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An ancient cholinergic cell triad of a light-sensitive, a pigmented and a glial cell could regulate stemness
No full textA close spatiotemporal relation between end of mitosis, of butyryl- (BChE) and then acetylcholinesterase (AChE) expressions in early neural tissues has been established, yet the underlying mechanisms are not understood. With this observation in mind, cell culture work analyzing cholinergic functions in the developing vertebrate retina was revealing. For proper cell stratification in avian and rodent retinal 3D-reaggregates (organoids) and explants, Müller glial cells (MCs) and the retinal pigmented epithelium (RPE) are essential actors. Network formation depends on a ChAT amacrine cell and BChE MCs. Further, cholinergic effects at the photoreceptor (PR) to RPE interface remain unclear. Acetylcholine (ACh) reportedly is produced in, and released from PRs, which is received by alpha-7 nicotinic acetylcholine receptors (α7-nAChRs) on adjacent RPE cells. If properly activated, RPE cells in turn signal ACh back to MCs. Notably, MCs under certain conditions act as stem cells in retinal regeneration. Hence, we postulate that a cholinergic signaling loop between MCs, PRs and RPE, which probably already constituted an ancient proto eye, can regulate stem cells. Since a similar cholinergic triad regulates skin regeneration, comparable cholinergic triads could appear at the core of stem cell biology, deserving more research (e.g., cancer biology, tissue regeneration)
Fluid imbibition into PMETAC functionalized mesoporous films
No full textFluid imbibition into nanoporous films is of relevance in water harvesting, separation, or sensing. Furthermore, grafting polymers from the mesopore walls affects the wettability and ionic accessibility of mesoporous films. Using poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) functionalized mesoporous films we observe that the imbibition of aqueous salt solutions depends on many parameters such as the fluid, the mesopore structure, polymer ion interaction and osmotic effects. Specifically, we observe that the imbibition length depends on the salt concentration and the type of salt as well as on the presence of PMETAC. We identified the PMETAC influence on an osmotically driven, self-amplified fluid pumping mechanism using PMETAC functionalized mesoporous silica films. The presence of the polyelectrolyte PMETAC offers a further parameter to tune fluid imbibition into mesoporous films, especially in the presence of interacting ions. The results give insights on how to design porous materials with applications in sensor or separation technology or in material system design e.g. looking at material exchange between drop compartments
Fatigue strength assessment of welded steel fasteners using structural stress concept with consideration of the mounting pre-load
No full textThe document presents a comprehensive investigation into the fatigue strength assessment of welded fasteners, specifically bolts and nuts, used in various engineering applications. A fatigue strength assessment approach using a structural stress concept is established, accounting for the influence of mounting pre-loads and residual stresses from the welding process. With the developed approach, the fatigue strength of all investigated variants can be assessed with a scatter of 1:2. The experimental investigations showed that an early decrease in pre-load forces negatively affects the fatigue strength. While pre-load forces can enhance fatigue strength, a reduction in pre-load during service loading must be avoided to ensure a safe life
Enhancing Life Satisfaction through Eudaimonic, Hedonic, and Combined Interventions: New Training Approaches Relevant to Theory and Practice
No full textIn recent scientific debates, eudaimonia and hedonia have been discussed as either complementary or opposing pathways to well-being. If they are opposites, a combination of the two would not have a positive effect. If they are complementary, their combination is of particular interest. Research to date has often been based on correlational designs that do not allow any conclusions to be drawn about causality. Therefore, we used randomized control designs not only to demonstrate the effectiveness of interventions for eudaimoina and hedonia but also to see whether or not a combination of hedonia and eudaimonia will lead to life satisfaction (full-life effectivity) or even outperforms single-component interventions (full-life superiority). Two randomized controlled studies were conducted with pre-, post- and follow-up measurements. In Study 1 (N = 265), we compared four groups: hedonia training, eudaimonia training, combined training and a control group. In Study 2 (N = 76), we compared three groups: eudaimonia training, combined training and a control group. Results showed positive effects on life satisfaction in the eudaimonia and hedonia groups. The combined training worked (full-life effectivity), although not more so than the single-component trainings (no full-life superiority). The expected mediating role of the art-of-living (a set of individual behavioral strategies) for training effects on life satisfaction was also supported. Results are discussed with reference to the synergetic change model, which offers further ideas to improve combined trainings
Large Eddy Simulation of the piston boundary layer evolution during the compression stroke in a motored internal combustion engine
