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Factors Affecting the Precipitation of Quartz Under Hydrothermal ConditionsPepple, Chris C. 11 February 2008 (has links)
No description available.
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Seafloor Spreading Processes in Protoarc-Forearc Settings: Eastern Albanian Ophiolite as a Case StudyPhillips, Charity M. 05 May 2004 (has links)
No description available.
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Experimental Deformation of O+ Oriented Synthetic Quartz Single CrystalsPoston, Edward J. 27 June 2017 (has links)
No description available.
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PHYSICALLY CROSSLINKED HYDROGELS: IMPACT OF INTERFACES AND STRESS ON STRUCTURE AND PROPERTIESWiener, Clinton G., Wiener January 2017 (has links)
No description available.
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Task-based Good Work Practice Control Guidance Intervention to Reduce Respirable Crystalline Silica Exposures in Small-scale Demolition OperationsMuianga, Custodio Valentim 07 August 2009 (has links)
No description available.
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An Electron Microscopy Investigation of Gold and Associated Minerals from Round Mountain, NevadaBurke, Michelle Lynn 06 August 2015 (has links)
No description available.
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Petrogenesis of Plagiogranite and Granitoid in the Oman Ophiolite: A Comparative StudyUsing Oxygen Isotopes and Trace Elements in ZirconAlberts, Rebecca C. January 2016 (has links)
No description available.
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Electrically Modified Quartz Crystal Microbalance to Study Surface Chemistry Using Plasma Electrons as Reducing AgentsNiiranen, Pentti January 2021 (has links)
Metallic films are important in various applications, such as electric devices where it can act as contacts. In electrical devices, the substrate typically consists of silicon dioxide (SiO2) which is a temperature-sensitive substrate. Therefore, plasma enhanced chemical vapor deposition (PECVD) are better suited than thermally activated chemical vapor deposition (CVD). Depositing metallic films with PECVD demands co-reactants that act as reducing agents. However, these are not well-studied and do not always have the power enough to perform the reduction reaction for metals. Recently it has been concluded that electrons can act as reducing agents in the deposition of first row transition metallic films in a PECVD process. By supplying a positive bias to the substrate, the electrons got attracted to the surface of the substrate, which facilitated metal growth. The study concluded that metal growth only occurred at conductive -and semiconductive substrates and that the substrate bias and plasma power affected the metal growth. The process is however not well understood, which causes a knowledge gap, signifying that studies of the surface chemistry are needed. Here a new modified analytical method to study the surface chemistry in the newly developed process mentioned above is presented. The analytical method consists of an electrically modified quartz crystal microbalance (QCM) with gold electrodes as a conductive substrate. This allows the electron current to run through the QCM during the measurement. By supplying a DC-voltage to the front electrode it gets readily biased (negative and positive) and by placing a capacitor in the circuit, it connects the AC-circuit (oscillator circuit) and the DC-circuit (DC-voltage bias circuit). At the same time, it blocks the DC-current from going back to the oscillator but allows the high-frequency signal to pass from the QCM. The results in this thesis concluded that the QCM can be electrically modified to allow an electron flux to the QCM while using it as a substrate when electrons are used as reducing agents. Scanning electron microscopy (SEM) of a QCM crystal revealed that a 2 µm film had been deposited while SEM coupled with energy dispersive X-ray spectroscopy (EDS) showed that the film indeed contained iron. Further analysis was made by high-resolution X-ray photoelectron spectroscopy (HR-XPS) to find the elemental composition of the film, which revealed that the thin film contained 41 at.% iron. In addition, this study investigated if the QCM could be used to study CVD processes where electrons were used as reducing agents. The results indeed revealed that it is possible to study the surface chemistry where electrons are used as reducing agents with the electrically modified QCM to gain knowledge concerning film deposition. Initial results of the QCM showed that film growth could be studied when varying the plasma power between 5 W to 15 W and the QCM bias between -40 V to +40 V. The method generated easily accessible data concerning the process where electrons are used as reducing agents, which gained insight to the method that never has been disclosed before.
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[pt] CRISTAIS OSCILADORES DE QUARTZO COMO SENSORES PARA MICROSCOPIA DE FORÇA ATÔMICA / [en] QUARTZ CRYSTAL OSCILLATORS AS ATOMIC FORCE MICROSCOPE SENSORSFELIPE PTAK LEMOS 13 October 2016 (has links)
[pt] A caracterização de cristais osciladores de quartzo (QTF) foi realizada
nesta dissertação com o objetivo de implementá–los como sensores de um
microscópio de força atômica (AFM). O QTF possui várias vantagens
em relação aos cantilevers tradicionais de silício. Utilizado em modos
dinâmicos de operação do AFM, o QTF possui maior fator de qualidade
e rigidez, permitindo melhor sensibilidade em força e o uso de baixas
amplitudes de oscilação para imageamento do que cantilevers tradicionais.
