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1
MARSALA, Valentina. "STUDY OF CHEMICAL-PHYSICAL PROPERTIES IN INDUSTRIAL BIOCHAR." Doctoral thesis, Università degli Studi di Palermo, 2014. http://hdl.handle.net/10447/90992.
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CARDELLI, VALERIA. "Changes occurring in the topsoil and in rhizosphere under fagus sylvatica along a small latitudinal-altitudinal gradient." Doctoral thesis, Università Politecnica delle Marche, 2017. http://hdl.handle.net/11566/245508.
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Durante il triennio di dottorato è stato studiato l'effetto del cambio di temperatura sulle proprietà chimiche e biochimiche di due componenti di suoli sotto faggio (Fagus sylvatica) dell'Appennino centrale (Italia): la rizosfera e il topsoil (orizzonti organici e il primo orizzonte minerale). Il disegno sperimentale ha considerato un transetto altitudinale (800 e 1000 m), con una differenza di temperatura media annua dell'aria di 1°C, e un transetto latitudinale, dove non si hanno differenze di temperatura media annua, ma ve ne sono in termini di escursione termica estate-inverno. La ricerca è stata preceduta dalla messa a punto di un metodo strumentale per ottenere più rapidamente dati di carbonio e azoto totali (TN) che siano affidabili e non distruttivi (Paper I). Risultati significativi sono stati ottenuti analizzando la rizosfera che, soprattutto a 1000 m, ha mostrato maggiori contenuti di carbonio organico totale (TOC), di sostanza organica estraibile in acqua (WEOM) e P disponibile del suolo bulk. Con l'aumento di 1°C si potrebbe così verificare un'accelerazione del ciclo dei nutrienti negli ambienti forestali a 1000 m (Paper II). Questo risultato è stato confermato da un maggior contenuto di zuccheri, fenoli solubili e tannini nella WEOM degli stessi suoli (Paper III). Comparando i risultati lungo la latitudine, gli orizzonti minerali sottosuperficiali sono risultati molto simili. Al contrario, il topsoil ha mostrato differenze chimiche e biochimiche attribuibili all’escursione di temperatura estate-inverno, con differenti andamenti delle attività enzimatiche secondo il ruolo degli enzimi nella degradazione della lettiera. In ogni caso, nel topsoil e negli orizzonti sottosuperficiali, l'altitudine è responsabile dell’incremento del TOC, del TN e dello spessore degli orizzonti organici, confermando che l'aumento di temperatura a queste quote potrebbe accelerare la velocità di mineralizzazione della sostanza organica (Paper IV).The research conducted during the three years doctoral activity was focused on the effect of temperature change on chemical and biochemical properties of two different soil components of beech (Fagus sylvatica) forest soils from central Apennines (Italy): i) rhizosphere, which was contrasted with the bulk soil, and ii) organic horizons (OLn, OLv, OH) and the first mineral horizon (A). In the experimental design a small altitudinal transect (800 and 1000 m) with a different mean annual air temperature of 1°C was considered, together with a latitudinal transect with no difference in the mean annual air temperature but different for the summer-winter thermal excursion. The research was preceded by the development of a method to obtain data of total carbon and nitrogen with non-destructive and less time-consuming instruments in order to develop rapid and reliable field analyses (Paper I). Significant results were obtained with the rhizosphere, which showed marked differences with respect to the bulk at 1000 m, particularly for the greater content of total organic carbon (TOC), water extractable organic matter (WEOM), and available P concentration due to rhizodeposition processes. The enriched micro-environment of the rhizosphere also fosters a rapid nutrients' cycle (Paper II). This was confirmed by the higher content of sugars, soluble phenols and tannins in the rhizosphere WEOM at 1000 m (Paper III). Comparing results along the latitudinal transect, in the subsoil only small differences were recorded. Conversely, the topsoil (O+A horizons) showed chemical and biochemical differences ascribable to the summer-winter thermal excursion trend, with different behaviors of the enzymatic activities depending on their role in litter decomposition. However, in both topsoil and subsoil, horizons thickness and the TOC and total nitrogen contents were higher at 1000 than at 800 m, so confirming that an increase of temperature at these altitudes will increase the mineralization rate (Paper IV).
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PUMA, SARA. "Chemico-mechanical improvement of bentonite barriers for pollutant containment." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2507922.
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Pollution control represents one of the main problems of public interest in all industrialised countries.
Since the 1970s, when the engineering of waste containment began, the overall objective of Environmental Geotechnics was to limit contaminant discharge to groundwater and subsoil. Since the 1990s design engineers and environmental agencies have shown a growing interest in the use of geosynthetic clay liners (GCLs) as an alternative to compacted clays in cover systems or in bottom lining of waste containment facilities because they have very low hydraulic conductivity to water and relatively low cost. GCLs contain a thin layer of sodium bentonite with a dry thickness between 5 and 10 mm, sandwiched between two geotextiles or glued to a geomembrane, GM. The excellent hydraulic performances of GCLs have to be attributed to bentonite characteristics and, since these last are greatly influenced by the chemical composition of the environment surrounding the barrier and by the state parameters, the performances of GCLs can be altered, and then worsened, by a simple variation of the chemical or physical boundary conditions. Aimed at solving this last issue, clay liners and GCLs have undergone great change during the last two decades, with new material being introduced (i.e. polymers) and new design methods being adopted (i.e. membrane behaviour investigation, contaminant diffusion estimation).
The research project developed during the Ph.D. has been focused on bentonite barriers. The term “bentonite barriers” includes bentonite or bentonite-based barriers which find application both in urban waste landfill, hazardous or radioactive wastes final disposal and in hydrocarbon containment. The developed theoretical and experimental study has had the aim of evaluating the possible improvement of containment performance of the bentonite barriers, towards standard and non standard liquids, acting on their state parameters, chemical composition, and boundary conditions at installation. The contents of the thesis are reported below:
Chapter 1 – Bentonite barriers.
This chapter is an introduction to the topic of the research activity: the improvement of contaminant containment performances of the bentonite barrier. Chapter 1 gives a phenomenological and physical description of the mineralogical, chemical and physical properties of sodium and calcium bentonite. Moreover, the main features and issues concerning Geosynthetic Clay Liners, and bentonite barriers in general, are introduced.
Chapter 2 – Containment performances of natural and polymer-modified bentonite barriers subjected to physical pre-treatments.
The role of physical pre-treatments, such as pre-hydration, pre-consolidation and salt removal, applied to sodium and polymer modified bentonites, has been analyzed in the Paper reported in chapter 2, titled: “THE ROLE OF PHYSICAL PRETREATMENTS ON THE HYDRAULIC CONDUCTIVITY OF NATURAL AND POLYMER MODIFIED SODIUM BENTONITES”. Moreover, the effect of the presence or absence of needling across the bentonite layer has been studied.
All these variables have been shown to influence the hydraulic performances of bentonite through hydraulic conductivity change in both short and long term conditions. Physical pre-treatments and polymer addiction, in fact, influence the swelling behaviour of bentonite and its response to the cation exchange phenomenon.
Chapter 3 – Osmotic and swelling properties of bentonite barriers.
