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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

A Fast NIR Spectrometer for Examining Explosive Events: Emission of PETN Based Explosives and H₂O Absorption Method Feasibility

Piecuch, Scott. January 2009 (has links)
Thesis (M.S.)--Marquette University, 2009. / Jon D. Koch, John P. Borg, James M. Lightstone, Advisors.
2

Explosive Residue Transfer from Various Explosive Ordinance Disposal (EOD) Render Safe Procedures (RSP)

Stein, Joseph A 01 January 2019 (has links)
Before an IED is sent to a laboratory for analysis, it needs to be rendered safe if it did not already initiate. Render safe procedures (RSPs) include utilizing a percussion-actuated non-electric (PAN) disrupter or a mineral water bottle disrupter. Each disrupter utilizes explosives to render the device safe by breaking open the container or disrupting the fuzing system. However, the same explosives used in the RSP are also used by criminals in IED construction. As such, the explosives used in the RSP can cause problems with the interpretation of the results from forensic analysis of the IED fragments. Compounds of analytical interest in residue include nitroglycerin (NG), diphenylamine (DPA), ethyl centralite (EC), methyl centralite (MC), and pentaerythritol tetranitrate (PETN). Instrumentation used in the analysis of the residues included a gas chromatograph/mass spectrometer (GC/MS), a liquid chromatograph/mass spectrometer (LC/MS), and a gas chromatograph with an electron capture detector (GC/ECD). The PAN disrupter smokeless powder contained NG, DPA, and EC while the bulk detonation cord contained PETN. Only DPA decomposed after being burned. No residue was detected on the PVC pipes while residue was detected on the steel pipes and backpack mock IEDs. Overall, finding such residue in casework should not rule out the possibility that an individual used a particular explosive in the construction of the IED, but examiners should be aware of residues left by disrupters especially if the device initiates during the RSP.
3

Fabrication of stable biocatalyst networks for the manufacture of fine chemicals

Hickling, Christopher January 2016 (has links)
There is an important need to immobilise enzymes for use in industry, to do this I have the promising idea that by conjugating the enzyme to a hydrogel network, thus fabricating a stable biocatalytic network would be a potential method for immobilising enzymes for the manufacture of fine chemicals, this has not been done before for octapeptide systems. Hydrogels have been previously shown as a viable way of immobilising and stabilising enzymes. In this thesis the octapeptide VKVKVEVK (V is valine, K is lysine and E is glutamic acid) is used to immobilise enzymes tagged with VKVKVEVK. This peptide sequence is chosen as it forms stable hydrogels at enzyme appropriate conditions (pH 7). The enzymes chosen are; PETNR as it is well understood and is therefore a good starting point, CDH and CHMO were also chosen as they could combine with PETNR to form a cascade reaction. PETNR was both chemically conjugated to VKVKVEVK (SpepPETNR) and also genetically modified to express the peptide tag (CpepPETNR), whilst CDH and CHMO were genetically modified to express the tag (NpepCDH and CpepCHMO respectively). For S/CpepPETNR retention within the hydrogels was superior to retention for untagged PETNR. NpepCDH was found to not precipitate within the hydrogel whilst untagged was found to do so. CpepCHMO functionalised hydrogels were found to be heterogeneous. Characterisation of CpepPETNR functionalised hydrogels was undertaken using micro differential scanning calorimetry (µDSC), rheology, small angle neutron scattering (SANS) and atomic force microscopy (AFM). From the µDSC evidence of 'protective immobilisation' was observed by the increase in denaturation energy (+253 kJ mol-1) in the hydrogel in comparison to in solution (+18 kJ mol-1). The ability of S/CpepPETNR functionalised hydrogels to perform the ketoisophorone to levodione biotransformation reaction was explored with yields of 86%. S/CpepPETNR within VKVKVEVK hydrogels was found to retain ~90% conversion for at least 9 months at room temperature. Incubation overnight at 90°C resulted in a yield of 84% of levodione. These two results added more evidence for 'protective immobilisation'. Hydrogels functionalised with NpepCDH or CpepCHMO were characterised using rheology and atomic force microscopy. The biotransformation ability of NpepCDH was elucidated; the overall yield of carvone was a maximum of 54% from the hydrogel phase. NpepCDH was used alongside CpepPETNR for the cascade reaction producing dihydrocarvone in low yields; however, an improvement from 2% to 13% in yield is presented. The yield of lactone products from CpepCHMO functionalised hydrogel was low at 15%. The CpepPETNR/ CpepPETNR cascade reaction proceeded with a yield of 36%. The initial activities of CpepPETNR, NpepCDH and CpepCHMO were assayed in both solution and in gel phase using a modified method. The activities were assessed with varying conditions; temperature, pH, quantity of ethanol and incubation at high and low temperatures. Generally, it was found that immobilisation within the hydrogel phase resulted in 'protective immobilisation' against non-optimal conditions. This work will be of benefit to those who are interesting immobilising enzymes within hydrogels in the future.
4

