Current Search: Elsheimer, Seth (x)
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- Title
- EXPLORATION OF BIOACTIVE COMPOUNDS OF GINGER AS A FOLK REMEDY FOR MIGRAINES.
- Creator
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Aleger, Nathan Vorbes, Elsheimer, Seth, Samsam, Mohtashem, University of Central Florida
- Abstract / Description
-
Ginger (Zingiber Officinale) has been used in Asia for centuries to treat various ailments. Ginger has been reported to alleviate migraine pain via four bioactive compounds that can reduce nitric oxide synthase (NOS) resulting in the inhibition of nitric oxide (NO). The inhibition of nitric oxide results in the vasoconstriction of the intracranial blood vessels alleviating migraine pain. It is hypothesized that ginger has structural similarities to vasoconstrictor drugs causing similar...
Show moreGinger (Zingiber Officinale) has been used in Asia for centuries to treat various ailments. Ginger has been reported to alleviate migraine pain via four bioactive compounds that can reduce nitric oxide synthase (NOS) resulting in the inhibition of nitric oxide (NO). The inhibition of nitric oxide results in the vasoconstriction of the intracranial blood vessels alleviating migraine pain. It is hypothesized that ginger has structural similarities to vasoconstrictor drugs causing similar receptor interactions. A review of the bioactive compounds in ginger and popular vasoconstrictor drugs was done to determine structural similarities. The results of this study show that the compounds in ginger share no structural similarities with vasoconstrictor drugs used in the treatment of migraine headaches.
Show less - Date Issued
- 2017
- Identifier
- CFH2000251, ucf:45962
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000251
- Title
- Synthetic Design and Characterization of Polycyclic Aromatic Compounds in Molecular and Extended System.
- Creator
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Pour, Gavin, Belfield, Kevin, Frazer, Andrew, Elsheimer, Seth, University of Central Florida
- Abstract / Description
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The work presented herein focuses on the synthesis and characterization of polycyclic aromatic compounds for a wide variety of toxicological, analytical, and electronic applications. First, the modular synthesis of 12 dibenzo- and naphtho- fluoranthene polycyclic aromatic hydrocarbons (PAHs) via a Pd-catalyzed five-membered ring closing procedure is discussed. By understanding the various modes through which the Pd migrates during transformation, structural rearrangements were bypassed,...
Show moreThe work presented herein focuses on the synthesis and characterization of polycyclic aromatic compounds for a wide variety of toxicological, analytical, and electronic applications. First, the modular synthesis of 12 dibenzo- and naphtho- fluoranthene polycyclic aromatic hydrocarbons (PAHs) via a Pd-catalyzed five-membered ring closing procedure is discussed. By understanding the various modes through which the Pd migrates during transformation, structural rearrangements were bypassed, obtaining regioselectivity through various redesigns in the synthetic route. Each compound in the serious was rigorously characterized via 1D/2D NMR, absorption and emission spectroscopy as well as cyclic voltammetry, which shows vast differences due to small structural changes between these constitutional isomers. Next, a series of polyphenylated organic ligands for zirconium metal organic frameworks is presented as materials for post-synthetic Scholl cyclodehydrogenation. Lastly, a series of organic linkers featuring covalently anchored redox-active pendants is explored for tuneable redox activity in Zr-based metal-organic frameworks. Thin-films were grown onto fluorine-doped tin-oxide glass electrodes and analyzed by cyclic voltammetry. This is the first reported pre-synthetic incorporation of covalently-bound ferrocenyl pendants into such a system. By attenuating the proportions of redox active and inactive links the oxidative peak currents could be tuned. This body of work represents a contribution toward the practical design and synthesis of polycyclic aromatic for a wide variety of analytical and electrochemical applications.
Show less - Date Issued
- 2019
- Identifier
- CFE0007512, ucf:52647
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007512
- Title
- Use of an Activated Magnesium/cosolvent System for the Desorption and Degradation of Polycyclic Aromatic Hydrocarbons and Their Oxygenated Derivatives in Contaminated Soils.
- Creator
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Elie, Marc, Yestrebsky, Cherie, Clausen, Christian, Elsheimer, Seth, Campiglia, Andres, Randall, Andrew, University of Central Florida
- Abstract / Description
-
The contamination of soils, with polycyclic aromatic hydrocarbons (PAHs), remains a widespread environmental concern. In the past two decades, many physical, chemical and biological methods have been developed and evaluated for the degradation of PAHs. However, due to their low aqueous solubility, high sorption affinity, hydrophobicity and recalcitrance, the environmental remediation of PAHs in soil continues to be economically challenging. In addition to PAH contamination, the presence of...