In the Paper included in this chapter, titled “COUPLED CHEMICAL-HYDRAULIC-MECHANICAL BEHAVIOUR OF BENTONITES”, a theoretical approach has been proposed in order to derive constitutive equations which describe the coupled chemical-hydraulic-mechanical behaviour of bentonite barriers, with the aim to assess their long term performance. The phenomenological parameters that govern the transport of electrolyte solutions through bentonites, i.e. the hydraulic conductivity, the reflection coefficient, which is also called the chemico-osmotic efficiency coefficient, and the osmotic effective diffusion coefficient, have been measured through laboratory tests on a natural sodium bentonite The obtained results have been interpreted by assuming that the microscopic deviations of the pore solution state variables from their average values are negligible. In this way, it is possible to interpret the macroscopic behaviour on the basis of the physical and chemical properties of the bentonite mineralogical components.
At the end of the chapter two further chemico-osmotic tests are described aimed at analysing (1) the osmotic behaviour of calcium bentonite and (2) the effects induced on osmotic behaviour by stress-strain properties. Moreover, the osmotic results are confronted with data from literature.
Finally, the design of a new osmotic apparatus to measure both the swelling pressure and the reflection coefficient is proposed.
Chapter 4 – Hydrocarbon containment performances of natural and polymer-modified bentonite barriers.
Background information on hydrocarbon behaviour in soils is reported in the first part of this chapter. In particular, the effects of capillary forces on the distribution of immiscible fluids in porous media and the theoretical aspects, regarding the formation of tactoids induced by the low dielectric constant that characterizes the most of hydrocarbon species, are studied.
An experimental study is presented in the Paper titled “HYDRAULIC PERFORMANCE OF GCLS WITH DIESEL OIL AND POLYMER TREATMENT PROPOSAL”, which is aimed at evaluating the hydraulic performance of a needle-punched GCL using both standard liquids (i.e. de-ionized water) and diesel oil in order to estimate the change in hydraulic conductivity and swelling ability upon contact or permeation with hydrocarbons. Moreover, the hydraulic conductivity to diesel oil of GCL samples saturated at different initial gravimetric water contents was investigated with the aim to analyse the effect of initial water saturation on hydrocarbon containment performances. Finally, the swelling and hydraulic performances to diesel oil of an innovative material, obtained by mixing sodium bentonite with a polymer, were measured.
Chapter 5 – Containment performances of a bentonite-based barrier constituted of municipal solid waste bottom ashes.
The research described in the Paper included in this chapter, titled “REUSE OF MSWI BOTTOM ASH MIXED WITH NATURAL SODIUM BENTONITE AS LANDFILL COVER MATERIAL” has the aim of evaluating the reuse of incinerator slag, mixed with sodium bentonite, for landfill capping system components. A chemical, hydraulic and mechanical characterization was performed on pure bottom ash (BA) samples from an incinerator in the North of Italy and on the BA-bentonite mixture. This study qualifies the BA-bentonite mixture as a suitable material for landfill cover in Italy. Moreover, owing to the low release of toxic compounds from BA, the proposed cover system does not affect the leachate quality in the landfill.
Chapter 6 – Finite difference modelling of diffusive flux of Calcium through a bentonite barrier in in-situ conditions.
The evidence of the strong degradation induced in the hydraulic performances of sodium bentonite barriers by the cation exchange phenomenon has been highlighted in the previous chapters. This experimental result underlines the need to study the transitional development of the cation exchange phenomenon with the aim to compare that to the period in which landfill barrier performances have to be guaranteed in in-situ conditions.
The mathematical study developed in this chapter is focused on the evaluation of the role of the diffusive component of Calcium flux in the cation exchange phenomenon which can develop in a sodium bentonite barrier, placed in an environment inexorably rich in chemical compounds containing soluble Calcium (i.e. the natural soil, the aquifer, the drainage layer saturated with waste leachate or raining water).
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Ercoli, Roberto. "Chemical neutralization of industrial by-products from the secondary aluminum industry: re-use as foaming agents for the synthesis of geopolymers and monitoring of the hydrogen-rich gas production." Doctoral thesis, Urbino, 2022. http://hdl.handle.net/11576/2698511.
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Barrett, Geraldine Patricia. "Synthesis and physico-chemical properties of chemically modified calixarene receptors." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333798.
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Adesina, Olumide, Cassandra T. Eagle, Ayobami Olukanni, and Reza Mohseni. "Purification of Cyclohexene for Cyclopropanation Reactions." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/143.
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Environmentally friendly reactions yielding cis-cyclopropanes are desired in the insecticide industry as these are most effective at reducing the population of insects while remaining benign to the environment. We are exploring the best parameters for the most effective cis-cyclopropanation reactions. An alkene and a diazo compound react together in the presence of a dirhodium catalyst to produce cyclopropanes. First however, the starting materials must be pure. Alfa Aesar supplies cyclohexene which is reported to be 99% pure, however, Gas column chromatography/Mass spectroscopy reveals that the sample is only 3% cyclohexene. Using an adopted published procedure, we discovered that distillation under nitrogen produces cyclohexene in greater than 95% pure. This is suitable for use in cyclopropanation reactions.
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Nilsson, Frederik. "Alkylglucosides physical-chemical properties /." Lund : Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/39761789.html.
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Olukanni, Ayobami, Cassandra T. Eagle, olumide Adesina, and Reza M. Mohseni. "Purification of Ethyl Diazoacetate by Vacuum Distillation for use in Cyclopropanation Reactions." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/135.
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Environmentally friendly insecticides have long been desired in the production of food. Pyrethiod compounds not only decompose under light and heat, but they are highly toxic to insects while having effectively no toxicity to mammals. The cis-cyclopropane ring in pyrethiod insecticides is the most challenging component to synthesize. We are exploring the best parameters for the most effective cis-Cyclopropanation reactions. An alkene and a diazo compound react together in the presence of a dirhodium catalyst to produce cyclopropanes. First however, the starting materials must be pure. My part of the project is to purify ethyl diazoacetate(EDA). Column chromatography has been used, but yielded no fraction containing EDA as determined by Gas chromatography/Mass spectrometry. Extraction of EDA with sodium carbonate solution yielded similar results. Thus, I turned to distillation at reduced pressure. This method produced EDA in high enough purity to be used in cyclopropanation reactions. The purity of EDA was determined by H-1 nuclear magnetic resonance spectroscopy.
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Papapanayotou, I. "Chemical properties and optical properties of carbonaceous particles." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383288.
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Indoitu, Rodica. "Chemical properties of aerosols over Israel /." [Sede Boker] : Albert Katz International School for Desert Studies, 2006. http://aranne5.lib.ad.bgu.ac.il/others/IndoituRodica.pdf.
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Potužák, Marcel. "Physico-Chemical Properties of Silicate Melts." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-55228.
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Whittaker, Andrew Gavin. "Some chemical properties of microwave radiation." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259845.
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Peyfoon, Elham. "Chemical and biological properties of propolis." Thesis, University of Strathclyde, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510828.
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Lim, Wen Huei. "Physico-chemical properties of ultraflexible vesicles." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417109.
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Serafin, Lukasz Michal. "Chemical bonding properties in substituted disilynes." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3638.