Contaminants and decomposition products in naturally aged pentaerythritol tetranitrate (PETN)

Brackett, Claudia L. 01 January 2005 (has links) (PDF)
PETN is characterized by its sensitivity to environmental conditions. However, anhydrous low-temperature decomposition is poorly understood. This research undertook the search for the decomposition products of naturally aged PETN. This study did not detect any decomposition products. The methods tried were NMR, HPLC, mass spectrometry, and HPLC. PETN's behavior was sensitive to mass spectral conditions and resulted in adduct formation and artifactual decomposition. Artifacts could be sources of misinterpretation for true decomposition. Such behaviors included PETN's autonitration and nitrate's clinging to instrument surfaces. Additionally, PETN seemed able to autooxidize which produced an [M] − ion and [M+H] − ion that obscured isotopic information. Conditions that enhanced the abundance of the [M−H] − ion also increased PETN artifactual decomposition. Because an ion at m/z 330 could represent PETRIN, it was studied and candidated to be an artifact. This PETRIN-acetate isobar was formed from PETN in the presence of acetate. An illusion that a new mass at m/z 330 materialized could be due to spray chamber temperatures. The ion stayed relatively constant throughout a temperature increase while the abundance for other PETN ions decreased. This created an illusion of increasing abundance when the mass spectrum was displayed in normalized mode. An HPLC gradient of acetonitrile/water with addition of 3% NH 4 OH and 0.1 M ammonium acetate in methanol produced chromatographic peaks. However, these species were artifacts formed in the presence of hydroxide ion. Hydroxide accelerated the disappearance of the ion at m/z 315, but not the ion at m/z 378. A second HPLC system used an acetonitrile/water gradient with added 3.3 M ammonium acetate in methanol. However, no difference between PETN and naturally aged PETN chromatograms was evident. In an additional experiment, with the HPLC effluent collected in aliquots and analyzed separately, no condensed phase decomposition product was observed. Because the NMR, HPLC and mass spectrometry experiments did not detect condensed phase decomposition products, the decomposition products might be gas(es). In support, the explosives HMX and RDX are known to decompose in gas phase reactions. It is reasonable that naturally aged PETN proceeds through the same mechanism. The findings of this dissertation supported this viewpoint.
5

Biodegradation and ageing of bio-based thermosetting resins from lactic acid

Gomes Hastenreiter, Lara Lopes January 2019 (has links)
The need for replacing petroleum-based polymers has been increasing and bio-based polymers prove to be a suitable solution. The aim of this thesis was to synthesize bio-based resins with different chemical architectures to evaluate the effect of the structure on the properties and on their response to ageing and biodegradation. For this, three different bio-based thermoset resins have been synthesised by reacting one of three distinct core-molecules with lactic acid. The options of core-molecules chosen for this work were ethylene glycol, glycerol and pentaerythritol. Lactic acid was first reacted with a core-molecule by direct condensation, the resulting branched molecule was then end-functionalized with methacrylic anhydride. The amount of moles of lactic acid varied according to which core-molecule it was reacted with, but the chain length (n) was always maintained as three. Part of the samples were characterised by Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile test. DSC and TGA were used for determining the thermal behaviour. FT-IR was used to verify the first and second stage of the reaction and to ascertain the occurrence of the crosslinking reaction. Tensile test was done for investigation of mechanical properties. The ageing and biodegradation tests are useful to ascertain the material possible applications. Therefore, the samples that went through the process of ageing or biodegradation were also characterised in the end of the procedures to further check the effect of those processes on the specimens. The test results indicated that the PENTA/LA cured resin was the most stable thermally. The cured resin’s mechanical properties were similar to each other, so there was no comparison to make in this area. The samples proved to be affected by the biodegradation and the ageing processes, both in visual and structural aspects.
6

