424 research outputs found
Microglia and astrocyte function and communication: what do we know in humans?
No full textMicroglia and astrocytes play essential roles in the central nervous system contributing to many functions including homeostasis, immune response, blood–brain barrier maintenance and synaptic support. Evidence has emerged from experimental models of glial communication that microglia and astrocytes influence and coordinate each other and their effects on the brain environment. However, due to the difference in glial cells between humans and rodents, it is essential to confirm the relevance of these findings in human brains. Here, we aim to review the current knowledge on microglia-astrocyte crosstalk in humans, exploring novel methodological techniques used in health and disease conditions. This will include an in-depth look at cell culture and iPSCs, post-mortem studies, imaging and fluid biomarkers, genetics and transcriptomic data. In this review, we will discuss the advantages and limitations of these methods, highlighting the understanding these methods have brought the field on these cells communicative abilities, and the knowledge gaps that remain.</p
Measurements of turbulence at stratocumulus top
No full textUsing 1m resolution airborne data from research flights we divide stratocumulus top region into sublayers and characterize properties of turbulence in each sublayer. Results indicate, that there are no clear differences of turbulence properties between thermodynamically different "calassical" and "non-classical" stratocumulus regimes, but there are clear signs of turbulence ainsotropy in stably stratified sublayers in the cloud top region
Application-oriented link adaptation for IEEE 802.11
No full textThe thesis addresses the ever-persistent problem of quality guarantees in wireless data networks. The quality guarantees are especially important for real-time streaming applications. While in fixed links most of the quality issues could be, and are still resolved by over-provisioning, in the world of wireless communications things get complicated. The main reason for wireless links being a bottleneck in terms of both achievable throughput and packet loss and delay guarantees, is the resource limitation that will always be there. Our work showed that while there is no magic solution that can resolve all link quality-related problems in wireless networks, a lot could be done to mitigate them. The first, and the most important, is to make the radio as adaptive to the changes of the link conditions as possible. This can be done through our advanced hybrid rate-control algorithm. The algorithm combines a stable throughput-based solution with a rapid link-quality feedback supplement into a novel controller that has both swift response and stable performance. The second solution, which is dependant on the first one, is the propagation of link status-related information from the link layer to the application. The latter can use this feedback to change its data stream properties to match those of the underlying wireless link. This behaviour proves most useful in cases when the radio cannot compensate for a deterioration of the radio connection such as a significant drop of the signal strength due to obstruction, or too many users competing to use the same medium.Electrical Engineering, Mathematics and Computer Scienc
Co-creatie in het publieke domein: Een vanzelfsprekendheid
No full textIndustrial DesignIndustrial Design Engineerin
Bubble velocity measurements using ultrasound
No full textApplied SciencesKramers Laboratorium voor Fysische Technologi
Experimental study on tranisitio characteristics of natural-concvection flow
No full textApplied Science
High temperature oxidation of ß-NiAICr model coating alloys: Effect of the reactive elements Y, Zr and Hf on growth and adhesion of the oxide layer
No full textMechanical, Maritime and Materials EngineeringTechnische Materiaalwetenschappe
Multiaxial fatigue criteria for offshore mooring chains subjected to out-of-plane bending
No full textThe out-of-plane bending of offshore mooring chains leads to a rapid deterioration of the chain, ultimately leading to failure in a period that is a fraction of the design-life. The deformation of the contact surface of the chainlinks leads to the interlocking of the link. This in turn causes the chain to behave like a bending beam. The combination of the chains behaving in this manner and the vessel movement leads to a bending moment in the chain link, especially in the top section, where the tensions are high. Due to the alternating nature of the loading, multiaxial fatigue effects cause chain failure. In this thesis, a literature study is performed, forming an introduction to the general concept of fatigue and the exploration of available methods. For multiaxial loadings, so-called critical plane methods are widely accepted as the most effective approach. This critical plane method search for the material plane experiencing most damage, according to the damage criterion that is assessed. Furthermore, a number of methods for the cycle decomposition are present. For uniaxial methods, the rainflow method is most used. Applying this method to multiaxial fatigue problems can lead to problems, which leads to the formation of alternative approaches. The other approaches being discussed are the Wang & Brown method and the Modified Wang & Brown method. The Bannantine & Socie method is discussed too, but could be classified as a critical plane search algorithm, instead of a novel cycle counting method. After the exploration of the problem, a finite element model is created. This model consists of multiple chain links, that are proofloaded while plastic deformation is allowed. This leads to the aforementioned deformation of the contact surfaces on the links. After the proofloading step is completed, three different cases are performed with an elastic material formulation. These cases comprise of varying angle ranges; Case 1 only induces an out-of-plane bending in the analysed link, Case 2 induces an out-of-plane and in-plane load, while Case 3 is similar to Case 2, apart from an added phase difference between the two angles. The stress and strain results from the finite element analyses are input in the Pragtic fatigue software. For each case, a number of fatigue criteria are calculated. These criteria are, named after the author, the following: McDiarmid, Dang Van, Matake, Liu & Mahadevan, Carpinteri & Spagnoli, Findley, Wang & Brown & Miller, Smith & Watson & Topper and Socie. Different critical plane search algorithms and/or cycle counting methods have been explored. Some of these criteria lead to a Fatigue Index, while others lead to an Accumulated Damage formulation. From the results it is clear that the cases combining two angles lead to higher damages, leading to the believe that the multiaxial behaviour should be taken into account when assessing fatigue damage of mooring chains. Furthermore, it seems that for the different cases, the SWT criterion gives either the highest or the lowest damage. As this is originally a multiaxial parameter, it shows that the use of traditional uniaxial methods could either over- or underestimate the damage, depending on the specific loading. Furthermore, results show that the criterion that is suggested by Bureau Veritas' Guidance Note on OPB, namely the Dang Van criterion, often gives the lowest fatigue index. This suggests that this criterion might not be conservative enough. This statement needs to be validated with the help of experiments. Furthermore, the method specifically aimed at multiaxial problems, the Wang & Brown method (including the multiaxial cycle counting method), leads to highest accumulated damage. As this method was aimed for multiaxial and non-proportional loading, it can be reasoned that this method makes a conservative, proper prediction. As for the critical plane orientation, it seems that the most damaging plane, likely the location of crack growth, is often close to the shear plane. This fuels the believe that the shear stress is the factor driving the OPB failure mode. However, since this problem inherently involves a mean stress (the tension on the mooring chain), the critical plane does not need to be the shear plane. When exploring this with the globe plane search algorithm, it seems that the critical plane is often a plane oriented at some angle in between the shear and normal plane. The results and statements made in this report are at this point mathematical. As the OPB concept is relatively newly discovered, more experiments are needed to be able to back up any statements that can be made. Furthermore, the research presented here could benefit from a larger group of cases, and added detail on the loading part of the analyses. Furthermore, as material fatigue parameters are limited, a sensitivity anayses on these parameters could shed some light on the influence of parameters used. The parameters used in this report are taken from similar materials and should at least give a very reasonable approximation of the material's fatigue behaviour.Section Ship and Offshore StructuresDepartment Maritime & Transport TechnologyMechanical, Maritime and Materials Engineerin
Het lage druk proces voor de bereiding van azijnzuur via carbonylatie van methanol
No full textDocument uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
From quantified self to quantified neighbourhood
No full textIndustrial DesignIndustrial Design Engineerin
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