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The molecular structures of the Si2HX, Si2Li2, SiGeHLi and C2H2 species (where X= H, Li, F and Cl) were studied. All of these species have more than one isomeric form. The critical points on the potential energy surfaces of the Si2HX, Si2Li2and C2H2 species and the minima on the SiGeHLi surface were located. The full six-dimensional potential energy surface (PES) of the Si2Li2 molecule was calculated (for the first time) using the CCSD(T)-F12a/cc-pVTZ-F12 level of theory. The core-valence, zero-point energy and relativistic corrections for the Si2HLi and Si2Li2 species were calculated. Additionally, the electron affinity and Li+ /H+ binding energies for the Si2HLi and Si2Li2 structures were investigated. Furthermore, the anharmonic vibrational-rotational properties for the Si2HLi and Si2Li2 structures were calculated using second-order perturbation theory. The recently developed CCSD(T)-F12a method with the cc-pVTZ-F12 basis set was employed to obtain geometries and relative energies (for the Si2HLi, Si2HF, Si2HCl and Si2Li2 structures) and vibrational frequencies (for the Si2H2 and Si2Li2 structures). The CCSD(T) method with the cc-pVXZ, aug-cc-pVXZ and aug-cc-pV(X+d)Z basis sets, CCSD(T)-F12a/cc-pVXZ (where X=2-4) and the B3LYP/6-311+G(d) levels of theory were also used. Comparison was made of the geometric properties and vibrational frequencies calculated at the different levels of theory. The calculated geometric properties for all the studied species and vibrational frequencies (for the Si2H2 structures) show good agreement with the experimental and theoretical literature. The PES of Si2Li2 was used to perform large scale variational vibrational calculations using the WAVR4 program. The first 2400 totally symmetric energy levels were calculated. The low-lying energy levels were qualitatively correct. Conclusive assignments of the vibrational modes of the Si2Li2 structures were made for the eleven lowest lying energy levels.
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Gupta, Saloni. "Physico-chemical properties of polypropylene glycols." Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/21538/.
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Poly(propylene glycol) (PPG) samples of different molecular mass were characterized using differential scanning calorimetry, modulated differential scanning calorimetry, thermogravimetry and thermally stimulated current (TSC) spectroscopy. It was shown, by TSC, that the glass transition temperature and the degree of molecular mobility increased with increasing molecular mass of PPG. Additional experiments showed that PPGs of molecular mass 425, 1000 and 2000 Da undergo one global relaxation process; however, PPG 2700 (Da) undergoes an additional relaxation process after the glass transition which has been attributed either to the release of the excess charge delocalised in the polymer structure or a liquid-liquid transition. Thermally induced phase separation in aqueous solutions of PPG has been examined using a variety of techniques including high sensitivity scanning calorimetry (HSDSC), hot stage microscopy, small angle neutron scattering, and turbidity measurements. The data suggest that phase separation is a consequence of PPG aggregation (droplets); the aggregates grow in size, as the temperature is raised further. It is postulated that phase separation occurs via nucleation and growth, which is corroborated by model fitting the calorimetric data using a mass action aggregation model. It is concluded that phase separation of PPG occurs as a result of the disruption of a hydrogen bonded network between water and PPG. The effect of five sugars (mannitol, maltose, raffinose, sucrose and trehalose) on the Tm (transition temperature) of aqueous PPG 1000 solutions was studied by HSDSC and turbidity measurements. All the sugars decreased the phase separation temperature of the PPG solutions, with trehalose and maltose showing the greatest effect. A series of experiments, using HPLC, showed that phase separated PPG (1000 Da) increased the apparent aqueous solubility of naphthalene.
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Richardson, Stephen. "Sulphide ore minerals : surface chemical properties." Thesis, Aston University, 1988. http://publications.aston.ac.uk/8068/.
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The surfaces of iron-containing sulphide minerals were oxidised by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The characterisation of surface oxidation is relevant to the alteration of ores in nature and their behaviour during flotation and leaching, of importance to the metallurgical industry. The sulphides investigated included pyrite (FeS2), hexagonal pyrrhotine (Fe9S10), monoclinic pyrrhotine (Fe7Se), violarite (FeNi2S4), pentlandite ((FeiNi)9Se), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). The surfaces were oxidised by various methods including acid (sulphuric), alkali (ammonium hydroxide), hydrogen peroxide, steam, electrochemical and air/oxygen (in a low-temperature (150ºC) furnace), The surfaces were examined using surface sensitive chemical spectroscopic methods including x-ray photoelectron spectroscopy (ms), Auger electron spectroscopy (LES) and conversion electron Mössbauer spectroscopy (CEKS). Physical characterisation of the surfaces was undertaken using scanning electron microscopy (SM), spectral reflectance measurements and optical microscopy. Bulk characterisation of the sulphide minerals was undertaken using x-ray diffraction and electron microprobe techniques. Observed phases suggested to form in most of the sulphide surfaces include Fe204, Fe1-x0, Fe202, Fe00H, Fe(OH)3, with iron II & III oxy-sulphates. The iron sulphides show variable extents of oxidation, indicating pyrite to be the most stable. Violarite shows stability to oxidation, suggested to result from both its stable spinel crystal structure, and from the rapid formation of sulphur at the surface protecting the sub-surface from further oxidation. The phenomenon of sub-surface enrichment (in metals), forming secondary sulphides, is exhibited by pentlandite and chalcopyrite, forming violarite and copper sulphides respectively. The consequences of this enrichment with regard to processing and leaching are discussed. Arsenopyrite, often a hindrance in ore processing, exhibits the formation of arsenic compounds at the surface, the dissolution of which is discussed in view of the possible environmental hazard caused by the local pollution of water systems. The results obtained allow a characterisation of the sulphides in terms of their relative stability to oxidation, and an order of stability of the sulphide surfaces is proposed. Models were constructed to explain the chemical compositions of the surfaces, and the inter-relationships between the phases determined at the surface and in the sub-surface. These were compared to the thermo-chemically predicted phases shown in Eh/pH and partial pressure diagrams! The results are discussed, both in terms of the mineralogy and geochemistry of natural ores, and the implications for extraction and processing of these ore minerals.
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Jacobsen, S. M. "Chemical, catalytic and spectroscopic properties of titanium (II)." Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381356.
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Maruatona, Gaamangwe Nehemiah. "Physico-chemical, nutritional and functional properties of defatted marama bean flour." Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06112009-142412/.
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Díez, Orrite Silvia. "Physico-chemical properties of polymers at interfaces." Doctoral thesis, Universitat Rovira i Virgili, 2002. http://hdl.handle.net/10803/8511.
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A polymer is a large molecule constructed from many smaller structural units calledmonomers joined together by covalent bonds. Polymers have existed in natural form
since life began and those such as DNA, RNA, proteins and polysaccharides are some
of the most important macromolecules found in plant and animal life. From the earliest
times, the man has used many of these polymers as materials for providing clothing,
decoration, tools, weapons and other requirements. However, the origins of today's
polymer industry commonly are accepted as being in the nineteenth century when
important discoveries were made concerning to the modification of certain natural
polymers, as cellulose. The use of synthetic and natural polymers as stabilisers for
colloid systems (sols, dispersions, microemulsions, etc.) is becoming more important
everyday in contemporary life. Polymer additives can be applied in preconcentrations
and dehydration of suspensions in mineral processing, purification of wastewater and
even in nutritional and pharmaceutical emulsions being their importance related to the
characteristics of the process and the properties that they show. The present work aims
to develop appropriate numerical and analytical modelling techniques, which can
describe (considering the formation of loops and tails) the structure of a polymeric layer
adsorbed on heterogeneous surfaces; this adsorbed layer is an relevant factor in the
properties showed by this kind of materials. Taking into account this, the methodology
known as Single Chain Mean Field (SCMF) (originally used to study micellar
aggregates and grafted polymers) was modified to apply on polymer adsorption
problems. In this way, it was possible to calculate numerically properties that can be
experimentally measured, such as total monomer volume fraction profiles, loop and tail
volume fraction profiles, adsorbance or the thickness of the adsorbed layer. The
structure of the polymeric layer was examined both for flat and spherical (colloidal
particles) surface geometries. When compared with other well established
methodologies for the numerical simulation of polymeric systems, this new version of
SCMF was found to be more efficient due to the improved sampling of the polymer
chain configuration space.
