in hams dry-cured without nitrates/nitrites, is an efficient photosensitizer, which upon absorption of visible light forms short-lived excited singlet state ((1)ZnPP*) and by intersystem crossing yields the very reactive triplet-excited state ((3)ZnPP*). Using nano-second laser flash photolysis and transient absorption spectroscopy NADH, ascorbic acid, hemin and dehydroascorbic acid were each found to be efficient quenchers of (3)ZnPP*. The deactivation followed, in homogeneous dimethyl sulfoxide (DMSO) or DMSO:water (1:1) solutions, second-order kinetics. The rate constant for ascorbic acid and NADH for reductive quenching of (3)ZnPP* was at 25 A degrees C found to be 7.5 +/- A 0.1 x 10(4) L mol(-1) s(-1) and 6.3 +/- A 0.1 x 10(5) L mol(-1) s(-1), respectively. The polyphenols catechin and quercetin had no effect on (3)ZnPP*. The quenching rate constant for oxidative deactivation of (3)ZnPP* by dehydroascorbic acid and hemin was at 25 A degrees C: 1.6 +/- A 0.1 x 10(5) L mol(-1) s(-1) and 1.47 +/- A 0.1 x 10(9) L mol(-1) s(-1), respectively. Oxidized glutathione did not act as an oxidative quencher for (3)ZnPP*. After photoexcitation of ZnPP to (1)ZnPP*, fluorescence was only found to be quenched by the presence of hemin in a diffusion-controlled reaction. The efficient deactivation of (3)ZnPP* and (1)ZnPP* by the metalloporphyrin (hemin) naturally present in meat may accordingly inherently protect meat proteins and lipids against ZnPP photosensitized oxidation.

Estratégias para conservação de carne armazenada sob refrigeração: embalagem em atmosfera modificada e processamento em alta pressão

A busca por produtos mais saudáveis e minimamente processados tem levado indústrias e pesquisadores a estudarem novas formas de preservação de alimentos. Os objetivos deste trabalho foram: 1) avaliar o efeito da embalagem com atmosfera modificada (ATM) na preservação de lombo ovino armazenado sob refrigeração e 2) Avaliar o efeito do processamento em alta pressão na conservação de carne bovina marinada e com teor de sódio reduzido. Em ambas as pesquisas, músculos Longissimus lumborum foram submetidos à contagem microbiana, avaliação de cor, pH, oxidação lipídica (TBARS), perdas por cocção (PPC) e força de cisalhamento. Para o estudo do efeito da embalagem em atmosfera modificada, as amostras foram acondicionadas em cinco sistemas de ATM, 15% O2 + 85% CO2; 30% de O2 + 70% de CO2; 45% de O2 + 55% de CO2; 60% de O2 + 40% de CO2 e Vácuo (controle) e armazenadas a 1°C durante 21 dias. As análises de cor, pH, TBARS, PPC e força de cisalhamento foram realizadas a cada sete dias e as microbiológicas duas vezes por semana. Diferentes concentrações de oxigênio dentro da embalagem trouxeram diferença significativa na intensidade de cor vermelha das carnes armazenadas em ATM. Até o sétimo dia de estocagem tratamentos com maior quantidade de O2 apresentaram melhor coloração, após esse período embalagens a vácuo conseguiram preservar melhor a mioglobina. Diferentes concentrações gasosas não trouxeram causaram diferença (p> 0,05) no pH da carne entre tratamentos. Nenhuma diferença significativa entre tratamentos foi encontrada para amostras embaladas em ATM nos parâmetros perda de peso por cocção e força de cisalhamento. A embalagem em atmosfera modificada foi capaz de retardar o crescimento da microbiota presente na carne. Isso levou á preservação da amostra por até 18 dias sob refrigeração, enquanto amostras a vácuo tiveram uma vida útil de 11 dias. Para o estudo do efeito da alta pressão em carne marinada com baixo teor de sódio, as carnes foram inoculadas com 106 UFC/g de carne com E. faecium e Listeria innocua e em seguida marinadas durante 18 horas, a 4°C, em diferentes soluções: 1% NaCl + 1% ácido cítrico, 1% NaCl + 2% ácido cítrico, 2% NaCl + 2% ácido cítrico e 2% NaCl + 2% ácido cítrico. Após a marinação as amostras foram submetidas ao tratamento nas seguintes pressões: Zero (controle), 300MPa, 450Mpa, 600MPa. As análises físico-químicas e microbiológicas foram realizadas logo após o tratamento. O tratamento em alta pressão foi capaz de reduzir a população microbiana em até seis ciclos logarítmicos quando 600Mpa foram aplicados em todas as soluções estudadas. A não aplicação de alta pressão proporcionou a redução de apenas um ciclo log na população de E. faecium quando as carnes foram marinadas com 2% NaCl + 2% ácido cítrico. A alta pressão e as diferentes concentrações de sal e ácido, não trouxeram diferença significativa na coloração das amostras. Já o maior teor de ácido cítrico na marinada causou maior (p<0,05) redução do pH da carne em comparação com as amostras em baixa concentração de ácido. Os experimentos demonstraram que a tanto embalagem a vácuo quanto a aplicação de ácido cítrico foram eficientes em retardar a oxidação lipídica. Pressões de 600Mpa tornaram a carne significativamente mais dura que as demais pressões aplicadas. Os resultados demonstraram a possibilidade de extensão da vida útil da carne refrigerada através da aplicação de diferentes tecnologias: a embalagem com atmosfera modificada para carne fresca e processamento em alta pressão de carnes marinadas com reduzido teor de sal.

