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Whole Body Angular Momentum Characterizes Reactive Balance Adaptations and Perturbation Intensity
No full textIdentifying measures which accurately quantify reactive balance adaptation during walking is essential to understand how emerging perturbation-based gait paradigms impact stability over the course of an intervention. These perturbation paradigms have shown promise in reducing falls for numerous clinical populations, however tracking progress in objective terms throughout an intervention remains challenging. Whole body angular momentum (H) may be particularly suited to detect subtle adaptations in the reactive balance response and is applicable within numerous perturbation environments. We assessed the ability of young healthy adults to adapt to varying intensities of discrete, unexpected, treadmill-based perturbations directed mediolaterally, anteriorly, and posteriorly during a single session while ambulating at their comfortable walking speed. We assessed corrective step length and width, trunk deviation and flexion, peak H over a stride, peak-to-peak differences in whole-body angular momentum over a stride (HR), and the participants ability to maintain their H trajectory within two standard deviations of their normal (PNT). Measures derived from H, particularly HR and PNT, demonstrated significant changes with increasing intensity and repetition. Corrective step length and width, trunk deviation and flexion, and peak H also demonstrated significant, but weaker, differences with increasing intensity and repetition. Derivatives of H are sensitive to changes in intensity and repetition, particularly when assessed as peak-to-peak differences and ability to maintain a normal trajectory over a stride. These measures may be utilized to detect changes in reactive balance during perturbation-based gait paradigms
Response to Michael Conway’s Review of \u3cem\u3eMaurice Blondel on the Supernatural in Human Action: Sacrament and Superstition\u3c/em\u3e (Boston & Leiden: Brill, 2017) by Cathal Doherty SJ.
No full textThis is a brief response (1000 words) to Michael A. Conway’s lengthy book review in Irish Theological Quarterly, Vol. 84, No. 2 (May 2019): 212–218
Advances in Noninvasive Imaging for Detecting Radiation-Induced Lung Injury (RILI)
No full textPurpose: Dr. Richard Hill performed pioneering work in the field of radiation-induced normal tissue injury to the lung including noninvasive imaging studies aimed at identifying imaging biomarkers of radiation-induced lung injury (RILI). RILI is a life-threatening toxicity of radiation exposure relevant to both cancer patients undergoing thoracic radiation therapy (RT) and victims of accidental radiation exposure. The ability to detect RILI noninvasively has the potential to guide treatment planning for RT and, in the case of victims of acute radiation exposures, inform the decision to start mitigative therapies. As part of this special issue of IJRB honoring Dr. Hill’s many contributions to the field of radiation biology, this article reviews current advances in noninvasive imaging of RILI including computed tomography (CT), magnetic resonance (MR), hyperpolarized MR, nuclear medicine (PET and SPECT), and optical imaging with near-infrared (NIR) probes. Conclusion: The imaging modalities reviewed have potential to not only provide early identification of RILI but may also provide mechanistic insights into the progression of RILI via noninvasive detection of characteristic RILI mechanisms including: inflammation, vascular damage, cell death, oxidative stress, and fibrosis
Disruption of Collective Behaviour Correlates With Reduced Interaction Efficiency
No full textGroup-living organisms commonly engage in collective behaviour to respond to an ever-changing environment. As animals face environmental change, establishing the mechanisms of information used to collectively behave is critical. Western honeybees (Apis mellifera) are highly social insects that tightly coordinate many individuals to ensure optimum colony function. We used fanning, a collective thermoregulatory behaviour that depends on both social and thermal contexts, as a case study for collective behaviour. To identify potential mechanisms behind the coordination of fanning, we used oxytetracycline, an antibiotic used in apiculture and known environmental pollutant that impairs bee physiology and behaviour. Specifically, we hypothesized that interactions drive the fanning response in honeybees and predicted that oxytetracycline would disrupt social interactions which will lead to a reduced fanning response. We found that longer exposure to antibiotics decreases fanning. Using automated tracking, we show that antibiotic treatment reduces the number of interactions, impeding the social dynamics within these small groups. Our results contribute strong evidence that interactions between individuals may drive the collective fanning response in honeybees. This work emphasizes the importance of understanding the social mechanisms that underlie collective animal coordination and how the effects of pollutants on an individual can scale to affect populations
