In preparation of gelant solution for making crosslinked polymer gels for water shutoff applications unpublished experiments plus chemical intuition suggest that, unless hydrolyzed polyacrylamide (HPAM) polymer is fully hydrated before addition of crosslinker, the final gel will have lower than optimum mechanical strength. It is suggested so because polymer chains need to be unfolded before proper crosslinking can occur. We have evaluated gel strengths of “flowing” gels for water shut off in natural fractures and other non-matrix features as a function of time of addition of crosslinker relative to time of hydration of polymer. Gels were prepared from moderately high molecular weight HPAM crosslinked with chromium(III) acetate (CrAc) or polyethyleneimine (PEI). Crosslinker was added after either (1) initial wetting of solid polymer particles or (2) complete hydration of polymer. HPAM can be purchased as a fine particulate hydrocarbon slurry or as a solution concentrate, either of which, when diluted into makeup water, rapidly provides fully hydrated polymer solution. However, dry HPAM is often preferred because of lower overall cost of active material and smaller storage footprint than slurry or liquid concentrates. The down side of using the solid product is that it generally requires two or more large blending tanks in order to fully hydrate polymer for large volume gel treatments. However, if conditions exist where crosslinker can be added to wetted but not fully hydrated polymer, then dry polymer and crosslinker can be blended in a small continuous flow unit, with full hydration occurring downhole prior to gelation. Gel strengths were determined using a common qualitative coding system for gels prepared in identical manner except for timing of crosslinker addition. Crosslinker was added immediately after wetting of polymer or after polymer had been agitated until complete hydration. Samples were prepared in fresh water or 4% NaCl brine and at ambient temperature or 122 °F. For almost all samples of polymer gels prepared with identical concentrations of HPAM and CrAc, there was no observable difference in gel strength regardless of time of addition of crosslinker. HPAM/CrAc polymer gels with 4wt% NaCl make up water were lower in strength by one code level with respect to those prepared with fresh water. For polymer gels hydrated at 122 °F with 4wt% NaCl there was no gel strength code level difference with respect to those prepared at ambient temperature with 4wt% NaCl. For HPAM/PEI polymer gels the majority of the samples showed similar gel strengths regardless of the timing of crosslinker addition. A few polymer gels showed weaker gel strengths when prepared from partially hydrated polymer solution before crosslinker addition. Presence of 4wt% NaCl in the makeup water gave weaker gel strengths than those prepared with fresh water with an average difference of four code levels. The pre-gel viscosity of a polymer solution was also compared to the timing of crosslinker addition at ambient temperature. For HPAM/PEI system the overall polymer solution viscosity decreased when PEI was added whereas for HPAM/CrAc system the polymer solution viscosity remained similar after crosslinker was added to the completely hydrated polymer solution but increased when crosslinker was added to partially hydrated polymer solution. The most significant result of this work is the demonstration that for most field applications optimum quality gel can be obtained using dry polymer and a small continuous mixing system for initial wetting of the polymer after which the crosslinker can be added to the polymer solution on the fly. This practice can decrease the footprint, equipment requirements and labor and thus the cost of large volume flowing gel treatments.

Part A of two parts. Part B titled: "Xenon Transient Studies For a CANDU Reactor". / <p> In CANDU reactors, mechanical devices called shutoff rods are used to shutdown the reactor if required. These rods are made of high thermal neutron absorbing material such as cadmium. The number and the locations of the shutoff rods are optimized for a given reactor configuration. Optimization here means minimizing the number of rods and maximizing their reactivity depth or effectiveness. </p> <p> Optimization may be studied in various ways but the method selected is both simple and basic. It is apparent that if the interaction effects between the individual shutoff rods are reduced, their worths will increase. The optimum distance between two rods was determined to be 130 cm. Also, the best location of a third rod with respect to two already placed at an optimum separation was studied. Finally, these results were used in order to determine the optimum distance between banks of shutoff rods. These banks of rods were arranged in such a way as to achieve maximum flux flattening with all the rods inserted in the core. A 22 shutoff rod configuration for an adjuster flattened CANDU reactor gave a total change of 5.6% in keff. </p> / Thesis / Master of Engineering (MEngr)

This file is officially titled as a project. This is Part B in connection with another project by the same author, titled "Part A: Adjuster Rod Design in a CANDU Reactor and Flux Distributions Due to an Arbitrary Source of Neutrons."http://hdl.handle.net/11375/15387 / In this report, the effectiveness of a proposed Shutoff Rod System a CANDU Reactor was investigated. A full core simulation was done, to study the neutronic power transient following a change in coolant conditions. / Thesis / Master of Engineering (ME)

Herpes Simplex virus (HSV) virions contain the protein vhs (virion host shutoff), which is known to trigger rapid shutoff of host protein synthesis and accelerated decay of viral and cellular mRNAs. HSV-1 strains generally cause weaker shutoff than HSV-2 strains. HSV viruses lacking the VP16 viral transactivator gene show uncontrolled shutoff late in infection (Lam et al., 1996); vhs is known to bind to VP16 (Smibert et al., 1994). In vitro experiments demonstrated that HSV-1 vhs protein (vhsTl) and an intertypic HSV-2 G vhs protein (vhsT2) did not differ in ability to effect mRNA degradation in a rabbit reticulocyte lysate (RRL) assay system, suggesting that virion factors might influence vhs shutoff phenotype. To investigate the possibility that VP 16 influences early shutoff during HSV infection, a virus was constructed containing the HSV-2 strain G VP16 in place of HSV-1 VP16. This virus (8MA2R) grew in a noncomplementing cell line and was unaltered in shutoff phenotype compared to wt strain. Cotransfection assays demonstrated vhsT2 had greater shutoff ability than vhsT1, and this was confirmed in a viral system by constructing intertypic viruses containing portions of the HSV-2 G vhs ORF in a vhs-null HSV-1 tk locus. All intertypic constructs conferred increased shutoff ability relative to vhsT 1, indicating that the strong shutoff ability of HSV -2 vhs is distributed along much of the vhs ORF. Also, to confirm the observation that UL13 null viruses show a lack of shutoff which is not due to lack of vhs in the virion (Overton et al., 1994) a number of wildtype viruses and their UL13-null derivatives were tested for ability to shutoff host translation. All showed near-wt or wt levels of shutoff. / Thesis / Master of Science (MS)

A crucial step of the viral life cycle of Kaposi’s Sarcoma Herpesvirus (KSHV) lytic infection is the triggering of a massive RNA decay event termed “Host Shutoff”. Host Shutoff is driven by the viral endonuclease SOX which leads to the destruction of over 70% of the total transcriptome. This process cripples cellular gene expression and allows for viral reprograming of the cell for the purpose of viral replication. Co-evolution has led to the host developing a multitude of antiviral defenses aimed at preserving certain cellular RNAs linked to antiviral responses. One such defense are RNA secondary structures located within the 3’UTR of select host transcripts that protect them from SOX degradation. This structure, known as the SOX Resistant Element or SRE, has previously been isolated to a 200-nucleotide region found within the 3’UTR of the host transcript Interleukin-6. In this thesis, I sought to further define the structure of the IL-6 and other SREs using SHAPE-MaP to generate chemically-probed RNA structural models. Through this work, I demonstrated that the IL-6 SRE confers a form of active resistance to SOX cleavage, and based on structural analyses, likely acts as a scaffold for the recruitment of a protective ribonucleoprotein complex. This research highlights the importance of RNA secondary structures in influencing mRNA fate during viral infection and establishes the groundwork for understanding how these structural features can facilitate escape of cellular transcripts from viral endonucleases.

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