Investigating the feasibility of characterising gasoline autoignition using a motored engine apparatus

Development of a predictive octane model is a potentially useful tool for designing fuel blends for meeting octane specifications. One of the approaches adopted is through chemical kinetic modelling of the autoignition properties of constituent compounds. The results obtained from models, however, are dependent on experimental data for validation. It was the intention of this thesis to provide empirical data that could be used confirm a recently proposed autoignition model based upon the results obtained from chemical kinetics modelling. Motored engines have been used extensively for the investigation of autoignition properties of fuels. They are useful in interpreting results from conventional ignition delay measuring systems as well as giving practical insight into the process of autoignition in spark ignition engines. The conditions required for autoignition reactions to take place are easily produced in a motored engine with a suitable compression ratio. A single cylinder engine was modified so that the inlet conditions could be adjusted and n-heptane was tested in the device. Fuelling was controlled with an injection system which was calibrated for n-heptane use in the engine. A range of inlet conditions were determined that would enable peak conditions in the engine to result in autoignition of the fuel. The autoignition data was then used in describing the ignition delay characteristics of the fuel and the range of interest, the so called negative temperature coefficient region. Autoignition experiments were performed in the engine and the data was analysed by the comparison of measured autoignition reactions with predicted reaction times; the predictions were calculated using the new empirical autoignition model. Direct analysis of the model resulted in good correlation of measured and predicted overall autoignition reaction times, with improved correlation of cool flame reaction times with initial temperature adjustment. Modification of initial temperature values in the indirect model application (whereby traces were generated using an engine model with autoignition prediction capabilities) resulted in similar observances. These initial results led to the conclusion that the temperature and Arrhenius parameter adjustments necessary to obtain a perfect fit in the autoignition model were indicative of errors involved in the temperature measurement or in the fuel metering. Recommendations for further work on the engine would be the investigation of a dynamometer system that would be free from noise transmission during operation and that would enable experimentation with lower engine speeds. Further work on the inlet system would be the installation of shielded thermocouples and a quicker acting heater controller. A fundamental change in fuel metering calibration is required. Further recommendation is that a variable compression ratio engine should be used to enable the attainment of a wider range of readings for fuel characterisation and possibly eradicate the problems experienced with fuelling

Mechanistic models for the interaction of Curium(III) and Europium(III) with crystalline rocks

