Shock tube measurements of growth constants in the branched chain formaldehyde-carbon monoxide-oxygen system

Exponential free radical growth constants were measured for formaldehyde carbon monoxide-oxygen systems by monitoring the growth of oxygen atom concentration as manifested by CO flame band emission. Data were obtained over the temperature range of 1200 to 2000 K. The data were analyzed using a formaldehyde oxidation mechanism involving 12 elementary reaction steps. The computed growth constants are roughly in accord with experimental values, but are much more temperature dependent. The data was also analyzed assuming formaldehyde is rapidly decomposed to carbon monoxide and hydrogen. Growth constants computed for the resulting carbon monoxide hydrogen oxygen mixtures have a temperature dependence similar to experiments; however, for most mixtures, the computed growth constants were larger than experimental values

Ignition delay times of benzene and toluene with oxygen in argon mixtures

The ignition delay times of benzene and toluene with oxygen diluted in argon were investigated over a wide range of conditions. For benzene the concentration ranges were 0.42 to 1.69 percent fuel and 3.78 to 20.3 percent oxygen. The temperature range was 1212 to 1748 K and the reflected shock pressures were 1.7 to 7.89 atm. Statistical evaluation of the benzene experiments provided an overall equation which is given. For toluene the concentration ranges were 0.5 to 1.5 percent fuel and 4.48 to 13.45 percent oxygen. The temperature range was 1339 to 1797 K and the reflected shock pressures were 1.95 to 8.85 atm. The overall ignition delay equation for toluene after a statistical evaluation is also given. Detailed experimental information is provided

Shock tube measurements of growth constants in the branched-chain ethane-carbon monoxide-oxygen system

Exponential free radical growth constants have been measured for ethane carbon monoxide oxygen mixtures by monitoring the growth of oxygen atom concentration as manifested by CO flame band emission. Data were obtained over the temperature range of 1200 to 1700 K. The data were analyzed using an ethane oxidation mechanism involving seven elementary reaction steps. Calculated growth constants were close to experimental values at lower temperatures, up to about 1400 K, but at higher temperatures computed growth constants were considerably smaller than experiment. In attempts to explain these results additional branching reactions were added to the mechanism. However, these additional reactions did not appreciably change calculated growth constants

Norwich COVID-19 testing initiative pilot: evaluating the feasibility of asymptomatic testing on a university campus

Background: There is a high prevalence of COVID-19 in university-age students, who are returning to campuses. There is little evidence regarding the feasibility of universal, asymptomatic testing to help control outbreaks in this population. This study aimed to pilot mass COVID-19 testing on a university research park, to assess the feasibility and acceptability of scaling up testing to all staff and students. Methods: This was a cross-sectional feasibility study on a university research park in the East of England. All staff and students (5625) were eligible to participate. All participants were offered four PCR swabs, which they self-administered over two weeks. Outcome measures included uptake, drop-out rate, positivity rates, participant acceptability measures, laboratory processing measures, data collection and management measures. Results: 798 (76%) of 1053 who registered provided at least one swab; 687 (86%) provided all four; 792 (99%) of 798 who submitted at least one swab had all negative results and 6 participants had one inconclusive result. There were no positive results. 458 (57%) of 798 participants responded to a post-testing survey, demonstrating a mean acceptability score of 4.51/5, with five being the most positive. Conclusions: Repeated self-testing for COVID-19 using PCR is feasible and acceptable to a university population

Mechanical loading: biphasic osteocyte survival and targeting of osteoclasts for bone destruction in rat cortical bone

Bone is removed or replaced in defined locations by targeting osteoclasts and osteoblasts in response to its local history of mechanical loading. There is increasing evidence that osteocytes modulate this targeting by their apoptosis, which is associated with locally increased bone resorption. To investigate the role of osteocytes in the control of loading-related modeling or remodeling, we studied the effects on osteocyte viability of short periods of mechanical loading applied to the ulnae of rats. Loading, which produced peak compressive strains of -0.003 or -0.004, was associated with a 78% reduction in the resorption surface at the midshaft. The same loading regimen resulted in a 40% relative reduction in osteocyte apoptosis at the same site 3 days after loading compared with the contralateral side (P = 0.01). The proportion of osteocytes that were apoptotic was inversely related to the estimated local strain (P < 0.02). In contrast, a single short period of loading resulting in strains of -0.008 engendered both tissue microdamage and subsequent bone remodeling and was associated with an eightfold increase in the proportion of apoptotic osteocytes (P = 0.02) at 7 days. This increase in osteocyte apoptosis was transient and preceded both intracortical remodeling and death of half of the osteocytes (P < 0.01). The data suggest that osteocytes might use their U-shaped survival response to strain as a mechanism to influence bone remodeling. We hypothesize that this relationship reflects a causal mechanism by which osteocyte apoptosis regulates bone's structural architecture