Detection of PETN Using Peptide Based Biologically Modified Carbon Nanotubes

Kubas, George D. 24 May 2017 (has links)
No description available.
7

Polymeric Monolithic Stationary Phases for Capillary Hydrophobic Interaction Chromatography

Li, Yuanyuan 06 October 2010 (has links) (PDF)
Rigid poly[hydroxyethyl acrylate-co-poly(ethylene glycol) diacrylate] (Poly(HEA-co-PEGDA) monoliths were synthesized inside 75-µm i.d. capillaries by one-step UV-initiated copolymerization using methanol and ethyl ether as porogens. The optimized monolithic column was evaluated for hydrophobic interaction chromatography (HIC) of standard proteins. Six proteins were separated within 20 min with high resolution using a 20 min elution gradient, resulting in a peak capacity of 54. The performance of this monolithic column for HIC was comparable or superior to the performance of columns packed with small particles. Monoliths synthesized solely from PEGDA were also found to show excellent performance in HIC of proteins. Continuing efforts showed that rigid monoliths could be synthesized from PEGDA or poly(ethylene glycol) dimethacrylates (PEGDMA) containing different ethylene glycol chain lengths for HIC of proteins. Effects of PEG chain length, bi-porogen ratio and reaction temperature on monolith morphology and back pressure were investigated. Monoliths prepared from PEGDA 258 were found to provide the best chromatographic performance with respect to peak capacity and resolution. An optimized PEGDA 258 monolithic column was able to separate proteins using a 20-min elution gradient with a peak capacity of 62. The preparation of these in situ polymerized single-monomer monolithic columns was highly reproducible. The single-monomer synthesis approach clearly improves column-to-column reproducibility.The highly crosslinked monolith networks resulting from single crosslinking monomers were found to enhance the surface area of the monolith and concentrations of mesopores. Thus, monolithic columns were developed from four additional crosslinking monomers, i.e., bisphenol A dimethacrylate (BADMA), bisphenol A ethoxylate diacrylate (BAEDA, EO/phenol = 2 or 4) and pentaerythritol diacrylate monostearate (PDAM) for RPLC of small molecules. Gradient elution of alkyl benzenes and alkyl parabens was achieved with high resolution using all monolithic columns. Porogen selection for the BADMA and PDAM was investigated in detail with the intention of obtaining data that could possiblly lead to a rational method for porogen selection.
8

Nanolithography on thin films using heated atomic force microscope cantilevers

Saxena, Shubham 01 November 2006 (has links)
Nanotechnology is expected to play a major role in many technology areas including electronics, materials, and defense. One of the most popular tools for nanoscale surface analysis is the atomic force microscope (AFM). AFM can be used for surface manipulation along with surface imaging. The primary motivation for this research is to demonstrate AFM-based lithography on thin films using cantilevers with integrated heaters. These thermal cantilevers can control the temperature at the end of the tip, and hence they can be used for local in-situ thermal analysis. This research directly addresses applications like nanoscale electrical circuit fabrication/repair and thermal analysis of thin-films. In this study, an investigation was performed on two thin-film materials. One of them is co-polycarbonate, a variant of a polymer named polycarbonate, and the other is an energetic material called pentaerythritol tetranitrate (PETN). Experimental methods involved in the lithography process are discussed, and the results of lithographic experiments performed on co-polycarbonate and PETN are reported. Effects of dominant parameters during lithography experiments like time, temperature, and force are investigated. Results of simulation of the interface temperature between thermal cantilever tip and thin film surface, at the beginning of the lithography process, are also reported.

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