In the 21st century the safe disposal of highly radioactive nuclear waste remains a major challenge to humanity. For the first 300 years nuclear fission products will be the main source of large amounts of the radioactivity, however, over a period of 100,000s of years most of the radiotoxicity of nuclear waste will originate from transuranium elements such as Pu, Am, and Cm. Because of the reducing conditions within a potential deep underground repository Am and Cm will exclusively – and Pu at least partially – be present in their trivalent state. For the safety case of a repository, it will be of importance to understand the mobility and retention behavior of those trivalent actinides within the host rock environment. Here, the focus is set on crystalline rock, a host rock under consideration in many countries such as Finland, Sweden, Czech Republic, and also Germany. Research in the last two decades has focused on determining the chemical speciation behavior of radionuclides on the molecular scale using primarily pure, individual mineral phases in their pulverized form. Real crystalline rock systems, on the km scale of a repository, are however much more complex, physically large and bulky, and heterogeneous. Parameters, such as heterogeneity of topography or composition, and competing surface processes have to be considered adequately in transport modelling as well as the safety assessment and thus large-scale experiments without the loss of molecular level information are needed. In this work, the focus was set on the assessment of parameters affecting chemical speciation and retention of Cm(III) and its chemical homologue Eu(III) at 5·10-7 M to 10-4 M concentrations on surfaces of crystalline rocks, relevant to potential future repositories. Correlative spectromicroscopy as a combination of spatially resolved techniques, was applied to study mineralogy, surface topography, quantitative metal ion uptake, and surface metal speciation on the same thin sections in the mm to cm scale with μm resolution. Cm(III) sorption experiments on cleaved K-feldspar crystals at pH 5.5 and 6.9 using autoradiography in conjunction with micro-focus time-resolved laser-induced fluorescence spectroscopy (μTRLFS), and vertical scanning interferometry, showed that sorption uptake and speciation is dependent on pH and surface roughness. In regions expressing a high surface roughness quantitatively more Cm(III) sorbed to the surface than in smoother regions. Further, the formed Cm(III) surface complexes are more strongly bound in regions with a high roughness, since they possess a higher number of strong sorption sites. The speciation between smooth and rough surfaces does not differ at pH 5.5. In contrast, at pH 6.9 in rougher areas, stronger species form favorably in addition to weaker surface sorption species. For comparison, Cm(III) sorption at pH 7.3 was conducted on a granodiorite crystalline rock thin section from the Grimsel Test Site, Switzerland with an inclusion of a large K-feldspar mineral grain. The spectromicroscopy approach was extended by Raman-microscopy to identify the surface mineralogy. From calibrated autoradiography of the entire thin section, it could be assessed that most sorption occurs on mica minerals rather than on feldspar. However, the K-feldspar grain was investigated in detail for a comparison of Cm(III) speciation on crystals and natural grains. On the grain, the sorption was heterogeneously distributed mainly occurring in rough surface regions. Since the overall sorption uptake was lower, the dominant species formed are bound strongly to the surface occupying strong sorption sites. Complexes were observed that were either the result of ternary complexation on the surface or incorporation. While sorption on K-feldspar crystals was higher than on the mineral grain, no ternary complexation could be observed, therefore the formation of this species is likely a result of the heterogeneous mineralogy. The formation of those complexes with carbonate is likely, whereas silicate does not seem to contribute. The exact complex structure determination will be the focus of future work. Increasing the complexity of the system, the next step was to study Cm(III) sorption at pH 8.0 on entire crystalline rock thin sections and analyzing speciation within and between different mineral gains. The focus was set on granite from Eibenstock, Germany and gneiss from Bukov, Czech Republic. On granite, sorption was highest on mica as well as feldspar and smallest on quartz as measured on the sub-mm to cm scale by quantitative autoradiography. On quartz regions, where surface roughness was higher, sorption quantities close to those on feldspar and mica could be observed. A detailed μTRLFS analysis shows highest sorption quantities on topaz, followed by feldspar, and only minor uptake was detected on quartz. Assessment of Cm(III) uptake on mica was not possible due to strong quenching of the Cm(III) luminescence through Fe as part of the mineral structure. Sorption on topaz, feldspar, and quartz occurred preferably in regions with a high surface roughness, such as surface pits, cracks, or mineral grain boundaries between the grains. Surface complexes in high roughness regions are bound more strongly than in smoother regions. A process that could either be Cm(III) ternary complexation or incorporation was exclusively observed on feldspar and quartz, likely because more sorption sites allowed for surface incorporation after which ternary complexation can occur. The experiments showed that mineralogy is the most important parameter when it comes to surface sorption, however it is closely followed by the surface roughness. On gneiss the overall mineralogy was different, which in turn affected the surface Cm(III) uptake. Combining the results from Raman microscopy and autoradiography, sorption was found almost exclusively on amphibole and mica, while little to no sorption was observed on feldspar and quartz. Due to the high Fe content of amphibole and mica, quenching hindered Cm(III) luminescence detection using μTRLFS. However, on feldspar and quartz μTRLFS allowed for uptake and speciation analysis. While no uptake was seen in smooth regions, uptake was increased in rougher regions. This highlights that in a competitive sorption environment, on low sorbing mineral phases, sorption is controlled by surface roughness. Cm(III) uptake and speciation analysis on mica using μTRLFS proved to be difficult because of luminescence quenching induced by structurally incorporated Fe in the minerals. However, to tackle this challenge, Cm(III) sorption experiments were performed on a granitic pegmatite from Olkiluoto, Finland at adjusted experimental settings, i.e., using a five times higher metal concentration than in previous experiments. Autoradiography as well as μTRLFS showed that Cm(III) sorption mainly occurred on mica, while uptake on feldspar and quartz was minor. Mica itself can be found as part of small cracks and pits, or as large grains. Inherently mica showed a high surface roughness, however Cm(III) uptake and speciation differed between the differently sized grains. On smaller grains, uptake was lower than on the larger grains, resulting in primarily stronger inner-sphere sorption species that formed. The high uptake on larger grains lead additionally to the formation of weaker inner-sphere sorption species. To compare the obtained Cm(III) results Eu(III) sorption was performed on a granite thin section. It was observed that Eu(III) uptake and speciation not only occurs heterogeneously between different minerals, but also within single grains particularly close to mineral grain boundaries. This implies that surface roughness, next to mineralogy, influences the sorption process. However, the detection of Eu(III) was hindered by surface precipitation, naturally incorporated Eu(III), and thus vague luminescence peak analysis. Spatially resolved correlative spectroscopy workflows that were further optimized in this thesis proved to be universally applicable in the range of mineral crystals to different crystalline rock thin sections and luminescent metals (Cm, Eu) and can be taken in the future as references for further studies with other luminescence metals such as Am(III) or U(VI). The derived findings show that in future assessments of the mobility of trivalent radionuclides in reactive transport modelling, parameters need to be selected carefully. Additional processes and parameters not considered before, like the surface roughness, will influence the retention of radionuclides within the geosphere. Those processes and parameters need to be quantified and implemented in the models to represent the deep repository system more reliable

