Dissertations / Theses on the topic 'Dehydration'

La habilidad de las levaduras de superar la deshidratación y de reactivar su metabolismo después de la rehidratación tiene una importancia en la industria de los alimentos y en la biotecnología. Nosotros hemos dirigido nuestro trabajo a mejorar la viabilidad y vitalidad de las levaduras después de la rehidratación. Se realizaron estudios desde el punto de vista fisiológico de las levaduras durante la optimización de las condiciones de rehidratación y estudios moleculares como la determinación de los genes esenciales de respuesta a Secado y Rehidratación (SR) y la caracterización de la muerte celular a consecuencia del SR. Se sobre expresaron genes que codifican péptidos que permiten superar la viabilidad alcanzada por las levaduras bajo estas condiciones de estrés.
Hipótesis de partida:
Algunos metabolitos y genes esenciales de respuesta a estrés por secado y rehidratación permiten a las levaduras tolerar la desecación
The ability of yeast to overcome dehydration and restart metabolism after rehydration has an importance in the food industry and biotechnology. We have directed our work to improve the viability and vitality of the yeast after rehydration. The studies were conducted in one hand from the physiological point of view to optimize rehydration conditions, and in the other hand from the molecular point of view. We identified the essential genes in response to drying and rehydration and its role in yeast cell death. Moreover we study the effect of over expressed some of this genes on yeast desiccation tolerance.
Hypothesis:
Some metabolites and essential genes in response to stress during drying and rehydration allow yeasts tolerate desiccation.

Les années 1990 ont été marquées par le développement de la Chimie Verte avec les premiers travaux sur le sujet et l’introduction des Douze Principes. Depuis, le nombre de recherches sur la Chimie Verte n’a cessé de croître. Ces travaux de thèse portent sur le développement de méthodes de déshydratation dans le but de former des molécules à haute valeur ajoutée en utilisant les Douze Principes de la Chimie Verte en tant que ligne directrice. Deux molécules cibles ont été sélectionnées : (i) le phénylacétaldéhyde, obtenu par déshydratation du 1-phényléthane-1,2-diol, qui est utilisé dans la composition de parfums, de médicaments, d’insecticides, etc., ou en tant qu’intermédiaire réactionnel ; et (ii) le furfural, formé par la triple déshydratation du D-xylose (monomère principal des hémicelluloses), qui peut être utilisé comme solvant sélectif ou comme molécule plateforme pour produire une large gamme de composés d’intérêt. Plusieurs points-clés ont été identifiés pour concevoir des procédés de déshydratation verts: le solvant (l’eau ou le solvant éco-compatible CPME), la méthode d’activation (utilisation d’irradiation micro-ondes ou d’un réacteur en flux continu) et le catalyseur (chlorures de métaux ou résine échangeuse d’ions)
The 1990s have witnessed the development of Green Chemistry with the first researches on the subject and the introduction of the Twelve Principles. Since then, the number of scientific works on Green Chemistry has continuously grown. This PhD work focus on the development of dehydration methods to form high added value molecules by using the Twelve Principles of Green Chemistry as a guiding framework. Two target molecules were selected: (i) phenylacetaldehyde, obtained by the dehydration 1-phenylethane-1,2-diol, which is used in perfume compositions, for the preparation of pharmaceuticals, insecticides, etc., or as a chemical intermediate; and (ii) furfural, formed thanks to the triple dehydration of D-xylose (the main sugar unit of hemicellulose), which can be used as a selective solvent or as a platform molecule to produce a wide range of high-value chemicals. The optimisation of green production processes was focused on several key points: solvents (water and the eco-friendly CPME), activation method (microwave irradiation and continuous flow) and catalysis (metal chlorides and ion-exchange resin)

The purpose of natural gas dehydration is to prevent condensation of water in production units and transport pipelines. Liquid water can cause severe problems such as corrosion and hydrate formation. The aim of this thesis is to evaluate various models used for simulation of triethylene glycol (TEG) dehydration plants by comparing simulation calculations to experimental and field data. Three different simulation tools are included in the evaluation: Pro/II (V9.1), Hysys (V8.3) and ProMax (V3.2). In Pro/II, the glycol package is applied for the simulations. Four different fluid packages are included in Hysys: Glycol Package (GP), Peng-Robinson (PR) and two versions of the Cubic-Plus-Association-model (CPA) developed at Technical University of Denmark (DTU, V3.8) and Statoil (NeqSim). Soave-Redlich-Kwong (SRK) and PR are included in ProMax. Statoil provided field data from Gullfaks A (March 2012) as a comparison for the simulation calculations. The dehydration unit on Gullfaks A utilizes an absorption process which consists of a contactor, a regenerator with condenser and reboiler, and a separate stripping column. TEG is used as absorbent. Relevant experimental data is also gathered and compared with the calculations done by the simulation tools. The thesis focuses on parameters relevant for gas dehydration: wet gas water content, dry gas water dew point, rich TEG composition, reboiler duty, lean TEG purity and TEG loss. Hysys CPA NeqSim proved to be the best suited fluid package for dehydration of natural gas using TEG as an absorbent. This fluid package provided results in good agreement with both experimental and field data for all relevant parameters. ProMax SRK and ProMax PR also provided accurate results, and only minor deviations were found such as a slightly high lean TEG purity. Both packages are well suited for dehydration of natural gas, and the simulations showed no significant difference between the two packages. Heating of TEG was shown to count for roughly 65 % of the calculated reboiler duty. Other heat consumptions were primarily related to evaporation of water (25 %). Pro/II and Hysys CPA DTU provided low reboiler duties. This was related to low calculated heat capacities of TEG. This was the only serious flaw discovered in Pro/II, making it better suited than both Hysys GP and Hysys PR, which provided inaccurate results for respectively wet gas water content and dry gas water dew point.The wet gas water content calculated by Hysys GP was 9 – 14 % lower than the field data. This was expected due to low calculated water content in methane. The low water content in wet gas in Hysys GP had a slight influence on the dry gas water dew point, reducing it by roughly 4 %. For the composition and flow rate of lean TEG given in the field data, the calculated dry gas water dew point was shown to be primarily dependent on the calculated water content in the vapor phase in equilibrium with TEG. Hysys CPA DTU provided consistently very low water dew points, while Hysys PR calculated values higher than both experimental and field data.Gases are soluble in TEG. This thesis studied the solubility of methane, ethane and CO2 in rich TEG. Hysys GP calculated the lowest solubility of these components in rich TEG and the largest solubility in binary simulations with TEG. These opposing results were shown to be related to the water content in rich TEG which decreased the solubility of especially methane and ethane significantly. No data were available as a comparison. However, considering the relatively low water content in rich TEG, the decrease was too large.The lean TEG purity from the reboiler was shown to be primarily dependent on the state of equilibrium between TEG and water. Hysys CPA DTU calculated a higher amount of water in the liquid phase, leading to lower purity from both reboiler and stripping column compared to the other fluid packages. The purity from the stripping column was lower than the measured value. In addition, Hysys CPA DTU calculated low circulation rate of TEG due to low TEG density. Consequently, Hysys CPA DTU was evaluated as the least suited fluid package for dehydration of natural gas of those included in this thesis.