No full textThis work examines the momentum boundary layer evolution on the piston top of the Darmstadt optically accessible Internal Combustion Engine (ICE). For this purpose, a 3D-CFD wall-resolved Large Eddy Simulation (LES) under motored conditions was deployed. The piston wall is resolved down to 25 µm, corresponding to y⁺ < 1 . For statistical purposes and to compare with experimental data, 33 consecutive engine cycles are simulated. A large-scale tumble motion characterizes the flow field. This flow impinges on the piston on the exhaust side, it moves along the flat piston wall and detaches on the intake side. The near-wall velocities of the simulations align well with the experiment. Analysis revealed regions of Favorable Pressure Gradient (FPG) on the exhaust side and Adverse Pressure Gradient (APG) on the intake side, separated by a sharp pressure inversion zone. The near-wall flow accelerates and then decelerates until detachment. Analysis of the non-dimensional u⁺ - y⁺ profiles reveals the absence of a logarithmic region in the boundary layer. This scaling procedure is sensitive to thermo-physical properties like density and viscosity that vary across the boundary layer, which complicates comparisons with canonical studies. The shape factor of the boundary layer suggests a fully turbulent state despite the low momentum thickness-based Reynolds number. The boundary layer height increases from the exhaust towards the intake side, especially in the presence of strong pressure gradients. Pressure gradients acting perpendicular to the boundary layer are observed. The comparison of ensemble-averaged and single-cycle instantaneous data shows high levels of cyclic fluctuations
Fuel consumption and thermal drive-off element load during drive-off procedures in a mild hybrid powertrain
No full textThis study focuses on investigating the role of electric motors in mild hybrid powertrains, particularly during drive-off procedures. Hybrid powertrains offer fuel efficiency benefits by shifting load from internal combustion engines to electric motors. The research analyzes the potential benefits of a 48 V mild hybrid powertrain during drive-off procedures, considering different accelerator pedal positions and the state of charge neutrality.
In this study, a realistic control logic for drive-off procedures is implemented in a mild hybrid vehicle model, enabling variations in drive torque according to accelerator pedal positions. The thermal load on the drive-off element, a wet friction clutch, and fuel consumption are analyzed for drive-offs with and without electric motor support. The thermal load on the clutch during drive-off procedures is assessed by calculating energy dissipation due to clutch slipping and temperature on friction surfaces using a thermal model of the clutch. Results indicate significant reductions in heat and temperature during drive-offs with electric motor support, particularly at low accelerator pedal positions. The heat reduction varies between 55.6 and 100% depending on the accelerator pedal position, which corresponds to a temperature reduction between 6.4 C° and 21.6 C°. The 100% reduction indicates an electrical operation.
Since the examined powertrain is a mild hybrid, some of the electrical energy consumed during drive-off procedures must be recuperated during deceleration or reproduced with the help of internal combustion engine. A control strategy incorporating an extended Adaptive Equivalent Consumption Minimization Strategy (A-ECMS) is used to coordinate power distribution between the internal combustion engine and electric motor during hybrid driving and battery recharging. Fuel consumption during drive-offs with and without electric motor support is comparatively analyzed using a segment of the low-speed driving cycle from the WLTC Class 3b, representing urban traffic. The precondition for the comparison is to ensure a neutral state of charge at the end of the driving cycle. Results show that using the electric motor during drive-offs with low accelerator pedal positions can reduce fuel consumption. The 10% accelerator pedal position shows a fuel consumption improvement of 0.8 g of gasoline for the observed driving cycle, in comparation, it is 0.1 g for the 30%. Nevertheless, this advantage is not observed during drive-offs with accelerator pedal positions higher than 30%
Experimental evidence of a size-dependent sign change of the Seebeck coefficient of Bi nanowire arrays
No full textThe electrical transport in bismuth nanowires is strongly influenced by both sample geometry and crystallinity. Compared to bulk bismuth, the electrical transport in nanowires is dominated by size effects and influenced by surface states, which gain increasing relevance with increasing surface-to-volume ratios, i.e. with decreasing wire diameter. Bismuth nanowires with tailored diameter and crystallinity constitute, therefore, excellent model systems, allowing to study the interplay of the different transport phenomena. Here, we present temperature-dependent Seebeck coefficient and relative electrical resistance measurements of parallel bismuth nanowire arrays with diameters between 40 and 400 nm synthesized by pulsed electroplating in polymer templates. Both electrical resistance and Seebeck coefficient exhibit a non-monotonic temperature dependence, with the sign of the Seebeck coefficient changing from negative to positive with decreasing temperature. The observed behavior is size-dependent and is attributed to limitations of the mean free path of the charge carriers within the nanowires. The observed size-dependent Seebeck coefficient and in particular the size-dependent sign change opens a promising avenue for single-material thermocouples with p- and n-legs made from nanowires with different diameters
