81 research outputs found
Letter to the editor RE: The association between high oral intake of acrylamide and risk of breast cancer: An updated systematic review and meta-analysis
No full textHogervorst, J (corresponding author), Hasselt Univ, Ctr Environm Sci, B-3590 Diepenbeek, Belgium.
[email protected]
Comparative study of the modulated structures in Rb2ZnBr4 and in related compounds
No full textApplied Science
Design, Fabrication and Characterization of a MEMS Thermal Displacement Sensor
No full textThis thesis is a part of the CLEMPS (Closed Loop Embedded MEMS-based Precision Stage) project. Within this project a MEMS-stage should be positioned using a feedback (displacement) signal with 10-nm accuracy over a 100 ?m range. This thesis investigates if thermal sensing can be used as a reliable sensing mechanism within the CLEMPS project. Lantz et al demonstrated a promising thermal displacement sensor that achieves nanometre resolution on a 100 ?m range [1]. Using this sensor as a basis, five conceptual designs for thermal displacement sensors are introduced, of which one concept operates in vacuum and four concepts operate in a normal environment. Basic analysis showed that each conceptual design is feasible, except for thermal sensing in vacuum. The designs have large variety in fabrication complexity and estimated performance. The behaviour of the sensors is strongly nonlinear due to dependencies of the material properties on temperature. Different thermo electrical models are introduced that quantify the performance of the designs. Those models are used to gain extensive insight in the behaviour of the sensors and to provide comparison between the performances of the different sensor designs. The models are also applied as design tool for investigating the influence of geometric variations on the sensing performance. Only two of the designs are compatible with the available SOI-wafer based processing. These sensor designs were actually fabricated and integrated within an actuated MEMS stage. For experimental evaluation of the general feasibility of thermal displacement sensing, the thesis focuses on the simplest design. An electronic measurement circuit is designed and fabricated that provides the actuator voltages and performs the differential current-to-voltage amplification for the measurement signal. The mechanical behaviour of the stage is experimentally characterized to determine the relation between the actuator voltage and stage displacement. Now, the (quasi-) static measurement performance of the fabricated sensor can be experimentally characterized by actuating the stage at a low frequency, while recording the applied actuator voltage, the resulting individual heater currents and the differential measurement current in xPC. This data is analysed to obtain the sensor performance in terms of offset, sensitivity, nonlinearity, noise and power consumption. The static measurements are repeated on many sensors to investigate the repeatability and influence of geometric variations. The influence of varying conditions in terms of heater supply voltage, environmental temperature and humidity is determined by performing many characterizations on one device using controlled measurement conditions. Also, the dynamic performance is evaluated in terms of sensor drift, frequency behaviour and hysteresis of the device by using supplementary measurements The feasibility of thermal displacement sensing within the CLEMPS is evaluated using the results on the sensor performance for design IV. Using acquired insight, the performance limiting effects are identified and recommendations for improvements are presented.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin
Design of low-voltage low-power CMOS operational amplifier cells
No full textElectrical Engineering, Mathematics and Computer Scienc
Productontwerp Electrisch geleidende lijm
No full textHet doel van dit productontwerp is het vervangen van de tot nu toe gebruikte electrisch geleidende lijmen, die bestaan uit een uithardende epoxymatrix, gevuld met zilverdeeltjes. Het ontwerp voor de electrisch geleidende lijm omvat twee aspecten: ten eerste het ontwerpen van een thermoplastisch verwerkbare, lijmende matrix en ten tweede gebruik van een intrinsiek geleidend polymeer als vulstof. De matrix van de door ons ontworpen lijm is een polyesterurethaan met een verwerkingstemperatuur van 139 °C. Deze is gevuld met 20 vol% polyanilinedeeltjes. De toepasbaarheid van de lijm is door de relatief lage geleidbaarheid van 5 (S/cm) beperkt. Gedeeltelijke vervanging van zilver door polyaniline biedt perspectieven als in de geleidbaarheid een synergetisch effect optreedt.Applied Science
Healthy lifestyles to prevent dementia and reduce dementia symptoms
No full text
Purpose
Dementia is a growing problem worldwide, due to an ageing population. It has significant human and economic costs. There is no effective medical treatment. The paper aims to discuss these issues.
