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An experimental study was performed to assess the combustion characteristics of iso-octane (a gasoline surrogate) at compression-ignition (CI) conditions. The fuel was injected into a quiescent-steady environment inside an optically accessible constant-volume combustion chamber with a 22.8 kg/m3ambient gas density and a 21 vol % O2concentration. Optical techniques including natural flame luminosity, OH-chemiluminescence, and shadowgraph imaging were performed to compare the combustion characteristics over ambient gas temperatures from 1000 to 1120 K. Measurements were also performed for n-heptane (a diesel surrogate) for reference purposes. Formaldehyde (CH2O) planar laser-induced fluorescence (PLIF) imaging was performed to confirm the presence of low-temperature reactions across the jet head, prior to the high-temperature ignition of iso-octane. From the measurement results, the lift-off lengths (LOLs), ignition delays (IDs), and their corresponding uncertainties for both fuels are observed to increase with lowering ambient temperature conditions. The LOLs, IDs, and their uncertainties for the iso-octane flames are also consistently measured to be higher than that of n-heptane, across the tested ambient temperature range. The results reveal that the highest variability detected for the flame stabilization distance of the iso-octane flame at the lowest tested ambient temperature condition (i.e., 1000 K) is attributable to the long transient stabilization phase that it exhibits after ignition. Additional tests performed using a single-injection test case with lower octane number fuel, as well as split-injection strategies with neat iso-octane as fuel, demonstrate their potentials to reduce the transient stabilization phase of the test flames when compared with those using a single-injection test case with neat iso-octane as fuel.

The aim of this study is to investigate the impact of walls on soot processes of a post-injection strategy at different dwell times. The experiments were performed in an optically accessible constant-volume combustion chamber simulating compression ignition engine conditions with moderate exhaust gas recirculation. The experiments with various injection strategies were performed under ambient conditions with gas density, pressure, and temperature of 20.8 kg/m3, 6 MPa, and 1000 K, respectively, and 15 vol % O2concentration. The main and post injections had a quantity ratio of 8:2 (main/post) totaling 10 mg, and a flat wall was placed 35 mm axially from the injector. The dwell time between the main and post injections was also varied to induce different levels of interaction between the injections. High-speed flame natural luminosity imaging and two-color pyrometry techniques were applied to observe flame characteristics and to obtain soot temperature and KL factor information, respectively. By comparing the wall jet and free jet cases with no direct jet interaction, it was found that the wall affected the post jet flame structure similarly to a single jet or the main jet. However, the post jet with a greater extent of interaction with the main jet induced by shorter dwell time can achieve better mixing for the wall jet case. Increased interaction between the main and post jets also appeared to induce a soot oxidation phase, which was otherwise not observed when the injections were more temporally separated.

Post injection is a multiple-injection strategy that is commonly used as a particulate matter control measure to reduce soot emissions, yet the mechanisms and the interactions between the main and post injections are only vaguely understood. For this work, experiments were performed to assess the effects of varying dwell time between the main and post injections in a compression-ignition (CI) engine environment simulated using a constant-volume combustion chamber. The ambient density, bulk temperature, and oxygen concentration used for this work were controlled at 19.4 kg/m3, 900 K, and 15 vol % O2, respectively. A canola oil-based biodiesel was tested and injected at a fixed injection pressure of 100 MPa into the simulated CI engine environment. A mass ratio of 80%–20% was maintained between the main and post injections, with the dwell time between the injections varied from 1.5 to 2.5 ms. Comparative measurements were performed using the same fuel and injection schedules, but at a higher ambient gas temperature condition of 1100 K. Optical diagnostics methods, including diffused-back illumination and high-speed flame luminosity imaging, were used to assess the spray and combustion processes of the post injection test case. Under the conditions of this work, it was found that the ignition delays, ignition locations, and flame lift-off lengths of the post injection flames are consistently shorter than those of the main injections, with the variations influenced by the extent of the interaction of the post injection with the combustion products from the main injection. A two-color pyrometry technique was also used to measure the soot temperature and soot concentration factor information on the main–post injection cases. The data revealed a greater interaction between the main and post injections resulted in a more rapid development of the soot zone of the post injection with higher temperature after ignition. The distribution of the most probable soot concentration factors of the post injection was also found to be narrower, with lower soot content values.