Show moreThe contamination of soils, with polycyclic aromatic hydrocarbons (PAHs), remains a widespread environmental concern. In the past two decades, many physical, chemical and biological methods have been developed and evaluated for the degradation of PAHs. However, due to their low aqueous solubility, high sorption affinity, hydrophobicity and recalcitrance, the environmental remediation of PAHs in soil continues to be economically challenging. In addition to PAH contamination, the presence of oxygenated derivatives of PAHs (OPAHs), in soils, has increasingly become a concern due to their greater toxic properties compared to parent PAH compounds. To date, no investigations on OPAH-remediation methods have been presented in the literature. The use of zero-valent metals (ZVMs) has been reported for several halogenated contaminants in solution systems, but the effectiveness of ZVM to degrade sorbed PAHs and OPAHs has been rarely addressed. This present research focuses on the development of a combined technique for the feasible desorption and degradation of PAHs and OPAHs in soils. PAH and OPAH degradation efficiency, using activated magnesium (Mg) metal combined with an ethanol-ethyl lactate cosolvent (1:1 ratio), was initially examined in soil-free systems. This metal/cosolvent system demonstrated adequate degradation (above 80%) for high-molecular-weight (HMW) PAHs, which were subsequently converted into hydroaromatic compounds; while OPAHs were degraded and converted into hydroxylated or hydrogenated derivatives. Further soil-free studies revealed that the degradation rate was affected by the surface or reactive sites of the metal and that optimum degradation efficiency were obtained with Mg ball milled with graphite (Mg/C).In a bench-scale feasibility test, the efficacy of this system was assessed on a soil spiked with a mixture of three HMW PAHs compounds and three OPAHs compounds with amounts ranging from 0.033 mmol to 0.060 mmol. The experimental results show that 2 mL of an ethanol-ethyl lactate solvent mixture resulted in 58% to 85% extraction efficiency for the selected contaminants in 1 g of spiked soil, followed by 64 - 87% degradation efficiency of the extracted contaminants with 4.11 mmol of the activated metal. This activated-Mg/cosolvent system can be considered as a promising alternative method for ex situ remediation of PAH and OPAH-contaminated soils.
Show less - Date Issued
- 2012
- Identifier
- CFE0004533, ucf:49259
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004533
- Title
- An Evaluation Study of the Effectiveness of Using a Reaction-Based Process for Hydrazine Remediation.
- Creator
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Oropeza, Cristina, Clausen, Christian, Yestrebsky, Cherie, Miles, Delbert, Elsheimer, Seth, Griffin, Timothy, University of Central Florida
- Abstract / Description
-
Hydrazine (HZ) and monomethylhydrazine (MMH) are used extensively as hypergolic propellants at Kennedy Space Center. These highly reactive fuels are considered highly toxic, and potentially carcinogenic. Consequently, the transport, handling, and disposal of hydrazines is strictly regulated to protect personnel and the environment. Currently, KSC generates large volumes of hydrazine-laden wastewater for disposal. This waste is contained and shipped on public highways for subsequent disposal...
Show moreHydrazine (HZ) and monomethylhydrazine (MMH) are used extensively as hypergolic propellants at Kennedy Space Center. These highly reactive fuels are considered highly toxic, and potentially carcinogenic. Consequently, the transport, handling, and disposal of hydrazines is strictly regulated to protect personnel and the environment. Currently, KSC generates large volumes of hydrazine-laden wastewater for disposal. This waste is contained and shipped on public highways for subsequent disposal by incineration presenting a potentially catastrophic threat to the environment and the general public in the event of an accidental release. Other existing remediation methods include oxidative and reductive pathways as well as biodegradation in fixed film reactors. Each of these methods has associated drawbacks and limitations that make them unsuitable for industrial use. Recently, hydrazine neutralization by reaction with alpha-ketoglutaric acid (AKGA) to form the stabilized pyridazine derivatives PCA and mPCA has been explored. The applicability of this technique for use at KSC has been established and procedural considerations for implementation have been addressed.Experimental evidence based on worst case scenario decontamination processing simulations and reaction characterization has suggested that AKGA can cost effectively function as a drop-in replacement for current neutralizers with minimal modification to existing infrastructure and operating procedures. Further work will be necessary to satisfy permitting requirements and verify that the reaction product stream is non-hazardous in light of limited toxicity data.