Design/methodology/approach
Using earlier reviews, the author discussed the difference between dementia and cognitive ageing and the different types of dementia, in terms of manifestation and pathology. The author reviewed non-modifiable risk factors for dementia, such as age, gender, genetics and education. Education can possibly have lifelong protective effects, as it may promote cognitive reserve. This paper focussed on lifestyle interventions to further increase brain reserve capacity. Findings from earlier reviews were summarised to provide guidelines for policymakers and practioners.
Findings
The reviews suggested that most nutritional approaches may have limited effectiveness, and should be implemented in midlife, before dementia symptoms are present and probably only in people who are actually nutritionally deficient. The author found a reasonable positive evidence base of engagement in cognitive and physical activities to prevent dementia, which may also help reduce symptoms of dementia.
Practical implications
From the studies reviewed, it was suggested that keeping physically and mentally active may help in all stages of life to prevent, but also reduce dementia symptoms. A focus on nutrition and treating heart disease risk factors is possibly limited to midlife, or before dementia symptoms are present.
Originality/value
The author used an evidence based approach to review which lifestyle interventions could help prevent dementia or reduce dementia symptoms. The main outcome of this paper was that stage of life and ability (dementia present or not) may interact with success of the intervention.
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Bifurcations of closed orbits in singlet helium Stark spectra
No full textWe measured constant-scaled-energy M ϭ0 spectra of helium Rydberg atoms (nϭ55 to 80͒ in an electric field, allowing for a test of closed-orbit theory under conditions where bifurcations from the uphill and downhill orbits are important. Recent advances in the theory ͑uniform approximation͒ were implemented for a comparison with experimental data. The observed recurrence spectra could be explained in detail as far as the actions of all hydrogenic orbits and the intensities of most recurrences are concerned. Additional peaks in the recurrence spectra that correspond to orbits with an action equal to the sum of two hydrogenic orbits were attributed to scattering at the He ϩ core. This was confirmed in a closed-orbit calculation including the quantum defects in helium. Small changes in the recurrence strength of the hydrogenic orbits were found both in experimental recurrence spectra and in the closed-orbit calculation for helium, and could be ascribed to the effect of core shadowing
A Neutrally Stable Quasi-Compliant Spherical Joint With a Remote Center of Rotation
No full textThis thesis presents the design of a quasi-compliant spherical joint which is neutrally stable in two DoF and has a remote center of rotation. Such a joint can be used, for example, as an exoskeleton's shoulder joint. The foundation of this joint design lies in previous work that has succeeded in designing a compliant spherical joint with a remote center of rotation, but without neutral stability. The existing joint is simulated and its energy properties are analysed. Thereafter it is adapted and optimized for an axi-symmetrical energy field. A spring is introduced to the joint and optimized such that the combined energy field of both spring and joint, is neutrally stable. Experimental verification of the simulation was achieved with a prototype for which a moment reduction of 83.69% was achieved through the addition of the spring
The effect of social identities on the opinion dynamics of nuclear energy: Exploring the emergence of public opinion patterns regarding nuclear energy
No full textThis research focuses on public attitudes toward nuclear energy in the context of reaching consensus on energy solutions for climate action. Using the Social Identity Approach, it analyzes how social groups shape opinions, with a spotlight on Germany and France. Political affiliation, age, socio-economic status, and gender are key identity factors. The study employs an agent-based model, revealing that discussing nuclear energy within multiple identity contexts promotes consensus and depolarization. The findings underscore the significance of social identities and context in shaping opinions, transcending the nuclear energy discourse to advocate for inclusive discussions in decision-making processes. Future research can delve into social influence, ongoing debates, and additional factors to comprehensively understand nuclear energy attitudes.https://github.com/nhogervorst13/thesis Nuclear energy opinion dynamics modelComplex Systems Engineering and Management (CoSEM
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