Dissertations / Theses on the topic 'School of Chemical and Physical Sciences'
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Holm, Sandra, and Ahlbin Mimmie Jönsson. "Naturvetenskap och estetik i förskolan : fysikaliska förändringar och upptäckande av vätskor med barn i förskolan." Thesis, Högskolan Kristianstad, Fakulteten för lärarutbildning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-21724.
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Det här examensarbetet fokuserar på hur man kan kombinera två innehållsaspekter i undervisning med barn i förskolan. Innehållet som bearbetas är naturvetenskap och estetik. Naturvetenskapsdelen i arbetet innefattar kemiska reaktioner och den estetiska delen innefattar drama. Dramat kommer att användas som ett verktyg för att lära om naturvetenskap med fokus på kemiska reaktioner. Studiens insamlingsmetod innefattar filmning och ljudinspelning. Resultatet i studien visar att barnens perspektiv blir synligt genom att barnen får berätta sina tankar om kemiska vätskor. Studiens resultat visar även att ett intresse har väckts bland barnen kring kemiska vätskor och detta lägger en grund för förskollärare att arbeta vidare med och utgå från barnens intresse.
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Öman, Sotterman Lars. "Undervisning i källkritik i grundskolans NO-ämnen åk 7–9 : En tematisk studie." Thesis, KTH, Lärande, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-301171.
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Syftet med denna uppsats är att undersöka på hur ämneslärare i grundskolans NO - ämnen företrädesvis kemi, men också biologi och fysik, i sin praktik bedriver undervisning om källkritik för att möta läroplanens mål och kunskapskrav inom detta område. Studien har baserats på inspelade kvalitativa semi-strukturerade intervjuer av åtta lärareverksamma i grundskolan. Resultaten har tagits fram genom tematisk analys och beskriverhur lärarna undervisar i källkritik i NO-ämnena, samt deras bedömning av de förmågor somde anser eleverna behöver för att tillgodogöra sig undervisningen i källkritik. Källkritiken behandlas främst som en aspekt i undervisningen tex i samband med olika påståenden eller frågor som eleverna tar upp baserat på information de tagit del av i samhällsdebatten eller i olika diskussionsforum. Lärarna diskuterar då tillsammans med eleverna vilka faktorer som gör att information är mer eller mindre trovärdig. Lärarna beskriver också att det är viktigt i undervisningen att lyfta fram att trovärdigheten för vetenskapliga påståenden är beroende av huruvida påståendet stöds av de vetenskapliga metoder som använts vid framtagningen och att påståendet har granskats av ämnes experter. Lärarna i denna studie beskriver att den viktigaste förmågan för att eleverna ska kunna källkritiskt granska information med ett naturvetenskapligt innehåll är deras kunskaper i de olika NO-ämnena. En annan viktig förmåga är att eleverna förstår hur de ska använda sökmotorer på internet för att kunna ta fram oberoende källor. Risken är annars att de hamnar i en s.k. sökbubbla och de inte erhåller relevant information.The purpose of this thesis is to investigate how science teachers in compulsory school, preferably chemistry, but also biology and physics, in their practice conduct teaching about source credibility to meet the curriculum's goals and knowledge requirements in this area. The study has been based on recorded qualitative semi-structured interviews of eight teachers active in primary school. The results have been produced through thematic analysis and describe how the teachers teach source criticism in the science subjects, as well as the capabilities that the teachers believe the students need to be able to benefit the teaching ofsource credibility. Source credibility is mainly treated as an aspect of ordinary teaching, for example in connection with various statements or questions that students address based on information they have taken part in in the public debate or in various discussion forums is mainly treated as an aspect of the usual teaching. The teachers then discuss with the pupils which factors make information credible. The teachers also describe that it is important in the teaching to emphasize that the credibility of scientific statements depends on the statement being supported by the scientific methods used in the development and that the statement has been reviewed by subject matter experts. The teachers in this study describe that the most important capability for students to critically review information with a scientific content is their knowledge of the various NO subjects. Another important capability is that students understand how to use search engines on the Internet to be able to find independent sources. The risk is otherwise that they end up in a so called search bubble and they do not receive relevant information.
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Grewal, Burrinder S. "Mechanisms of chemical and physical transdermal penetration enhancement." Thesis, Aston University, 1999. http://publications.aston.ac.uk/10978/.
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The underlying theme of this thesis is one of exploring the processes involved in the enhancement of percutaneous absorption. The development of an attenuated total reflectance Fourier-Transform infrared (ATR-FTIR) spectroscopic method to analyse diffusion of suitable topically applied compounds in membrane is described. Diffusion coefficients (D/h2) and membrane solubility (AO) for topically applied compounds were determined using a solution to Fick's second law of diffusion. This method was employed to determine the diffusional characteristics of a model permeant, 4-cyanophenol (CP), across silicone membrane as a function of formulation applied and permeant physicochemical properties. The formulations applied were able to either affect CP diffusivity and/or its membrane solubility in the membrane; such parameters partially correlated with permeant physicochemical properties in each formulation. The interplay during the diffusion process between drug, enhancer and vehicle in stratum corneum (SC) was examined. When enhancers were added to the applied formulations, CP diffusivity and solubility were significantly enhanced when compared to the neat propylene glycol (PG) application. Enhancers did not affect PG diffusivity in SC but enhancers did affect PG solubility in SC. PG diffusion closely resembled that of CP, implying that the respective transport processes were inter-related. Additionally, a synergistic effect, which increases CP diffusivity and membrane solubility in SC, was found to occur between PG and water. Using 12-azidooleic acid (AOA) as an IR active probe for oleic acid, the simultaneous penetration of CP, AOA and PG into human stratum corneum was determined. It was found that the diffusion profiles for all three permeants were similar. This indicated that the diffusion of each species through SC was closely related and most likely occurred via the same route or SC microenvironment.
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Mahama, Wundow. "High school learners’ attitudes towards physical sciences." Thesis, University of Zululand, 2018. http://uzspace.unizulu.ac.za:8080/xmlui/handle/10530/1639.
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A dissertation submitted to the Faculty of Education in fulfillment of the requirements for the Degree of Master Of Education in Research Methodology in the Department of Educational Psychology and Special Education at the University Of Zululand, 2018The investigation of high school learners’ attitudes towards physical science has been one of the prominent areas of research for the science education research community globally for some time now. However, its current importance in South Africa is emphasised by the mounting evidence of poor performance in physical science at matriculation level. Consequently, identifying the nature of learners’ attitudes towards physical science, and promoting favourable attitudes towards physical science is increasingly a matter of concern. The present study therefore investigated high school learners’ attitudes towards physical science and the relationship between their attitudes and learners’ biographical data such as gender, age and grade level. Both systematic and stratified sampling techniques were used to select a sample size of 298 respondents from five high schools in the Nongoma circuit in KwaZulu-Natal province of South Africa. The research was based on descriptive research design to obtain information from respondents in their natural environment through the use of adopted attitude scale. Permission was sought and obtained through email to use the attitude scale. Descriptive and inferential statistics were used to present and analyse the data. The findings from the present study suggest that majority of high school learners hold positive attitudes towards physical science. Findings with regard to the relationship between learners’ attitudes and their biographical data reveal that there is no association between attitudes and learners’ biographical data such as gender, age and grade level. The findings from this study will add value to education policy pertaining to science education in the country. It will also contribute to the theory of attitudes towards physical science. However, there is a need in future to study ways of encouraging learners to have positive attitudes towards physical science.
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Brooker, Michael R. "Physical and Chemical Characterization of Self-Developing Agricultural Floodplains." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1513778530623727.
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Yimamu, (Imam) Maiwulidan (Mewlude). "Chemical vapour deposition of boron-carbon thin films from organoboron precursors." Licentiate thesis, Linköpings universitet, Tunnfilmsfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-123909.
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Boron-carbon (BxC) thin films enriched in 10B are potential neutron converting layers for 10Bbased solid-state neutron detectors given the good neutron absorption cross-section of 10B atoms in the thin film. Chemical Vapour Deposition (CVD) of such films faces the challenge that the maximum temperature tolerated by the aluminium substrate is 660 °C and low temperature CVD routes for BxC films are thus needed. This thesis presents the use of two different organoboron precursors, triethylboron –B(C2H5)3 (TEB) and trimethylboron – B(CH3)3 (TMB) as single-source precursors for CVD of BxC thin films. The CVD behaviour of TEB in thermal CVD has been studied by both BxC thin film deposition and quantum chemical calculations of the gas phase chemistry at the corresponding CVD conditions. The calculations predict that the gas phase reactions are dominated by β-hydride eliminations of C2H4 to yield BH3. In addition, a complementary bimolecular reaction path based on H2-assisted C2H6 elimination to BH3 is also present at lower temperatures in the presence of hydrogen molecules. A temperature window of 600 – 1000 °C for deposition of X-ray amorphous BxC films with 2.5 ≤ x ≤ 4.5 is identified showing good film density (2.40 – 2.65 g/cm3) which is close to the bulk density of crystalline B4C, 2.52 g/cm3 and high hardness (29 – 39 GPa). The impurity level of H is lowered to < 1 at. % within the temperature window. Plasma chemical vapour deposition has been studied using TMB as single-source precursor in Ar plasma for investigating BxC thin film deposition at lower temperature than allowed by thermal CVD and further understanding of thin film deposition process. The effect of plasma power, total pressure, TMB and Ar gas flow on film composition and morphology are investigated. The highest B/C ratio of 1.9 is obtained at highest plasma power of 2400 W and TMB flow of 7 sccm. The H content in the films seems constant at 15±5 at. %. The B-C bond is dominant in the films with small amount of C-C and B-O bonds, which are likely due to the formation of amorphous carbon and surface oxidation, respectively. The film density is determined as 2.16±0.01 g/cm3 and the internal compressive stresses are measured to be <400 MPa.