The primary aim of the thesis is to provide a comprehensive investigation of the osmotic dehydration processes in plant tissue. Effort has been concentrated on the modelling for simulating the processes. Two mathematical models for simulating the mass transfer during osmotic dehydration processes in plant tissues are developed and verified using existing experimental data. Both models are based on the mechanism of diffusion and convection of any mobile material that can transport in plant tissues. The mass balance equation for the transport of each constituent is established separately for intracellular and extra-cellular volumes with taking into account the mass transfer across the cell membrane the intracellular and extra-cellular volumes and the shrinkage of the whole tissue. The contribution from turgor pressure is considered in both models. Model two uses Darcy’s law to build the relation between shrinkage velocity and hydrostatic pressure in each volume because the plant tissue can be considered as the porous medium. Moreover, it has been extended to solve the multi-dimensional problems. A lot of efforts have been made to the parameter study and the sensitivity analyses. The parameters investigated including the concentration of the osmotic solution, diffusion coefficient, permeability of the cell membrane, elastic modulus of the cell wall, critical cell volume etc. The models allow us to quantitatively simulate the time evolution of intracellular and extra-cellular volumes as well as the time evolution of concentrations in each cross-section.

Plant seeds, yeasts, bacterial spores, rotifers, and other organisms are capable of suspending their metabolism and entering a state of latency when dehydrated. These organisms may maintain this state for extremely long periods of time, yet upon rehydration resume normal metabolism, without evidence of severe membrane disruption. With many of these organisms, the ability to survive dehydration has been correlated to the production of large amounts of carbohydrates, including glycerol, glycogen and the disaccharide trehalose. Trehalose has been shown to protect isolated sarcoplasmic reticulum microsomes and phospholipid vesicles from dehydration damage, implying that the site of protective action of trehalose and other carbohydrates is the lipid portion of membranes. In this thesis, the effects of carbohydrate composition, vesicle size, and lipid composition on the protection of liposomes from dehydration was investigated, as was the structure of the solid lipid-trehalose complex. Electron microscopy of dried liposomes indicated that vesicles protected with trehalose remain essentially intact even when dry, while vesicles not protected by sugar are severely disrupted by drying . ³¹-P and ¹³-C NMR results suggested that the lipid of protected vesicles is in a similar phase as that of unprotected vesicles, and that this state is similar to powdered anhydrous phospholipid. Using carboxyfluorescein as a probe, it was demonstrated that trehalose, other sugars can prevent vesicle disruption upon dehydration. Different lipid compositions of the liposomes showed nearly identical behavior, with the exception of vesicles composed of dipalmitoylphosphatidylcholine and egg phosphatidylcholine, which showed greater and lower stability to dehydration respectively. Light scattering experiments indicated that a wide variety of carbohydrate and lipid vesicle combinations can withstand dehydration and maintain their original size when protected by sugars. The implications of these results in the development of liposomes as pharmaceuticals are discussed, and a hypothesis is advanced regarding the role of carbohydrates in the preservation of dry lipid membranes.
Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate

Great challenges remain in our understanding of biomineralisation which impede the design and production of a new class of materials. Recent studies have suggested that calcium carbonate clusters are stable in solution before nucleation, and that these participate in the formation of amorphous calcium carbonate (ACC). The structure and stability of these clusters has not been fully determined. Furthermore, the dehydration of stable ACC before crystallisation remains ambiguous. Exhaustive computational searches have been carried out to provide a sample of clusters up to the sizes suggested for particles persisting before nucleation. A large sample of clusters were simulated at high concentration in water using molecular dynamics (MD). The results suggest that cluster stability is a balance between ionic coordination and ion hydration. At high concentration clusters are generally dynamic in the lower limit of stability, forming chains to which ions frequently aggregate and dissolve. Free energy calculations showed a transition in the favoured coordination levels with cluster size. One dimensional Umbrella Sampling calculations showed that at small sizes a collection of clusters with low average cation–anion coordination were thermodynamically stable. For systems containing sixty ions and above, more compact clusters with internal water, close to the stoichiometries identified for stable hydrated ACC in vivo, were lower in free energy. From MD simulations at experimental concentrations and pH, while dynamic ordering was found, ion pairs dominated in solution and the largest clusters observed contained no more than four ions. These findings, combined with the data at high concentration, allow for a re-evaluation of the proposed nucleation mechanisms for calcium carbonate from solution. ACC simulations identified water–filled channels within the ionic framework. Percolating clusters were found when H2O/CaCO3 was greater than 0.75–0.8. The ACC system fitted well with the percolation theory on a simple cubic site lattice for water, and critical exponents showed a good fit to the theoretical values. Non–standard diffusion was found for water, with a “jump” mechanism of diffusion observed and a cascade of molecule displacements within channels. This original result allows new light to be shed on the dehydration mechanism of ACC.

