Browsing by Author "Evans, David"

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    Molecular Imprinting of Metal-Organic frameworks (MOFs) for Selective Separations
    (2022-04) Evans, David; Shimizu, George; Ling, Chang-Chun; Jalilehvand, Farideh
    This thesis explores the idea of using chromium(III) ions and an orthogonal polyaromatic phosphonate linker to produce a stable metal-organic framework (MOF) for the separation of xylene isomers. This began by creating a charge-assisted hydrogen-bonded metal-organic framework (HMOF) that uses weaker interactions to hold the framework together. The orthogonalized phosphonate creates pores due to its bulky nature that prevents efficient ligand packing. In tandem, this allows for the inclusion of guest molecules within the HMOF structure. Once the guest-incorporated structure is formed, heating can remove water molecules from the HMOF to form coordination bonds between the chromium and the phosphonate ligand. This dehydration locks the template in place as it converts to a coordinated metal-organic framework (MOF). The template for this technique is of great importance since you can imprint the pore to a specific molecule. For this study, the xylene isomers ortho, meta, and para, were looked at for separation. The separation of xylenes is of great importance since the different isomers are used in a variety of different applications, such as para-xylene for terephthalic acid (TPA) to manufacture polyethylene terephthalate (PET). The problem with separating xylenes is how expensive the separation is. Since the xylene isomers have very similar boiling points and sizes, either cryogenic distillation or recrystallization has to be performed to acquire a pure product. On this note, three different chromium phosphonate HMOFs were developed. The first structure incorporated a para-xylene template (HCALF 50αP) while the second structure incorporated ortho-xylene as the template (HCALF 50α)). The final structure used meta-xylene as a template (HCALF 50M). These HMOFs were dehydrated into the corresponding MOF structures and used to test selective xylene separation. Initial studies using a static separation and nuclear magnetic resonance (NMR) spectroscopy were conducted followed by a flow-through separation using high-pressure liquid chromatography (HPLC) and a MOF-packed column. The findings were intriguing showing selectivity towards para-xylene for some of the materials. Most notable is that HCALF 50βM showed anti-selectivity towards para-xylene allowing it to flow freely through and making it easier to collect.
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    Patient and ward related risk factors in a multi-ward nosocomial outbreak of COVID-19: Outbreak investigation and matched case–control study
    (2023-03-22) Leal, Jenine; O’Grady, Heidi M.; Armstrong, Logan; Dixit, Devika; Khawaja, Zoha; Snedeker, Kate; Ellison, Jennifer; Erebor, Joyce; Jamieson, Peter; Weiss, Amanda; Salcedo, Daniel; Roberts, Kimberley; Wiens, Karen; Croxen, Matthew A.; Berenger, Byron M.; Pabbaraju, Kanti; Lin, Yi-Chan; Evans, David; Conly, John M.
    Abstract Background Risk factors for nosocomial COVID-19 outbreaks continue to evolve. The aim of this study was to investigate a multi-ward nosocomial outbreak of COVID-19 between 1st September and 15th November 2020, occurring in a setting without vaccination for any healthcare workers or patients. Methods Outbreak report and retrospective, matched case–control study using incidence density sampling in three cardiac wards in an 1100-bed tertiary teaching hospital in Calgary, Alberta, Canada. Patients were confirmed/probable COVID-19 cases and contemporaneous control patients without COVID-19. COVID-19 outbreak definitions were based on Public Health guidelines. Clinical and environmental specimens were tested by RT-PCR and as applicable quantitative viral cultures and whole genome sequencing were conducted. Controls were inpatients on the cardiac wards during the study period confirmed to be without COVID-19, matched to outbreak cases by time of symptom onset dates, age within ± 15 years and were admitted in hospital for at least 2 days. Demographics, Braden Score, baseline medications, laboratory measures, co-morbidities, and hospitalization characteristics were collected on cases and controls. Univariate and multivariate conditional logistical regression was used to identify independent risk factors for nosocomial COVID-19. Results The outbreak involved 42 healthcare workers and 39 patients. The strongest independent risk factor for nosocomial COVID-19 (IRR 3.21, 95% CI 1.47–7.02) was exposure in a multi-bedded room. Of 45 strains successfully sequenced, 44 (97.8%) were B.1.128 and differed from the most common circulating community lineages. SARS-CoV-2 positive cultures were detected in 56.7% (34/60) of clinical and environmental specimens. The multidisciplinary outbreak team observed eleven contributing events to transmission during the outbreak. Conclusions Transmission routes of SARS-CoV-2 in hospital outbreaks are complex; however multi-bedded rooms play a significant role in the transmission of SARS-CoV-2.