Show less - Date Issued
- 2011
- Identifier
- CFE0004148, ucf:49060
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004148
- Title
- Investigation of a Novel Magnesium and Acidified Ethanol System for the Degradation of Persistent Organic Pollutants.
- Creator
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Maloney, Phillip, Yestrebsky, Cherie, Clausen, Christian, Elsheimer, Seth, Frazer, Andrew, Quinn, Jacqueline, University of Central Florida
- Abstract / Description
-
For centuries chemists have sought to improve humankind's quality of life and address many of society's most pressing needs through the development of chemical processes and synthesis of new compounds, often with phenomenal results. Unfortunately, there also are many examples where these chemicals have had unintended, detrimental consequences that are not apparent until years or decades after their initial use. There are numerous halogenated molecules in this category that are globally...
Show moreFor centuries chemists have sought to improve humankind's quality of life and address many of society's most pressing needs through the development of chemical processes and synthesis of new compounds, often with phenomenal results. Unfortunately, there also are many examples where these chemicals have had unintended, detrimental consequences that are not apparent until years or decades after their initial use. There are numerous halogenated molecules in this category that are globally dispersed, resistant to natural degradation processes, bioaccumulative, and toxic to living organisms. Chemicals such as these are classified as persistent organic pollutants (POPs), and due to their negative environmental and health effects, they require safe, effective, and inexpensive means of remediation.This research focuses on the development and optimization of a reaction matrix capable of reductively dehalogenating several POPs. Initial experiments determined that powdered magnesium and 1% V/V acetic acid in absolute ethanol was the most effective system for degrading polychlorinated biphenyl (PCB), an extraordinarily recalcitrant environmental contaminant. Further studies showed that this matrix also was capable of degrading polychlorinated dibenzo-p-dioxins (PCDDs), polybrominated diphenyl ethers (PBDEs), and four organochlorine pesticides (OCPs); dieldrin, heptachlor, heptachlor epoxide, and chlordane. During this phase of testing, field samples contaminated with chlordane were washed with ethanol and this ethanol/chlordane solution was degraded using the same reaction matrix, thereby demonstrating this technology's potential for (")real-world(") remediation projects. Finally, a set of experiments designed to provide some insight into the mechanism of dechlorination seems to indicate that two distinct processes are necessary for degradation to occur. First, the passivated outer layer of the magnesium must be removed in order to expose the zero-valent magnesium core. Next, an electron is transferred from the magnesium to the target molecule, causing the cleavage of the halide bond and the subsequent abstraction of either a hydrogen or proton from a solvent molecule. It is anticipated that an understanding of these fundamental chemical processes will allow this system to be tailored to a wide range of complex environmental media.
Show less - Date Issued
- 2013
- Identifier
- CFE0005109, ucf:50723
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005109
- Title
- Trace Contaminant Control: An In-Depth Study of a Silica-Titania Composite for Photocatalytic Remediation of Closed-Environment Habitat Air.
- Creator
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Coutts, Janelle, Yestrebsky, Cherie, Clausen, Christian, Sigman, Michael, Elsheimer, Seth, Wheeler, Raymond, University of Central Florida
- Abstract / Description
-
This collection of studies focuses on a photocatalytic oxidation (PCO) system for the oxidation of a model compound, ethanol (EtOH), using an adsorption-enhanced silica-titania composite (STC) as the photocatalyst. Studies are aimed at addressing the optimization of various parameters including light source, humidity, temperature, and possible poisoning events for use as part of a system for gaseous trace contaminant control in closed-environment habitats.The first goal was to distinguish the...
