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Visual quantification of motor function during awake brain surgery: Towards a Neuro Research Operating Room
No full textDuring a brain tumour resection, a neurosurgeon is constantly navigating a delicate balance between resecting as much of the tumour as possible, while avoiding any damage to healthy brain tissue. This challenge is particularly difficult when the tumour is located in a critical functional area, involved in for example language or motor function. For these types of tumours, the awake craniotomy was developed. During this surgery the patient wakes up to perform language and motor tasks, to enable the surgeon to localize these functions inside the brain. In this thesis, we investigate and develop a new quantitative method to monitoring motor function that could potentially improve intraoperative decision making and enables neuroscientific and neurosurgical research. Chapter 1 provides a background about surgical strategies and technologies that have been developed to aid surgeons’ decisions during complex brain tumour resections. We will explain the complexity of robust research in the neurosurgical environment and the need for a dedicated Research Operating Room to create an environment to improve neurosurgical and neuroscientific research. In Chapter 2 we make an overview of the possible solutions to quantify motor function before, during and after awake craniotomies and discuss the best solution for the Erasmus MC. In Chapter 3 we present a new frame to create a standardized environment inside the operating room for good quality data collection of patient functionality. To design this frame, we identified and interviewed all the important stakeholders and designed three prototypes. The two most promising prototypes were developed. The final prototype was implemented during three awake craniotomies.This newly developed frame was used in Chapter 4 to explore video tracking as a new tool to quantify hand motor function. Three patients were followed one day prior to the surgery, during the awake craniotomy, and one day postoperatively. During these three cases, we identified several prerequisites for a reliable recording set-up and explored the potential to detect clinically relevant events during fingertapping and direct electrical stimulation (DES). This showed promising results and underscores the potential for video tracking to be further investigated for quantification of hand motor function.In Chapter 5 we put the discussed work into context, discussing it’s clinical and scientific relevance and future perspectives. In this thesis, we have demonstrated that it is possible to implement a new quantitative measurement method to monitor hand function in the challenging environment of an operating room. Quantification of visual observations has shown to be low-cost, easily available and implementable in clinical context, because of the fast technological advancements in this field. Video tracking can be used for future research to investigate the relation between intraoperative findings and long-term outcomes, and has the potential to add valuable information for neurosurgical and neuroscientific research.TM30004; 35 ECTSTechnical Medicin
A cable-based parallel mechanism for increasing shear stiffness
No full textTo transfer motion, compliant mechanisms are commonly used. Compliant mechanisms are preferred over rigid body mechanisms for their properties like low friction, no need for lubrication, and no backlash. While having good properties, compliant mechanisms also come with certain disadvantages like limited range of motion and the occurrence of stress concentrations on deflecting segments. Another disadvantage is the presence of axis-drift, which is parasitic motion where the center of rotation shifts when deforming. Axis-drift can be prevented by increasing the stiffness in-plane with the center of rotation. This can be achieved with a parallel mechanism. This thesis presents a cable-based parallel mechanism, inspired from tensegrity, that can be used in combination with a revolute or universal joint to increase shear stiffness, while also allowing for rotation. During this thesis, the parallel cable mechanism was intended to increase the shear stiffness of the closed form pressure balanced joint. 2D and 3D analytical design models were made for the cable mechanism to obtain design parameters and determine the reaction force behaviour. The analytical design models were validated with finite element models (FEM) and an experimental setup. The 2D analytical design model was used to determine the reaction force behaviour of the cable mechanism when a shear-displacement was applied, while the 3D design model covers a combined shear-compression case.From the experimental validation of the 2D design model, the shear stiffness of the cable mechanism fell below the prediction of the analytical design model but improved the shear stiffness of the closed cell by a factor of at least thirty. The experimental validation of the 3D design model consisted of two cases: full compression and a shear combined with compression. In full compression, the cable mechanism increased the axial stiffness of the closed cell slightly. The increase of the axial stiffness of the closed cell due to the cable mechanism was expected to be zero from the design model. From the experimental validation of the 3D design model in combined shear and compression, while increasing the stiffness of the closed cell, the cable mechanism increased the stiffness less than what was predicted. It was also meant that the cable mechanism does not provide any rotation stiffness to the closed cell, this was proven not to be the case.Mechanical Engineerin
