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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Phosphomolybdic Acid Catalysis of Cellulose Hydrolysis

Dolmetsch, Troy R 01 May 2017 (has links)
Renewable sources such as cellulose derived biofuels are sought after in order to replace fossil fuel sources that are currently used to meet energy demands. Cellulose is a biological polymer composed of a chain of glucose molecules. Hydrolysis of cellulosic materials then has potential to serve as a source of renewable energy in the form of biofuels. The crystalline structure of cellulose is very stable, and current methods of catalyzed hydrolysis are inefficient for industrial application. This project explores the use of phosphomolybdic acid (PMA) in water to catalyze hydrolysis of microcrystalline cellulose. Temperature of hydrolysis was varied from 40 °C – 100 °C. The amount of soluble hydrolysis product was determined through wet oxidative total organic carbon analysis using a Hach method kit. Total organic carbon content is compared between equimolar amounts of PMA and sulfuric acid, the current industry preference. The yield of total organic carbon in parts per thousand (ppt) is directly correlated to increasing temperatures. Across these temperatures, PMA is more efficient than sulfuric acid in hydrolysis of cellulosic materials. Work is ongoing for glucose-specific product detection as well as evaluating the recyclability of the catalyst.
2

Novel techniques for the development of latent fingermarks

Davis, Lloyd W. L. January 2017 (has links)
The scientific study of fingerprints/fingermarks—dactyloscopy—is one of the most important fields in forensic science today. Fingermarks are amongst the most common type of evidence recovered from crime scenes and are arguably the most valued due to the fact that they are, unlike deoxyribonucleic acid (DNA), completely unique to an individual. Fingermarks recovery techniques are constantly evolving and new reagents are always being sought. This project aims to develop and access new fingermark enhancement procedures. The efficacy of an ethanoic solution of phosphomolybdic acid, has been investigated as a latent fingermark enhancement reagent, primarily on porous substrates. After treating samples and exposing them to ultraviolet radiation, the phosphomolybdic acid solution was shown to develop fingermarks to a high quality. Unlike the common amino acid reagents used for the enhancement of fingermarks on porous substrates, ninhydrin and 1,8-diazafluoren-9-one, phosphomolybdic acid stains a range of other compounds found within fingermark deposits, including lipids. The lysochrome diazo dye Oil Red O was used for comparative purposes due to its application in staining some of the same components of fingermark residues that phosphomolybdic acid would be proposed for. Initial results indicate that phosphomolybdic acid is comparable to Oil Red O at developing fingermarks on porous surfaces and may also have applications on non-porous surfaces. A systematic evaluation of solvent carriers was conducted, and whilst many solvents were insufficient, others did show some potential. Primary alcohols such as ethanol, methanol and propan-1-ol all developed fingermarks with identifiable ridge detail. Attempts to mix phosphomolybdic acid with other reagents which react with different fingermark constituents than those phosphomolybdic acid targets were, for the most part unsuccessful. However, not entirely ruled out. Many substrates were tested to observe which developed fingermarks when treated with the phosphomolybdic acid solution. Whilst marks were detected on numerous substrates, paper proved to be the most receptive. Similar stains to the phosphomolybdic acid were tested under the same conditions, however, none were as effective as the phosphomolybdic acid. A non-destructive, non-invasive technique was developed, utilising cuprous metals and their reactions with rubeanic acid. By bringing substrates with fingermarks deposited upon their surface into contact with a copper or copper alloyed plate, it was possible to transfer the fingermark residues to the plate. Forensic gelatin lifters could then be used to lift the marks from the metal plates, these lifted marks could subsequently be treated with a rubeanic acid solution to visualise the fingermarks. The rubeanic acid reacted with the Cu(II) which had been transferred to the fingermark residues to produce a dark product in the pattern of fingermark ridges. The technique was successful at developing fingerprints on semi-porous substrates. The technique was as effective on non-porous substrates, such as glass, but an investigation into the process on porous surfaces was less positive. Attempts to reuse the cuprous metals for the transference of fingermarks