Development of Prechamber Enabled Mixing-Controlled Combustion Strategy for Ultra-Low Methane Emissions From Lean Burn Natural Gas Engines
No full textThis numerical study explores the optimization of Prechamber Enabled Mixing-Controlled Combustion (PC-MCC) using natural gas in heavy-duty engines, aiming to enhance combustion efficiency to minimize methane slip and NOx emissions. The approach involves a prechamber ignition system, distinct from conventional spark ignition (SI) systems, to initiate combustion of direct injected natural gas. By leveraging the robust ignition characteristics of the prechamber, the PC-MCC method demonstrates significant potential in achieving efficient combustion akin to diesel engines but with lower greenhouse gas emissions. The research evaluates the effects of various geometric and operational parameters on the combustion process and emissions, including prechamber volume, nozzle diameter, direct injector (DI) geometry, and engine operating strategies. Computational Fluid Dynamics (CFD) simulations are utilized, focusing on a heavy-duty, single-cylinder engine modeled after the Caterpillar C9.3B engine. Key findings indicate that a prechamber volume of 3 cc, coupled with a nozzle diameter of 2.75 mm for two prechamber holes, strikes an optimal balance between combustion efficiency and emissions reduction. This configuration ensures robust combustion across a range of operating conditions while maintaining methane slip within targeted limits. Further investigation into DI geometry shows the significance of the injector umbrella angle and nozzle diameter in shaping the fuel-air mixing and combustion dynamics. An umbrella angle of 130° and a nozzle diameter of 300 microns are identified as optimal, promoting rapid and efficient combustion with minimized methane and NOx emissions. The study also investigates the impact of injection timing and pressure, highlighting their roles in controlling combustion timing and influencing emissions levels. Advanced injection timing is found to be crucial in achieving the desired low methane slip, whereas retarded injection timing assists to reduce NOx emissions while having a slight increase in methane emissions. Operating strategies incorporating various levels of Exhaust Gas Recirculation (EGR) are assessed for their effectiveness in further reducing emissions. The research demonstrates that a judicious combination of internal hot EGR and careful calibration of DI pressure and SOI timing can achieve significant reductions in NOx emissions while keeping methane slip under control. Specifically, an internal EGR level of 15%–25%, combined with DI pressures of 200–300 bar and injection timings at or after top dead center, is recommended. These findings contribute valuable insights into the development of advanced combustion techniques for natural gas engines, offering a viable pathway to reduce methane slip without compromising engine efficiency or performance. The PC-MCC system presents a promising solution for the future of heavy-duty natural gas engine technology to reduce methane emissions
Mixing-Controlled Compression Ignition of Ethanol Using Exhaust Rebreathe at a Low-Load Operating Condition—Single Cylinder Experiments in a Heavy-Duty Diesel Engine
No full textAs pollutant emissions regulations in the heavy-duty sector become further stringent, the energy requirements in this sector continue to increase. Due to the high-power density and operating period requirements within this sector, full electrification is challenging. A viable solution to meet the stringent requirements for criteria pollutant and greenhouse gas (GHG) emissions is the use of low carbon renewable fuels. Low carbon renewable fuels are desirable due to their lower carbon content per unit energy compared to conventional fossil diesel fuel. However, implementing some low carbon renewable fuels in the heavy-duty sector poses challenges due to their low reactivity and the prevalent mixing-controlled compression ignition (MCCI) combustion strategy. Because of this, ignition assistance is needed to ignite low reactive renewable fuels in MCCI. This work investigates the use of a variable valve actuation (VVA) strategy, exhaust rebreathe, as an ignition assistance method to ignite pure fuel grade ethanol (E98) in MCCI. Exhaust rebreathe utilizes the hot combustion products from the previous cycle by reinducing the exhaust back into the cylinder during the intake stroke from a secondary exhaust valve event. The reinduction of exhaust into the cylinder increases the in-cylinder bulk gas temperature aiding in the ignitability of the low reactive fuel. The exhaust rebreathe strategy as an ignition assistance method is investigated in this work by conducting single cylinder engine experiments on a heavy-duty diesel engine