Show moreThis collection of studies focuses on a photocatalytic oxidation (PCO) system for the oxidation of a model compound, ethanol (EtOH), using an adsorption-enhanced silica-titania composite (STC) as the photocatalyst. Studies are aimed at addressing the optimization of various parameters including light source, humidity, temperature, and possible poisoning events for use as part of a system for gaseous trace contaminant control in closed-environment habitats.The first goal was to distinguish the effect of photon flux (i.e., photons per unit time reaching a surface) from that of photon energy (i.e., wavelength) of a photon source on the PCO of ethanol. Experiments were conducted in a bench-scale annular reactor packed with STC pellets and irradiated with either a UV-A fluorescent black light blue lamp (?peak = 365 nm) at its maximum light intensity or a UV-C germicidal lamp (?peak = 254 nm) at three levels of light intensity. The STC-catalyzed oxidation of ethanol was found to follow zero-order kinetics with respect to CO2 production, regardless of the photon source. Increased photon flux led to increased EtOH removal, mineralization, and oxidation rate accompanied by lower intermediate concentration in the effluent. The oxidation rate was higher in the reactor irradiated by UV-C than by UV-A (38.4 vs. 31.9 nM s-1) at the same photon flux, with similar trends for mineralization (53.9 vs. 43.4%) and photonic efficiency (63.3 vs. 50.1 nmol CO2 (&)#181;mol photons-1). UV-C irradiation also led to decreased intermediate concentration in the effluent compared to UV-A irradiation. These results demonstrated that STC-catalyzed oxidation is enhanced by both increased photon flux and photon energy.The effect of temperature and relative humidity on the STC-catalyzed degradation of ethanol was also determined using the UV-A light source at its maximum intensity. Increasing temperature from 25(&)deg;C to 65(&)deg;C caused a significant decrease in ethanol adsorption (47.1% loss in adsorption capacity); minimal changes in EtOH removal; and a dramatic increase in mineralization (37.3 vs. 74.8%), PCO rate (25.8 vs. 53.2 nM s-1), and photonic efficiency (42.7 vs. 82.5 nmol CO2 (&)#181;mol photons-1); as well as a decrease in intermediate acetaldehyde (ACD) evolution in the effluent. By elevating the reactor temperature to 45(&)deg;C, an ~32% increase in photonic efficiency was obtained over the use of UV-C irradiation at room temperature. Increasing the reactor temperature also allowed for increased energy usage efficiency by utilizing both the light and heat energy of the UV-A light source. Higher relative humidity (RH) also caused a significant decrease (16.8 vs. 6.0 mg EtOH g STC-1) in ethanol adsorption and dark adsorption 95% breakthrough times (48.5 vs.16.8 hours). Trends developed for ethanol adsorption correlated well with studies using methanol as the target VOC on a molar basis. At higher RH, ethanol removal and ACD evolution were increased while mineralization, PCO rate, and photonic efficiency were decreased. These studies allowed for the development of empirical formulas to approximate EtOH removal, PCO rate, mineralization, and ACD evolution based on the parameters (light intensity, temperature, and RH) assessed.Poisoning events included long-term exposure to low-VOC laboratory air and episodic spikes of either Freon 218 or hexamethylcyclotrisiloxane. To date, all poisoning studies have shown minimal (0-6%) decreases in PCO rates, mineralization, and minimal increases in ACD evolution, with little change in EtOH removal. These results show great promise for this technology as part of a trace contaminant control system for niche applications such as air processing onboard the ISS or other new spacecrafts.
Show less - Date Issued
- 2013
- Identifier
- CFE0005092, ucf:50741
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005092
- Title
- A Study of the Degradative Capabilities of the Bimetallic System: Mg(Pd/C) as Applied in the Destruction of Decafluoropentane, an Environmental Contaminant.
- Creator
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Tomlin, Douglas, Clausen, Christian, Yestrebsky, Cherie, Hampton, Michael, Elsheimer, Seth, Griffin, Timothy, University of Central Florida
- Abstract / Description
-
Pollution from hydrofluorocarbons (HFCs) poses a serious challenge to the environmental community. Released from industrial operations, they have contaminated both the atmosphere and groundwater and are considered persistent in both media. For over the past 20 years, the practice of synthesizing HFCs as alternatives to chlorofluorocarbons (CFCs) has been conducted in an effort to reverse the effects of stratospheric ozone layer depletion. HFCs also exhibit desirable properties as precision...