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Gerothanassis, I. P. "Application of a DSc in the School of Chemical Sciences." Thesis, University of East Anglia, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539366.
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Chen, James. "In-situ study of the chemical composition of photochromic Yttrium Oxy-Hydrides thin films." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-389390.
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Amini, Tina. "Chemical and physical methods of enhancing the percutaneous absorption of antimicrobial agents." Thesis, Aston University, 2001. http://publications.aston.ac.uk/10994/.
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The underlying theme of this study is to enhance the permeation of a antimicrobial agent in the skin by employing chemical (enhancers and supersaturated systems) or physical (iontophoresis) techniques. The hydrochloride salt of chlorhexidine (CHX), a poorly soluble salt, was used throughout this study. The effect of ionisation on in vitro permeation rate across the excised human epidermis was investigated using Franz-type diffusion cells. Saturated solutions of CHX were used as donor and the variable studied was vehicle pH. Permeation rate was increased with increasing vehicle pH. The pH effect was not related to the level of ionisation of the drug. The effect of donor vehicle was also studied using saturated solutions of CHX in 10% and 20% ethanol as the donor solutions. Permeation of CHX was enhanced by increasing the concentration of ethanol which could be due to the higher concentration of CHX in the donor phase and the effect of ethanol itself on the membrane. The interplay between drug diffusion and enhancer pretreatment of the epidermis was studied. Pretreatment of the membrane with 10% Azone /PG demonstrated the highest diffusion rate followed by 10% oleic acid/PG pretreatment compared to other pretreatment regimens (ethanol, dimethyl sulfoxide (DMSO), propylene glycol (PG), sodium dodecyl sulphate (SDS) and dodecyl trimethyl ammonium bromide (DTAB). The potential of supersaturated solutions in enhancing percutaneous absorption of CHX was investigated. Various anti-nucleating polymers were screened in order to establish the most effective agent. Polyvinylpyrrolidone (PVP, K30) was found to be a better candidate than its lower molecular weight counterpart (K25) and hyroxypropyl methylcellulose (HPMC). The permeation studies showed an increase in diffusion rate by increasing the degree of saturation.
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Demyan, Michael Scott. "Chemical and Physical Changes in Twenty Five Year-Old Minesoils in Southeast Ohio." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419259892.
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Barnett, Tracie. "Predictors of physical inactivity among elementary school children." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37089.pdf.
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Poirier, Phillip A. "Physical and chemical correlates of Sacramento County vernal pool crustaceans." Scholarly Commons, 2012. https://scholarlycommons.pacific.edu/uop_etds/801.
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Vernal pools are temporary aquatic habitats that can be home to dozens of 4 invertebrate species. Unfortunately, over 90 percent of California vernal pool habitat has been destroyed. To better understand the remaining habitat, this study focused on the species community structure of the pools, determined similarity among sites, and the pool characteristics important to survival of these organisms. Vernal pools at four distinct sites in the Sacramento Valley during winter 2012 were sampled for crustaceans and water characteristics every 2 weeks for 14 weeks. Twenty-two species of crustaceans were identified, 13 of which are possibly new species. In this dry, late rainfall year, fairy shrimp and copepods were the first species to emerge in large numbers. Ostracods, Cladocera and clam shrimp experienced large populations later in the season. Temperature showed strong correlations with most species and likely affected growth rates and emergence; conductivity, depth, and surface area were also positively correlated with several species abundance. Understanding the emergence and distribution of these crustaceans is necessary to protection of remaining habitat.
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Kalmoni, Iman. "Extraction and determination of chemical and physical properties of antimicrobial compounds from a Swedish mushroom." Thesis, Umeå universitet, Kemiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-137294.
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Dowell, Richard Marshall. "School Administrator Impact Upon Physical Restraints in Public Schools." Youngstown State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1403081916.
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Lagacé, Pascale. "Physical-chemical treatment of TMP-newsprint mill effluent as a closed cycle technology." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26398.
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Pulp and paper mills have to comply to increasingly more stringent environmental regulations. Only one solution can satisfy all present and future effluent regulations, and eliminate all impact on receiving waters. This solution is to recycle the whole effluent back to the mill, after treatment.The subject of this research was to develop a physical-chemical process that would be suitable for the treatment of TMP-Newsprint effluent as a closed cycle technology.
A mixture composed of 80% TMP cleaner rejects, 10% contaminated condensate from the heat recovery and 10% chip wash water was used to approximate the effluent from a very low water usage mill.
Preliminary experiments were performed using lime, magnesium oxide, activated carbon, potassium phosphate and alum. The most promising treatment identified was using a combination of magnesium oxide, lime and potassium phosphate. It was found that 300 mg/L of MgO, 1000 mg/L of CaO and 500 mg/L of KH$ sb2$PO$ sb4$ gave over 90% extractives removal, a reduction of 60% in colour and 75% in turbidity, while maintaining a low water hardness. It was also found that MgO addition was not required at the dosages used.
Tests were also performed on effluent with an elevated level of inorganic dissolved solids that would be typical of a closed cycle mill. It was found that higher dosages of lime would be required, and that potassium phosphate would no longer be necessary.
The results of this study have shown that there is great promise in using a physical-chemical process as part of a closed cycle treatment scheme.
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Montreuil, Richard. "High school sports: The perspectives of the school principals." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27537.
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The Canadian School Sport Federation, responsible for interscholastic sport, provides a mission to extend physical and athletic development, as well as, moral and social development (Canadian School Sport Federation, n.d.). To reach this mission, participation is needed not only by the coaches, who's role is central to the athletes experience (Roy, Trudel, & Lemyre, 2001), but also the school principals. As part of a research program examining the practice of interscholastic sports, we conducted interviews with 11 school principals and documented 'who' are the high school principals i.e. documented their past experiences and their role and perspective regarding high school sports. The main results showed that (a) most school principals had experience in sport as an athlete or a coach, (b) being a physical education teacher often led to the position of school principal, (c) the principals were conscious of the importance of school sports, and (d) they preferred to select coaches from within their school.
Keywords: school sport/interscholastic sports, school principal
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Gowda, Vasantha. "Experimental and Computational Magnetic Resonance Studies of Selected Rare Earth and Bismuth Complexes." Doctoral thesis, Luleå tekniska universitet, Kemiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65378.
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The rare-earth elements (REEs) and bismuth, being classified as the ‘most critical raw materials’ (European Raw Materials Initiatives, 2017), have a high economic importance to the EU combined with a high relative supply risk. REEs are highly important for the evolving technologies such as clean-energy applications, high-technology components, rechargeable batteries, permanent magnets, electric and hybrid vehicles, and phosphors monitors.This scientific research work aims at building a fundamental knowledge base concerning the electronic/molecular structure and properties of rare-earth element (REE) and bismuth complexes with dithiocarbamate (DTC) and 1,10-phenanthroline (PHEN) by employing state-of-the-art experimental techniques such as nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction (XRD) techniques together with ab initioquantum mechanical computational methods. This combination of methods has played a vital role in analysing the direct and significant effect of the heavy metal ions on the structural and magnetic resonance properties of the complexes, thereby, providing a framework of structure elucidation. This is of special importance for REEs, which are known to exhibit similar chemical and physical properties. The objectives of the work involve i) a systematic investigation of series of REE(III) as well as bismuth(III) complexes to get a profound understanding of the structure-properties relationship and ii) to find an appropriate theoretical modelling and NMR calculation methods, especially, for heavy metal systems in molecular and/or solid-state. This information can later be used in surface interaction studies of REE/bismuth minerals with DTC as well as in design and development of novel ligands for extraction/separation of metal ions.The REE(III) and bismuth(III) complexes with DTC and PHEN ligands have all provided aunique NMR fingerprint of the metal centre both in liquid and solid phase. The solid-state 13C and 15NNMR spectra of the diamagnetic REE(III) and bismuth(III) complexes were in accord with their structural data obtained by single crystal XRD. The density functional theory (DFT) methods were used to get complementary and refined structural and NMR parameters information for all diamagnetic complexes in the solid-state. The relativistic contributions due to scalar and spin-orbit correlations for the calculated 1H/13C/15N chemical shifts of REE complexes were analysed using two-component zeroth-order regular approximation (ZORA)/DFT while the ‘crystal-lattice’ effects on the NMR parameters were calculated by combining DFT calculations on molecular and periodic solid-state models. The paramagnetic REE complexes display huge differences in their 1H and 13C NMR spectral patterns. The experimental paramagnetic NMR (pNMR) chemical shifts, as well as the sizable difference of the 1H and 13C NMR shifts for these isoelectronic complexes, are well reproduced by the advanced calculations using ab initio/DFT approach. The accuracy of this approach is very promising for further applications to demanding pNMR problems involving paramagnetic f-block elements.The results presented in this thesis demonstrate that a multidisciplinary approach of combined experimental NMR and XRD techniques along with computational modelling and property calculations is highly efficient in studying molecular complexes and solids containing heavy metal systems, such as rare-earths and bismuth.
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Sandoval, Kathia a. "Physical and Chemical Characterization of Crude Oil-Water Mixtures: Understanding the Effects of Interfacial Process to Chemical Bioavailability." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2464.