Thus, SCMF method results, in the case of the adsorption on flat surfaces, compare well
with those obtained either with Monte Carlo simulations or with the method developed
in the 80s by Scheutjens and Fleer (SCF). Due to the lack of studies focusing to polymer
adsorption on colloidal particles, our results have been the first to present quantitative
predictions of the structure of the polymeric layer adsorbed on a spherical surface. Thus,
we have demonstrated the dependence of the adsorbed polymer layer with the size of
the colloidal particle as well as the characteristic lengths that influence on it. Finally, in
this work an analytical approach for the description of polymer-colloidal mixtures has
been developed which compares well with the numerical results obtained from the
SCMF methodology. Furthermore, the analytical approach is able to predict system
behaviours, as for example the formation of gels.
Un polímero es una molécula de grandes dimensiones formada de pequeñas unidades
llamadas monómeros, los cuales se encuentran unidos por medio de enlaces covalentes.
Los polímeros han existido de forma natural desde el comienzo de la vida, y aquellos
como el DNA, RNA o las proteínas son algunos de los polímeros más importantes
encontrados tanto en la vida animal como en la vegetal. Desde siempre el hombre ha
utilizado muchos de estos polímeros como materiales para hacer ropa, decoración,
herramientas, etc. Sin embargo, el origen de la industria de polímeros que conocemos
hoy en día se produjo en el siglo 19, gracias a importantes descubrimientos dentro de la
modificación de ciertos polímeros naturales, como la celulosa. El uso de polímeros
sintéticos y naturales como estabilizadores de sistemas coloidales (dispersiones,
microemulsiones, etc.) juega en nuestros días un papel importante. Los polímeros
utilizados como aditivos, pueden ser aplicados en preconcentraciones y deshidratación
de suspensiones dentro de procesos minerales, tratamiento de aguas residuales e incluso
los podemos encontrar dentro de la industria farmacéutica y alimentaria, donde su
importancia es debida a la procesabilidad y propiedades que ellos exhiben. El trabajo
que se presenta es orientado al desarrollo de técnicas de modelización, tanto analíticas
como computacionales, y su aplicación en la descripción (por medio de la formación de
bucles y colas) de la estructura de la capa de polímeros adsorbida en superficies
heterogéneas, siendo dicha capa de polímeros un factor importante en las propiedades
que este tipo de materiales presentan. Con este propósito, la metodología conocida
como Single Chain Mean Field, utilizada anteriormente tanto para el estudio de
agregados micelares como de polímeros anclados en superficies, ha sido modificada
para describir la adsorción de polímeros en superficies. Así se han podido calcular
numéricamente propiedades medibles experimentalmente como los perfiles de la
fracción en volumen de monómeros totales, además de los pertenecientes a los bucles y
colas, adsorbancia o el espesor de la capa adsorbida, para geometrías de la superficie
absorbente tanto plana como esférica (partículas coloidales). En su comparación con
otras metodologías, ya establecidas para la simulación numérica dentro de la física de
polímeros, la aplicación de esta nueva versión del Single Chain Mean Field (SCMF)
ha resultado ser más eficiente debido a un mejor muestreo del espacio de
configuraciones de las cadenas poliméricas. De este modo, comparando los resultados
obtenidos a partir del SCMF, con aquellos obtenidos mediante técnicas de simulación
Monte Carlo o la teoría desarrollada en los años 80 por Scheutjens y Fleer (SCF), se ha
podido encontrar un buen acuerdo en las propiedades calculadas para el caso de la
adsorción en superficies planas. Debido a la dificultad intrínseca del estudio de la
adsorción en superficies curvadas, nuestros resultados son los primeros que presentan
predicciones cuantitativas sobre la estructura de la capa que se forma sobre una
partícula coloidal. Así hemos podido comprobar la dependencia de la estructura de la
capa de polímeros adsorbidos con el tamaño de la partícula sobre la que se encuentran
adsorbidos además de las longitudes características de las cuales depende. Finalmente,
en este trabajo se ha desarrollado, también, una teoría analítica para la descripción de la
mezcla polímero-coloide. De este modo, los resultados numéricos obtenidos con el
SCMF han podido ser comparados con dicha teoría, obteniendo, de nuevo, un buen
acuerdo y predecir, además, comportamientos colectivos como la formación de geles.
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Churakov, Sergey. "Physical-chemical properties of complex natural fluids." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962849723.
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Hirano, Shin-ichi, Toshinobu Yogo, Wataru Sakamoto, Ko-ichi Kikuta, Kazumi Kato, Yoshikuni Takeichi, Yasushi Araki, et al. "Chemical processing and properties of functional ceramics." IEEE, 1999. http://hdl.handle.net/2237/6125.
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Zysman-Colman, Eli. "The chemical and physical properties of polychalcogens." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84864.
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The optimized synthesis of acyclic dialkoxy disulfides and aromatic polysulfides is described and their physical properties probed. A theoretical survey of dialkoxy disulfides and thionosulfites was undertaken in order to determine the most efficacious method for accurately modeling these compounds. In particular, the origin of the high barrier to rotation in the dialkoxy disulfides was determined to be due to a generalized anomeric effect resulting from two lone pair donations of each sulfur atom into each of their respective sulfur-oxygen antibonding orbitals. The origin of the high rotational barrier was also verified experimentally, in particular with respect to solvent and substituent effects. Complimentary to this thermal process, the decomposition of dialkoxy disulfides was also investigated. It was determined that these compounds decompose under first order kinetics via an initial asymmetric S-O homolytic cleavage. Activation parameters for both of these processes were determined.Theoretical modeling on the relative ground state energies of dialkoxy disulfides is also described. It has been ascertained that the equilibrium position between the two isomers can be influenced by the ring size of the molecule; larger rings promote the dialkoxy disulfide isomer. These modeling studies were successfully corroborated experimentally. Of note is the synthesis of a new 8-membered ring dialkoxy disulfides as well as novel 7-membered ring thionosulfites. These compounds were also confirmed by single X-ray crystallography.
The kinetics of desulfurization of acyclic aromatic tri- and tetrasulfides is described. Tetrasulfides were found to transfer a sulfur atom to triphenylphosphine over ten times faster than their trisulfide analogues.
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Tullett, Jayne Margaret. "Chemical and biological properties of S-nitrosothiols." Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30786.