Abstract Lignocellulosic biomass, such as wood or agricultural residues, is a resource widely available for use in chemical production. In a lignocellulosic feedstock biorefinery, the major parts of biomass, cellulose, hemicellulose and lignin, are converted to valuable chemicals, materials and energy. Furfural production is one option for the use of the pentose sugars available in hemicellulose, and the process could be integrated with the pulp or cellulosic ethanol industry. In the past, furfural production catalysed by organic acids has been in industrial use, but no detailed studies about the kinetics exist. However, the use of organic acid would prevent the waste problems linked to the mineral acids widely used in the furfural industry. In this thesis, furfural formation in formic acid media was studied. The major part of this work concerns the kinetics of xylose dehydration into furfural and further furfural degradation. Based on the results of this thesis and a literature review, adequate prediction of furfural yield in the conditions used can be achieved using a simple kinetic model, including three reactions: 1) Xylose dehydration into furfural, 2) Furfural degradation, and 3) Xylose degradation to products other than furfural. Moreover, it was shown that the overall order of the furfural degradation reaction, usually modelled as a first order reaction, changes with acidity (H+-concentration). Suggestions for a possible reaction mechanism have been made based on the results. In the last part of this thesis, furfural formation in the presence of kraft lignin (Indulin AT) was considered. Sulphuric acid was used as a baseline for formic acid. It was shown that the lignin has an acid-neutralising capacity, but the higher pH did not explain all the changes in the xylose conversion and the furfural yield. Thus, it is highly likely the lignin inhibits the formation of furfural. Altogether, the effects were smaller in formic acid than in sulphuric acid. This thesis confirms the fact that formic acid is an effective catalyst for furfural production. The focus of the thesis was on the reaction kinetics, and the results can be used in conceptual process design. Moreover, the results emphasise the importance of including acidity explicitly in the kinetic model and monitoring acidity changes when real process streams are used
Tiivistelmä Lignoselluloosaa, kuten puita tai maanviljelyn jäännösmateriaaleja, on laajasti saatavilla kemiallisen tuotannon raaka-aineeksi. Biojalostamossa lignoselluloosan pääjakeet, selluloosa, hemiselluloosa ja ligniini, muutetaan arvokkaiksi kemikaaleiksi, materiaaleiksi ja energiaksi. Furfuraalin tuotanto on yksi vaihtoehto hemiselluloosan sisältämien pentoosien hyödyntämiseksi. Furfuraaliprosessi voidaan yhdistää sellun tai bioetanolin tuotantoon, ja orgaanisia happoja käyttämällä voitaisiin välttää mineraalihappoihin liittyvät jäteongelmat furfuraalin tuotannossa. Tämän väitöskirjan aiheena on muurahaishappokatalysoitu furfuraalin muodostuminen ksyloosista. Pääpaino on reaktiokinetiikassa, ja työssä on kehitetty kineettinen malli ksyloosin dehydraatiolle furfuraaliksi ja sitä seuraaville furfuraalin sivureaktioille. Tehdyn tutkimuksen ja kirjallisuusselvityksen perusteella yksinkertainen kolmen reaktion malli antaa riittävän tarkan ennustuksen furfuraalisaannoista käytetyissä olosuhteissa. Reaktiot ovat 1) ksyloosin dehydraatio sekä 2) furfuraalin ja 3) ksyloosin reaktiot sivutuotteiksi. Lisäksi huomattiin, että reaktion, jossa syntyy furfuraalin häviämistuotteita, reaktioaste on riippuvainen happamuudesta (H+-konsentraatio). Työssä onkin ehdotettu mahdollisia reaktiomekanismeja furfuraalin sivureaktioille. Työn viimeisessä osassa tutkittiin ligniinin vaikutusta furfuraalin muodos¬tu¬miseen. Vertailukohtana muurahaishapolle käytettiin rikkihappoa. Tutkimuksessa selvisi, että käytetty ligniini, Indulin AT, huononsi furfuraalisaantoa. Suurin osa vaikutuksesta johtui ligniinin neutralointikapasiteetista, jolloin reaktioliuoksen happamuus laski, mutta mahdollisia sivureaktioita ei voitu sulkea pois. Kaiken kaikkiaan vaikutukset olivat pienempiä muurahaishapolla kuin rikkihapolla. Tämä väitöskirjatutkimus osoitti, että muurahaishappo katalysoi furfuraalin tuotantoa tehokkaasti. Tutkimuksessa muodostettiin reaktiokineettinen malli, jota voidaan käyttää käsitteellisessä prosessisuunnittelussa. Tulosten perusteella on tärkeää huomioida reaktioliuoksen happamuus kinetiikassa ja tarkkailla happamuuden muutoksia käytettäessä prosessisivuvirtoja

Controversy exists among clinicians and caregivers as to whether reduced fluid intake contributes to the suffering of those dying of advanced cancer. This study explored the distribution of proposed "dehydration state" symptoms among inpatient palliative care cancer patients. Fifty-two subjects responded to a seven item self-report questionnaire using visual analogue scales. Associations were determined between the symptom self-reports and the possible predictor variables fluid intake, serum sodium, urea and osmolality. Confounding variables considered were age, oral disease and mouth care regime. Mean symptom ratings (range 0-100 mm) were: thirst 53.8, dry mouth 60.0, bad taste 46.6, nausea 24.0, pleasure to drink 61.6, fatigue 61.8, and pain 33.5. No significant association was determined between symptom ratings and the predictor or confounding variables. Although the symptoms appear to be rated moderately severe, there was no demonstrable association between severity and fluid intake, the key concern of clinicians and families.