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This work detailed the physical and chemical characterization of oil water mixtures prepared using fresh and weathered Macondo related oils under different conditions of mixing energy/time and in the presence/absence of chemical dispersants. The results indicated that WAFs produced consistent, droplet free solutions for both source and weathered oils with concentration ranges that represented the soluble components of the oil used. Chemically enhanced WAFs prepared with the source oil generated a large amount of micron-size droplets; however the viscosity of the weathered oils were a limiting factor for the preparation of CEWAFs with weathered oils. Droplet size distributions were influenced by the amount of energy in the system and the oil weathering stage, when high energy WAFs were made the increase in weathering of the oil resulted in the formation of smaller droplets that were more stable over time.
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Williams-Jones, Leigh-Ann. "A chemical and thermal modelling study of the active layer on Herschel Island, Yukon Territory." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114312.
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An essential requirement in evaluating the potential impacts of climate warming in Polar Regions, is a greater understanding of the nature and behavior of the active layer and the permafrost system. Numerous studies have documented the inherent capacity of permafrost to limit significant degradation from seasonal thawing because of the ability of overlying soil layers to dissipate influxes of heat. However, information on the degree to which these layers are able to act as buffers to permafrost degradation is limited, and thus further research on this system is needed.The research presented in this thesis in the form of two manuscripts. The first manuscript (Chapter 3) discusses the role of chemical processes in the soil weathering regime on Herschel Island. Three distinct cryostratigraphic layers were observed in the soil profiles, including; (1) the modern active-layer located immediately below the ground surface (0 – 39 cm); (2) a paleo-active (transition layer), extending from the bottom of the modern active layer to the top of an undisturbed permafrost layer (39 – 192 cm); and (3) the underlying permafrost. These layers are marked by two thaw unconformities that separate the modern active layer from the transition layer and the transition layer from the permafrost layer, respectively. The two thaw unconformities were distinguished by abrupt breaks in the cryogenic texture and peaks in the concentrations of several chemical components. The upper thaw unconformity, located at the base of the modern active layer, coincided with a doubling in the concentration of major soluble cations and a tripling in the organic matter content compared to those of the overlying soil horizons. The lower thaw unconformity is marked by the highest concentration of Al2O3 and K2O in the entire profile and the second highest concentration of Na2O. Between these two unconformities, (i.e. in the transition zone), soluble cation concentrations varied considerably, the bulk soil SiO2 concentration increased significantly and there was a noticeable decrease in the concentrations of Al2O3, Fe2O3, CaO, MgO and K2O in the depth interval of 82-107 cm. Chemical weathering indices recorded an overall decrease in the intensity of chemical weathering with depth; the soil layers immediately above the first thaw unconformity were the most weathered and the deeper permafrost layer was the least weathered.The second manuscript (Chapter 4) employs a heat conduction algorithm (Stefan equation) based on the composition and thermal properties of the soils discussed in Chapter 3, and measured active layer depth values, to evaluate heat transfer from the ground surface to the underlying permafrost. Thermal constants (the square root of the ratio of twice the thermal conductivity of the unfrozen soil to the latent heat of fusion of ice) were calculated using the De Vries method and were compared to empirical thermal constants derived from measurements of active layer depths and the corresponding thawing degree days using the Stefan equation. The theoretical constants are approximately 38% lower than those derived empirically, a difference that is likely due to the fact that the Stefan equation does not consider advective heat transfer and that the active layer depths were probably overestimated because of the method of measurement (resistance to penetration of a metal probe). Third generation Canadian Global Coupled Models (CGCM 3.1/T63) from the Canadian Centre for Climate Modelling and Analysis (CCCma), based on the IPCC SRES A2 and B1 scenarios, were used in conjunction with the theoretically and empirically derived thermal constants to predict active layer depths for 2050 and 2100. These calculations suggest that the active layer will thicken by up to 41.76 % before the end of this century. This thesis provides new insights into the important role that the active and transition layers play in controlling the response of permafrost systems to climate change.Une condition essentielle pour évaluer les impacts potentiels du réchauffement climatique dans les régions polaires est l'acquisition d'une meilleure compréhension de la nature et du comportement de la couche active du pergélisol. La recherche présentée dans cette thèse est présentés sous la forme de deux manuscrits. Le premier manuscrit examine le rôle des processus chimiques dans le régime d'altération du sol sur l'île Herschel. Trois couches distinctes cryostratigraphiques ont été observées dans les profils de sol: (1) la couche active moderne située immédiatement sous la surface du sol (0 - 39 cm), (2) la couche paléo-active (couche de transition) s'étendant de la base de la couche moderne active à la partie supérieure de la couche de pergélisol non perturbée (39 - 192 cm) et (3) le pergélisol sous-jacent. Ces couches sont marquées par deux discordances de dégel séparant la couche active moderne de la couche de transition et la couche de transition de la couche de pergélisol, respectivement. Ces deux discordances de dégel ont été identifiées grâce à la présence de ruptures brutales dans la texture cryogénique et par des pics dans la concentration de plusieurs composants chimiques. La discordance de dégel supérieure, située à la base de la couche moderne active, coïncide avec un doublement de la concentration des principaux cations solubles et un triplement de la teneur en matière organique par rapport aux horizons sus-jacents. La discordance de dégel inférieure est marquée par la plus forte concentration en Al2O3 et en K2O de l'ensemble du profil et par la deuxième plus forte concentration en Na2O. Entre ces deux discordances, les concentrations en cations solubles varient considérablement, la concentration en SiO2 du sol brut s'accroit de façon significative et on observe une diminution notable des concentrations en Al2O3, Fe2O3, CaO, MgO et K2O dans l'intervalle de profondeur de 82-107 cm. Les indices d'altération chimique ont enregistré une diminution globale de l'intensité de l'altération chimique avec la profondeur ; les couches de sol immédiatement au-dessus de la première discordance de dégel sont les plus altérées et la couche profonde du pergélisol est la moins altérée.Le second manuscrit utilise un algorithme de conduction de la chaleur basé sur la composition et les propriétés thermiques des sols examinés au chapitre 3 et sur les mesures des valeurs de profondeur de la couche active afin d'évaluer le transfert de chaleur de la surface du sol au pergélisol sous-jacent. Des constantes thermiques (la racine carrée du rapport entre deux fois la conductivité thermique du sol non gelé et la chaleur latente de fusion de la glace) ont été calculées en utilisant la méthode de De Vries et comparées aux constantes thermiques empiriques issues des mesures de profondeur de la couche active et des degrés-jours de dégel correspondant en utilisant l'équation de Stefan. Les constantes théoriques sont environ 38% inférieures à celles obtenues empiriquement, une différence qui s'explique probablement par le fait que l'équation de Stefan ne considère pas le transfert de chaleur par advection et que les profondeurs de la couche active ont probablement été surestimées en raison de la méthode de mesure (résistance à la pénétration d'une sonde métallique). La troisième génération du modèle couplé climatique global canadien (CGCM 3.1/T63) du Centre canadien de la modélisation et de l'analyse climatique (CCmaC), basée sur les scénarios A2 et B1 du IPCC SRES, a été utilisée en conjonction avec les constantes thermiques théoriques et empiriques pour prédire les profondeurs de la couche active pour 2050 et 2100. Ces calculs suggèrent que la couche active s'épaissira de jusqu'à 41,76% avant la fin du siècle.Ce mémoire apporte un nouvel éclairage sur le rôle important que les couches actives et de transition jouent dans le contrôle de la réponse des systèmes de pergélisol au changement climatique.
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NOKURA, KENJI. "Real time monitoring of surface chemical events by streaming potentials in microfluidic channels." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3299.
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Zeta potential is one of the tools to measure the surface charge of materials, and Alvarez et al. have developed a microchannel device to measure zeta potentials in real time for label-free sensing using immobilized receptors on microchannel surfaces. However, the challenge has been the charge interference of surface modifiers on analyte detection. Therefore, it was necessary to find the best strategy to regenerate minimal surface charge after modifying the channel with polymer films that would anchor the affinity groups for the analyte. It was demonstrated that adsorption of positively and negatively charged analytes were monitored via real time zeta potential measurements by using surface-immobilized polystyrene nanospheres, and the best discrimination of analyte binding on the nanoparticles was observed when the underlying film was a non-ionic polymer. Titanium oxide nanoparticles (TiO2) were immobilized on microchannels modified with non-ionic polymers to investigate if the surface charge of the microchannel was induced by the concomitant surface charge reactions of the TiO2 nanoparticles upon UV exposure. Analysis by XPS indicates that desorption of proteins monitored by zeta potential changes are induced by UV exposure.
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Booth, Bryan C. "An Investigation of the Effects of Chemical and Physical Weathering on Submerged Karst Surfaces." Thesis, University of South Florida, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3740302.