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Since its discovery, nitric oxide (NO) has been identified to influence a large number of physiological processes. This project examines S-nitrosothiols (RSNO) as pro-drugs of NO. The overall aim of this project was to improve our present understanding of the chemical and biological properties of RSNOs. This project has demonstrated that under physiological conditions the stability of RSNOs varies with structure. Results have shown that S-nitrosocysteine and S-nitroso-L-cysteinylgylcine were the least stable of the RSNOs investigated, whereas S-nitroso-N-acetyl-L-cysteine, S-nitroso-3-mercaptopropionic acid and S-nitroso-2-mercapto-ethane sulphonic acid were the most stable. The decomposition of certain RSNOs is catalysed by trace amounts of copper. This phenomenon was particularly evident with the RSNOs, S-nitrosocysteine and S-nitroso-L-cysteinylglycine. Copper catalysed decomposition appears to occur more readily with RSNOs that allow the formation of a stable ring structure, in which Cu+ is bound to the nitrogen of the NO group and another electron-rich atom such as the nitrogen of an amino group. Copper catalysed the decomposition of S-nitrosoglutathione and S-nitroso-L--glutamyl-L-cysteine, but to a lesser extent. Investigations have shown that the decomposition of a stable RSNO is more rapid in the presence of a thiol which gives rise to an unstable RSNO via a transnitrosation reaction. In contrast, decomposition of an unstable RSNO is slower in the presence of a thiol which leads to the formation of a stable RSNO. All RSNOs studied inhibited platelet aggregation and relaxed vascular smooth muscle in a dose dependent manner. In addition, all the RSNOs exhibited a dose-dependent inhibition of growth of A549 cells. Generally no real correlation between the chemical and biological properties of RSNOs was observed. It is clear that there are many factors controlling the release of NO from RSNOs which may have implications regarding the biological activity of these compounds.
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Alves, Luis. "Physical and chemical properties of gold nitride." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512027.
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Tjandra, Juhana. "Eucalyptus oil: Sources, analysis and chemical properties." Thesis, Tjandra, Juhana (1986) Eucalyptus oil: Sources, analysis and chemical properties. PhD thesis, Murdoch University, 1986. https://researchrepository.murdoch.edu.au/id/eprint/51658/.
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A rapid and accurate solvent extraction - gas chromatographic analytical procedure was developed for the combined qualitative and quantitative chemical analysis of terpenoids from the leaves of eucalypts. The solvent extraction method was also applied successfully to the dry weight determination of the plant materials. The proposed method is efficient in time, cost and space. In comparative studies, it was shown to be more reliable than previous techniques.
Using the new procedure, leaf oils of naturally occurring eucalypts in Western Australia were analysed systematically for the first time. Eucalyptus Kochii subsp. kochii and E. kochii subsp. plenissima were selected as the outstanding oil producing species yielding up to 8% on a dry weight basis. Analysis of the volatile oil revealed a composition of 90% 1,8-cineole and 5% other monoterpenoids. The significant seasonal trends and intraspecies variation in the essential oil yield were investigated over a two year period.
The volatile oil composition patterns of various eucalypts obtained from high resolution capillary gas chromatography were shown to serve as finger prints, providing additional information at species and subspecies level to assist in the more difficult Eucalyptus taxonomic problems.
Eucalyptus oil and its main components were investigated as potential cosolvents for aqueous ethanol/petrol fuel mixtures. Results showed that the incorporation of 1 to 3% eucalyptus oil or its main components such as 1,8-cineole increased the water tolerance and long-term phase stability of the fuel mixtures.
Eucalyptus-derived fuels were found to have calorific values in the range of 4000 to 4500 kJ/kg similar to those of petroleum fuels.
Liquid-liquid equilibrium data for the system unleaded petrol/ ethanol/water/1,8-cineole, and the ternary system ethanol/water/1,8-cineole were investigated isothermally. An apparatus replacing the less sensitive visual observation and facilitating cloud point determination was designed for this purpose. Ternary phase diagrams were determined, complete with tie-lines, thus fully characterizing the two-phase area. The tie-line data were correlated by the methods of Hand and Othmer-Tobias.
A brief account of the history, economics and future viability of the eucalyptus oil industry is presented.
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Ghorai, Suman. "Chemical, physical and mechanical properties of nanomaterials and its applications." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2501.
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The contribution of atmospheric aerosols towards radiative forcing has a very high uncertainty due to their short atmospheric lifetime. The aerosol effects are largely controlled by the density, elemental composition, and hygroscopic properties of the aerosol particles. Therefore, we have performed designed new methodology using Scanning Transmission X-ray Microscopy (STXM), Atomic force spectroscopy (AFM), micro-FTIR spectroscopy and Scanning Electron Microscopy (SEM) to quantify these important aerosol properties. Hygroscopic properties are quantified by plotting the mass of water on a single particle basis, calculated from STXM, as a function of relative humidity. Alternatively, micro-FTIR spectra have been used to study the effect of composition of aerosol particles on the hygroscopic properties of NaCl. Moreover, a unique combination of STXM and AFM has been utilized to quantify density and elemental composition of micrometer dimensional particles. This method has also been extended towards exploring mixing state of particles, consisting of heterogeneously mixed inorganic and organic compounds. In addition to these above mentioned properties, the fate of an atmospheric particle is often altered by chemical transformation and that in turn is influenced by the atmospheric RH. Therefore, we have studied an unusual keto-enol tautomerism in malonic acid particles at high RH, which is not observed in bulk. This observation could potentially be utilized to significantly improve the models to estimate Secondary Organic Aerosols (SOA). Using STXM and micro-FTIR technique, RH dependent equilibrium constant of the tautomerism reaction has been quantified as well.
Organic nanocrystals capable of undergoing solid state photochemical changes in a single-crystal-to-single-crystal (SCSC) manner have been particularly important in fabricating molecular switches, data storage devices etc. Mechanical properties of these nanomaterials may control its SCSC reactivity. In addition, investigation of mechanical stiffness is important to define allowable limit of stiffness towards device application. Therefore, we studied mechanical properties of series organic nano cocrystals primarily consisting of trans-1,2-bis(4-pyridyl)ethylene and substituted resorcinol using AFM nanoindentation technique. Dependence of mechanical properties and SCSC reactivity on the resorcinol structure is also investigated as well. Moreover, photolithography on the thin film of these organic cocrystals has been performed to demonstrate its applicability as a photoresist.
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Wang, Junwei. "Chemical doping of metal oxide nanomaterials and characterization of their physical-chemical properties." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1333829935.
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Liang, Heyi. "Rational Design of Soft Materials through Chemical Architectures." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1573085345744325.
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Jefferey, W. A. "Bisdioxopiperazines and related prodrugs : Physico-chemical and anti-tumour properties." Thesis, Institute of Cancer Research (University Of London), 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377564.
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Blum, Monika. "Electronic and Chemical Properties of Liquids and Solutions." Doctoral thesis, kostenfrei, 2009. http://nbn-resolving.de/urn/resolver.pl?urn=nbn:de:bvb:20-.
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Guyon, Pascal. "Chemical and physical properties of Amazonian aerosol particles." [S.l. : s.n.], 2002. http://ArchiMeD.uni-mainz.de/pub/2003/0035/diss.pdf.
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Brodin, Ida. "Chemical Properties and Thermal Behaviour of Kraft Lignins." Licentiate thesis, KTH, Fibre and Polymer Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11010.