Drying of silty soil treated with superabsorbent hydrogels: Retention behaviour and cracking
No full textDesiccation cracks in soils pose risks to the serviceability and safety of geotechnical infrastructure worldwide. This paper aims to investigate the potential of superabsorbent hydrogels (SAH) as innovative soil amendment to mitigate soil drying effects and cracking. Laboratory tests were conducted on an initially saturated silty soil treated with different types and dosages of SAH. Desiccation cracking tests, shrinkage tests, and water retention tests were performed to analyse the cracking process, evaporation rate, and retention properties. The tests were integrated with micro-CT scan analyses to observe changes in soil fabric due to the SAH addition. The results indicate that SAH particles serve as internal water reservoirs, extending the normal shrinkage stage and maintaining higher suctions without significant desaturation, in comparison to untreated soil. The addition of SAH reduces the evaporation rate, particularly at a dosage of 0.1%. The progression of cracking occurs at suctions below the air entry value, and the inclusion of SAH reduces the rate of crack development. These findings highlight the need for additional research on SAH as a promising soil treatment for geotechnical applications.Geo-engineerin
Bistable Interlocking Mechanism in SHCC-to-SHCC Interfaces: An Experimental Study
No full textThe current structural demands include complex designs, efficient utilization of material resources, and maintenance of existing structures and infrastructure. In all these cases, the connections between structural components are the main focus of design since they are widely considered the weakest link in a structural system. The demand for strong and durable connections with cementitious materials is higher than ever. Creating reliable connections is largely connected to material reuse, waste reduction, ease of disassembly, and the ability to extend the life cycle of structures. These principles contribute to a more sustainable approach to construction.Recent research shows that by implementing intricate interlocking geometries, toughness can be added to inherently brittle materials like ceramics or polymers. With the concept of "toughness by segmentation," new metamaterials emerge with enhanced properties compared to the monolithic material they are made of. In this study, the focus is on bistable interlock, a new type of connection. Inspired by nature, the connection is based on double-radii morphologies that geometrically lock into two equilibrium positions under tensile load, exhibiting two distinctive peaks in their force-displacement diagram. When the bistable interlock mechanism was applied to Acrylonitrile Butadiene Styrene (ABS), a relatively brittle yet strong polymer, the sutured material was up to 10 times tougher than monolithic ABS. The focus of this research is to manufacture the bistable interlock mechanism with cement-based materials and specifically, Strain Hardening Cementitious Composite (SHCC). SHCC belongs to the category of fiber-reinforced concrete and is distinguished by its tensile hardening behavior and pseudo-ductility stemming from its fiber-bridging property. Combined with the geometrical hardening of bistable interlock, the ultimate goal is to create resilient connections that balance toughness and strength.The performed literature study was focused on three areas: the bistable interlock mechanism, interfacial load transfer mechanisms in concrete-to-concrete interfaces such as friction, chemical bond, and mechanical interlock, and the material and mechanical properties of Strain-Hardening Cementitious Composites (SHCC).Two main areas of interest were the objects of the experimental study. The first was to understand the tensile behavior of bistable interlocks, and the second was to optimize it by appropriately tailoring the interface and geometry. The design of the experiments featured three parameters: the key shape (straight & curved keys), the interface treatment (untreated & lubricated interface between the two parts), and the geometry (based on width-to-height ratios for straight keys & radii ratios for curved keys). From the experimental results, it was found that the shape of the keys changed the tensile response of the specimens greatly. The influence was different for untreated and lubricated interface specimens. For the untreated specimens, the complex shape of the bistable interlocked geometry combined with interface adhesion led to 78% of the untreated specimens rupturing at the interface. Only 44% of the straight keys showed failure under the same conditions. In this application of bistable interlock, no benefits of geometrical hardening could be exploited due to the strong adhesive bond causing premature failure of the keys at the interface. For the lubricated specimens, shifting from straight to curved geometry brought simultaneous increases in force and energy (i.e. defined as the area under the force-displacement diagram) for all the specimens, fully exploiting the benefits