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Reports an investigation of the effects of chemical and physical weathering on submerged karst surfaces that pairs laboratory studies with computer modeling studies. The first study attempts to quantify the production of carbonate fines; soluble sediments produced by the incomplete dissolution of karst minerals during chemical weathering. Results show carbonate fine production in relation to dissolutional action; Chalk: 42.8%; Coquina: 2.6%; Dolomite: 3.1%; Gray Limestone: 4.8%; Ocala Limestone: 3.1%; Shell Limestone: 6.1%; Travertine: 8.6%. Due to the use of hydrochloric acid as opposed to carbonic acid these results may not be fully valid for application to natural speleogenic processes. The Limestone Weathering Model, a numerical-computer model, was developed using these experimental findings as minimal values compared with published rates. Reported as the actual volume of rock mass lost to both dissolution and to carbonate fine production, the rates for carbonate fine production ranged from 5.8% to 10.9% (year 1-5.8%, year 2-8.5%, year 3-9.7%, year 4-10.3%, year 5-10.9%), with a mean value for carbonate fine production of 9%, but a continuing rate after five years approaching 11%. The second study uses metrological laser scanning to measure the erosive loss due hydraulic shearing force and corrasion on submerged limestone surfaces. The rates for material removed using increasing velocity values (0.3m/s, 0.5m/s, 1.0m/s, 1.5m/s, 2.0 m/s, 2.5m/s) during flow durations of less than 6 minutes duration were : 1) Hydraulic shearing force- 0.3µm/s, 0.5µm/s, 0.4-1.7µm/s, 2.5 µm/s, 5.5 µm/s, 2) Corrasion- 0.3 µm/s, 0.7 µm/s, 1.5 µm/s, 1.5-1.8 µm/s, 8.9 µm/s, 8.1 µm/s. The study model was modified to return these rates for hydraulic shearing force limited by the depth of the chemical corrosion of the surface. The model returns % rock volume lost to hydraulic shearing force compared to dissolutional rate (1mm/y) for 3 flow velocities (0.03m/s<, 1.0m/s<, 2.5m/s<) on 4 timing schedules: Annual- 7.8,14.3,19.6, Semiannual- 21.1,21.1,69.7, Quarterly- 32.8,43.6, 70.9, Monthly- 80.0, 109.3, 200.3. Model demonstrates significant effect (7.8% to 200% over dissolutional rate) on speleogenic rates from even infrequent, moderate changes in flow velocities due to storm events. Investigation’s results support the significance of chemical weathering by disaggregation and physical weathering by hydraulic shearing force as major factors in the processes of karst speleogenesis.
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Simon, Zoé. "Design of a lensless imaging system in the mid-IR range for generation of chemical images of histological samples." Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235474.
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Lohse, Peter A. (Peter Andreas). "Distribution of knowledge production in the chemical sciences in the US." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65786.
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Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 43-44).
A citation analysis was carried out to gain an understanding of the geographical and institutional distribution of highly cited articles in the chemical sciences in the US over the last thirty years. The contribution of US chemistry departments was determined by quantifying the number of highly cited articles published by individual authors or groups of authors from the same department. Articles stemming from collaborative research across schools were not considered. The results show that a dilution in intradepartmental knowledge production has occurred both on a geographical and institutional level. Three chemistry departments have emerged as strong producers of high impact articles over the last thirty years: the University of North Carolina, Texas A&M University and the University of Utah. In terms of aggregate numbers of highly cited articles these three schools are in the top ten of over seventy schools which were evaluated; their chemistry departments are en par in terms of scientific impact with those from Ivy League schools like Stanford University, Harvard University and the California Institute of Technology. While the literature reports increasing concentration for the US research base, the present analysis shows a dilution in chemical knowledge production when collaborative efforts across departments and schools are excluded. This finding suggests that the increase in concentration in the US science base is not a uniform trend when studied on a more granular level.
by Peter A. Lohse.
M.B.A.
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Parks, Krystyn. "Nutrition and physical activity curriculum for before and after school daycares." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1528021.
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The purpose of this project is to create fun and educational lesson plans for before and after school childcare providers of children in kindergarten through fifth grade. The lesson plan will incorporate aspects of physical activity and nutrition into the basic curriculum for this age group. The nutrition and physical activity curriculum contains four themed weekly lessons. Each lesson incorporates a nutrition discussion, an activity related to the discussion, and one group game. The lessons and activities were designed to incorporate minimal materials so that any facility could easily incorporate them. A committee of nutrition professionals and educators reviewed the curriculum and improvements were made based on their recommendations.
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Myrdal, Paul Brian. "A simple scheme for estimating environmentally relevant physical properties of organic compounds." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186674.
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Aqueous solubility, vapor pressure, and Henry's law constant are among the most important properties for the environmental assessment of an organic pollutant. In this dissertation a simple scheme is developed that allows for the calculation of the above properties directly from chemical structural information and the knowledge of a single transition temperature (melting point or boiling point). This work introduces AQUAFAC (AQUeous Functional group Activity Coefficients), a simple group contribution approach for estimating aqueous activity coefficients. Also presented is a thermodynamically sound equation for estimating pure component vapor pressures. The utilization of the vapor pressure equation, and AQUAFAC, gives a convenient means by which to estimate Henry's law constants. In addition, a new method is presented for the calculation of either the boiling point or the melting point of an organic compound from a simple atom count and a knowledge of the other value.
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Guzman, Veloso Viviana. "Physical and Chemical Conditions in the Horsehead Photodissociation Region." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00950116.
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Les raies moléculaires tracent la structure du milieu interstellaire ainsi que les conditions physiques du gaz dans différents environnements allant des galaxies à haut redshift aux disques protoplanétaires. Pour bénéficier des diagnostics moléculaires les voies de formation et de destruction des molécules doivent être comprises quantitativement, tout comme les couplages entre la chimie en phase gazeuse et solide. Des jeux bien compris de données concernant des sources simples sont essentiels pour tester les prédictions des modèles théoriques. Cette thèse présente l'analyse d'un relevé spectral systématique à 1, 2 et 3mm avec le télescope IRAM-30m dans la Tête de Cheval, offrant une combinaison inédite de bande passante, haute résolution spectrale et sensibilité, en direction de deux positions: la région de photodissociation (PDR) et une cœure froid à proximité. Environ 30 espèces avec un maximum de 7 atomes sont détectées sans compter les isotopologues. Ces données sont complétées par des cartes interférométriques IRAM-PdBI à haute résolution d'espèces spécifiques. Les résultats de cette thèse incluent la detection de CF+, un nouveau diagnostic de gaz exposé à l'UV lointain; la détection d'une nouvelle molécule interstellaire, que nous attribuons au petit hydrocarbure C3H+; une étude approfondie des molécules organiques H2CO, CH3OH et CH3CN, qui indique que la photodésorption des glaces est un mécanisme efficace pour relâcher ces molécules en phase gazeuse; et la première détection de molécules organiques complexes, comme HCOOH, CH2CO, CH3CHO et CH3CCH dans une PDR, qui révèle la complexité chimique dans le gaz neutre éclairé en UV lointain.
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Spencer, David Lowell. "Physical and Chemical Properties of a New Mineral Trioxide Aggregate Material." VCU Scholars Compass, 2004. http://scholarscompass.vcu.edu/etd/647.
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The objective of this study was to compare the time to final set and compressive strength of the white mineral trioxide aggregate (MTA) formulation to the original grey MTA. To test compressive strength, each MTA formulation was placed into Teflon split molds for four hours at 37° Celsius (C) and 100% humidity. Compressive strength of both MTA formulations was measured at 24 hours (n=12) and 21 days (n=19) using an Instron Testing Machine. For determination of time to final set, each MTA formulation (n=6) was placed into a metal mold and maintained at 37° C and 100% humidity while setting. At five-minute time intervals, an indenter needle was lowered onto the surface of the MTA material and allowed to remain in place for five seconds before it was removed from the specimen surface. This process was repeated until the needle failed to make a complete circular indentation in the MTA specimen. Results of a two-way ANOVA indicate that white MTA had a significantly higher compressive strength (mean=32.7 MPa) than grey MTA (mean=25.2 MPa) at 24 hours and no statistically significant differences at 21 days (white mean=38.6 MPa and grey mean=38.0 MPa). Using one-way ANOVA, results indicate that grey MTA had a significantly longer time to final setting time (mean=296 min) compared to white MTA (mean=276 min). Based on this study, the results suggest that white MTA is an effective substitute for grey MTA.
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Campbell, Alex E. "Chemical, physical and mineralogical properties associated with the hardening of some South African fly ashes." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/19250.
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Coal combustion for power generation is relied on heavily in South Africa. The main residue from the combustion process is fly ash, with about 22 million tons being produced in 1994, of which only about 1 million tons is utilised, the remainder requiring disposal as waste. Various environmental impacts are associated with the disposal of fly ash in surface impoundments, including loss of usable land, contamination of groundwater, and production of wind-blown particulates, effects on vegetation and aesthetic impacts. Ultimately the disposal of fly ash in the mined-out underground workings is highly sought after, as it may limit many of the impacts which fly ash induces on the environment. The main purpose of this study was to assess the degree of hardening of four South African fly ashes from power stations at Kriel, Lethabo, Matla and Sasol in terms of their chemical, physical and mineralogical properties. Samples were taken of fresh and unweathered ashes from each power station. Unweathered ash samples analysed by XRFS were found to have high contents of Si0 2 (49.9-56.3%), Al 2 0 3 (27.2-31.5%), CaO (4.2-8.6%Y and Fez03 (3.1-3.9%) with varying contributions from loss on ignition (L.O.I.) (0.4-4.4%) and MgO (1.1- 2.2%). The major mineral phases detected in unweathered ash by XRD include quartz, mullite and glass, with smaller contributions from hematite and lime. Laser particle size analysis and liquid limit determination (Atterberg tests) were also conducted. The exceptionally high L.O.I of Sasol ash (4.4%) was attributed to the presence of partially burned coal, based on DTA and TGA investigation. Modulus of rupture experiments were conducted on briquettes (dimensions 7.0 x 3.5 x 1.0 em) of unweathered ash from Kriel, Matla, Lethabo and Sasol, which were wetted to their liquid limit and cured for 24 h under ambient conditions. The tests indicated that there is a strong linear relationship between total Ca content and the modulus of rupture for 3 of the 4 unweathered ashes. The fly ash from Kriel deviates from this relationship, providing evidence that other chemical (e.g. form of Ca) and physical factors (e.g. particle size) may also play a role in hardening.