This work investigates the effects of ambient and injection parameters on the ignition and combustion characteristics of hydrogen (H2)–methane (CH4) jet (50% H2by volume, with the remaining CH4) in simulated direct-injection, compression-ignition conditions. Parameter variations include ambient gas temperature (1060–1200 K), ambient oxygen (O2) concentration (10–21 vol %), and injection pressure (10–20 MPa reservoir pressure). The results show that the ignition delay of the H2–CH4jet decreases with increasing ambient temperature. In most cases, the ignition initiates from a localized kernel before spreading across the jet volume downstream. The lower ambient O2cases display a more voluminous ignition sequence. The results also show that the jet flame recesses upstream to attach or stabilize close to the nozzle but becomes increasingly lifted with lower ambient temperature and O2conditions. The flame autoignition process displays increased variation at the lowest tested ambient temperature condition in this work, which affects the ensuing flame evolution and heat release profile.

Introduction An association between cartilaginous endplate (CEP) defects and intervertebral disk (IVD) degeneration has been previously suggested in animal and cadaveric studies. There have been no previous reports in the literature that describe the use of ultrashort time-to-echo (UTE) magnetic resonance imaging (MRI) to assess the CEP in humans in vivo. As such, the purpose of this study was to report the feasibility of the UTE MRI technique to assess CEP defects in humans in vivo using and to assess their relationship with IVD degeneration.Materials and Methods Nine volunteer subjects (mean age 43.9 years; range: 22 to 61 years) were recruited, representing 54 IVDs and 108 CEPs. The subjects underwent T2-weighted and UTE MRI to assess for the presence and severity of IVD degeneration, and for the presence of CEP defects, respectively, from T12 to S1. Intervertebral disk degeneration was graded according to the Schneiderman et al classification on T2-weighted MRI. CEP defects were defined on UTE MRI as discontinuity of high-signal over 4 consecutive images and were independently assessed by two observers.Results Total 37% out of 108 (34.3%) CEPs had defects, which mainly occurred at T12/L1, L1/L2, and L4/L5 (p= 0.008). Multivariate logistic regression revealed that lower BMI (p= 0.009) and younger (p= 0.034) individuals had a decreased likelihood of having CEP defects. A statistically significant association was found to exist between the presence of CEP defects and IVD degeneration (p= 0.036).A higher prevalence of degenerated IVDs with CEP defects were found at L4/5 and L5/S1, while degenerated IVDs with no CEP defects were found throughout the whole lumbar region. Mean IVD degeneration scores of the L4/5 and L5/S1 levels with CEP defects were higher in comparison to those with no CEP defects.Conclusion Our study demonstrates the feasibility of using UTE MRI in humans in vivo to assess the integrity of the CEP. A statistically significant association was found to exist between the presence of CEP defects and IVD degeneration. In the lower lumbar region, more severe degeneration was found to occur in the IVDs with CEP defects than in those without defects. Such imaging technology may broaden the understanding of IVD degeneration and facilitate management options that target IVD repair/regeneration. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared

Introduction Magnetic resonance imaging (MRI) has been shown to improve the diagnosis and management of patients with intervertebral disk (IVD) related disorders. Multiparametric MRI offers the possibility of noninvasively assessing multiple aspects of pathophysiological processes that exist simultaneously, thereby further assisting in patient treatment management. The purpose of this study is to determine the correlation between relaxation parameters (T1-rho and T2), diffusion properties including fractional anisotropy (FA) and mean diffusivity (MD) measured by diffusion tensor imaging (DTI), and degenerative grades in human IVD based on T2-weighted MRI.Materials and Methods Total 21 subjects (mean age 41.3 years; age range: 24 to 61 years; gender: 10 females, 11 males) with no prior spine surgery were recruited. Sagittal T2-weighted, T1-rho, T2, FA and MD MRI of the lumbar spine were obtained. All images of the lumbar spine were acquired using a 3T Achieva scanner. High-resolution T2-weighted discs were qualitatively graded by two spine specialists in consensus according to Schneiderman's classification (score range: 0 to 3). T1-rho, T2, FA, and MD maps were quantitatively assessed based on a voxel-by-voxel basis.Results By visual inspection, the nucleus pulposus (NP) and annulus fibrosus (AF) in IVDs were distinctively separable on all quantitative maps while some of the discs on T2-weighted images did not show a clear difference between the NP and the AF. The Schneiderman grades and subjects' age significantly correlated with all parameters (p< 0.001). Univariate analysis demonstrated that T1-rho correlated significantly with MD and FA (r = 0.729 and −0.715, respectively; p< 0.001 for both). Quantitative T2 also correlated significantly with MD and FA (r = 0.805 and −0.811, respectively; p< 0.001 for both). In addition, T1-rho showed significant correlation with quantitative T2 (r = 0.824; p< 0.001).Conclusion In this study, we performed quantitative multiparametric MRI to investigate its sensitivity to changes in tissue microstructure of in vivo human lumbar IVDs. Our results suggest that each imaging parameter may attribute different sensitivity to tissue properties. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared

Introduction Intervertebral disk degeneration (IVD) on magnetic resonance imaging (MRI) is an etiological factor associated with low back pain. The (IVD) has been well acknowledged to degenerate as characterized by biochemical and morphological changes. T2 relaxation time has been suggested to be sensitive to changes in collagen and water content in cartilage and in the IVD. In the disk, the investigators have quantified chemical exchange saturation transfer (CEST) and its specificity as well as its correlation capacity for glycosaminoglycan (GAG) content (gagCEST). However, the correlation between conventional qualitative MRI assessment (T2-weighted) and quantitative MRI measurement, such as T2 and CEST, remains unknown. In this study, we aimed to investigate the association between CEST, T2 and degenerative grades in IVD using T2-weighted MRI in human subjects.Materials and Methods Total 21 subjects (8 females, 13 males; median age 34; age range: 24 to 58 years) with no prior spine surgery were recruited. Sagittal T2-weighted, CEST, and T2 MRI of the lumbar spine were obtained. All images of the lumbar spine were acquired using a 3T Achieva scanner. High-resolution T2-weighted disks were qualitatively graded according to Schneiderman's classification (score range: 0 to 3). CEST and T2 maps were quantitatively assessed based on a voxel-by-voxel basis.Results A decreasing trend of CEST and T2 values with increasing grade of degeneration was noted. The mean CEST values in L3/4, L4/5 and L5/S1 discs with Schneiderman grades 0 (n= 41), 1 (n= 10), 2 (n= 7) and 3 (n= 5) were 7.17 ± 1.10%, 6.00 ± 0.83%, 2.85 ± 0.39%, and 1.84 ± 0.27%, respectively. The mean T2 values in discs with Schneiderman grades 0 (n= 41), 1 (n= 10), 2 (n= 7) and 3 (n= 5) were 109.74 ± 12.40 ms, 83.84 ± 6.19 ms, 71.70 ± 3.44 ms, and 65.16 ± 2.97 ms, respectively. Schneiderman grade was correlated with both CEST (r = -0.67, p< 0.001) and T2 (r = -0.71, p)Conclusion Our results showed that CEST and T2 decreases with increasing grade of disk degeneration and that CEST values significantly correlated with T2. Our findings propose useful quantitative imaging tools with discriminatory capacity to assess early and end-stage IVD degeneration. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared

Water based electrolyzers offer a promising approach for generating hydrogen gas for renewable energy storage. 3M's nanostructured thin film (NSTF) catalyst technology platform has been shown to significantly reduce many of the performance, cost and durability barriers standing in the way of H2/air PEM fuel cells for vehicles. In this paper we describe results from the first evaluations of low loaded NSTF catalysts in H2/O2electrolyzers at Proton OnSite and Giner, Inc. Over two dozen membrane electrode assemblies comprising nine different NSTF catalyst types were tested in 11 short stack durability tests at Proton OnSite and 14 performance tests in 50 cm2single cells at Giner Electrochemical Systems. NSTF catalyst alloys of Pt68Co29Mn3, Pt50Ir50and Pt50Ir25Ru25, with Pt loadings in the range of 0.1 to 0.2 mg/cm2, were investigated for beginning-of-life performance and durability up to 4000 hours as both electrolyzer cathodes and anodes. Catalyst composition, deposition and process conditions were found to be important for meeting the performance of standard PGM blacks on electrolyzer anodes while using only 10% as much PGM catalyst. Analyses of MEA's after the durability tests by multiple techniques document changes in catalyst alloy composition, loading, crystallite structure and support stability.