Show morePollution from hydrofluorocarbons (HFCs) poses a serious challenge to the environmental community. Released from industrial operations, they have contaminated both the atmosphere and groundwater and are considered persistent in both media. For over the past 20 years, the practice of synthesizing HFCs as alternatives to chlorofluorocarbons (CFCs) has been conducted in an effort to reverse the effects of stratospheric ozone layer depletion. HFCs also exhibit desirable properties as precision cleaning solvents due to their low surface energies but that use has lead to releases contaminating groundwater resulting in recalcitrant pollution in the form of dense non-aqueous phase liquids (DNAPLs). Results from studies requested by the EPA have shown HFCs to exhibit developmental and neurological damage in animal life along with their impact to humans remaining not completely understood. Therefore, the potential hazards of HFCs to human health and the environment necessitates the development of an effective and environmentally responsible technology for their remediation from groundwater. The National Aeronautics and Space Administration (NASA) has employed the use of various halogenated solvents in its spacecraft cleaning operations at its facilities for many years and in that time experienced accidental releases which eventually resulted in environmental contamination. Many of the organic solvents employed in these operations consisted of halogenated compounds with most being partially chlorinated and fluorinated hydrocarbons. Through normal use and operation, releases of these materials found their way into the environs of atmosphere, soil and groundwater. Remediation of fluorinated compounds has not followed the successful path laid by clean-up technologies developed for their chlorinated counterparts. Fluorinated compounds are resistant however to those methods due to their unreactive nature stemming from the properties of the strong carbon-fluorine bond. This unique bonding property also ensures that their environmental persistence endures. One particular fluorinated groundwater contaminant, the HFC 1,1,1,2,2,3,4,5,5,5-decafluoropentane (DFP), which has been used by NASA since the late 1990's was selected as the focus of this study. For this study, various reductive metal systems were evaluated for their capability towards effective degradation of DFP. These included the metals: iron, magnesium, aluminum and zinc and several bimetallic alloys as well as on carbon support. Variations in protic solvent reaction media and acidic metal activation were also explored. The bimetallic reductive catalytic alloy Magnesium with Palladium on Carbon, Mg(Pd/C), in aqueous media proved to be the successful candidate with 100% conversion to simple hydrocarbons. Mechanistic evaluation for degradation is proposed via a series of stepwise catalytic hydrodefluorination reactions. Kinetic studies revealed degradation to obey second order reaction kinetics. Further study should be conducted optimizing an in situ groundwater delivery method for field application. Additionally, the developed technology should be assessed against other groundwater fluorocarbon pollutants; either as a method for remediating multiple fluorinated polluted sites or as a polishing agent where all other pollutants have been abated.
Show less - Date Issued
- 2012
- Identifier
- CFE0004798, ucf:49742
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004798
- Title
- Design, Synthesis, and Biological Evaluation of Novel Polyamine Transport System Probes and their Application to Human Cancers.
- Creator
-
Muth, Aaron, Phanstiel, Otto, Ye, Jingdong, Elsheimer, Seth, Miles, Delbert, Vonkalm, Laurence, University of Central Florida
- Abstract / Description
-
The mammalian polyamine transport system (PTS) has been of interest due to its roles in cancer and maintaining cellular homeostasis. Polyamines are essential growth factors which are tightly controlled via a balance of biosynthesis, metabolism, import, and export. This work focused on the development and biological testing of polyamine transport probes to help understand the molecular requirements of the PTS. This was mediated through the use of a CHO (PTS active) and CHO-MG* (PTS deficient)...
Show moreThe mammalian polyamine transport system (PTS) has been of interest due to its roles in cancer and maintaining cellular homeostasis. Polyamines are essential growth factors which are tightly controlled via a balance of biosynthesis, metabolism, import, and export. This work focused on the development and biological testing of polyamine transport probes to help understand the molecular requirements of the PTS. This was mediated through the use of a CHO (PTS active) and CHO-MG* (PTS deficient) screen, where compounds demonstrating high toxicity in CHO and low toxicity in CHO-MG* were considered PTS selective. The first chapter focused on the development of polyamine-based drugs which are both metabolically stable to polyamine oxidase (PAO) activity and are hyperselective for targeting the PTS. This approach was optimized by combining a di-substituted aryl design with terminal N-methylation of the appended polyamine chains to generate a new class of superior PTS agonists. The metabolic stability of these compounds was demonstrated in CHO and CHO-MG* in the presence and absence of a known PAO inhibitor, aminoguanidine (AG). Highly PTS selective compounds were then tested in the NCI-60 cell line screen to demonstrate the effectiveness of polyamine-based drugs in cancer therapy. During this screen, the MALME-3M (human melanoma) cell line was identified as being very sensitive to these PTS targeting drugs. Further studies using MALME-3M and its normal counterpart, MALME-3, showed excellent targeting of the cancer line over MALME-3. For example, The MeN44Nap44NMe compound showed 59-fold higher toxicity in MALME-3M over MALME-3.The second chapter focused on the development of potential polyamine transport inhibitors (PTIs) for use in combination therapy with ?