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Naini, Venkatesh. "Physical and Chemical Stability of Spray Dried Sugars and Protein-Sugar MolecuIar Mixtures for Inhalation." VCU Scholars Compass, 1996. http://scholarscompass.vcu.edu/etd/4982.
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The feasibility of producing inhalable microparticles of sugars and protein-sugar molecular mixtures using spray drying was investigated as an alternative to conventional micronization techniques. Four sugars; lactose (L), trehalose (T), sucrose (S) and mannitol (M) were spray dried using a commercial bench-top spray dryer and their physicochemical stability, with respect to particle size, moisture uptake and crystallinity changes, investigated after storage at 23%, 52%, 75% and 93% relative humidity (RH) and 25 °C for 30 days. Two crystalline size fractions (“coarse” = 125-212 μm and “fine” = 44-74 μm) of each sugar, were also characterized, as possible replacements for lactose as carriers for admixture with drugs in dry powder inhalers (DPIs). Sieve fractions of lactose, trehalose and mannitol failed to show significant moisture uptake at RHs ≤ 93% and 25 °C indicating their thermodynamic stability under most realistic storage conditions. While sucrose failed to show moisture uptake at ≤ 75% RH, it dissolved in sorbed moisture at 93% RH. Spray dried sugars were collected successfully in particle sizes suitable for inhalation. Spray dried lactose, trehalose and sucrose were amorphous and remained in this state after storage at 23% RH. At higher RHs, however, they recrystallized completely in ≤ 30 days. Spray dried mannitol was completely crystalline after collection from the spray dryer. It did not show moisture uptake or physical state changes at all RHs.
A fine particle collection apparatus incorporating a nebulizer and a wire-in-tube type electrostatic precipitator (EP), built and characterized for particle collection efficiency, was used to review protein activity following spray drying with or without the four sugars as stabilizers. Bacterial (BAP) and bovine intestinal alkaline phosphatase (BIAP) were used as model proteins. Sugar free BAP solutions (apparent protein concentration ~120 μg/ml) lost 23% of initial enzyme specific activity after spray drying at ~63 °C and collection in the EP. Protection offered by the sugars to BAP during drying, was however statistically indistinguishable from the sugar-free protein solution (dried from the same protein concentration solution). When BIAP was dried from sugar free solutions (apparent protein concentration ~1 mg/ml), it lost 31% of its initial specific activity; activity which could be completely recovered when BIAP was co-dried with L, T or S (ANOVA, p < 0.05). However, M which crystallized during spray drying failed to protect the enzyme from this loss of activity. These results implied that the physical state of sugar (amorphous or crystalline) in the final dried product may be an important determinant for offering protection to proteins during spray drying and storage. Even so, multiple factors could potentially influence the selection of a sugar to form inhalable microparticles with a protein. These factors are described and discussed in this thesis, whether or not they appeared to be important with respect to the drying and stability of particular proteins selected for experimental investigation.
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Boza, Arauz Andrea. "Evaluation of Chemical, Physical, and Sensory Properties of Tortillas Prepared from Nixtamalized Oats." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/9058.
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Background and objectives: While alkaline nixtamalization has historically been used for corn, this process may have application in other cereals. Drawbacks to wider use include the lengthy steep time, as well as the volume of alkaline wastewater produced. This study evaluated a novel, waste-effluent-free nixtamalization process for oat (Avena sativa) masa, and compared properties of oat masa and tortillas prepared with 1, 1.5 and 2% lime, with and without steeping. Findings: A minimal water-addition, 45-min, simmering process, without steeping, was effluent-free, and produced oat tortillas comparable to those produced using a traditional overnight steep. The pH increased significantly with increasing lime content (r=0.982). Consumer overall-liking scores did not significantly differ across treatments, though appearance scores were significantly higher for 2% lime samples (p<0.05), which were significantly darker and more yellow, based on L* and b* values. Masa adhesiveness means ranged from 1.49-1.52 N, with no significant differences between the no-steep treatments. Higher lime addition (1.5-2%) in the no-steep process significantly improved tortilla flexibility, based on extensibility and rollability scores, though tortilla rupture force did not vary significantly across treatments. Tortilla rollability scores at 3-days were lowest (x=1.1 + 0.31, indicating less cracking) for the 1.5-2% lime no-steep treatments, which were significantly better than the steeped treatment (x=3.7 + 0.48). Consumers rated the steeped sample as significantly less flexible. B-vitamins were negatively impacted by increasing lime, while calcium increased significantly with lime addition. Conclusions: The no-steep, effluent-free nixtamalization process produced oat tortillas with good masa and tortilla texture, which were not significantly different in consumer liking to tortillas produced via a traditional process. Significance and novelty: This research suggests nixtamalization can be applied to other grains in a shorter, environmentally-friendly process, with broader commercial applicability.
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Toerien, René. "Mapping the learning trajectories of physical sciences teachers' topic specific knowledge for teaching chemical bonding." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25508.
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Education in South Africa is a national concern and the training and professional development of teachers, especially in science and mathematics, has consequently been prioritised by the National Government. More than 60 percent of the teachers in South Africa are older than 40 years of age, which means that within the next 10-15 years many experienced teachers will exit the system, leaving a younger and less experienced cohort of teachers behind. This study aims to make explicit the learning trajectories of physical sciences teachers, specifically with respect to their knowledge for teaching chemical bonding, in order to support other teachers and thereby accelerating the route to expertise. Learning can be viewed as change, and change has a trajectory. Mapping the learning trajectories, and the significant events that influenced teachers' learning over time, can give insight into how the change had taken place. This study used a mixed methods approach within the pragmatic research paradigm to map learning trajectories for a group of 60 South African physical sciences teachers. Pedagogical content knowledge (PCK), the unique knowledge held by teachers, was used for the theoretical framing of the study. An adapted version of the Model of Teacher Professional Knowledge and Skill, including PCK, was used as an analytical framework. A measuring instrument for topic specific knowledge for teaching chemical bonding was designed and validated using the Rasch measurement model. Quantitative and qualitative analysis of the teachers' responses to the instrument and a grounded analysis of story-line interview data from ten purposively selected teachers were used to identify the factors that played a role in the development of the teachers' knowledge. A further qualitative analysis of PCK episodes from the interview data revealed how the above factors influenced the teachers' knowledge. Findings revealed that teaching the same content multiple times and at multiple grade levels, embracing changes in the curriculum as opportunities for learning, and further studies at tertiary level, especially completing post-graduate studies in education, all played a role in the teachers' perceived shifts in their topic specific knowledge for teaching (TSKFT). Three learning trajectories were identified for the teachers in this study: teachers shifted towards deeper conceptual understanding of the content and used more sophisticated explanatory frameworks; teachers shifted towards more integrated topic specific knowledge for teaching; and teachers shifted from being text book bound and teacher-focussed towards becoming more student-focussed in their approach to teaching. The findings from this study provide guidelines for professional development programmes in terms of differentiated support to teachers according to their career stages and the inclusion of content specific training programmes which makes teaching for conceptual progression explicit. A further recommendation includes encouraging teachers to embark on post-graduate studies in education as this played a pivotal role in shifting teachers' topic specific knowledge for teaching chemical bonding.
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Botello-Ruvalcaba, Martin Armando. "Physical, chemical, biological and management aspects of coastal ecosystems facing eutrophication : the Guaymas Bay, Sonora, Mexico." Thesis, University of Hull, 1999. http://hydra.hull.ac.uk/resources/hull:16865.
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The present study has encompassed a series of field observations and theoretical considerations related to physical, chemical, and biological factors defining the process of eutrophication in the Guaymas system. Additionally, the work has produced the basic ecosystem model of the system through the modelling of the hydrodynamics, sediment dynamics, budget dynamics, net ecosystem metabolism and the potential for eutrophication. These findings produce an overall assessment of the system, which together with the environmental legislation and socio-economic concerns, allows those factors influencing decision making to be highlighted. In general, the knowledge of the hydrodynamic features indicates that the flushing capacity of the system may be insufficient to remove pollution discharged into the Guaymas sub-system and Estero el Rancho. There is a residual mass of water that exchanges from the Empalme sub-system to the Guaymas sub-system. Simulation of the trends for potential net transport of sediment indicates that bedload transport is likely to occur toward the head of the Guaymas sub-system. For the Empalme subsystem, there was a net bedload displacement toward the mouth. Mathematical interrelationships between measured phytoplankton biomass and environmental parameters shows through a MRA model that nearly 100% of its variance is influenced by nutrients, pH, temperature and salinity. The stoichiometric Redfield approach indicates that nitrogen is a limiting factor of the phytoplankton biomass growth in the Guaymas system, when other factors such as light, sinking, grazing, temperature and salinity gradients are not. However, an analysis of the two major subsystems shows that nutrients limiting in the Guaymas sub-system are closely related to phosphorus loads from wastewater sources, whereas for the Empalme sub-system, nutrient limitation was alternately by nitrogen and phosphorus. A primary quantitative outcome of the eutrophic status is given, using a simple biochemical budgetary approach, indicating that the Guaymas system is a net heterotrophic system, with a value of -4811.72 mmol.C.m^.y'1. Using a simple box model to characterise the potential hyper-trophic conditions suggests that phosphorus reduction in the system is accompanied by an improvement in water quality, hence management strategies must encourage P control from wastewater discharges into the sub-system. An analysis of the particular case of the Guaymas system in the context of the Mexican Environmental Legislation indicates that the quality standards set for the system will depend very much upon the designation ultimately used for the system. For instance, if some areas of the Guaymas sub-basin are designated for industrial use, a polluted influence is likely to occur in an area near the development. However, the areas influenced by this development must not pose a threat for the people living the Guaymas basin as stated in the Mexican Environmental Legislation.