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Research concerning lignin has increased during the last years due to its renewability and ready availability in black liquor at pulp mills. Today, the kraft lignin found in black liquor is used as a fuel to gain energy in the recovery boiler at the mill. However, a new isolation concept, LignoBoost®, has enabled isolation of part of the lignin while allowing the use of black liquor as a fuel. This isolated lignin can be utilised as a fuel in, for example, thermal power stations or further upgraded to more value-added products. In this context, the most interesting value-added product is carbon fibre. The demand for carbon fibre has increased, but the biggest obstacle for a more extended use is the high production cost. About half of the production cost is related to the raw material.
In this work, the possibility of using kraft lignin as a precursor for carbon fibre production has been investigated through fundamental studies. Kraft lignins originating from birch, Eucalyptus globulus, softwoods and softwoods from liner production have been studied. By separating the lignin while still in solution in the black liquor, unwanted large particles such as carbohydrates can easily be removed. After isolation according to the LignoBoost process and purification with the use of an ion-exchanger, the lignins have been both chemically and thermally characterised. Identification of the released compounds at different temperatures has been performed because only 40% of carbon relative to original lignin remains, down from theoretical 60% after thermal treatment up to 1000°C. The main released compounds were phenols, as revealed by pyrolysis-GC/MS. Additionally, a pre-oxidation was done in order to try to stabilise the lignins. It was shown that an oxidation prior to the thermal treatment increases the yield by more than 10% and that the main release of compounds takes place between 400°C and 600°C. Fractionated lignin is better qualified as raw material for carbon fibre production because it is purer and its softening temperature can be detected. Fractionated kraft lignins from all investigated wood sources have high possibilities to act as precursors for the manufacture of carbon fibre.
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Chaudhiury, Umme Salma. "Mechanical and chemical properties of rotator cuff tendons." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601169.
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Shoulder disease is the third most common musculoskeletal problem, and rotator cuff tendon tears account for the greatest proportion of shoulder complaints. Rotator cuff tears are estimated to affect between 5-30% of adults, with higher incidences of tearing and fa ilure to heal in elderly patients, placing a huge socioeconomic burden on an ageing British population. Serious concern arises as a large proportion of technically correct surgical repairs re-rupture. The intra-articular environment of the tendon often precludes nonnal healing and surgical repair is often necessary to improve pain and restore some function. It is feasible that there may be an inherent phys iological or biomechanical defect in the tissue that prevents complete heal ing without some further augmentation to the surgical repair. Improved understanding of the biochemical and biomechanical changes in tom rotator cuff tendons may help to reduce the high rerupture rates. This study aimed to characterise nonnal, and different sized rotator cuff tendon tears from small samples obtained intraoperatively to try to use tests that may potentially be clinica lly usefu l in the future. Tendon samples were mechanically tested using dynamic shear analysis, a fonn of rheology, to overcome gripping and slippage problems of very small specimens. It was found that tom tendons had a significandy reduced storage modulus compared to normal tendons, particularly for massive tears. Chemical analysis of tendons using Fourier transform infrared spectroscopy revealed that partial and different sized rotator cuff tendon tears are chemically distinguishable. The onset of rotator cuff tear pathology is mainly due to an alteration of the collagen structural arrangements, with associated changes in lipids and carbohydrates. Collagen structural changes in small and massive tendons were quantified us ing differential scanning calorimetry, which allows measurement of coHagen thermal properties as a reflection of their structural integrity. Small and massive tendon tears had reduced thermal properties and hence reduced collagen integrity when compared to normal tendons, although there was no difference between the two tear groups. Gene expression differences between the small, massive tears and normal tendons were studied using microarray analysis, and revealed that the different groups were biologically distinguishable.
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Barrier, Sylvain. "Physical and chemical properties of sporopollenin exine particles." Thesis, University of Hull, 2008. http://hydra.hull.ac.uk/resources/hull:6412.
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The chemical structure of sporopollenin was extensively reviewed, along with some considerations pertaining to its physical and biological properties. A comparative study is presented of extraction protocols to isolate exines from L. clavatum, in particular, but with extension to spores from other species, namely, Lycopodium spec., Ambrosia trifida, Aspergillus niger and Chlorella vulgaris. Physical aspects of the materials extracted were studied, including size (highlighting large and small types of commercial “Lycopodium”), wall thickness, mechanical resistance and density. Encapsulation of a wide variety of compounds in sporopollenin microcapsules was investigated using passive, vacuum, compression and centrifugation methods. Diverse products, with molecular weights ranging from less than 1kDa to 464kDa, were successfully encapsulated in exines, including both polar (e.g. dyes, proteins, carbohydrates and oligonucleotides) and non-polar products (e.g. oils and waxes). It was shown that a protein, alkaline phosphatase, does not lose its initial activity after it has been encapsulated in exines and subsequently released. Sporopollenin was found to grant oils protection against photooxidation triggered by UV light and the extinction coefficient of sporopollenin was determined (20,000-40,000m¯¹). Protective abilities offered by exines to oils against aerial oxidation, and refining effects of sporopollenin on rancid fats, were studied, completed by a preliminary investigation of sporopollenin’s redox characteristics. A flavour test on 20 volunteers showed that exines mask the taste of encapsulated cod liver oil up to a 1/1 (w/w) loading level. Sporopollenin was also used in solid-phase organic synthesis. It was established that the reaction of ammonia, primary aliphatic amines and aniline with sporopollenin formed an amide bond on a carboxylic group of the sporopollenin. A short diamine was attached to sporopollenin in order to construct a spacer arm by further reaction between the free amino end and succinic anhydride. Sporopollenin was derivatised with bromine and chlorine by addition to the unsaturated functional groups, substitution of the hydroxyl groups and chloromethylation of the aromatic rings. The attached halogen atoms were then successfully substituted by azide and thiols. The thiol availability to nucleophilic substitution and formation of disulphide bridges was assessed.
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Souza, Sofia Leite. "On the physical-chemical properties of ceramide C16." Doctoral thesis, Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica, 2012. http://hdl.handle.net/10362/12024.
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Dissertation presented to obtain the Ph.D degree in Chemistry.Ceramides are known to be involved in cell signalling and are proposed to assist in the formation of laterally segregated membrane domains, known as ceramide rich domains in cell lipid bilayers. The lipid matrix of the stratum corneum, the uppermost layer of the skin, which is responsible for its water barrier properties, is mainly composed of ceramides, associated with cholesterol, long chain fatty acids and cholesteryl esters.(...)
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Le, Roex Tanya. "The physio-chemical properties of organic inclusion compounds." Doctoral thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/15435.
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Includes bibliographical references.In this thesis the inclusion properties of the host compounds trans-9,10-dihydroxy-9,10-bis(p-tert-butylphenyl)-9, 10-dihydroanthracene (TBDDDA), 9.9'-(Biphenyl-4,4'diyl) difluoren-9-ol (WEB24) and 1â ´ ,1â ¶,5â ´,5â ¶-tetrahydroxy-2,4,6,8-tetrapentyl-3â ´,3â ¶,7â ´,7â ¶-tetra(p-toluenesulfonyl-oxy)-1,3,5, 7(1,3)-tetrabenzenacyclooctaphane (TTRSC) were investigated. Each of these host compounds is bulky and rigid and in addition contains high-affinity functional groups which can engage in specific host-guest interactions, such as hydrogen bonding.
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Franzyshen, Stephen Keith. "Acidic and Chemical Properties of Molten Salt Hydrates." W&M ScholarWorks, 1985. https://scholarworks.wm.edu/etd/1539625305.