Experimental assessment of the effects of gas composition on volatile flames of coal and biomass particles in oxyfuel combustion using multi-parameter optical diagnostics
No full textThis experimental study examines the particle-level combustion behavior of high-volatile bituminous coal and walnut shell particles in oxyfuel environments, with a particular focus on the gas-phase ignition characteristics and the structural development of volatile flames. Particles with similar size and shape distributions (a median diameter of about 126 µm and an aspect ratio of around 1.5) are combusted in hot flows generated using lean, flat flames, where the oxygen mole fraction is systematically varied in both CO2/O2 and N2/O2 atmospheres while maintaining comparable gas temperatures and particle heating rates. The investigation employs a high-speed multi-camera diagnostic system combining laser-induced fluorescence of OH, diffuse backlight-illumination, and Mie scattering to simultaneously measure the particle size, shape, and velocity; the ignition delay time; and the volatile flame dynamics during early-stage volatile combustion. Advanced detection algorithms enable the extraction of these multiple parameters from spatiotemporally synchronized measurements. The results reveal that the ignition delay time decreases with an increasing oxygen mole fraction up to 30 vol%, beyond which point further oxygen enrichment no longer accelerates the ignition, as the process becomes limited by the volatile release rate. In contrast, the reactivity of volatile flames shows continuous enhancement with an increasing oxygen mole fraction, indicating non-premixed flame behavior governed by the diffusion of oxygen toward the particles. The analysis of the flame stand-off distance demonstrates that volatile flames burn closer to the particles at higher oxygen mole fractions, consistent with the expected scaling of O2 diffusion with its partial pressure. Notably, walnut shell and coal particles exhibit remarkably similar ignition delay times, volatile flame sizes, and OH-LIF intensities. The substitution of N2 with CO2 produces minimal differences, suggesting that for 126 µm particles under high-heating-rate conditions, the relatively small variations in the heat capacity and O2 diffusivity between these diluents have negligible effects on the homogeneous combustion phenomena observed
Acoustic Energy Transfer for Integrated Sensor Systems
No full textPowering embedded sensors in metal-enclosed environments poses significant challenges such as structural constraints, battery dependency, and electromagnetic shielding. This work investigates using acoustic energy transfer (AET) as a viable approach and explores key factors influencing performance. A parametric study examines various parameters affecting energy transfer, which is followed by an experimental demonstration in a sensor-integrated bolt. Results indicate that electrical impedance matching greatly enhances power transfer but also alters the optimal transmission frequency. Elevated temperatures reduce the transducers' resonance frequency. This potentially impacts performance if only a single transducer is subjected to a temperature gradient, which can be caused by nearby machinery, exposure to hot industrial processes or self-heating due to inefficiencies. Pure sine wave excitation increases power transfer up to 2.5 times over pulse-width modulation at the expense of increased circuit complexity. Given that multiple parameters influence not only peak output power but also its frequency, active resonance tracking is essential for optimal energy transfer. Ultrasonic communication enables receiver-side frequency tracking, improving efficiency and adaptability in dynamic conditions. The final bolt-integrated setup achieves an output power of 0.38mW, demonstrating the feasibility of AET while also revealing size-related inefficiencies in embedded sensors
Simplified data acquisition for product carbon footprints in the automotive industry and their accuracy
No full textManufacturing processes significantly impact greenhouse gas (GHG) emissions, but can also contribute to climate change mitigation through sustainable practices and product stewardship. Life cycle assessments (LCAs) and product carbon footprints (PCFs) are crucial tools for assessing the environmental impact of products. However, the data acquisition process for conducting such analyses can be complex and time-consuming. This article delves into the comparative analysis of different PCF studies for a vehicle component. Our detailed PCF study is mainly based on measured data and used as the reference value for accuracy. The other three PCFs were derived from available data sources, such as technical drawings or the International Material Data System (IMDS). Our research reveals that the determined value of the detailed study is significantly higher than the results that only take material input into account, but 18% lower than the PCF, which is based on rough assumptions and secondary data. This indicates a relationship between the depth of information available and the accuracy of outcomes. However, less accurate methods may be suitable for initial estimations, especially when resources are lacking or production has not yet begun