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Few, Julian William. "FTIR studies of chemical processes." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:b7dbc587-fb9e-46de-8f04-44892fde0bf4.
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This thesis presents the study of a selection of gas phase chemical processes using time-resolved Fourier transform infrared (FTIR) emission spectroscopy. Such processes include molecular energy transfer, chemical reaction and photodissociation. The major focus of this thesis was the investigation of collisional energy transfer from the electronically excited states of NO and OH, with particular attention paid to the fate of the electronic energy. NO A2Σ+(v = 0) is prepared by laser excitation, pumping the overlapped Q1 and P21 band heads of the NO A-X (0,0) transition at 226.257 nm. The quenching of this state by O2 and CO2 was studied. Experiments were performed to investigate what channels contribute to the quenching process, the branching ratio of these different channels and the partitioning of energy among the various products. Quenching by O2 was found to proceed mostly through non-reactive channels. High vibrational excitation of NO X 2Π was observed, with population detected in v = 22, representing 79% of the available energy. The O2 product was found to be formed in more than one electronic state: the ground state, X 3Σ-g, and a high-lying electronically excited state, such as the A 3Σ+u, A' 3Δu or c 1Σ-u states. A reactive channel producing vibrationally excited NO2 was observed, but was found to be a minor process with an upper limit of 18% for the branching ratio. In contrast the quenching of NO A 2Σ+(v = 0) by CO2 was found to proceed predominately by reaction, with a branching ratio of 76 %. While emission from NO2 was observed, it was weak, and therefore it was concluded that the main reaction products were CO, O(3P) and NO X 2Π(v = 0). The nascent strong CO2 v3 emission band from the non-reactive channel exhibited a large red-shift from its fundamental position. This indicates that the CO2 vibrational distribution is significantly hotter than statistical. Investigations were then performed studying the quenching of NO A 2Σ+(v = 1) by NO and CO2, with both systems exhibiting similar characteristics to the quenching of the ground vibrational level of NO A 2Σ+. From comparison of the emission intensity of the CO fundamental and CO2 v3 mode following quenching of the v = 0 and 1 levels of the NO A 2Σ+ state, it was concluded that the branching ratio for reactive quenching was larger in the latter case. Secondly, experiments were performed to measure the rate constants for the quenching of NO A 2Σ+(v = 0) by the noble gases. The noble gases are inefficient quenchers of electronically excited NO and therefore careful experimental design was required to minimise the influence of impurities on the results. All the rate constants were found to be of the order of 10-14 cm3 molecule-1 s-1. The value for Xe was 50 times smaller than reported previously in the literature. In light of this new measurement, a re-analysis of experiments, performed previously in the group, on the electronic quenching of NO A 2Σ+(v = 0) by Xe was performed. A very hot vibrational distribution of NO X 2Π was obtained. Next, the collisional quenching of OH A 2Σ+(v = 0) by H2 was investigated. OH radicals were generated in situ by the photolysis of HNO3 at 193 nm, which were excited to the A 2Σ+(v = 0) state on the overlapped Q1(1) and P21(1) rotational lines at 307.935 nm. Reactive quenching was found to be the major pathway, in agreement with the literature. Copious emission from vibrationally excited water was observed. Comparison of this emission with theoretical calculations revealed a hotter distribution than predicted. It was concluded that the energy channelled into the vibrational modes of H2O is in excess of 60% of the available energy. Experiments performed with D2 allowed the non-reactive channel to be studied; a cold vibrational distribution of the OH X 2Π was observed. Finally the reaction between CN radicals and cyclohexane was studied. CN was generated by the photolysis of ICN at 266 nm. Prompt emission from HCN in the C-H stretching region was observed meaning the new bond was formed in a vibrationally excited state. Analysis of the emission revealed HCN was populated up to v3 = 2. Excellent agreement with the results of a theoretical study of the system was found.
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Gao, Min. "CHEMICAL CHARACTERIZATION OF SOIL ORGANIC MATTER IN AN OLIGOTROPHIC, SUBTROPICAL, FRESHWATER WETLAND SYSTEM: SOURCES, DIAGENESIS AND PRESERVATION." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/3625.
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Freshwater wetland soils of the Everglades were studied in order to assess present environmental conditions and paleo-environmental changes using organic geochemistry techniques. Organic matter in dominant vegetation, peat and marl soils was characterized by geochemical means. Samples were selected along nutrient and hydrology gradients with the objective to determine the historical sources of organic matter as well as the extent of its preservation.
Effective molecular proxies were developed to differentiate the relative input of organic matter from different biological sources to wetland soils. Thus historical vegetation shifts and hydroperiods were reconstructed using those proxies. The data show good correlations with historical water management practices starting at the turn of the century and during the mid 1900’s. Overall, significant shortening of hydroperiods during this period was observed.
The soil organic matter (SOM) preservation was assessed through elemental analysis and molecular characterizations of bulk 13C stable isotopes, solid state 13C NMR spectroscopy, UV-Vis spectroscopy, and tetramethyl ammonium hydroxide (TMAH) thermochemolysis-GC/MS. The relationship of the environmental conditions and degradation status of the soil organic matter (SOM) among the sites suggested that both high nutrient levels and long hydroperiod favor organic matter degradation in the soils. This is probably the result of an increase in the microbial activity in the soils which have higher nutrient levels, while longer hydroperiods may enhance physical/chemical degradation processes. The most significant transformations of biomass litter in this environment are controlled by very early physical/chemical processes and once the OM is incorporated into surface soils, the diagenetic change, even over extended periods of time is comparatively minimal, and SOM is relatively well preserved regardless of hydroperiod or nutrient levels. SOM accumulated in peat soils is more prone to continued degradation than the SOM in the marl soils. The latter is presumably stabilized early on through direct air exposure (oxidation) and thus, it is more refractory to further diagenetic transformations such as humification and aromatization reactions.
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Gao, Min. "Chemical characterization of soil organic matter in an oligotrophic, subtropical, freshwatwer wetland system : sources, diagenesis and preservation." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/3618.
Full textAbstract:
Freshwater wetland soils of the Everglades were studied in order to assess present environmental conditions and paleo-environmental changes using organic geochemistry techniques. Organic matter in dominant vegetation, peat and marl soils was characterized by geochemical means. Samples were selected along nutrient and hydrology gradients with the objective to determine the historical sources of organic matter as well as the extent of its preservation.
Effective molecular proxies were developed to differentiate the relative input of organic matter from different biological sources to wetland soils. Thus historical vegetation shifts and hydroperiods were reconstructed using those proxies. The data show good correlations with historical water management practices starting at the turn of the century and during the mid 1900’s. Overall, significant shortening of hydroperiods during this period was observed.
The soil organic matter (SOM) preservation was assessed through elemental analysis and molecular characterizations of bulk 13C stable isotopes, solid state 13C NMR spectroscopy, UV-Vis spectroscopy, and tetramethyl ammonium hydroxide (TMAH) thermochemolysis-GC/MS. The relationship of the environmental conditions and degradation status of the soil organic matter (SOM) among the sites suggested that both high nutrient levels and long hydroperiod favor organic matter degradation in the soils. This is probably the result of an increase in the microbial activity in the soils which have higher nutrient levels, while longer hydroperiods may enhance physical/chemical degradation processes. The most significant transformations of biomass litter in this environment are controlled by very early physical/chemical processes and once the OM is incorporated into surface soils, the diagenetic change, even over extended periods of time is comparatively minimal, and SOM is relatively well preserved regardless of hydroperiod or nutrient levels. SOM accumulated in peat soils is more prone to continued degradation than the SOM in the marl soils. The latter is presumably stabilized early on through direct air exposure (oxidation) and thus, it is more refractory to further diagenetic transformations such as humification and aromatization reactions.
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Huynh, An Ngoc Hiep. "Evaluating UVB and UVA Boosting Technologies for Chemical and Physical Sunscreens." University of Toledo Health Science Campus / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=mco158889865268024.
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Belcher, Kelly Leigh. "Evidentiary Value of Condoms: Comparison of Durable Physical and Chemical Characteristics of Condoms." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2481/.
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Condom trace evidence must not be overlooked in sexual assault cases; understanding the chemical and physical characteristics of condoms is imperative if condoms are to be useful evidence. Previous research shows that condom identification is possible, but it is equally important to evaluate durability of condom residues versus time. Using FT-IR, this study examined vaginal swabs from subjects who self-sampled at intervals for up to 72 hours after having intercourse with a condom. This study investigated whether age and the stage of the menstrual cycle affected the durability of residues in the vagina over time. This study revealed that condoms containing nonoxynol-9, silicone-based lubricants, and particulates provide valuable information for identification, and that nonoxynol-9 specifically withstands the vaginal environment for up to 72 hours. Additionally, age and menstrual cycle both appeared to have an effect on the durability of residues although larger sample size is desirable.
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Gray, Martha Lane. "Physical regulation of epiphyseal cartilage biosynthesis : responses to electrical, mechanical, and chemical signals." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/17205.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Harvard-MIT Division of Health Sciences and Technology Program in Medical Engineering and Medical Physics, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 194-205.
by Martha Lane Gray.