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Kilinkissa, Ornella Edlyne Youdaga. "Physical chemical properties of selected pharmaceutical co-crystals." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/731.
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Thesis submitted in fulfilment of the requirements for the degree
Magister Technologiae: Chemistry
in the Faculty of Applied Sciences at the
CAPE PENINSULA UNIVERSITY OF TECHNOLOGY
2014The solid state modification of a given active pharmaceutical ingredient is a desired way to alter its physicochemical properties, such as solubility or bioavailability. The solubilitymelting point relationship of the ensuing co-crystal or salt is not fully understood. In this thesis, a series of model co-crystals and pharmaceutical co-crystals and salts of baclofen were investigated. The model co-crystals were prepared from 4,4’-bipyridine (BIPY) and 1,2-bis(4-pyridyl)ethane (ETBIPY) used as host compounds which were combined with a series of carboxylic acids as co-formers, such as p-toluic acid (PTA), rac-phenylbutyric acid (racPBA), racemic and S-phenylsuccinic acid (racPSA and S-PSA, respectively). In the second part, six new multicomponent crystals of baclofen (BAC, (RS) 4-amino-3-(4- chlorophenyl)-butanoic acid), were prepared with mono- and dicarboxylic acids: two pharmaceutical co-crystals obtained with benzoic acid (BAC•BA) and p-toluic acid (BAC•PTA) and four pharmaceutical salts with 1-hydroxy-2-naphthoic acid, (BAC+)(HNA-), oxalic acid, 2(BAC+)(OA2-), maleic acid, (BAC+)(MA-) and p-toluene sulfonic acid, (BAC+)(PTSA-)•IPA. The compounds prepared were analysed by single crystal and powder X-ray diffractometry, differential scanning calorimetry and their solubility was measured in water and ethanol. From the analysis of the model co-crystals it was concluded that their aqueous solubility is inversely related to the melting point values and this can be explained by packing features. Also, the introduction of a chiral building block, compared to its racemic counterpart, is a valuable way to limit the formation of the intermolecular interactions in the new multicomponent crystal and thus decrease the efficiency of the packing which eventually leads to lower melting points and better solubility. The analysis of the baclofen crystals suggests that a strong, robust and predictable hydrogen bonding network with a combination of molecular building blocks which show acceptable molecular flexibility is a good recipe for successful co-crystal design.
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Glicerina, Virginia Teresa <1979>. "Physico-chemical and microstructural properties of food dispersions." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6412/1/Glicerina_Virginia_tesi.pdf.
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The macroscopic properties of oily food dispersions, such as rheology, mechanical strength, sensory attributes (e.g. mouth feel, texture and even flavour release) and as well as engineering properties are strongly determined by their microstructure, that is considered a key parameter in the understanding of the foods behaviour . In particular the rheological properties of these matrices are largely influenced by their processing techniques, particle size distribution and composition of ingredients. During chocolate manufacturing, mixtures of sugar, cocoa and fat are heated, cooled, pressurized and refined. These steps not only affect particle size reduction, but also break agglomerates and distribute lipid and lecithin-coated particles through the continuous phase, this considerably modify the microstructure of final chocolate. The interactions between the suspended particles and the continuous phase provide information about the existing network and consequently can be associated to the properties and characteristics of the final dispersions. Moreover since the macroscopic properties of food materials, are strongly determined by their microstructure, the evaluation and study of the microstructural characteristics, can be very important for a through understanding of the food matrices characteristics and to get detailed information on their complexity.
The aim of this study was investigate the influence of formulation and each process step on the microstructural properties of: chocolate type model systems, dark milk and white chocolate types, and cocoa creams. At the same time the relationships between microstructural changes and the resulting physico-chemical properties of: chocolate type dispersions model systems dark milk and white chocolate were investigated.Le proprietà macroscopiche di dispersioni alimentari a base oleosa tra cui quelle reologiche, meccaniche e sensoriali (consistenza, texture, palatabilità, viscosità, stabilità fisica, ecc.) sono fortemente influenzate dalla loro microstruttura che è considerata un parametro chiave nella comprensione del “comportamento macroscopico” degli alimenti. In particolar modo le proprietà reologiche di tali matrici alimentari sono direttamente influenzate sia dalla formulazione che dal processo di produzione. Durante la produzione di cioccolato e/o surrogati a base di cacao, miscele di zucchero, cacao e grassi vengono riscaldate, raffreddate, pressurizzate e raffinate (Beckett 2000). Questi operazioni tecnologiche la contribuiscono a ridurre la dimensione delle particelle, a rompere gli agglomerati e a distribuire grassi e lecitina attorno alle singole particelle, modificandone la loro microstruttura . Poiché le proprietà macroscopiche di tali matrici alimentari sono fortemente determinate dalla loro microstruttura, la valutazione delle caratteristiche microstrutturali risulta essere molto importante al fine di studiare e ottenere dettagliate informazioni sulla loro complessità. Il presente studio si è proposto pertanto di valutare, mediante tecniche dirette di microscopia ed indirette di laser light diffraction, l’influenza delle diverse formulazioni e di ogni singola fase del processo produttivo sulle proprietà microstrutturali di: sistemi modello a base oleosa, cioccolato fondente, al latte e bianco e surrogati a base di cacao. Parallelamente sono state investigate le relazioni esistenti tra le caratteristiche micro strutturali delle suddette matrici e le loro proprietà reologiche e chimico-fisiche.
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Glicerina, Virginia Teresa <1979>. "Physico-chemical and microstructural properties of food dispersions." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6412/.
Full textAbstract:
The macroscopic properties of oily food dispersions, such as rheology, mechanical strength, sensory attributes (e.g. mouth feel, texture and even flavour release) and as well as engineering properties are strongly determined by their microstructure, that is considered a key parameter in the understanding of the foods behaviour . In particular the rheological properties of these matrices are largely influenced by their processing techniques, particle size distribution and composition of ingredients. During chocolate manufacturing, mixtures of sugar, cocoa and fat are heated, cooled, pressurized and refined. These steps not only affect particle size reduction, but also break agglomerates and distribute lipid and lecithin-coated particles through the continuous phase, this considerably modify the microstructure of final chocolate. The interactions between the suspended particles and the continuous phase provide information about the existing network and consequently can be associated to the properties and characteristics of the final dispersions. Moreover since the macroscopic properties of food materials, are strongly determined by their microstructure, the evaluation and study of the microstructural characteristics, can be very important for a through understanding of the food matrices characteristics and to get detailed information on their complexity.