of the frictional contact of the bistable interlock mechanism. The increase in force documented ranged from 41-62% and in energy from 9–96%.The aforementioned difference in tensile response highlights that the interface treatment is a governing parameter. Only 56 and 22% of untreated straight and curved specimens fully delaminated (e.g. instead of breaking) in comparison to 89% of their lubricated equivalents. The rest of the specimens exhibited (localized) SHCC failure due to the strong interface bond. Untreated specimens showed a higher resistance force (approximately 20% for straight and 10% for curved keys) but a more brittle response, resembling a monolithic connection, while lubricated specimens showed less resistance to tension, resembling a sliding connection. This trend is consistent with broader findings in the literature: inherently brittle monolithic materials compared to their architectured counterparts exhibit greater strength but lower toughness. For the straight keys, lubrication made the failure mode more uniform but decreased the strength and energy. The strong bond of untreated specimens, accompanied by a hardening response due to fiber activation against torsion and/or bending, was responsible for this result. Specimen imperfections caused this state of combined loading. Curved lubricated keys showed an enhancement in energy absorption (i.e. area under the force-displacement diagram) due to the exploitation of the bistable interlocks. Special curved keys made of assembled parts were investigated, simulating a precast-to-precast connection. The assembled keys did not outperform the lubricated and untreated curved keys in terms of strength and energy absorbed. Their benefits lie in two areas: they were easier to manufacture, and they attained a larger second peak than the first in the force-displacement diagram. This characteristic is beneficial for the mechanical stability of the system.To optimize the response, the specific geometry of the specimens was analyzed (w/h and 𝑅1/𝑅2). The influence of the geometry on the tensile response was not as prominent as the interface treatment. However, improvements were noticed when increasing geometry parameters. For untreated and lubricated straight keys, increasing the length led to a proportional increase in absorbed energy but not in strength. For the curved untreated specimens, the increase in geometry yielded no major differences since the interface treatment governed the response. Conversely, for the lubricated specimens, with a geometry increase, the response was enhanced in both strength and energy and eventually, a design threshold at 𝑅1/𝑅2 = 1.10 was noticed. A clear trend of an increase in the first peak, and a decrease in the second peak as the geometry increased, existed. Extensive cracking and loss of stiffness after the second equilibrium position due to the geometrical interference of larger keys were responsible for that.Overall, the architectured SHCC material, straight or curved, attained 1/3 of the strength of the monolithic SHCC. This was even lower for lubricated keys. When it came to energy absorption, the lubricated curved keys with bistable interlocks performed better, reaching up to 75% of the SHCC’s energy. This is contrary to the literature findings, where bistable interlocked materials made of ABS were tougher than monolithic ABS. In the case of SHCC, the material properties were different. Due to the extensive cracking of the key, reduced frictional contact occurred, and reduced energy was absorbed. However, a beneficial characteristic of the architectured SHCC keys was their sustained resistance to tension at higher strain levels. That makes them beneficial for many engineering applications where energy absorption and resistance to impact loads and thermal and/or hygral effects are prioritized. Another benefit exists in the customization of their tensile response by fine-tuning geometrical parameters. For a radii ratio of 1.10 in bistable interlocked keys, a satisfactory balance of strength and toughness was achieved, showing that with appropriate design, the connections have promising results.Civil Engineering | Structural Engineering | Concrete Structure
Contested port cities: Logistical frictions and civic mobilization in Genoa and Venice
No full textThis article examines the increasingly conflictual relationship between ports and their surrounding communities at a time of wide-reaching infrastructural expansion. It highlights how the centralization of power and logistical gigantism produce deterritorializing frictions, decoupling inhabitants from their territories and creating the conditions for social contestation. It calls for a rethinking of the role of communities in contemporary port-city governance, with an emphasis on imaginaries of re-territorialization produced through social mobilization. I frame the increasing contestation in port cities through a critical approach to logistics, arguing that citizen engagement holds the potential to drastically readdress the port-city relationship. It examines the cases of Genoa and Venice using ethnographic methods and reconstructs a historically in-depth counter-narrative of interactions between port, city and citizen. I contextualize specific frictions between port and city through the rise in social mobilizations. The article shows how social mobilization challenges the status quo in different ways, producing changes and illuminating pathways toward more sustainable forms of coexistence between ports and cities.History, Form & Aesthetic