Ph.D.
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Shore, Stuart Mitchell. "The H.Y.P.P.E. Initiative: A School-Based Physical Activity Promotion Program." Diss., Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/68297.
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KinesiologyPh.D.
Physical activity promotion in schools is a critical component of adolescent health. The main purpose of this study was to test the efficacy of a school-based program to increase the physical activity of 6th grade students. A total of 113 students in a large suburban public middle school participated in the 11 week study. A quasi-experimental design was used. Physical education (PE) classes served as the unit of randomization. Six PE classes were assigned to the control condition and six PE classes to the experimental condition. Control group students were asked to wear unsealed pedometers throughout the day in school and at home and to record their daily step-counts in school. Experimental group students also wore unsealed pedometers throughout the day and logged their daily step-counts in school, but additionally received a 10,000 step per day goal, were asked to attain an increased step-count goal during PE class, and received an enhanced PE curriculum. Pre- and post-test data were gathered for all dependent measures including average daily step-counts by week, GPA, attendance, tardiness, attitude and self-efficacy toward physical activity, and Presidential Physical Fitness Tests. The data analysis was completed using analyses of variance (ANOVAs), analysis of covariance (ANCOVA), paired sample t-tests, and independent sample t-tests. Results revealed significant gains in physical activity for both treatment conditions. Both groups demonstrated significantly increased step-counts relative to their baseline step-counts. The intervention did not produce significant changes in attitude or self-efficacy. There were some significant improvements in physical fitness and the scholastic measures, but these changes were not attributed to the intervention. Very low attrition, a high compliance rate, and favorable participant feedback were also noted. Overall, this study revealed that, in the short-term, it is possible to significantly improve physical activity without changing an adolescent's self-efficacy or attitude. An important finding of this study was that multi-faceted self-monitoring was the most critical factor that contributed to increased physical activity.
Temple University--Theses
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Alhammad, Khalid Sulaiman. "Designing, implementing and evaluating a teaching sequence about physical and chemical change for Saudi school students aged 15-16." Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595672.
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Differentiation between physical and chemical change in chemistry teaching is both fundamental and problematic. Teaching approaches often rely on using macroscopic descriptions of change processes, which by their nature cannot differentiate between physical and chemical change. The aim of this study was to develop. implement, and evaluate a teaching sequence concerning students' understanding of physical and chemical change processes, based upon a submicroscopic model of the structure of matter. The teaching sequence was implemented with secondary students aged 15•16 in the target Saudi school. A case study approach was employed (one school). Three year 10 classes from the selected school (90 male students) and two chemistry teachers were recruited. For the purpose of designing the teaching sequence, the Leeds Group model was used. In the implementation and evaluation phases the focus was on measuring what teachers and students were expected to do and what they actually did, as well as evaluating what students were expected to learn compared to what they actually learnt. Furthermore, an interview approach was used to explore teachers' and students' views about the designed teaching sequence. A conceptual analysis was conducted which identified six broad areas (families) of key scientific ideas (FKSO. The results of this study indicated that the implementation of the designed teaching sequence, to a large extent, covered the required conceptual content. The results also showed that the students talked to the teacher (and each other), as well as the teacher talking to students. So, the students could control the meaning-making process by their interventions, rather than placing sole responsibility for this on the teacher. The designed teaching sequence was, to some extent, effective in relation to students' learning of physical and chemical change across all six FKSls. However, what students found most difficult in the understanding of the physical and chemical change, through the particle model (submicroscopic level), was how macroscopic descriptions and the submicroscopic level relate to each other and differ from one another. The results demonstrated increases in the level of conceptual understanding achieved by students following the designed teaching sequence, compared to students following the normal teaching approach.
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Wanli, Hadia. "Matematik i förskolan / Mathematics in Pre-school." Thesis, Malmö högskola, Lärarutbildningen (LUT), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-27789.
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Grunden för utvecklingen av ett barns matematikkunskaper lägger man redan i förskolan. Attarbeta med matematik i förskolan är oerhört viktigt för att förbereda barnen för skolan ochlivet. Under min undersökning kommer jag därför att undersöka på vilket sättmatematiklärande genomförs i förskolan samt hur pedagogerna synliggör matematiken iförskolan. Under min verksamhetsförlagda tid (VFT) upptäckte jag variation i pedagogernasarbetssätt med matematik. Vissa fokuserade mycket på matematik undervardagsverksamheten medan andra knappt var engagerade i att lära barnen matematik.Min undersökning är baserad på intervjuer av sex pedagoger från två olika förskolor.Resultatet av intervjuerna visade att alla pedagoger var överens om att matematiken iförskolan förbereder barnen inför matematiken som kommer framöver i skolan och livet. Devar även överens om att matematiken finns i alla vardagsrutiner. Vissa pedagoger tyckte attman inte behöver planera in matematiken i förskolan på samma sätt som de gör i skolan, denkommer naturligt in i vardagsrutinerna. Däremot var alla pedagoger ense om att pedagogenmåste vara medveten om matematiken för att kunna lyfta fram den. Resultatet visade även attnågra pedagoger synliggör matematiken med hjälp av konkreta material, medan andraanvänder sig av det matematiska språket för att lyfta fram olika matematiska begrepp.
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Bassolino, Giovanni. "Tuning ultrafast chemical reaction dynamics in photoactive proteins." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:42c19c5c-c6df-48e9-bb1c-8a7098eca8b4.
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This dissertation investigates the origins of tunable and efficient photochemistry in three different photoactive proteins, bacteriorhodopsin (BR), rhodopsin (RHO) and green fluorescent protein (GFP). In all cases, significant differences exist between the photoreactivity of model chromophores in solution and in the protein environment, in terms of excited state lifetime and efficiency of the primary photochemical process (opsin proteins) or the type of reaction (excited state proton transfer versus C=C double bond photoisomerisation for GFP). The work presented here investigates for each case to what extent the protein environment is necessary to alter the photochemistry of model chromophores in solution. For GFP and BR steric and electrostatic interactions between the protein pocket and the chromophore are shown to be likely responsible for shaping the excited state surface along which the photoreactions take place. For RHO it is suggested, contrary to current belief, that selection of a reactive ground state conformer might be the main effect generating the observed differences between solution and protein environment. The solution photochemistry of structurally modified retinal protonated Schiff bases, taken as model chromophores for the opsin proteins, is studied with continuous wave irradiation experiments and ultrafast transient spectroscopies. Surprisingly large differences are observed for the isomerisation reaction depending on the starting configuration (trans or cis) of the photoactive double bond. The current model for BR based on the tuning of the excited state barrier encountered along the isomerisation coordinate is expanded to include the changes in selectivity, speed and efficiency observed for a series of all-trans derivatives. For 11-cis, the photoisomerisation in solution is proposed to take place along a barrierless isomerisation coordinate, in contrast with the models currently available in literature. It is suggested that the protein might be discriminating between ground state conformers rather than significantly changing the topography of the reaction coordinate. For GFP, excited state Raman spectra are recorded for the wild-type protein, two mutants and a model chromophore in solution. It is suggested that the high frequency vibrational modes observed in the excited state spectra of the proteins but not of the model chromophore in DMSO are a sign of a tighter chromophore environment that inhibits the photoisomerisation reaction occurring in solution.
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Luque, Carolina E. "Evaluating a Peer-Implemented Intervention for Increasing Physical Activity During School Recess." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7332.
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Physical inactivity is a significant issue in the United States that has been linked to multiple health concerns. Few studies have used behavioral interventions during opportunities available in school, such as recess. There is a need for low effort and accessible interventions to increase children’s physical activity during these opportunities. The purpose of the current study was to evaluate the efficacy of a peer-implemented recess intervention that uses student pairing and feedback to increase physical activity. Step count was recorded by a pedometer. Peer leaders were trained in a group using behavioral skills training. A new leader performed the task-analyzed duties each week of intervention. An ABAB reversal design was used to evaluate the efficacy of the intervention. The results were mixed across the participants, but generally this study did not achieve experimental control in an ABAB design.
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Cassity, Kelby Brandan. "CHEMICAL MODIFICATION AND CHARACTERIZATION OF CARBON NANOTUBES." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/73.
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Carbon nanotubes (CNTs) are a relatively new allotrope of carbon that possess very unique and exciting physical characteristics. However, much is still unknown regarding their physical structure and chemical reactivity. The focus of this dissertation is to utilize the chemical modification of these filamentous carbon structures as a probe to investigate the structure and reactivity of carbon nanotubes. Also discussed is the ability of CNTs, once chemically modified, to interact with specific polymer matrices and how the addition of modified and unmodified CNTs affects the physical properties of these matrices.
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Speers, Jimmy D. (Jimmy Dale). "Motion Versus Non-Motion in Interactive Video Lessons in High School Physical Science." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc279141/.
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The most important question addresed in this study was whether there is any difference in student learning between a motion group and a non-motion group. The interactive video courseware is currently a part of the curriculum in this district. It was used in its original form with the contrast group. For the
experimental group one unit of the courseware was modified to remove the motion video and replace it with photorealistic graphics that served as the non-motion part of the study. Covariates were selected to compensate for any differences in the two groups. A pretest and posttest was administered to both groups. Analysis of the posttest scores indicated that there was no difference in learning if motion in the presentation was the only variable.
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Zetréus, Emma, and Moa Olsson. "To design security : A quantitative study of high school students security in the physical school environment." Thesis, Högskolan i Halmstad, Akademin för lärande, humaniora och samhälle, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-40085.