The aim of this study was investigate the influence of formulation and each process step on the microstructural properties of: chocolate type model systems, dark milk and white chocolate types, and cocoa creams. At the same time the relationships between microstructural changes and the resulting physico-chemical properties of: chocolate type dispersions model systems dark milk and white chocolate were investigated.Le proprietà macroscopiche di dispersioni alimentari a base oleosa tra cui quelle reologiche, meccaniche e sensoriali (consistenza, texture, palatabilità, viscosità, stabilità fisica, ecc.) sono fortemente influenzate dalla loro microstruttura che è considerata un parametro chiave nella comprensione del “comportamento macroscopico” degli alimenti. In particolar modo le proprietà reologiche di tali matrici alimentari sono direttamente influenzate sia dalla formulazione che dal processo di produzione. Durante la produzione di cioccolato e/o surrogati a base di cacao, miscele di zucchero, cacao e grassi vengono riscaldate, raffreddate, pressurizzate e raffinate (Beckett 2000). Questi operazioni tecnologiche la contribuiscono a ridurre la dimensione delle particelle, a rompere gli agglomerati e a distribuire grassi e lecitina attorno alle singole particelle, modificandone la loro microstruttura . Poiché le proprietà macroscopiche di tali matrici alimentari sono fortemente determinate dalla loro microstruttura, la valutazione delle caratteristiche microstrutturali risulta essere molto importante al fine di studiare e ottenere dettagliate informazioni sulla loro complessità. Il presente studio si è proposto pertanto di valutare, mediante tecniche dirette di microscopia ed indirette di laser light diffraction, l’influenza delle diverse formulazioni e di ogni singola fase del processo produttivo sulle proprietà microstrutturali di: sistemi modello a base oleosa, cioccolato fondente, al latte e bianco e surrogati a base di cacao. Parallelamente sono state investigate le relazioni esistenti tra le caratteristiche micro strutturali delle suddette matrici e le loro proprietà reologiche e chimico-fisiche.
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Delle, Site Luigi. "Ab initio study of water." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322621.
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BONARI, GIANMARIA. "DIFFERENT HABITAT AND TAXA: VARIOUS APPROACHES AND THEIR IMPLICATIONS FOR A LONG-SIGHTED MANAGEMENT AND CONSERVATION." Doctoral thesis, Università di Siena, 2017. http://hdl.handle.net/11365/1010508.
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The thesis starts in the continental context of the White Carpathians Protected Landscape Area and UNESCO Biosphere Reserve (Czech Republic), a protected area famous for its grasslands with the globally highest fine-scale plant species richness. The effects of management on species richness and composition of both plants and animals were tested in relation to different management practices (mowing, grazing, abandonment and mixed management) for several years at several sites, clarifying the disagreements that have occurred among conservationists and practitioners to date. The thesis continues with a focus on the Mediterranean context. Here, the distribution patterns of understorey assemblages of coastal pine stands on sand dunes were studied, given the scarcity of literature due to scholarly disdain. Using more than a hundred plots along Italian coastlines in different pine forest types, community similarity and specificity was assessed in order to provide lacking management clues. Subsequently, focusing on a pine forest stand located in Southern Tuscany, the thesis aimed to solve another pivotal question, namely by investigating the concordance of species assemblages between vascular plants, oribatid mites and soil chemical properties with special attention to the role of vegetation structure (i.e. tree, shrub and herbaceous cover) for biological components. This part provides new answers about congruence among communities and following appropriate management practices to be fulfilled for communities. The last part, performed along a wide range of Tuscan coasts, deals with one of the most extreme habitats in the Mediterranean basin: coastal dunes. Here, the understanding of the response of plant species to soil factors was estimated. This provides concrete proposals for the effective conservation of coastal habitats.
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Bengtsson, Felix. "Depth-resolved Raman Spectroscopy and X-ray Photoelectron Spectroscopy to Evaluate the Structural and Chemical Properties of Chemically Strenghtened Glasses." Thesis, Uppsala universitet, Fasta tillståndets fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-427072.
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In this thesis, the structural and chemical properties of a series of titanosilicate glasseswere investigated. The glasses were subjected to a chemical strengthening process(with K^+ replacing Na^+) at four different treatment temperatures and studied withXPS- and Raman spectroscopy. From the XPS analysis, the interdiffusion coefficientsand activation energies were calculated to be between 3.9*10^-12–4.3*10^-11 cm^2/sand 101.1-103.6 kJ/mol respectively. An increase in the TiO2 content lead to adecrease in the interdiffusion coefficients and consequently to an increase in theactivation energies. From the Raman analysis, the presence of compressive stressescould be observed as well as an indication of viscous relaxation from the Raman shifts.An attempt to model the compressive stresses as a function of depth was alsoperformed using a modified version of a stress evaluation method proposed byTerakado, Nobuaki, et al. "A novel method for stress evaluation in chemicallystrengthened glass based on micro-Raman spectroscopy." Communications Physics3.1 (2020): 1-7. The calculated values of the compressive stresses were found to bereasonable for the measurements that followed the requirements of the method, butas this modified version is based on assumptions, no direct conclusions could bedrawn regarding its validity.
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Trevett, Adrian S. "The mechanical properties of hydrogel polymers." Thesis, Aston University, 1991. http://publications.aston.ac.uk/9692/.
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Henriksson, Marielle. "Cellulose nanocomosite films : processing, structure and properties." Licentiate thesis, KTH, Aeronautical and Vehicle Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-350.
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Swaddling, Paul. "The chemical and magnetic structures of rare-earth superlattices and thin films." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670271.
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Johnson, Carter David. "Examination of lignocellulosic fibers for chemical, thermal, and separations properties addressing thermo-chemical stability issues /." [Ames, Iowa : Iowa State University], 2007.
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Zhou, Qian. "Thermophysical Properties of Ionic LiquidâLiX Mixtures." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-07062009-150951/.
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Ionic liquids (ILs) have attracted strong interest due to their high chemical, thermal and electrochemical stability; wide liquid range; high ionic conductivity and low volatility. The research objective of this project has been to explore the thermophysical properties of ILs and their mixtures with lithium salts (LiX). These mixtures may become the electrolyte materials essential for the success of safer, high-voltage next-generation lithium batteries targeted for plug-in hybrid electric vehicles (PHEVs) and/or electric vehicles (EVs). At present, there is only a limited amount of data available in the literature regarding the thermal stability and phase behavior of IL-LiX electrolytes. Such information, however, is crucial for determining the electrolyte safety characteristics and useful operating temperature range, as well as for clarifying the composition-temperature relationship for other properties such as ionic conductivity. The thermal phase behavior, thermal stability and other properties (viscosity and density) are reported here for the neat ILs containing 1-alkyl-3-methylimidazolium (IM10R+, R = 1, 2 and 4 for methyl, ethyl and butyl, respectively) or N-alkyl-N-methylpyrrolidinium (PY1R+, R = 3-5) cations with TFSI- or FSI- anions, as well as their mixtures with LiTFSI or LiFSI salts. Three components electrolytes (1-x) PY14TFSI-(x) PY13FSI-LiX mixtures (X = TFSI- and PF6-) have also been examined. Such electrolytes show great promise for meeting the strick demands in properties necessary to achieve the superb Li battery performance and longevity required for the successful widespread use of PHEVs and/or EVs.
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Demarquette, Nicole Raymonde. "Nonlinear viscoelastic properties of polystyrene solutions." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60004.
Full textAbstract:
In this work the nonlinear behavior of concentrated polystyrene solution was examined using sliding plate rheometer developed at McGill University. In this rheometer a novel transducer is used to measure the shear stress and an optical system is used to measure birefringence during flows involving high shear rates.The steady shear stress was found to be independent of shear rate at high shear rates. The Cox-Merz rule was found to be valid for concentrations less than 0.199 g.cm$ sp{-3}$, but a deviation from the rule was observed for higher concentrations. Sigmoidal damping functions, based on both the shear stress measurements and the birefringence measurements, were determined. The exponential stress coefficient and the third normal stress difference were calculated from experimental data for different values of exponential rate constant and different strain scale factor. The exponential rate constant was shown to have a strong influence on both the exponential stress coefficient and the third normal stress difference.