-difluoromethylornithine (DFMO). This therapy is predicated upon reducing sustained polyamine depletion within cells by inhibiting both polyamine biosynthesis with DFMO and polyamine transport with the PTI ligand. Potential PTIs were identified by blocking the uptake of spermidine in DFMO-treated CHO and L3.6pl cells. Previous work has identified a tri-substituted polyamine-based design as an effective PTI. Low toxicity and a low Ki value in a L1210 screen were good predictors for PTI efficacy. The structural requirements for a potent PTI were explored by modulating the toxicity through the introduction of amide bonds, and also by determining the number and orientation of the polyamine messages (appended to an aryl core) required for efficient inhibition of polyamine uptake. These experiments showed that a tri-substituted design and a triamine message (homospermidine) appended was optimal for PTI potency. The final chapter focused on the development of Dihydromotuporamine C derivatives as non-toxic anti-metastatic agents. Dihydromotuporamine C demonstrated good anti-invasive properties with tumor cells. Derivatives were made in an effort to reduce the cytotoxicity of the parent and improve the anti-migration potency. The motuporamine derivatives all have a polyamine message (norspermidine or homospermidine) appended to make a macrocycle core, making them prime targets to evaluate as potential PTS ligands in the CHO and CHO-MG* screen. Each compound was also tested in the highly metastatic pancreatic cancer cell line L3.6pl to determine both its IC50 value and maximum tolerated dose (MTD). The anti-migration assay was performed at the lowest MTD obtained (0.6 (&)#181;M) in order to compare the series at the same non-toxic dose. The results suggested that as the N1-amine center was moved further from the macrocyclic ring, an increased ability to inhibit cell migration and reduced toxicity was observed. These collective findings provide new tools for cell biologists to modulate and target polyamine transport in mammalian cells. Future applications of these technologies include new cancer therapies which are cell-selective and inhibit the spread of tumors.
Show less - Date Issued
- 2012
- Identifier
- CFE0004636, ucf:49895
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004636
- Title
- Photophysical and photochemical factors affecting multi-photon direct laser writing using the cross-linkable epoxide SU-8.
- Creator
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Williams Jr., Henry, Kuebler, Stephen, Elsheimer, Seth, Zhai, Lei, Liao, Yi, Heinrich, Helge, University of Central Florida
- Abstract / Description
-
For the past decade, the epoxy based photoresist SU-8 has been used commercially and in the lab for fabricating micro- and nano-structures. Investigators have studied how processing parameters such as pre- and post-exposure bake temperatures affect the resolution and quality of SU-8 structures patterned using ultraviolet or x-ray lithography. Despite the advances in understanding the phenomena, not all of them have been explored, especially those that are specific to multi-photon direct laser...
Show moreFor the past decade, the epoxy based photoresist SU-8 has been used commercially and in the lab for fabricating micro- and nano-structures. Investigators have studied how processing parameters such as pre- and post-exposure bake temperatures affect the resolution and quality of SU-8 structures patterned using ultraviolet or x-ray lithography. Despite the advances in understanding the phenomena, not all of them have been explored, especially those that are specific to multi-photon direct laser writing (mpDLW). Unlike conventional exposure techniques, mpDLW is an inherently three-dimensional (3D) process that is activated by nonlinear absorption of light.This dissertation reports how several key processing parameters affect mpDLW using SU-8 including pre-exposure bake duration, focal depth, incident laser power, focal-point scan speed, and excitation wavelength. An examination of solvent content of films at various stages in the mpDLW by 1H-NMR shows that even moderate solvent content (over 1 wt-%) affects film viscosity and photoacid diffusion lengths, and can greatly affect the overall fidelity of small features. A study of micro-fabricated feature size versus writing depth in the material shows that even slight refractive index mismatch between SU-8 and the medium between it and the focusing objective introduces spherical aberration that distorts the focus, causing feature size to decrease or even increase in size with writing depth, depending on the average exposure power used. Proper adjustment of the average exposure power was demonstrated as a means to fabricate more uniform features with writing depth. Third, when varying the power and scan speed, it was observed that the feature-size scales with these two parameters in a manner that is consistent with a three-photon absorption mechanism at an excitation wavelength of 800 nm. When aniiiexcitation wavelength of 725 nm is used, the feature-size scaling becomes consistent with that of two photon absorption. This shows that the photoinitiators in the SU-8 can be activated by either two- or three-photon absorption over this wavelength range. Using an irradiance of ~2 TW cm-2 and elongated femtosecond pulses resulted in an observed fourth order power dependence. This observation is in agreement with the literature and suggests that the effective absorptive nonlinearity is also sensitive to pulse duration. These findings will be useful for creating accurate models of the process of mpDLW in SU-8. These models could be used to optimize the processing parameters and develop new processing methods and materials for high-resolution fabrication of robust 3D microstructures. Some of the findings were used to develop a method for fabricating functional microlenses on the tip of optical fibers. This approach opens a new route to functional integrated photonic devices.