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High school students' schooling is preparing for their future. It is therefore important that their school time is characterized by security and a good physical school environment. The purpose of this thesis is to investigate how the physical school environment outside the classroom affects the safety of high school students. The aim of the study is also to highlight a possible connection between how the design of various places in the school affects the safety of the students, connected to where the students mostly stay during the school day. Previous science and background facts about safety in the physical school environment emphasize how important it is with the school's design. There are numbers of relevant factors to consider when designing a school and how to promote security in the physical school environment. To be able to answer the issues of the thesis, quantitative surveys have been sent out to high schools students at a secondary school. Through bar charts, the result is presented and then analyzed based on the method bivariate analysis. The theoretical framework of the thesis consists of Simmel's sociological theory and the spatial theory perspective. The results of the study are analyzed on the basis of the theory perspective and compared with previous science and other background facts. The results of this study shows that students are safest in the dining room, the library and in the places where they mostly stay daily. The factors that contribute to security are mainly that people they feel safe with are there, open spaces and comfortable sound levels.
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Winchester, Geoff. "Understanding How High School Teacher-Coaches Learn to Coach." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28759.
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Ndi, Cornelius Ndi. "Synthesis of Chemical Models of Hydrolase Enzymes for Intramolecular Catalysis." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etd/1356.
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Most nuclease enzymes can hydrolyze phosphoester bonds (in DNA and RNA) by using metal ions cofactors that coordinate and activate water molecules in the enzymes' active sites. However, there are some hydrolase enzymes (including nucleases) that can function without the aid of metal ions. 2,6-Di(1H-imidazol-2-yl)phenol, a model compound for hydrolase enzyme, was synthesized by the reaction between ethylenediamine and dimethyl-3-carboxysalicylate, initially resulting in the formation of diimidazoline. The diimidazoline was subsequently aromatized to the diimidazole by dehydrogenation over palladium. The overall reaction yield was low; therefore, other dehydrogenation transformation reactions were tried but all failed to improve the yield. Converting this diimidazolphenol into diimidazolphenyl monophoshpate derivative was attempted but failed to give desired products.
Synthesis of 2,2'-anthracene-1,8-diylbis-1H-imidazole, another model compound for hydrolase enzymes, was attempted using dimethyl-1,8-anthracenedicarboxylate, but synthesis was unsuccessful due to solubility problem.
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Roy, Choudhury Adarsh. "Defining Black: Characterization of Soot Reactivity with Thermogravimetrical Methods : Definiera svart: Karaktärisering av sotreaktivitet med termogravimetriska metoder." Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287478.
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Exhaust emissions in a vehicle has to flow through an exhaust aftertreatment in a diesel vehicle. In a diesel engine, the exhaust emissions are treated with Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), and Selective Catalytic Reduction (SCR). Every engine produces a different kind of soot depending on the drive cycle. In this thesis, a study was made on the soot oxidation in DPF so as to reduce the net fuel consumption and hence optimising the engine.This project focuses on DPF, where the soot and ash are trapped on the walls of the filter when the emissions flow through the DPF. Over a period of time, the soot accumulates and causes the pressure inside the filter to increase. To reduce the backpressure due to soot accumulation, soot has to be removed from the filter which is done by a regeneration process in which soot is oxidized. To understand the soot oxidation in the DPF, we study the chemical kinetics of the soot.The soot reacts with NO2, O2, and N2 in a Thermogravimetric Analysis (TGA) instrument, in isothermal conditions. Two soot samples, SORT-1 and FORCED 360 were analyzed with TGA, the rate equations were derived from using Arrhenius type kinetics and the data was processed by MATLAB. The rate at which the soot is oxidized by NO2 and O2 for SORT-1 is higher than for FORCED 360. This trend is observed similarly when both the soot samples react with only O2. When soot oxidation reaction takes place with O2 and NO2 they require a lower temperature of 250 °C-400 °C than compared to samples reacting with only O2 with a temperature of 350 °C - 500 °C. To understand the conditions that affect soot oxidation, the concentration of oxygen was varied and it was found that at higher oxygen concentration the soot oxidized is almost constant. Then soot kinetics were analysed by finding the rate of the reaction, the order of the reaction, and finally the activation energy. The order of the reaction for FORCED 360 and SORT-1 vary and slope of the graph, logarithm of reaction constant vs logarithm of mass shows a non-linearity in the former due to the slower rate of the reaction in SORT-1 than in FORCED 360. The activation energy was found to be 39.3 kJ/mol for SORT-1 and FORCED 360 is 60.8 kJ/mol.Avgasutsläpp i ett fordon måste strömma genom avgasefterbehandling i ett dieselfordon. I en dieselmotor behandlas avgasutsläppen med dieseloxidationskatalysator (DOC), dieselpartikelfilter (DPF) och selektiv katalytisk reduktion (SCR). Varje motor producerar olika typer av sot beroende på körcykeln. I denna avhandling gjordes en undersökning av sotoxidationen i DPF för att minska nettobränsleförbrukningen och därmed optimera motorn. Detta projekt fokuserar på DPF, där sot och aska fångas på filterväggarna när utsläppen flyter genom dieselpartikelfiltret. Under en tidsperiod ackumuleras sot och får trycket inuti filtret att öka. För att minska mottrycket på grund av sotansamling måste sot avlägsnas från filtret, vilket görs genom en regenereringsprocess där sot oxideras. För att förstå sotoxidationen i DPF studerar vi sotens kemiska kinetik. Sotet reagerar med NO2, O2 och N2 i ett instrument för termogravimetrisk analys (TGA) under isotermiska förhållanden. Två sotprover, SORT-1 och FORCED 360 analyserades med TGA, hastighetsekvationerna härleddes från användning av Arrhenius-typskinetik och data bearbetades av MATLAB. Den hastighet med vilken sot oxideras av NO2 och O2 för SORT-1 är högre än för FORCED 360. Denna trend observeras på liknande sätt när båda sotproverna reagerar med endast O2. När reaktion genom sotoxidation äger rum med O2 och NO2 kräver de en lägre temperatur på 250 ° C - 400 ° C än jämfört med prover som bara reagerar med O2 med en temperatur på 350 ° C - 500 ° C. För att förstå de förhållanden som påverkar sotoxidation varierades syrekoncentrationen och det visade sig att vid högre syrekoncentration var sotet oxiderat nästan konstant. Därefter analyserades sotkinetiken genom att hitta reaktionshastigheten, reaktionsordningen och slutligen aktiveringsenergin. Reaktionsordningen för FORCED 360 och SORT-1 varierar och lutningen i diagrammet, logaritmen för reaktionskonstanten mot logaritmen av massan visar en icke-linjäritet i den tidigare på grund av den långsammare reaktionshastigheten i SORT-1 än i FORCED 360. Aktiveringsenergin konstaterades vara 39,3 kJ / mol för SORT-1 och för FORCED 360, 60,8 kJ / mol.
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"Chemical vapor sensing, luminescence pH sensing, solvatochromism and photoisomerization of phenylene-vinylene derivatized terpyridine molecules." Tulane University, 2008.
Find full textAbstract:
Photophysics of fluorescent dyes is a field of constant interest because a better understanding of the excited-state properties helps in the design of new molecules as fluorescent probes for sensing and highly luminescent materials, especially for organic light emitting devices. Organic compounds with extended pi-systems, conjugated polymers, well defined oligomers have become an important class of electronic materials. The polypyridine complexes have been studied for their wide applications in varied fields. Introduction of fluorescence properties to the terpyridine and pyridine derivatives via linking them to phenylene vinylenes might open the way for further application as a new series of photofunctional compounds This work deals with the synthesis of some phenylene vinylene terpyridine/pyridine molecules, studying their photophysics and then demonstrating their ability for sensing applications Photophysical properties of phenylene-vinylene terpyridine/pyridine systems has been studied. These properties can be tuned by varying the donor and acceptor moieties in these systems. One such molecule is the MNpvpt, which has a strong electron-donating Me2N- group at one end and an electron accepting terpyridine at the other. The luminescence of this complex is highly solvatochromic, ranging from blue emission in hexane (lambdaem = 450 nm) to red emission in dimethylsulfoxide (lambda = 630 nm) with high quantum yields (0.65) in most organic solvents. This solvatochromic chromophore was incorporated into polymer matrices of polystyrene (PS) and polymethylmethacrylate (PMMA) and thin films of this was coated on quartz. Films containing the MNpvpt chromophore exhibit blue luminescence in air and, interestingly, exhibit rapid and reversible changes in the luminescence maxima in the presence of vapors of a wide variety of solvents MNpvpt contains two different types of nitrogen donors, i.e. , the hetero aromatic donors and the aliphatic amine group, as potential binding site for acidic protons and/or metal cations. This property was exploited and films containing the MNpvpt chromophore show interesting effects of vapors of acid and base on the emission of the ligand due to protonation and deprotonation at the potential binding sites. To further understand this a detailed study of the acid-base chemistry of MNpvpt and its analogue pvpt in solution was carried out. These experiments yielded the ground and excited state pka's of these molecules which gave a better understanding of their behavior in films. The surface morphology of these films were looked at using profilometry and AFM Photoisomerization of phenylene-vinylene terpyridine/pyridine is an interesting phenomenon. Effect of solvent polarity, acceptor group and donor group on isomerization has been studied Time Dependent Density Functional (TDDFT) calculations were employed to study excited state properties, affect of protonation and charge transfer characteristics of some of these systems using Gaussian 03. These calculations correlated reasonably well with experimental results and gave a good understanding of the structural and electronic factors associated with these moleculesacase@tulane.edu