The application of pervaporation to the dehydration of aprotic solvents was investigated in this study. The performance of a commercial membrane, Celfa CMC-VP-31, was evaluated for the dehydration of tetrahydrofuran (THF) and dimethylformamide (DMF). The membrane was demonstrated to successfully dehydrate THF and calculations of water and THF permeance performed. When the membrane was applied to the dehydration of DMF, delamination of the top selective layer was observed and thus the membrane was deemed unsuitable for DMF dehydration. ' Polyaniline (PAni) was identified as a suitable candidate polymer for the formation of an aprotic solvent stable hydrophilic pervaporation membrane. PAni was synthesised in the lab and preparation conditions optimised and scaled-up to produce polymer with consistent batch to batch properties, in suitable quantities, to fabricate���· membrane sheets with sufficient surface area for testing. Casting solutions comprising of 20 wt% PAni were stabilised using an amine, 4-methyl piperidine, to prevent gelation and cross-linking prior to casting. Membranes were cast on a polyester non-woven backing and phase inverted in water to produce an asymmetric membrane structure. Scanning Electron Microscopy was used to examine the structure of the membranes formed. The effects of thermal treatment on the membrane film and polymer were investigated by a number of analytical techniques in order to devise a suitable procedure for membrane stabilisation. Thermally cross-linked PAni membranes were demonstrated to be water selective and stable in THF, DMF, ethyl acetate and ethanol. Permeance correlations with temperature were constructed to describe the performance of the membrane discs tested during solvent dehydration and compared to experimental data. Transport across the membrane was reported to be solubility dominated for all of the solvent systems tested. Finally, an examination of the reproducibility of membrane performance was made and further tests performed, to better understand variations observed in membrane pervaporation performance.

Solid acid catalysts were prepared through silicon substitution into aluminophosphate frameworks. Silicon incorporation was confirmed using solid state nuclear magnetic resonance spectroscopy. The nature of the acid sites generated was determined using Fourier Transform infrared spectroscopy. These materials were tested as catalysts for the dehydration of ethanol to ethylene at low operating temperatures. The materials were active for dehydration of ethanol to ethylene with significant differences observed between aluminophosphate frameworks both in terms of selectivity to the desired product but also in terms of the nature of the silicon substitution and the active sites. Links have been made between these properties and the observed catalytic behaviour. The effect of the catalytic framework is further explored though the testing of cobalt substituted aluminophosphates for ethanol dehydration. Silicon substituted aluminophosphates have been tested for the dehydration of 1-phenylethanol to styrene as an example of catalysis in the liquid phase. Here the influence of framework was particularly significant due to the large substrate. The effect of redox metals in the aluminophosphate framework has been investigated through the use of calcined and pre-reduced cobalt substituted aluminophosphates for the dehydration of ethanol to ethylene. Analysis of the catalytic product stream was combined with UV-Visible measurements to investigate potential redox processes occurring during the reaction time on stream and the influence of the oxidation state of the redox metal on the catalytic products of the reaction.

A numerical model for describing the kinetics of intracellular water transport during cryopreservation was developed. As ice is formed outside the cell, depleting the extracellular liquid of water, the cell will experience an osmotic pressure difference across its membrane, which causes cell dehydration and concomitant shrinkage. Although Mazur (1963) has previously modeled this phenomenon as a two-compartment system with membrane limited transport, the assumption of well-mixed compartments breaks down at large Biot numbers. Therefore, we have developed a numerical solution to this moving-boundary problem, including diffusive transport in the intracellular liquid, in addition to the osmotically driven membrane flux. Our model uses a modified Crank-Nicolson scheme with a non-uniform Eulerian-Lagrangian grid, and is able to reproduce predictions from Mazurs model at low Biot numbers, while generating novel predictions at high Biot numbers. Given that cell damage may result from excessive water loss, our model can be used to predict freezing methods that minimize the probability of cell injury during the cryopreservation process.

Aprotic solvents are organic solvents which do not easily react with a substance dissolved in it and they do not exchange protons despite of their high ion and polar group dissolving power. Therefore, this characteristic property makes aprotic solvents very suitable intermediates in many industries producing pharmaceuticals, textile auxiliaries, plasticizers, stabilizers, adhesives and ink. Dehydration of these mixtures and recirculation of valuable materials are substantial issues in industrial applications. The conventional method for recovery of aprotic solvents has been distillation, which requires excessive amount of energy to achieve desired recovery. Hydrophilic pervaporation, which is a membrane based dehydration method with low energy consumption, may become an alternative. Because of high dissolving power of aprotic solvents only inorganic membranes can be employed for this application. In this study three types of inorganic membranes (NaA zeolite, optimized silica and HybSi) were employed. Main objective of this studys to investigate effect of membrane type and various operationg parameters (feed composition at a range of 50-5% and temperature at a range of 50-100oC) on pervaporative dehydration of aprotic solvents
dimethylacetamide, dimethylformamide and n-methylpyrrolidone. During the experiments, feed samples were analyzed with Karl Fischer Titration Method
permeate samples were analyzed with Gas Chromatography. Experiments showed that proper dehydration of aqueous aprotic solvent mixtures was succeded with all three membranes investigated. In the target feed water content range (50 to 20%wt), permeate water contents were higher than 98%wt which was quite acceptable for all membranes. Moreover, NaA zeolite membrane performed higher fluxes than optimized silica and HybSi in composition range of 50 to 15% water at 50oC. It was also observed that HybSi membrane had higher fluxes and permeate water contents than optimized silica membrane for all solvents. On the other hand, the rates of decrease in permeate fluxes changed depending on the type of solvent for optimized silica and HybSi membranes. With both membranes, permeate flux of dimethylformamide decreased much slower than that of n-methylpyyrolidone. Furthermore, the results showed that permeate fluxes of HybSi membrane increased with increasing operation temperature due to the change of solvent activity in mixture. In addition, an Arrhenious type equation was used to describe changes in fluxes with changing temperature. It was also found that activation energy of water for diffusion through HybSi membrane was calculated as 8980 cal/mol.

A novel and accurate method of chemical analysis was developed to identify and assay the products of the hydrolysis that occurred when magnesium chloride hexahydrate was heated and held at temperature and reacted with its own liberated waters of hydration. The novel method took advantage of the solubility of magnesium chloride and magnesium chloride hydrates in methanol and the concomitant insolubility of magnesium oxide and magnesium hydroxychlorides in methanol. The method was found to have a precision of 5-7 % and represents a substantial improvement over previous analytical methods. The method is also readily applied to any methanol soluble salt containing insoluble impurities, meaning that it can also be used for the monitoring of the fused salt electrolyte present the magnesium electrolysis cells. [...]
Une nouvelle méthode d'analyse chimique a été développée pour identifier et tester les produits d'hydrolyse qui se forment quand le chlorure de magnésium hexahydrate est chauffé, maintenu à température constante et qu'il réagit avec les eaux d'hydratation qu'il libère. La nouvelle méthode tire avantage de la solubilité du chlorure de magnésium, hydraté ou non, et en parallèle de l'insolubilité de l'oxyde et des hydroxychlorures de magnésium dans le méthanol. Il s'avère que la méthode a montré une précision de 5-7 %, ce qui apporte une importante amélioration aux méthodes analytiques précédentes. La méthode est aussi facilement applicable a tout sel soluble, qui contiendrait des impuretés insolubles, dans le méthanol, ce qui signifie qu'elle peut aussi être utilisée pour le suivi de l'électrolyse de sel fondu présent dans les cellules d'électrolyse du magnésium. [...]

Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: The assessment of dehydration is an ever elusive golden standard, even given the plethora of hydration markers that exist to date. Many literature sources acknowledge the need for a portable device that can be used as an indicative tool for hydration. This project sought to find a solution for assessing dehydration on a micro level looking for an indication of hydration by investigating the levels of water concentration in the skin and water compartments of the body using bioelectrical impedance, stratum corneum impedance and infrared spectrometry. Two studies were conducted to evaluate the efficacy of these devices: an infield study to assess the efficacy of the devices for measuring dehydration brought on by exercise in adults and an infant study where the devices where used to assess its ability to measure dehydration in infants who have succumbed to diarrhoea. The studies showed that the devices are not applicable in measuring real time hydration in exercising subjects as sweat was a perturbing factor in the measurements. The infant study provided promising results with regards to the usage of the infrared device. It is believed that these results could spur further investigation into the field of using infrared spectrometry as a dehydration marker. Dehydration still remains to be an ever elusive standard but the importance of finding a solution to quantitatively assess hydration is a field which could benefit the general population and its importance should not be underestimated.
AFRIKAANSE OPSOMMING: Die assessering van dehidrasie is steeds 'n ontwykende goue standaard selfs gegewe die oorvloed van hidrasiemerkers wat bestaan tot op datum. Baie literatuurbronne erken egter die behoefte aan 'n draagbare toestel wat as 'n hulpmiddel kan dien vir die evaluering van die vlakke van dehidrasie. Hierdie projek streef daarna om ondersoek in te stel tot die assessering van dehidrasie op 'n mikrovlak deur die waterkonsentrasies te meet in die vel en die verskeie waterkompartemente in die liggaam via die gebruik van bio-elektriese impedansie analise, stratum corneum impedansie analise en infrarooi-spektrometrie. Twee studies is gedoen om die doeltreffendheid van die toestelle te evalueer: 'n inveldstudie wat die hidrasievlakke van volwassenes meet wat ly aan dehidrasie weens oefening en 'n studie wat dehidrasie meet in neonate wat ly aan dehidrasie weens diarree. Die studies het bewyse gelewer dat die toestelle nie effektief is met betrekking tot die meet van dehidrasie in aktiewe volwassenes nie, weens die rede dat sweet 'n verstorende faktor is. Die neonate studie het belowende resultate verskaf met betrekking tot die gebruik van die infrarooi toestel. Daar word geglo dat hierdie resultate verdere ondersoek in die veld met betrekking tot infrarooi spektrometrie as 'n hidrasie merker kan motiveer. Finale bevindinge wys dat die kwantifisering van dehidrasie steeds 'n ontwykende standaard is, maar die belangrikheid van 'n moontlike oplossing sal voordelig wees vir die wêreld se volke en moet dus nie onderskat word nie.

It is well known that the digestive system is very sensitive to a large number of different negative factors. In particular, frequent lesions in the stomach is exposed as its organ and the main reservoir of mechanical and chemical processing of food. It is necessary to say that the effect of dehydration of the stomach has not been adequately studied. The significant amount of water and electrolytes is deposited in the gastrointestinal tract and is involved in the exchange, circulating between blood and content of the digestive tract. That is why the aim of this thesis was to discover structural and morphological changes in stomach due to the total dehydration.

This thesis describes an experimental and modelling study of the kinetics of silver-catalysed formaldehyde production via methanol partial oxidation and dehydrogenation. In methanol oxidation, the reaction is controlled by the gas phase diffusion of reactants towards the catalyst surface. The methanol-to-oxygen ratio at the catalyst wall is 100-200 times higher than that in the feed, which means that the reaction operates with large excess of methanol and therefore is solely controlled by the availability of O2 at the surface. A constant stoichiometry = 2.25 is found. In methanol dehydrogenation, the strongly-bound surface oxygen (Oγ) catalyses the formation of CH2O and H2 without any by-product. The decline in methanol conversion over time is attributed to the gradual consumption of Oγ due to the thermal decomposition. During the surface pre-oxidation, the surface oxygen penetrates into the silver bulk and diffuses back to the surface after O2(g) is withdrawn. The H2 production during methanol oxidation is solely via the dehydrogenation channel occurring on the whole catalyst surface independently but concurrently with the oxidation, which only happens on the surface that is in contact with O2(g). Without pre-treatment, the “oxidation surface” is the only active surface for both oxidation and dehydrogenation. A transient penetration layer of active oxygen species is formed and catalyses the methanol dehydrogenation. The near constant stoichiometry is a fundamental constant describing the ratio of the dehydrogenation channel over the oxidation channel on the same surface area. Surface characterization (ex-situ XPS and SEM analysis) were performed over silver foil showing the dynamic picture of oxygen evolution and further supporting the proposed reaction mechanisms in this work.