fueled with E98. Exhaust pressure is varied for the exhaust rebreathe strategy to achieve combustion characteristics with E98 similar to diesel at a low-load, high engine speed operating condition. Additionally, an elevated intake air temperature strategy is implemented to compare to the exhaust rebreathe strategy as another form of ignition assistance with the objective to induce heat in-cylinder prior to combustion without the presence of diluent. Furthermore, zero-dimensional (0D) constant pressure chemical kinetic simulations are conducted to evaluate the most reactive conditions for ethanol to achieve ignition delay times similar to n-heptane. The experimental results demonstrate that at a high speed, low load condition—the elevated intake air temperature strategy with ethanol requires 120°C intake temperature to yield an ignition delay similar to diesel. When accounting for the energy required to heat the intake air, the brake thermal efficiency is 40% lower than the diesel baseline. On the contrary, the exhaust rebreathe strategy with an exhaust pressure of 1.5 bar-a, is able to achieve the same ignition delay with an MCCI combustion process but maintain a brake thermal efficiency within 5% of the baseline diesel engine
Mitochondrial Reactive Oxygen Species Production in Lungs of Rats With Different Susceptibilities to Hyperoxia-Induced Acute Lung Injury
No full textAdult rats exposed to hyperoxia (\u3e95 % O2) die within 60–72 h from respiratory failure. However, when preconditioned with either \u3e95 % O2 for 48 h followed by 24 h in room air (H-T) or 60 % O2 for 7 days (H-S), they acquire tolerance or susceptibility to hyperoxia, respectively. The aim was to quantify H2O2 production rate and identify sources in isolated lung mitochondria and isolated perfused lungs (IPLs) of normoxia, H-T, and H-S rats. Mitochondria were isolated from lungs, and H2O2 production rates were quantified in the presence of pyruvate-malate or succinate, with and without inhibitors of mitochondrial complex I (CI), complex II (CII), and/or H2O2 scavenging systems. Lung rate of H2O2 release was quantified in IPLs with and without CII inhibitor. Results from isolated mitochondria show that CII is the main H2O2 source, and that both H2O2 production rate and scavenging capacity were ~48 % lower in H-S mitochondria compared to normoxia. Results from IPLs show that CII is also the dominant H2O2 source from lung tissue, and that H2O2 release rate was lower in H-T lungs compared to normoxia and H-S lungs. These results suggest that for H-S rats, both mitochondrial rate of H2O2 production and scavenging capacity were significantly lower than those in normoxia mitochondria and may contribute to their increased hyperoxia susceptibility. The lower H2O2 release rate from H-T IPLs, along with no change in mitochondrial H2O2 production rate, is consistent with higher antioxidant capacity in the lungs of H-T rats, which may contribute to their hyperoxia tolerance
A whole-brain voxel-based analysis of structural abnormalities in PTSD: An ENIGMA-PGC study
No full textBackground
Patients with posttraumatic stress disorder (PTSD) exhibit smaller regional brain volumes in commonly reported regions including the amygdala and hippocampus, regions associated with fear and memory processing. In the current study, we have conducted a voxel-based morphometry (VBM) meta-analysis using whole-brain statistical maps with neuroimaging data from the ENIGMA-PGC PTSD working group. Methods
T1-weighted structural neuroimaging scans from 36 cohorts (PTSD n = 1309; controls n = 2198) were processed using a standardized VBM pipeline (ENIGMA-VBM tool). We meta-analyzed the resulting statistical maps for voxel-wise differences in gray matter (GM) and white matter (WM) volumes between PTSD patients and controls, performed subgroup analyses considering the trauma exposure of the controls, and examined associations between regional brain volumes and clinical variables including PTSD (CAPS-4/5, PCL-5) and depression severity (BDI-II, PHQ-9). Results
PTSD patients exhibited smaller GM volumes across the frontal and temporal lobes, and cerebellum, with the most significant effect in the left cerebellum (Hedges’ g = 0.22, pcorrected = .001), and smaller cerebellar WM volume (peak Hedges’ g = 0.14, pcorrected = .008). We observed similar regional differences when comparing patients to trauma-exposed controls, suggesting these structural abnormalities may be specific to PTSD. Regression analyses revealed PTSD severity was negatively associated with GM volumes within the cerebellum (pcorrected = .003), while depression severity was negatively associated with GM volumes within the cerebellum and superior frontal gyrus in patients (pcorrected = .001). Conclusions
PTSD patients exhibited widespread, regional differences in brain volumes where greater regional deficits appeared to reflect more severe symptoms. Our findings add to the growing literature implicating the cerebellum in PTSD psychopathology