Nesse trabalho, parâmetros mecânicos e elétricos do QTF foram medidos.
Além disto, um estudo da influência da adição de massa nos braços do
QTF foi realizado. Para a implementação do QTF no AFM, um sistema de
feedback composto de um amplificador lock–in e um amplificador diferencial
foi desenvolvido e testado. Adicionalmente, um novo cabeçote para o
microscópio foi desenvolvido para adaptar o QTF ao microscópio. / [en] The characterization of quartz tuning forks (QTF) was performed in
this dissertation, aiming to implement them as sensors at an atomic force
microscope (AFM). The QTF has several advantages over traditional silicon
cantilevers. Used in dynamic AFM modes, the QTF has higher quality
factor and stiffness, allowing better force sensitivity and lower amplitudes of
oscillation for imaging than traditional cantilevers. In this work, electrical
and mechanical parameters of the QTF were obtained. Furthermore, a study
of the influence of additional mass on the QTF prongs was performed. To
implement the QTF at the AFM, a feedback system composed of a lock–in
amplifier and a differential amplifier was developed and tested. Additionally,
a new microscope head was designed to adapt the QTF to the microscope.
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Controlled Release from Agricultural Spray DepositsWang, Fengyan January 2020 (has links)
Copper chlorophyllin (CuChl) is an antioxidant from renewable sources, which has shown as a potential active ingredient in agricultural crop sprays. The major objectives of this thesis are to understand the colloidal and interfacial behaviors of CuChl, and to develop strategies for improving its effectiveness in field applications. In this project, the following three areas are examined and analyzed.
In practice, CuChl-based formulations are sprayed directly onto a plant’s foliage. As such, there is a need to understand how CuChl interacts with relevant plant surfaces. To this end, quartz crystal microbalance with dissipation (QCM-D) was used to quantify the adsorption of CuChl aqueous solutions onto four model surfaces: polystyrene, cellulose, pullulan, and silica. The results showed that cellulose adsorbed the highest amount of CuChl, followed by polystyrene and pullulan. In addition, the results also showed that the surfactants, SDS or DTAB, could alter the binding of CuChl to cellulose when used in concentrations above the critical micelle concentration.
CuChl is composed of water-soluble and dispersed components, therefore it is not intrinsically rainfast, which limits its field application. To immobilize CuChl on leaves, a polymer combination of CMC (carboxymethyl cellulose) and PAE (polyamidoamine-epichlorohydrin) was designed for use as a spray adjuvant. The release behaviors of CuChl from dried spray deposits were investigated using varied polymer compositions and concentrations and compared with those of a water-soluble dye, brilliant sulfaflavine (BSF). The results indicated that a small amount of CuChl was immediately released upon exposure to water whereas BSF’s release behavior was dependent on the square root of time. The unusual behavior of CuChl was attributed to the presence of particles in the solution. These nanoparticles were coated with CMC:PAE complex, with the result of being immobilized on parafilm.
Suspoemulsion is the most complex agricultural formulation that is composed of both dispersed particles and emulsion droplets. The objective of this work is to understand the relationship between the solution properties of suspoemulsions and the resulting dried deposits on hydrophobic surfaces. The results showed that the distribution of polychlorinated Cu (II) phthalocyanine (PG7) particles in dried deposits was related to the extent to which PG7 particles were adsorbed on or entrained in oil droplets. The PG7 particles that mainly ended up in the center (dome) area after drying were bound to the oil/water interface in the suspoemulsion, whereas individually dispersed particles ended up in the annulus. / Thesis / Doctor of Philosophy (PhD) / Agricultural formulations have been developed and widely applied to crops in an effort to maximize yields to keep up with the food demands of the world’s ever-growing population. However, there are still many challenges associated with the application of these formulations, such as huge losses due to spray drift, wash-off, and degradation during spraying. These issues can reduce the formulation’s overall efficacy and pose serious risks to the environment and human health.
The primary objective of this thesis is to explore the agricultural application of a new environmentally-friendly active ingredient, copper chlorophyllin (CuChl). To this end, this work begins by determining CuChl’s colloidal and adsorption behaviors, with a particular focus on its binding tendencies for relevant plant surfaces. Next, a polymer combination was designed as a spray adjuvant to enhance CuChl’s rainfastness performance and CuChl’s release from dried deposits was characterized. Finally, the distribution of dispersed particles in dried suspoemulsion deposits was determined.
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