No description available.

<p>  </p> <p>Monolithic catalyst beds have been used extensively in other industries and are gaining interest for space propulsion applications. Additive manufacturing of monolithic supports allows for catalyst beds with a wider range of geometries than could be produced using conventional methods, potentially allowing for higher performance monoliths that can compete with conventional packed beds in performance. Achieving these gains requires a consistent, even, and well-adhering washcoating procedure for the additively manufactured supports, one which works well on varied geometry and on support materials that can be readily printed. I conducted an extensive development process on improving methods of surface preparation and coating for high temperature ceramic monoliths that resulted in improvements in the state of the art. The materials and methods used are appropriate for rocket grade hydrogen peroxide, hydrazine, or other monopropellants with similar operating temperatures. Using existing published coating methods resulted in uneven coating distribution and poor adhesion. I demonstrate that this was due to the substrate surface morphology producing a hydrophobic effect. Surface morphology plays a significant role in coating coverage and adhesion and differences in initial support surfaces likely account for much of the variation in results seen across the literature. I present a method of controlled thermochemical surface etching using pure sodium hydroxide at 420°C that can reliably produce a roughened hydrophilic surface from a variety of starting morphologies. I also present several modifications to the primer formulation that improve evenness of coverage, the most significant of which is the inclusion of a surfactant at a concentration of 1 g per 36 g water. The surface treatment and coating formulation improvements combine well and produce an even coating with strong adhesion to the substrate. I also conducted preliminary work on the investigation of novel geometric designs for monolithic catalyst beds, and on the reactivity of different transition metal oxide catalysts for rocket grade hydrogen peroxide decomposition. </p>

Previous studies involving copper (II) complexed with a dissymmetric Schiff base and imidazole derivatives had identified catalase activity of these complexes towards H2O2. Reactions such as this are of great interest due to the important role of copper-based complexes in biological systems. Our research has been conducted to add to the base of knowledge regarding the efforts of other researchers to investigate copper complexes that exhibit similar reactivity as copper-based proteins towards dioxygen. The copper complex chosen for this study contained a tri-dentate Schiff base adduct which, when complexed with an imidazole derivative, limited the manner in which peroxo adducts could bind while providing distinct spectral peaks which were used to conduct kinetic studies. Our results indicate a reaction mechanism by which the role of the complexed copper (II) ion is to activate the peroxo adduct for decomposition through reactions with other peroxide molecules, dioxygen, and water.

No description available.

Parkinson's disease (PD) is a neurodegenerative condition that affects millions of people worldwide. The exact etiology of PD is unknown. However, it is well established that environmental factors contribute to the onset of PD. In particular, chemicals such as the insecticide Rotenone have been shown to increase the death of dopaminergic (DA) neurons by increasing levels of reactive oxygen species (ROS). ROS such as hydrogen peroxide (H2O2) have been shown to be elevated above basal levels in PD patients. Currently, to measure H2O2 concentrations, a commercially available (Amplex® Red) fluorescent assay is used. However, the assay has limitations: it is not completely specific to hydrogen peroxide and can only measure extracellular ROS concentrations. This research focuses on testing an electrochemical sensor that uses cyclic voltammetry to quantitatively determine concentrations of H2O2 released from a cell culture. The sensor was first tested in normal cell culture conditions. Next, chemical interference was reduced and the sensor was optimized for accuracy by altering protein concentrations in the media. Finally, Rotenone was added to a cell culture to induce H2O2 production. Near real-time measurements of H2O2 were taken using the sensor and comparisons made to the fluorescent assay method. Overall, we are trying to determine if the electrochemical sensor can selectively and quantitatively measure H2O2 released from cells. Being able to track the production, migration and concentration of H2O2 in a cell can help researchers better understand its mechanism of action in cell death and oxidative damage, thus getting closer to finding a cure for PD.