Show less - Date Issued
- 2013
- Identifier
- CFE0005441, ucf:50403
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005441
- Title
- Magnesium and Acidified Ethanol Based Treatment Systems for the Extraction and Dechlorination of Polychlorinated Biphenyls from Contaminated Oils, Paints, and Soils.
- Creator
-
Novaes-Card, Simone, Yestrebsky, Cherie, Clausen, Christian, Elsheimer, Seth, Frazer, Andrew, Duranceau, Steven, University of Central Florida
- Abstract / Description
-
Polychlorinated biphenyls (PCBs) are a class of environmentally persistent halogenated organic compounds that were once used as stabilizers to improve the properties of a variety of materials such as lubricants, heat transfer fluids, paints, and caulking materials. PCBs are also capable of migration through processes such as spillage into soils, leaching into groundwater, and volatilization into the atmosphere. Although banned in 1979 over health concerns, PCBs persist in these materials to...
Show morePolychlorinated biphenyls (PCBs) are a class of environmentally persistent halogenated organic compounds that were once used as stabilizers to improve the properties of a variety of materials such as lubricants, heat transfer fluids, paints, and caulking materials. PCBs are also capable of migration through processes such as spillage into soils, leaching into groundwater, and volatilization into the atmosphere. Although banned in 1979 over health concerns, PCBs persist in these materials to this day because they are resistant to biotic degradation and natural weathering processes. The wide variety of contaminated materials means that many existing treatment options cannot be used across all media. This research focuses on the adaptation of a reductive dehalogenation system for dechlorination of PCBs from machine oils, paints, sludges, and soils. The system utilizes magnesium, glacial acetic acid, and ethanol in order to remove the chlorine atoms from the biphenyl backbone, which is less toxic and can be broken down biotically.A treatment plan was devised for machine oil contaminated with PCBs, involving sorption of PCBs onto a column of super activated alumina followed by desorption into hexane and treatment of the hexane with magnesium and acidified ethanol to dechlorinate the PCBs. In a small-scale study, 98.5% of PCBs from an oil sample were sorbed to the column, and the PCBs that were subsequently desorbed were dechlorinated to below detectable levels within one day of magnesium and acidified ethanol treatment. Information from small-scale studies was used to design larger sorption columns intended for use at a field site.A field study was conducted to compare the effectiveness of two different treatment system pastes at removing PCBs from painted surfaces. These pastes were formulated with bulking and viscosity control agents in order to cling to vertical surfaces, and contained either acidified ethanol and magnesium (Activated Metal Treatment System, AMTS) or acidified ethanol only (Non-Metal Treatment System, NMTS). AMTS was capable of 64.8% average removal of PCBs from paint, while NMTS demonstrated 89.5% average removal but required a second step to dechlorinate the extracted PCBs. This system allows for treatment of surfaces without demolishing the structure. AMTS was also studied for in situ dechlorination of PCBs in soils, and NMTS enclosed in a polyethylene barrier was studied for extraction of PCBs from sludges.A two-step system was devised for the ex situ treatment of PCB-contaminated soils. Solvent extraction with ethanol or an ethanol/ethyl lactate cosolvent is followed by dechlorination using magnesium and glacial acetic acid. Studies included the optimization of extraction solvent, cosolvent ratio, cost, and reuse of magnesium or extraction solvent. Surface analysis of magnesium particles used in dechlorination showed a precipitate occluding part of the surface, which was thought to be a combination of magnesium ethoxide and magnesium hydroxide. This precipitate is thought to come from the reaction of magnesium ethoxide formed during the PCB dechlorination process with pore water extracted from the soil.
Show less - Date Issued
- 2013
- Identifier
- CFE0005222, ucf:50630
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005222
- Title
- Monitoring Crystal Structure Refinements Using Solid-State NMR Chemical Shift Tensors.
- Creator
-
Kalakewich, Keyton, Harper, James, Campiglia, Andres, Elsheimer, Seth, Chumbimuni Torres, Karin, Masunov, Artem, Moore, Sean, University of Central Florida
- Abstract / Description
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Inclusion of lattice-fields in density functional theory (DFT) methods has enabled the accurate calculation of solid-state nuclear magnetic resonance (SSNMR) chemical shift tensors. Calculated 13C and 15N tensors (i.e. 3 principle values per nucleus) can be used to monitor crystal structure refinements and to select the correct structure from a large population of computationally generated candidates. In this dissertation, chapter 2 describes a methodology to improve established crystal...