Nearly one-third of all pharmaceutical substances on the market are able to sorb water into their crystal lattices to form hydrates, which can often compromise stability during processing and/or storage[1]. The tendency of a hydrate to lose its water of crystallization during the manufacturing process of tablet compression is of particular concern to formulation scientists. The amount of water freed as a function of increasing compaction pressure can be explained by the mobility of water within the compact. The mobility of water is determined by the size and shape of the crystal lattice, the numbers and strengths of the hydrogen bonds, and the presence of high-energy sites of disorder[2]. Due to their differing crystal structures, theophylline monohydrate (THM), citric acid monohydrate (CAM), theophylline-water-citric acid cocrystal hydrate (CATHP hydrate), and dicalcium phosphate dihydrate (DCPD) make for interesting model systems to examine the dehydration under mechanical load. The thermal dehydration of both powders and tablets was carried out via thermal gravimetric analysis (TGA). By comparing the temperatures required to start removal of water loss from the powder to that of the tablet, the average amount of water of crystallization that is freed by the compaction process may be quantified. The average amount of water freed by the compaction process results from a competition between the mechanically-induced disorder of the crystal structure that increases the molecular mobility of water within the tablets, and the trapping of water within the interparticulate void spaces at high compaction pressures. The compressibilities, compactabilities, and tabletabilities of the materials were calculated as a function of increasing compaction pressure. The consolidation of the powder bed under pressure was modeled by out-of-die Heckel Analysis which demonstrated the ease of deformation of the model compounds. XRD was utilized to show the decrease in overall order of the crystal lattice as a result of compression as well as anisotropy within the tablets. Crystallographic approaches were utilized to demonstrate the compactness of the crystal structure, and how it affects water mobility. Relaxation pulse experiments (T1, T2) utilizing solid-state NMR were used to directly probe the mobilities of the water molecules within the crystal lattice of THM. The results from T1 and T2 relaxation experiments directly measure the change in molecular mobility of water within the tablets as a function of compaction pressure. This provided independent verification of the trends in molecular mobility and average water freed as a function of compaction pressure observed during TGA dehydration. Raman spectroscopy was used to indirectly measure the polarizability and vibrational motions of THM, and these results corroborate those obtained from ssNMR and TGA dehydration experiments. Overall, this work highlights the potential impact that tablet compression can have on API hydrate stability. 1. Hilfiker R (editor). 2006. Polymorphism in the Pharmaceutical Industry. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co, KGaA. 2. Byrn SR, Pfeiffer RR, Stowell JG. 1999. Solid-state chemistry of drugs. SSCI, Inc.

El procesado de alimentos conlleva, en mayoría de los casos, la generación de subproductos o residuos que pueden ser reutilizados o revalorizados mediante la utilización de técnicas de separación por membrana. Estas técnicas ofrecen la posibilidad de tratar las soluciones en condiciones de operación muy suaves, y no comportan en mayoría de las ocasiones, una alteración de los componentes a recuperar. Actualmente, las técnicas de separación por membrana, debido a su alta calidad y relativamente bajos costes, se encuentran completamente integradas en la mayoría de procesos productivos que requieren de una etapa de separación. Sin embargo, la investigación en el área de las técnicas de separación por membrana sigue abriendo nuevos campos de aplicación, que surgen con la mejora de las condiciones tecnológicas de los equipos y la posibilidad de obtener nuevas membranas adaptables a necesidades específicas.

En concreto, en este proyecto se utilizaron técnicas de separación por membranas para concentrar soluciones de azúcar procedentes de deshidratación osmótica (en adelante OD). El principal objetivo fue estudiar el potencial de varias técnicas de separación, haciendo hincapié en los flujos obtenidos durante la reconcentración y en la calidad de la solución reconcentrada.

La deshidratación osmótica es un tratamiento que permite una eliminación parcial del agua en un alimento y/o la incorporación de solutos de una manera controlada, respetando la calidad inicial del producto. El proceso consiste en introducir los alimentos en una solución hipertónica, controlando las condiciones de operación para favorecer, en mayor o menor grado la incorporación de solutos y la deshidratación del alimento. La aplicación de OD puede resultar en la mejora de las propiedades nutricionales y funcionales de los alimentos y en la reducción de la energía requerida para la deshidratación. El principal problema de la aplicación industrial de la OD radica en la gestión de la solución procedente del proceso. La reutilización de esta solución plantea una doble ventaja: primero desde el punto de vista ambiental, ya que se elimina un efluente del proceso que a menudo no puede ser vertido directamente, y segundo el ahorro económico que representa la recuperación de las materias primas que muchas veces contienen solutos de importante valor económico.

Los métodos de separación por membrana utilizados para recuperar las soluciones de OD fueron los siguientes: nanofiltración, osmosis directa y destilación osmótica por membranas. La nanofiltración (NF) presenta altos niveles de retención y un menor gasto de energía que la osmosis inversa, y en la industria azucarera se aplica como uno de los pasos en la clarificación y concentración de jarabes. En los procesos de contactores de membranas: osmosis directa (DO) y destilación osmótica por membranas (OMD), a diferencia de los procesos basados en el tamizaje, el flujo depende solamente de la diferencia de potencial osmótico. Las únicas presiones hidráulicas requeridas son las necesarias para bombear la solución de azúcar y la solución osmótica hasta la superficie de la membrana. Estas características hacen que estos procesos presenten como muy prometedores para la reconcentración de soluciones de azúcar de concentraciones elevadas.

Los experimentos de filtración se llevaron a cabo utilizando plantas piloto diseñadas y construidas expresamente para el presente proyecto. Durante todos los procesos de separación por membranas, se empleó como solución modelo una solución de sacarosa a diferentes concentraciones (5-60 ºBrix), debido a que las soluciones aplicadas en la deshidratación osmótica de frutas son habitualmente soluciones de azucares (sacarosa, glucosa o jarabes).

Durante los experimentos de NF se evaluó el funcionamiento de las membranas planas: Desal5 DK (GE- Osmonics), MPF-34 (Koch Membrane), NFT-50 (DSS) y tubulares: MPT-34 (Koch Membrane) y AFC 80 (PCIMembranes). Además de la solución de azúcar de diferentes concentraciones (5-20 ºBrix), se concentraron zumos de pera y manzana.