Advances in the interconnection technology have played a key role in the continued improvement of the integrated circuit (IC) density, performance and cost. Copper (Cu) metallization, dual damascenes processing and integration of copper with low dielectric constant material are key issues in the IC industries. Chemical mechanical planarization of copper (CuCMP) has emerged as an important process for the manufacturing of ICs. Usually, Cu-CMP process consists of several steps such as the removal of surface layer by mechanical action of the pad and the abrasive particles, the dissolution of the abraded particles in the CMP solution, and the protection of the recess areas. The CMP process occurs at the atomic level at the pad/slurry/wafer interface, and hence, slurries and polishing pads play critical role in its successful implementation. The slurry for the Cu-CMP contains chemical components to facilitate the oxidation and removal of excess Cu as well as passivation of the polished surface. During the process, these slurry chemicals also react with the pad. In the present study, investigations were carried out to understand the effect of hydrogen peroxide (H2O2) as an oxidant and benzotriazole (BTA) as an inhibitor on the CMP of Cu. Interaction of these slurry components on copper has been investigated using electrochemical studies, x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). In the presence of 0.1M glycine, Cu removal rate was found to be high in the solution containing 5% H2O2 at pH 2 because of the Cu-glycine complexation reaction. The dissolution rate of the Cu was found to increase due to the formation of highly soluble Cu-glycine complex in the presence of H2O2. Addition of 0.01M BTA in the solution containing 0.1M glycine and 5% H2O2 at pH 2 exhibited a reduction in the Cu removal rate due to the formation of Cu-BTA complex on the surface of the Cu further inhibiting the dissolution. XPS and SIMS investigations revealed the formation of such Cu-glycine complex, which help understand the mechanism of the Cu-oxidant-inhibitor interaction during polishing. Along with the slurry, pads used in the Cu-CMP process have direct influence an overall process. To overcome problems associated with the current pads, new application specific pad (ASP) have been developed in collaboration with PsiloQuest Inc. Using plasma enhanced chemical vapor deposition (PECVD) process; surface of such ASP pads were modified. Plasma treatment of a polymer surface results in the formation of various functional groups and radicals. Post plasma treatment such as chemical reduction or oxidation imparts a more uniform distribution of such functional groups on the surface of the polymer resulting in unique surface properties. The mechanical properties of such coated pad have been investigated using nanoindentation technique in collaboration with Dr. Vaidyanathan’s research group. The surface morphology and the chemistry of the ASP are studied using scanning electron microcopy (SEM), x-ray photoelectron spectroscopy (XPS), and fourier transform infrared spectroscopy (FTIR) to understand the formation of different chemical species on the surface. It is observed that the mechanical and the chemical properties of the pad top surface are a function of the PECVD coating time. Such PECVD treated pads are found to be hydrophilic and do not require being stored in aqueous medium during the not-in-use period. The metal removal rate using such surface modified polishing pad is found to increase linearly with the PECVD coating time. Overall, this thesis is an attempt to optimize the two most important parameters of the Cu-CMP process viz. slurry and pads for enhanced performance and ultimately reduce the cost of ownership (CoO).

Hydrogen peroxide and chlorine detection is critical for many biological and environmental applications. Hydrogen peroxide plays important roles in a variety of fields including plant physiology, medical, environmental and biochemical applications. Its role in plant defense and signal transduction, diseases such as Parkinson's and Alzhemier's, industrial processes such as disinfection and wastewater treatment and biochemical enzymatic reactions is critical. Given the gamut of areas that hydrogen peroxide is a key component of; its detection assumes great importance. Similarly chlorine has long been used as a disinfectant for making drinking water safe, but excessive chlorination is an environmental and health hazard in itself. In this work, micromachining techniques have been used to design, fabricate and test electrochemical sensors and microneedle structure that can be integrated for detection of hydrogen peroxide and free chlorine. A novel nanomaterial has been integrated with the hydrogen peroxide microsensor, which greatly increases the sensor lifetime and robustness. Miniaturization, low detection limits, high sensitivity and selectivity, as well as ease of fabrication are some of the other advantages of this work.