Effect of small, acid-soluble proteins on spore resistance and germination under a combination of pressure and heat treatment

To find the range of pressure required for effective high-pressure inactivation of bacterial spores and to investigate the role of alpha/beta-type small, acid-soluble proteins (SASP) in spores under pressure treatment, mild heat was combined with pressure (room temperature to 65 degrees C and 100 to 500 MPa) and applied to wild-type and SASP-alpha(-/)beta(-) Bacillus subtilis spores. On the one hand, more than 4 log units of wild-type spores were reduced after pressurization at 100 to 500 MPa and 65 degrees C, On the other hand, the number of surviving mutant spores decreased by 2 log units at 100 MPa and by more than 5 log units at 500 MPa. At 500 MPa and 65 degrees C, both wild-type and mutant spore survivor counts were reduced by 5 log units. Interestingly, pressures of 100, 200, and 300 MPa at 65 degrees C inactivated wild-type SASP-alpha(+)/beta(+) spores more than mutant SASP-alpha(-)/beta(-) spores, and this was attributed to less pressure-induced germination in SASP-alpha(-)/beta(-) spores than in wild-type SASP-alpha(+)/beta(+) spores. However, there was no difference in the pressure resistance between SASP-alpha(+)/beta(+) and SASP-alpha(-)/beta(-) spores at 100 MPa and ambient temperature (approximately 22 degrees C) for 30 min. A combination of high pressure and high temperature is very effective for inducing spore germination, and then inactivation of the germinated spore occurs because of the heat treatment. This study showed that alpha/beta-type SASP play a role in spore inactivation by increasing spore germination under 100 to 300 MPa at high temperature.

The relationship between membrane damage, release of protein and loss of viability in Escherichia coli exposed to high hydrostatic pressure

The aim of this work was to examine a possible association between resistance of two Escherichia coli strains to high hydrostatic pressure and the susceptibility of their cell membranes to pressure-induced damage. Cells were exposed to pressures between 100 and 700 MPa at room temperature (~20C) in phosphate-buffered-saline. In the more pressure-sensitive strain E. coli 8164, loss of viability occurred at pressures between 100 MPa and 300 MPa and coincided with irreversible loss of membrane integrity as indicated by uptake of propidium iodide (PI) and leakage of protein of molecular mass between 9 and 78 kDa from the cells. Protein release increased to a maximum at 400 MPa then decreased, possibly due to intracellular aggregation at the higher pressures. In the pressure-resistant strain E. coli J1, PI was taken up during pressure treatment but not after decompression indicating that cells were able to reseal their membranes. Loss of viability in strain J1 coincided with the transient loss of membrane integrity between approximately 200 MPa and 600 MPa. In E. coli J1 leakage of protein occurred before loss of viability and the released protein was of low molecular mass, between 8 and 11 kDa and may have been of periplasmic origin. In these two strains differences in pressure resistance appeared to be related to differences in the ability of their membranes to withstand disruption by pressure. However it appears that transient loss of membrane integrity during pressure can lead to cell death irrespective of whether cells can reseal their membranes afterwards.

High hydrostatic pressure resistance of Campylobacter jejuni after different sublethal stresses

Aims: To study the development of resistance responses in Campylobacter jejuni to High Hydrostatic Pressure (HHP) treatments after the exposure to different stressful conditions that may be encountered in food processing environments, such as acid pH, elevated temperatures and cold storage. Methods and Results: C. jejuni cells in exponential and stationary growth phase were exposed to different sublethal stresses (acid, heat and cold shocks) prior to evaluate the development of resistance responses to HHP. For exponential-phase cells, neither of the conditions tested increased nor decreased HHP resistance of C. jejuni. For stationary-phase cells, acid and heat adaptation sensitized C. jejuni cells to the subsequent pressure treatment. On the contrary, cold-adapted stationary-phase cells developed resistance to HHP. Conclusions: Whereas C. jejuni can be classified as a stress sensitive microorganism, our findings have demonstrated that it can develop resistance responses under different stressing conditions. The resistance of stationary phase C. jejuni to HHP was increased after cells were exposed to cold temperatures. Significance and Impact of the Study: The results of this study contribute to a better knowledge of the physiology of C. jejuni and its survival to food preservation agents. Results here presented may help in the design of combined processes for food preservation based on HHP technology.