The neuroanatomical correlates of repetitive negative thinking: A systematic review

Repetitive negative thinking (RNT) is a cognitive process characterised by intrusive, repetitive, and difficult-to-disengage-from negative thoughts. Heightened RNT levels are prevalent across clinical disorders and have been associated with ill-health (e.g. cardiovascular disease), even at lower, non-clinical levels. Identifying the neuroanatomical correlates of RNT could help characterise structural alterations that transcend diagnostic boundaries and further understanding of the pathogenesis of clinical disorders. We therefore conducted a systematic review to investigate associations between RNT and brain morphology. Following title/abstract and full-text screening, 24 studies were included. We found evidence that RNT severity is associated with grey and white matter volumes/microstructure, particularly in the dorsolateral prefrontal cortex, anterior cingulate cortex and superior longitudinal fasciculus, regions heavily implicated in cognitive control, and emotional processing and regulation. However, inconsistent associations, potentially due to the heterogeneity of included studies (e.g. methodological differences, type of RNT assessed), preclude specific conclusions being reached regarding any one region's association with RNT. Further, given the defuse nature of thoughts, it may be that RNT is associated with distributed brain regions operating within large-scale networks, rather than with a single structure. High quality longitudinal studies, investigating structural networks, are required to confirm the neuroanatomical basis of RNT and elucidate the direction of relationships

Associations between Mobility, Cognition, and Brain Structure in Healthy Older Adults.

Mobility limitations lead to a cascade of adverse events in old age, yet the neural and cognitive correlates of mobility performance in older adults remain poorly understood. In a sample of 387 adults (mean age 69.0 ± 5.1 years), we tested the relationship between mobility measures, cognitive assessments, and MRI markers of brain structure. Mobility was assessed in 2007-2009, using gait, balance and chair-stands tests. In 2012-2015, cognitive testing assessed executive function, memory and processing-speed; gray matter volumes (GMV) were examined using voxel-based morphometry, and white matter microstructure was assessed using tract-based spatial statistics of fractional anisotropy, axial diffusivity (AD), and radial diffusivity (RD). All mobility measures were positively associated with processing-speed. Faster walking speed was also correlated with higher executive function, while memory was not associated with any mobility measure. Increased GMV within the cerebellum, basal ganglia, post-central gyrus, and superior parietal lobe was associated with better mobility. In addition, better performance on the chair-stands test was correlated with decreased RD and AD. Overall, our results indicate that, even in non-clinical populations, mobility measures can be sensitive to sub-clinical variance in cognition and brain structures

Effect of iron addition to the electrolyte on alkaline water electrolysis performance