Aufgrund ihrer Fähigkeit, sich an wechselnde Umgebungsdrücke anzupassen, ist die Aerospikedüse eines von mehreren Düsenkonzepten, welches die Effizienz von weitgehend technologisch ausgereiften chemischen Raumfahrtantrieben weiter steigern kann. Darüber hinaus kann die Höhenadaptivität der Düsenart eine wichtige Voraussetzung für Landungsszenarien oder Probenrückführungsmissionen auf Planeten und Monden mit dichter Atmosphäre sein. Um den technologischen Reifegrad der Aerospikedüse zu erhöhen, wurde im Rahmen dieser Arbeit ein additiv gefertigtes Aerospikedemonstratortriebwerk entwickelt und getestet. Als Treibstoffe kommen Kerosin und der als nachhaltig klassifizierte Treibstoff Wasserstoffperoxid zum Einsatz. Beide lagerfähigen Treibstoffe erlauben prinzipiell den Einsatz in Missionsszenarien außerhalb der Erdatmosphäre. In diesem Zusammenhang wird die Auslegung des Demonstrators vorgestellt. Das Triebwerk ist für einen Schub von 6 kN bei einem Brennkammerdruck von 2,0 MPa ausgelegt und wird aus der Nickelbasis-Superlegierung Inconel® 718 im selektiven Laserschmelzverfahren (LPBF) hergestellt. Es wird ein gestuftes Konzept verwendet, bei dem Wasserstoffperoxid durch einen Katalysator zersetzt und die Verbrennung durch Selbstzündung von Kerosin eingeleitet wird. Die Konfiguration der Zersetzungskammer wird als austauschbare Unterbaugruppe konzipiert und besteht aus einem Parallelinjektor, einem Gehäuse und einer Verteilerplatte. Somit können mehrere Katalysatorzusammensetzungen während der experimentellen Validierung getestet werden. Der Kerosininjektor nutzt das Konzept der transversalen Injektion, bei dem der Treibstoff orthogonal zum zersetzten Wasserstoffperoxid eingespritzt wird. Die beiden Hauptkomponenten des Triebwerks, der Zentralkörper Spike und die Brennkammeraußenwand Shroud, werden additiv gefertigt und enthalten Kühlkanäle für ein Wasserkühlsystem. Die Arbeit erläutert neben der Konstruktion Herausforderungen und Lösungsansätze, welche während der Fertigung des Demonstrators aufgetreten sind. Hierbei ist vor allem die konsequente Optimierung des belichteten Querschnitts zu nennen. Abschließend werden die Resultate der experimentellen Demonstratorvalidierung zusammengefasst. Zuerst wurde dazu das Triebwerk nur in Hinblick auf Druckverlust und Dichtigkeit der Kühlung validiert. Anschließend fand eine Heißgastestkampagne im Einstoffbetrieb statt, bei dem der Demonstrator über 2,7 s seine Funktionstüchtigkeit nachweisen konnte. Da signifikante Leckagen festgestellt wurden, musste die Testkampagne anschließend abgebrochen werden, um Reparaturversuche zu unternehmen.

Spermatogenesis is a complex process of male germ cell development from diploid spermatogonia to haploid fertile spermatozoa. Apoptosis plays a vital role in limiting cell numbers and eliminating defective germ cells. This requires novel gene products, and precise and well-coordinated programmes of gene expression. It is therefore possible that a disruption of transcription factor function would significantly impact germ cell development. The present work was undertaken to use Staput separation followed by culture of purified germ cells of rodent testis since mammalian spermatogenesis cannot yet be recreated in vitro. Specificity of separation was assessed using immunocytochemistry to identify spermatogonia, spermatocytes and spermatids. The genotoxins H2O2, doxorubicin, N-ethyl-N-nitrosourea, N-methyl-N-nitrosourea, 6-mercaptopurine, 5-bromodeoxyuridine, methyl methanesulphonate and ethyl methanesulphonate were investigated. Cells were cultured and treated with different concentrations for each agent. DNA damage and apoptosis were measured by Comet and TUNEL assay respectively. Up-regulation of expression of the transcription factors Tbpl1, FHL5 and Gtf2a1l that are important post-meiotically, were examined using RT- PCR and qPCR. Protein production was evaluated using Western blotting. Tbpl1, FHL5 and Gtf2a1l were cloned in-frame into the inducible expression vector pET/100-TOPO. The recombinant clones were induced and successful expression of the proteins in E. coli was confirmed by SDS-PAGE and Western blotting. The recombinant clones obtained were used to demonstrate genotoxin induced impairment of gene expression. Thus, Staput-isolated rodent testicular germ cells seem to be a suitable model to study genotoxicity in vitro yielding result comparable to those reported in vivo. Furthermore, the work shows that genotoxins can impair gene expression.

Hemerythrin-like protein Rv2633c is a small 18 kDa protein that is expressed in Mycobacterium tuberculosis (Mtb). Sequence analysis of Rv2633c predicts the presence of a hemerythrin-like domain, which binds dioxygen using a µ-oxo-bridge (Fe-O-Fe), rather than a heme group. Though it is noticeably upregulated during macrophage infection and during in vitro acidification, the role of Rv2633c in Mtb survival has yet to be elucidated. This project aims to characterize the function of Rv2633c by studying the in vitro response of the recombinant protein to conditions present in the macrophage lysosome, such as reduced oxygen levels or the presence of reactive oxygen species. UV-visible spectroscopy is used to observe these changes, as the spectrum shows a characteristic peak at 330 nm that likely corresponds to the diiron cofactor in its native state. Our results show this spectrum shifts in response to hydrogen peroxide addition, showing the proposed environmental conditions can affect the active site. Bioinformatics techniques, such as the 3D modeling program SWISS-MODEL, have been used to hypothesize possible structure and function. Determining the function of Rv2633c may help explain how Mtb so readily evades the human immune system to reside in the macrophage.