La reconcentración mediante osmosis directa se realizó utilizando dos modos de operación: off-site e on-site. En el modo off-site, la reconcentración por ósmosis directa se llevó a cabo en una planta de filtración provista de un módulo plano o tubular, dependiendo de la membrana. En el módulo se llevó a cabo la concentración. En el modo on-site, la deshidratación se realizaba conjuntamente con la reconcentración de la solución osmótica. La solución de reconcentración de la osmosis directa en off-site (offsiteDO) fue NaCl, mientras la solución de reconcentración de la osmosis directa on-site (on-site DO) fue una solución de sacarosa más concentrada que la solución osmótica (60 para una solución osmótica de 40 y 68 para una solución de 50 ºBrix). Para garantizar el flujo de agua entre las dos soluciones y altas retenciones de azúcar durante la off-site DO, se utilizaron membranas de NF planas (Desal5-DK y MPF-34) y tubulares (MPT-34 y AFC80). La reconcentración por osmosis directa on-site se levó a cabo empleando una membrana de microfiltración (Durapore, Millipore), ya que la solución de reconcentración (SS) es la misma que la solución osmótica y la alta viscosidad de la SS restringe mucho el flujo de agua si se utiliza una membrana más densa.

En la deshidratación por membranas (OMD) se utilizaron membranas hidrófobas (11806, Sartorius) que presentan una retención teórica del 100 %. Se comparó el rendimiento de dos soluciones de reconcentración: NaCl y CaCl2.

Con el fin de obtener información referente a la influencia de las propiedades de las membranas sobre el desarrollo del proceso de concentración de las soluciones procedentes de la deshidratación osmótica, se realizó un estudio detallado de las propiedades de las membranas aplicadas mediante AFM, SEM, FTIR, ángulo de contacto y medidas de potencial zeta. Con la finalidad de generar soluciones osmóticas para someterlas a reconcentración, y también para disponer de productos procedentes de deshidratación osmótica con soluciones frescas que pudieran compararse con aquellas procedentes de OD con solución reconcentrada, se deshidrataron diferentes lotes de manzana (Granny Smith) con soluciones de sacarosa de 40, 50 y 60 ºBrix. Estas pruebas permitieron determinar también el tímelo de operación para una máxima pérdida de agua con relativamente poca impregnación de las manzanas. Después de cada experimento se analizaron los siguientes parámetros: concentración de azúcar, pH, absorbancia a 420 nm de las soluciones y humedad de las manzanas.

La nanofiltración, aplicada en la primera fase del presente estudio, resultó ser viable solamente para la reconcentración de soluciones de concentraciones hasta 24 ºBrix. El aumento de la temperatura de 25 hasta 35 ºC para las dos membranas tubulares ocasionó un incremento del flujo de permeado, y el mismo efecto tuvo el aumento de presión transmembranaria de 8 a 12 bar.

Se comprobó que el factor más importante para la eficacia del proceso es disponer de una membrana que combine altos flujos y retenciones durante el proceso. La deposición de las partículas de sacarosa y/o los zumos se caracterizó mediante SEM y la topología de la capa filtrante de la membrana se identificó usando AFM. La topología de la capa filtrante de las membranas era diferente para cada una de ellas, a pesar de que todas estaban preparadas con el mismo material (poliamida). En las imágenes de los cortes transversales de las membranas realizados con SEM, se observaron los cambios en la estructura de las membranas producidos por la aplicación de presión durante los experimentos y las altas temperaturas empleadas durante su acondicionamiento. Gracias a las imágenes de SEM se pudo verificar también la eficacia del proceso de acondicionamiento de membranas.

A diferencia de NF, tanto la ósmosis directa como la destilación osmótica por membrana permiten la reconcentración de soluciones concentradas de sacarosa (hasta60 ºBrix). La eficacia de estas dos últimas técnicas se evaluó en unción de los flujos de agua obtenidos.

El sistema de ósmosis directa on-site propuesto para la reconcentración de las soluciones de OD permitió reutilizar las soluciones osmóticas como mínimo cuatro veces. Para la solución osmótica de 40 ºBrix la humedad de las manzanas fue similar utilizando solución fresca o reconcentrada. En cambio, una solución osmótica de 50 ºBrix, la pérdida de agua de las manzanas fue mayor cuando la deshidratación osmótica se llevó a cabo con reconcentración on-site de la solución osmótica. Los análisis de concentración de azúcar de las soluciones osmóticas y de la solución de reconcentración indican que la membrana elegida para los experimentos facilita el transporte óptimo de solutos y agua entre las dos soluciones. Además, el sistema de reconcentración por membrana propuesto es muy sencillo y de bajo coste porque no requiere presurización.

La osmosis directa en off-site proporcionó flujos mucho mayores que los obtenidos con el sistema on-site (1.3 kg/m2h para la solución osmótica de 50 ºBrix respecto a 0.0023 kg/m2h durante on-site DO para la misma solución). Sin embargo, el transporte de solutos de la solución de reconcentración hacía la solución osmótica puede ser considerado un obstáculo para su aplicación a escala industrial.

Los flujos de agua más elevados fueron obtenidos utilizando la OMD (2.01 kg/m2h para la solución osmótica de 50 ºBrix y con CaCl2 con la solución de reconcentración). Otra gran ventaja de este proceso es la retención de solutos que proporciona, hecho confirmado por los análisis realizados.

El estudio sobre el transporte durante los procesos de contactores de membranas indicó que la viscosidad es la propiedad limitante para la solución osmótica y la actividad de agua/alta presión osmótica como la propiedad más importante a la hora de elegir una solución de reconcentración. Para todos los procesos de separación aplicados, el aumento de la concentración de azúcar de la solución osmótica comporta una disminución notable del flujo de agua.

El desarrollo de un posible proceso de deshidratación osmótica con una etapa de reconcentración de la solución osmótica mediante procesos con contactores de membrana ha permitido calcular el área requerida para realizar la reconcentración: 3.6,9.7, 1608 m2 para OMD, off-site DO e on-site DO, respectivamente.