Improvement of alkaline water electrolysis is a key enabler for quickly scaling up green hydrogen production. Fe is omnipresent within most industrial alkaline water electrolyzers and its effect on electrolyzer performance needs to be assessed. We conducted three-electrode and flow cell experiments with electrolyte Fe and Ni electrodes. Three-electrode cell experiments show that Fe ([Fe] = 6–357 μM; ICP-OES) promotes HER and OER by lowering both overpotentials by at least 100 mV at high current densities (T = 35°C–91°C). The overpotential of a zero-gap flow cell was decreased by 200 mV when increasing the Fe concentration ([Fe] = 13–549 μM, T = 21°C–75°C). HER benefits from the formation of Fe dendrite layers (SEM/EDX, XPS), which prevent NiHx formation and increase the overall active area. The OER benefits from the formation of mixed Ni/Fe oxyhydroxides leading to better catalytic activity and Tafel slope reduction

Kultursensible Suchtprävention: Ein Projekt des SPIKE DRESDEN e. V.

Mit dem Projekt „Kultursensible Suchtprävention“ wurde ein neuer Weg beschritten, um Erfahrungen zu sammeln, Methoden zu erproben, Vernetzung voranzutreiben, einen Überblick über die Situation zur kultursensiblen Suchtpräventionsarbeit in Dresden zu erlangen und das daraus entstandene Wissen für Fachkräfte zugänglich zu machen. In dieser Broschüre werden die gewonnenen Erkenntnisse und Erfahrungen aus dem Projekt, die aus der Zusammenarbeit mit der Zielgruppe im SPIKE Dresden entstanden sind, gebündelt und interessierten Fachkräften zur Verfügung gestellt. Die Broschüre dient dabei als Wissensspeicher und Werkzeugkiste für all jene, die sich mit der Materie befassen. Dabei wird kein Anspruch auf Vollständigkeit und Allgemeingültigkeit erhoben, vielmehr basiert diese Broschüre auf den im Rahmen des Projektes erlangten Erfahrungen, die in dem spezifischen Setting des SPIKE Dresden gemacht wurden. Auch wenn die erprobten Möglichkeiten den Fokus auf Suchtprävention legen, lassen sich viele der Erkenntnisse auch auf weitere Arbeitsfelder übertragen. Die Broschüre soll dazu einladen, sich mit den Ergebnissen auseinanderzusetzen, sie im Team zu diskutieren, mit ihnen weiterzuarbeiten und eigene Ideen zu entwickeln. Stand: Dezember 202

Association between anxiety symptoms and Alzheimer's disease biomarkers in cognitively healthy adults: A systematic review and meta-analysis

Objective: Anxiety has been identified as both a risk factor and prodromal symptom for Alzheimer's disease (AD) and related dementias, however, the underlying neurobiological correlates remain unknown. The aim of this systematic review and meta-analysis was to examine the association between anxiety symptoms and two defining markers of AD neuropathology: amyloid-beta (Aβ) and tau. Methods: Systematic literature searches were conducted across 5 databases. Studies investigating the relationship between anxiety and AD neuropathology (i.e., Aβ and/or tau) in cognitively healthy adults were eligible. Where possible, effect sizes were combined across studies, for Aβ and tau separately, using random-effects meta-analyses. Sensitivity analyses were performed to assess whether results differed according to anxiety type (i.e., state and trait) and biomarker assessment modality (i.e., positron emission tomography and cerebrospinal fluid). Results: Twenty-seven studies reporting data from 14 unique cohorts met eligibility criteria. Random-effects meta-analyses revealed no associations between self-reported anxiety symptoms and either Aβ (13 studies, Fisher's z = 0.02, 95% confidence interval [CI] -0.01–0.05, p = 0.194) or tau (4 studies, Fisher's z = 0.04, 95% CI -0.02–0.09, p = 0.235). Results remained unchanged across sensitivity analyses. Conclusions: In cognitively healthy adults, meta-analytic syntheses revealed no associations between anxiety symptoms and either Aβ or tau. There is a critical need, however, for larger studies with follow-up periods to examine the effect of anxiety symptom onset, severity, and chronicity on AD neuropathology. Additionally, further research investigating other potential neurobiological correlates is crucial to advance scientific understanding of the relationship between anxiety and dementia