Show moreInclusion of lattice-fields in density functional theory (DFT) methods has enabled the accurate calculation of solid-state nuclear magnetic resonance (SSNMR) chemical shift tensors. Calculated 13C and 15N tensors (i.e. 3 principle values per nucleus) can be used to monitor crystal structure refinements and to select the correct structure from a large population of computationally generated candidates. In this dissertation, chapter 2 describes a methodology to improve established crystal structures from three different diffraction techniques involving geometric refinement monitored using SSNMR tensor values. The calculated 13C tensors for three relatively simple organic compounds (i.e. acetaminophen, naphthalene, and adenosine) are shown to markedly improve upon DFT refinement. The so-called GGA-PBE functional provided the best agreement with experimental data. The use of the three principle values of the tensor is required for such results as the average (i.e. the isotropic) is less accurate. Chapter 3 applies this method to differentiate between hundreds of computationally predicted crystal structures. Typically, lattice energy of each candidate is used to select the correct structure, a process which is seldom successful. Herein, it is demonstrated that when 13C tensors from DFT refined structures are used for structural ranking by comparison to experimental data, only the correct structure agrees with experimental data in all cases. Chapter 4 illustrates the use of 15N tensors to monitor DFT refinement as an alternative to the 13C approach of Chapter 2. 15N tensors have been very difficult to obtain previously, thus a novel experimental method is developed here which improves signal-to-noise by as much as 300% and allows routine measurement. This improvement also improves the accuracy of the tensor values. Overall, the 15N tensors are found to be at least 5 times more sensitive to DFT refinements than 13C values.
Show less - Date Issued
- 2017
- Identifier
- CFE0006888, ucf:51726
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006888
- Title
- Remediation of Polychlorinated Biphenyl (PCB) Contaminated Building Materials Using Non-metal and Activated Metal Treatment Systems.
- Creator
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Legron-Rodriguez, Tamra, Yestrebsky, Cherie, Clausen, Christian, Elsheimer, Seth, Sigman, Michael, Chopra, Manoj, Quinn, Jacqueline, University of Central Florida
- Abstract / Description
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PCBs are recalcitrant compounds of no known natural origin that persist in the environment despite their ban by the United States Environmental Protection Agency in 1979 due to negative health effects. Transport of PCBs from elastic sealants into concrete, brick, and granite structures has resulted in the need for a technology capable of removing these PCBs from the materials. This research investigated the use of a nonmetal treatment system (NMTS) and an activated metal treatment system ...
Show morePCBs are recalcitrant compounds of no known natural origin that persist in the environment despite their ban by the United States Environmental Protection Agency in 1979 due to negative health effects. Transport of PCBs from elastic sealants into concrete, brick, and granite structures has resulted in the need for a technology capable of removing these PCBs from the materials. This research investigated the use of a nonmetal treatment system (NMTS) and an activated metal treatment system (AMTS) for the remediation and degradation of PCBs from concrete, brick, and granite affixed with PCB-laden caulking. The adsorption of PCBs onto the components of concrete and the feasibility of ethanol washing were also investigated.NMTS is a sorbent paste containing ethanol, acetic acid, and fillers that was developed at the University of Central Florida Environmental Chemistry Laboratory for the in situ remediation of PCBs. Combining NMTS with magnesium results in an activated treatment system used for reductive dechlorination of PCBs. NMTS was applied to laboratory-prepared concrete as well as field samples by direct contact as well as by a novel sock-type delivery. The remediation of PCBs from field samples using NMTS and AMTS resulted in a 33-98% reduction for concrete, a 65-70% reduction for brick, and an 89% reduction in PCB concentration for granite. The limit of NMTS for absorption of Aroclor 1254 was found to be roughly 22,000 mg Aroclor 1254 per kg of treatment system or greater. The activated treatment system resulted in a 94% or greater degradation of PCBs after seven days with the majority of degradation occurring in the first 24 hours. The adsorption of PCBs to individual concrete components (hydrated cement, sand, crushed limestone, and crushed granite) was found to follow the Freundlich isotherm model with greater adsorption to crushed limestone and crushed granite compared to hydrated cement and sand. Ethanol washing was shown to decrease the concentration of laboratory-prepared concrete by 68% and the concentration of PCBs in the ethanol wash were reduced by 77% via degradation with an activated magnesium system.
Show less - Date Issued
- 2013
- Identifier
- CFE0005197, ucf:50625
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005197