Breakout Session 5 & Vignettes

Christopher Pitsch, D.O.: Hospice and Palliative Medicine: Where we are Now and Ideas for the Future. Speaker Bio: Currently a Fellow in Geriatric Medicine at PCOM, Dr. Christopher Pitsch is a Family Medicine Physician who graduated from WVSOM and completed his Family Medicine Residency at Aria Health while serving as Chief Resident. Dr. Pitsch will be leading Hospice and Palliative Medicine: Where We Are Now and Ideas for the Future

Numerical Simulations and Experiments of Ignition of Solid Particles in a Laminar Burner:Effects of Slip Velocity and Particle Swelling

Ignition and combustion of pulverized solid fuel is investigated in a laminar burner. The two-dimensional OH radical field is measured in the experiments, providing information on the first onset of ignition and a detailed characterization of the flame structure for the single particle. In addition, particle velocity and diameter are tracked in time in the experiments. Simulations are carried out with a Lagrangian point-particle approach fully coupled with an Eulerian solver for the gas-phase, which includes detailed chemistry and transport. The numerical simulation results are compared with the experimental measurements in order to investigate the ignition characteristics. The effect of the slip velocity, i.e. the initial velocity difference between the gas-phase and the particle, is investigated numerically. For increasing slip velocity, the ignition delay time decreases. For large slip velocities, the decrease in ignition delay time is found to saturate to a value which is about 40% smaller than the ignition delay time at zero slip velocity. Performing a simulation neglecting the dependency of the Nusselt number on the slip velocity, it is found that this dependency does not play a role. On the contrary, it is found that the decrease of ignition delay time induced by the slip velocity is due to modifications of the temperature field around the particle. In particular, the low-temperature fluid related to the energy sink due to particle heating is transported away from the particle position when the slip velocity is non-zero; therefore, the particle is exposed to larger temperatures. Finally, the effect of particle swell is investigated using a model for the particle swelling based on the CPD framework. With this model, we observed negligible differences in ignition delay time compared to the case in which swelling is not included. This is related to the negligible swelling predicted by this model before ignition. However, this is inconsistent with the experimental measurements of particle diameter, showing a significant increase of diameter even before ignition. In further simulations, the measured swelling was directly prescribed, using an analytical fit at the given conditions. With this approach, it is found that the inclusion of swelling reduces the ignition delay time by about 20% for small particles while it is negligible for large particles

Homogeneous ignition and volatile combustion of single solid fuel particles in air and oxy-fuel conditions

The ignition and volatile combustion of single coal particles were investigated under laminar conditions. Relevant physico-chemical processes were analyzed under conventional and oxy-fuel atmospheres with varying O2 contents in experiments and simulations. An optically accessible laminar flow reactor with well-defined boundary conditions measured with PIV and quantitative OH-LIF was employed. Multi-parameter optical diagnostics were conducted, including OH-LIF, luminescence imaging, and backlight illumination. Simultaneously acquired experimental data allowed for the evaluation of particle size, ignition delay time, and volatile combustion duration for individual particles. A statistical analysis revealed the improved accuracy of OH-LIF compared to luminescence imaging regarding ignition detection. Simulations within an Eulerian-Lagrangian framework were introduced and validated against experiments. On this basis, particle temperatures, local gas temperatures, and fuel mass fraction were evaluated, providing insights into the devolatilization. Both experimental and numerical results indicated that increasing particle sizes significantly retarded homogeneous ignition and volatile consumption. When increasing the O2 content, a shorter ignition delay time and volatile combustion duration were observed experimentally, which was more significant for larger particles. High slip velocities accelerated convective transport resulting in an earlier ignition and faster volatile combustion. An atmosphere change from N2 to CO2 showed an earlier ignition and increased volatile combustion duration for larger particles, whereas the differences were insignificant for small particles. Simulation results suggested that the local heat transfer was improved by CO2, mainly due to the lower temperature sink close to particles and hence higher volatile release rates. As the initial ambient temperatures were similar, the introduction of CO2 favored homogeneous ignition and slowed down the volatile consumption

SCN1A overexpression, associated with a genomic region marked by a risk variant for a common epilepsy, raises seizure susceptibility

Mesial temporal lobe epilepsy with hippocampal sclerosis and a history of febrile seizures is associated with common variation at rs7587026, located in the promoter region of SCN1A. We sought to explore possible underlying mechanisms. SCN1A expression was analysed in hippocampal biopsy specimens of individuals with mesial temporal lobe epilepsy with hippocampal sclerosis who underwent surgical treatment, and hippocampal neuronal cell loss was quantitatively assessed using immunohistochemistry. In healthy individuals, hippocampal volume was measured using MRI. Analyses were performed stratified by rs7587026 type. To study the functional consequences of increased SCN1A expression, we generated, using transposon-mediated bacterial artificial chromosome transgenesis, a zebrafish line expressing exogenous scn1a, and performed EEG analysis on larval optic tecta at 4 day post-fertilization. Finally, we used an in vitro promoter analysis to study whether the genetic motif containing rs7587026 influences promoter activity. Hippocampal SCN1A expression differed by rs7587026 genotype (Kruskal-Wallis test P = 0.004). Individuals homozygous for the minor allele showed significantly increased expression compared to those homozygous for the major allele (Dunn's test P = 0.003), and to heterozygotes (Dunn's test P = 0.035). No statistically significant differences in hippocampal neuronal cell loss were observed between the three genotypes. Among 597 healthy participants, individuals homozygous for the minor allele at rs7587026 displayed significantly reduced mean hippocampal volume compared to major allele homozygotes (Cohen's D = - 0.28, P = 0.02), and to heterozygotes (Cohen's D = - 0.36, P = 0.009). Compared to wild type, scn1lab-overexpressing zebrafish larvae exhibited more frequent spontaneous seizures [one-way ANOVA F(4,54) = 6.95 (P < 0.001)]. The number of EEG discharges correlated with the level of scn1lab overexpression [one-way ANOVA F(4,15) = 10.75 (P < 0.001]. Finally, we showed that a 50 bp promoter motif containing rs7587026 exerts a strong regulatory role on SCN1A expression, though we could not directly link this to rs7587026 itself. Our results develop the mechanistic link between rs7587026 and mesial temporal lobe epilepsy with hippocampal sclerosis and a history of febrile seizures. Furthermore, we propose that quantitative precision may be important when increasing SCN1A expression in current strategies aiming to treat seizures in conditions involving SCN1A haploinsufficiency, such as Dravet syndrome