A systematic review of MRI studies examining the relationship between physical fitness and activity and the white matter of the ageing brain

Higher levels of physical fitness or activity (PFA) have been shown to have beneficial effects on cognitive function and grey matter volumes in older adults. However, the relationship between PFA and the brain's white matter (WM) is not yet well established. Here, we aim to provide a comprehensive and systematic review of magnetic resonance imaging studies examining the effects of PFA on the WM of the ageing brain. Twenty-nine studies were included in the review: eleven examined WM volume, fourteen WM lesions, and nine WM microstructure. While many studies found that higher levels of PFA were associated with greater WM volumes, reduced volume or severity of WM lesions, or improved measures of WM microstructure, a number of negative findings have also been published. Meta-analyses of global measures of WM volume and WM lesion volume yielded significant, but small, effect sizes. Overall, we found evidence for cautious support of links between PFA and WM structure, and highlighted key areas for future research including the extent to which the relationship between PFA and WM structure is anatomically specific, the influence of possible confounding factors, and the relationship between PFA, WM and cognition

Associations between Mobility, Cognition, and Brain Structure in Healthy Older Adults

Mobility limitations lead to a cascade of adverse events in old age, yet the neural and cognitive correlates of mobility performance in older adults remain poorly understood. In a sample of 387 adults (mean age 69.0 ± 5.1 years), we tested the relationship between mobility measures, cognitive assessments, and MRI markers of brain structure. Mobility was assessed in 2007–2009, using gait, balance and chair-stands tests. In 2012–2015, cognitive testing assessed executive function, memory and processing-speed; gray matter volumes (GMV) were examined using voxel-based morphometry, and white matter microstructure was assessed using tract-based spatial statistics of fractional anisotropy, axial diffusivity (AD), and radial diffusivity (RD). All mobility measures were positively associated with processing-speed. Faster walking speed was also correlated with higher executive function, while memory was not associated with any mobility measure. Increased GMV within the cerebellum, basal ganglia, post-central gyrus, and superior parietal lobe was associated with better mobility. In addition, better performance on the chair-stands test was correlated with decreased RD and AD. Overall, our results indicate that, even in non-clinical populations, mobility measures can be sensitive to sub-clinical variance in cognition and brain structures

Correlation between Cognition and Balance among Middle-Aged and Older Adults Observed through a Tai Chi Intervention program

Background: Age-associated decline in cognition and balance may cause severe ability loss for daily living activities among middle-aged and older adults. The relationship between cognition and balance in this aging population remains to be explored. Objective: The present study Is exploratory in nature and aimed to examine the relationship between balance (both static and dynamic components) and global cognitive function among middle-aged and older adults through Tai Chi (TC) practice as a research avenue. Methods: A short-term (12 weeks) intervention of TC was conducted among middle-aged and older adults in the community setting. Global cognitive function (using the Chinese version of the Montreal Cognitive Assessment score (MoCA) and balance (i.e., one leg standing test score; Timed Up and Go Test score, TUGT) of all participants were assessed before and after the intervention. Age, body mass index (BMI), sex, and physical fitness variables (Chair Stand Test, CST; the 6-Meter Walk Test, 6MWT) were also collected as confounding factors. Results: Significant moderator effects of baseline CST on the association between the dichotomized baseline MoCA score and the baseline left leg balance score (p = 0.0247), the baseline right leg balance score (p = 0.0140) and the baseline TUGT score (p = 0.0346) were found. Change score of left score balance (p = 0.0192) and change score of TUGT (p = 0.0162) were found to be significantly associated with change score of cognitive function. Conclusion: Cognitive function and balance are interrelated in middle-aged and older adults. The association between global cognitive function and balance Is moderated by strength of lower limbs. The change scores of cognitive function and balance introduced by TC training were found to be positively correlated. Future research Is warranted to further confirm the cause-effect relationship of cognitive function and balance and its influencing factors among middle-aged and older adults utilizing intervention studies with larger sample sizes