Las conclusiones del trabajo confirman la posibilidad de utilizar procesos por membrana para realizar la reconcentración de soluciones osmóticas. No obstante se ha constatado que técnicas más tradicionales basadas en diferencias de presión (NF) no son

As a renewable energy source, bioethanol is widely used for blending in gasoline in an attempt to partly alleviate the energy crisis and reduce the greenhouse gas emissions. To produce fuel grade ethanol, the dehydration process of bioethanol is a critical step for the economic viability of the whole process. With a single distillation column it is not possible to overcome the azeotropic point of the ethanol/water mixture. In addition, the distillation process is a very energy intensive and costly process. In this thesis, two major topics concerning the dehydration process of bioethanol are discussed. First, the multiple objective optimization of the fuel grade bioethanol dehydration is performed along with a parametric analysis of A-type zeolite membrane pervaporation. Three cases were investigated using the ranked Pareto domain that was obtained in each case. The optimal results were identified as attractive compromised solutions considering the four objectives: the total number of stages, the total area, the energy consumed, and the exergy loss. The temperature drop per stage was found to be the dominating factor. The second theme is the exergy loss minimization of the pervaporation/distillation hybrid system at the tangent pinch on the vapor-liquid equilibrium curve. Results show that both the exergy loss and the reflux ratio of the hybrid system are reduced compared to a single distillation column. In addition, the exergy loss of the hybrid system is correlated with the variation of the reflux ratio.

In the brewing industry it is standard practice to propagate a pure yeast culture and inoculate (pitch) it into the fermentation vessel. Once fermentation is complete, yeast is recovered and reused in subsequent fermentations (known as serial repitching) until a decline in performance occurs or the required number of successive fermentations has been conducted. Propagation is currently required to initiate the entire process again, which requires additional equipment, energy, water inputs and time. It has long been proposed that Active Dried Yeast (ADY) offers an alternative method of yeast supply. Adoption of this innovation by the brewing industry has been low because of perceived issues with the fermentation performance of ADY, the availability of strains and hygiene concerns. In the current study the fermentation performance of ADY has been assessed with respect to viability, genomic stability, membrane integrity, yeast growth, attenuation, uptake of wort nutrients and aspects of flavour development. ADY requires rehydration before use and it has been demonstrated that viability is impaired in these slurries, though the extent of viability loss was dependent on strain and rehydration conditions. The source of cell death is unclear. Mitochondrial and genomic DNA integrity was assessed using a variety of techniques and shown to be unaffected by dehydration and rehydration. In contrast membrane integrity was affected. Changes in membrane fluidity, sterol content and fitness to perform could be detected in ADY. Performance of ADY in fermentation was also impaired. A lag in cell growth, attenuation and sugar and amino acid uptake were noted. Diacetyl formation occurred more rapidly and end fermentation diacetyl levels were higher for ADY. These differences were not maintained during serial repitching. It is proposed that ADY could be utilised to replace freshly propagated yeast, but direct addition to fermenters would require an improvement of performance during the first fermentation.

Objective: The aim of this pilot study is the evaluation and measurement of color stability from baseline until stabilization of color associated with bleaching and the dehydration and rehydration process of the teeth. Method: Six extracted intact human third molars were randomly selected, cleaned, and stored in artificial saliva at 370C. A custom positioning jig was fabricated for each tooth for reproducible color measurement. A baseline shade was recorded according to the Commission Internationale de l'Eclairage L*a*b* (CIE-L*a*b*) using a Minolta Chromameter CR-(200). Color measurement for all testing was taking at baseline, 15 min, 30 min, 2h, 12h and every 2 h thereafter until color stabilization occurred. Phase 1(dehydration-rehydration w/o bleaching): For dehydration, all teeth lightened and color stability occurred at 6 h. Rehydration of teeth to the baseline of color was achieved after 14 hours. Phase 2 (Effect of bleaching): An in-office bleach material (Zoom 25% HP) was applied to each tooth according to the Kwon technique (polyethylene wrap placed to cover the gel) for one hour. All comparisons were made to a Delta value of 2.6 (perceivable difference). Result: Phase 1: A mean äL*=-13.05(±15.62) was observed for tooth dehydration with no perceivable changes in chroma äa* and äb*. Phase 2: In-office bleaching produced dehydration and chroma changes when measured immediately after bleaching with a mean of äL*=-12.45(±2.4), äa*=0.31(±0.53), and äb*= 3.67(±1.76). After rehydration of bleached teeth, luminosity values (äL*) returned to normal and only chromaticity changes (äb#8727;) were observed with a mean of 4.77(%B11.91). Conclusion: Within the limits of this study, in-office bleaching produced dehydration and chroma changes, represented by äL* and äb*. Upon rehydration, the color changes were not as discernible. Further study will be conducted to determine the validity of these findings.

The cost of pretreatment process for saccharification from biomass and the cost of dilute ethanol purification are significant components of the overall cost for fuel grade ethanol production through fermentation or other biological routes. This work focuses on developing optimal designs of dilute ethanol purification process and the new acid hydrolysis technology for the production of fermentable sugars from biomass where the overarching goal is to reduce the cost of ethanol production from biomass. In this thesis, the ethanol separation process with the reverse osmosis membrane pretreatment is developed to reduce separation cost and energy consumption especially when the feed is dilute. In addition, the new solid phase reactive separation system for biomass saccharification via acid hydrolysis is proposed. This new process is applied for both dilute and concentrated acid hydrolysis where the goal is to increase sugar yield and to reduce byproduct formation. The reaction kinetics of the concentrated acid hydrolysis is investigated through batch experiment. All of these use optimization approaches for seeking the best process designs and for parameter estimations.

This PhD thesis is concerned with improving the retention of volatiles in the manufacture of instant coffee powders. Two processes have been studied in depth: spray drying and spray freeze drying. Spray freeze drying consisted of a combined spraying and freezing operation, followed by sublimation in a fluidised bed under partial vacuum. The aroma quality was measured using headspace solid-phase micro-extraction (HS-SPME) technique followed by gas chromatography coupled with mass spectrometry (GC/MS). Experiments were also performed with maltodextrin as the encapsulating matrix for comparison.

This thesis contributes to our understanding of temperature driven dehydration of rock forming minerals. It investigates the impact of crystallographic preferred orientation (CPO) on the dehydration of gypsum to bassanite through in-situ heating experiments on natural gypsum rock. The dehydration progress was monitored with synchrotron transmission, small- and wide-angle X-ray scattering (SAXS/WAXS) and tracked by the intensity evolution of three discrete Bragg diffraction peaks. A comparison of the conversion rates for satin spar (strong CPO) with whole-rock alabaster (weak CPO) reveals that a strong CPO decreases the reaction rate of dehydration.