after an initial lift resulted in double or ghosted marks being developed, after a thorough wash with soap and water. This was overcome by cleaning with the metal cleaner Brasso. Copper cleaned with Brasso was reused 5 times to show its effectiveness, and adverse effects were minimal. The UK s recent move to polymer banknotes has seen some of the currently used fingermark enhancement techniques for currency potentially become redundant, due to the substrate characteristics of the polymer surfaces. Possessing a non-porous surface with some semi-porous properties, alternate processes are required for polymer banknotes. A preliminary investigation was conducted in to the recovery of fingermarks from polymer notes via vacuum metal deposition using elemental copper. The study successfully demonstrated that fresh latent fingermarks, from an individual donor, could be clearly developed and imaged in the near infrared. By varying the deposition thickness of the copper, the contrast between the fingermark minutiae and the substrate could be readily optimised. Where the deposition thickness was thin enough to be visually indistinguishable, forensic gelatin lifters could be used to lift the fingermarks. These lifts could then be treated with rubeanic acid to produce a visually distinguishable mark. The technique has shown enough promise that it could be effectively utilised on other semi- and non-porous substrates. A follow up group study was less effective than the aforementioned initial study. Many samples were processed using the vacuum metal deposition; incorporating a comparison study between copper and the gold/zinc standard and a depletion trial. However, when imaging was attempted a week after treatment, the results experienced before were unable to be replicated. Attempts to recover samples of radioactive nickel isotope from metal substrates using forensic gel lifters were initially unexceptional. Wipe tests were more successful at recovering the isotope. Experimentation using some non-metallic substrates was more fruitful, the gel lifters were able to recover the radioisotope more readily. Autoradiography showed that, although a weak beta emitter, nickel could be imaged when in sufficient quantities. By using nickel and a short half-life isotope of phosphorus in conjunction with patterned stamps and patterned deposits it was possible to image these patterns by autoradiography of the gels used to lift from the substrates these were deposited upon. These autoradiography images showed enough detail to warrant attempts with a synthetic finger, however, the imaging was insufficient to image the fine details of the friction ridges. Fingermarks deposited on the surface of agar gels showed bacterial growth after incubation for 24 hours. Aseptic transfer of bacterial colonies to fresh agar plates in a typical streak pattern were fruitful. Further transference to a nutrient broth were effective, however, attempts to seed bacterial agar plates for use in inhibition tests were unsuccessful. Overall, phosphomolybdic acid proved to be relatively effective, being able to develop fingermarks on a number of substrates. The copper transfer method, although, less fruitful than PMA showed promise. This lead to the idea of gel lifting from copper VMD treated polymer banknotes which was much more effective. Although, the radioactive and biological techniques showed promise, they were unfortunately unsuccessful at developing fingermarks. A number of the techniques evaluated and developed were successful enough to be published in forensic journals.
3

Immobilization of Heteropolyacids in Silica Gel

Adetola, Opeyemi 01 May 2016 (has links)
Silica gels containing incorporated heteropolyacids (HPAs) were synthesized in acidic media by co-condensation of tetraethoxysilane (TEOS) with phosphotungstic or phosphomolybdic acids using sol-gel technique. Effect of the synthesis conditions on their structure and morphology was studied. Yields of modified materials were some lower as compared to non-modified silica gels. All materials were mesoporous but contained micropores in their structures. Presence of bands of Keggin’s structures in FT-IR spectra along with absence of XRD patterns of crystalline HPAs confirmed their fine incorporation into silica network. Particle sizes of modified materials were 800-1100 nm excepting for W-containing sample obtained with trimethylstearylammonium chloride. This unusual effect was attributed to stabilization of primary silica nanoparticles by interaction between surfactant and HPA. High ratio HPA/TEOS resulted in partial loss of porosity. Obtained results might be used for optimization of synthesis of effective catalysts and adsorbents containing HPAs in mesoporous structure.

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