Profiling university students based on their acoustical and psychosocial preferences and characteristics of their home study places
No full textUnderstanding students' preferences of their study place, in particular acoustical and psychosocial preferences, is important to students' health and comfort. This study aimed to identify clusters of students with similar acoustical and psychosocial preferences, and to identify reasons for certain preferences of students in each cluster. A mixed-methods approach was applied, consisting of a questionnaire, which was completed by 451 bachelor students, and a field study conducted with 23 students from the same sample. The questionnaire data included among others acoustical and psychosocial preferences scores, while the field study data comprised interview transcripts, building checklists, and sound pressure level measurements. The questionnaire data were analysed using TwoStep cluster analysis to identify clusters of students based on their acoustical and psychosocial preferences. This produced five clusters of students that significantly differed in 14 variables, including preferences and perception of indoor environmental quality (e.g., noise from outside). Then, the field study data were analysed and categorised based on the five clusters of the students. The outcome explained the aspects associated with the acoustical preferences of students in each cluster. Building-related indicators such as the location of the building were found as an aspect that could affect the student's acoustical preferences. This study provides insight into the profiles of students based on their acoustical and psychosocial preferences, which are important for their health and comfort at their study places.Environmental & Climate Desig
4D printed shape-shifting biomaterials for tissue engineering and regenerative medicine applications
No full textThe existing 3D printing methods exhibit certain fabrication-dependent limitations for printing curved constructs that are relevant for many tissues. Four-dimensional (4D) printing is an emerging technology that is expected to revolutionize the field of tissue engineering and regenerative medicine (TERM). 4D printing is based on 3D printing, featuring the introduction of time as the fourth dimension, in which there is a transition from a 3D printed scaffold to a new, distinct, and stable state, upon the application of one or more stimuli. Here, we present an overview of the current developments of the 4D printing technology for TERM, with a focus on approaches to achieve temporal changes of the shape of the printed constructs that would enable biofabrication of highly complex structures. To this aim, the printing methods, types of stimuli, shape-shifting mechanisms, and cell-incorporation strategies are critically reviewed. Furthermore, the challenges of this very recent biofabrication technology as well as the future research directions are discussed. Our findings show that the most common printing methods so far are stereolithography (SLA) and extrusion bioprinting, followed by fused deposition modelling, while the shape-shifting mechanisms used for TERM applications are shape-memory and differential swelling for 4D printing and 4D bioprinting, respectively. For shape-memory mechanism, there is a high prevalence of synthetic materials, such as polylactic acid (PLA), poly(glycerol dodecanoate) acrylate (PGDA), or polyurethanes. On the other hand, different acrylate combinations of alginate, hyaluronan, or gelatin have been used for differential swelling-based 4D transformations. TERM applications include bone, vascular, and cardiac tissues as the main target of the 4D (bio)printing technology. The field has great potential for further development by considering the combination of multiple stimuli, the use of a wider range of 4D techniques, and the implementation of computational-assisted strategies.Biomaterials & Tissue Biomechanic
Incorporating Safety-II in future gas systems
No full textThis article studies safety management in future gas systems. It is structured around the compatibility of its technological and institutional coordination. We identify how the current mode of safety management is not in harmony with increasingly complex technological and institutional arrangements, and combine safety science with institutional analysis to improve safety management. For our case study of biogas quality monitoring in the Netherlands, we offer structured recommendations for the reallocation of monitoring and enforcement mechanisms based on Safety-II. This article provides insights for users of gas systems and other infrastructures alike, and it offers safety scholars an approach to safety management that incorporates a novel focus on institutions.Economics of Technology and Innovatio
Design and Operation Optimization of Hybrid Energy Systems for a General Cargo Vessel: Well-to-Wake Emission Analysis and Plant Lifetime Estimation
No full textThe Global Shipping industry is responsible for transporting 90% of global commerce and is responsible for 3% of global greenhouse gas (GHG) emissions. Addressing this, the International Maritime Organization (IMO) aims to reduce GHG emissions from international shipping by 40% by 2030 and achieve net zero by 2050. This study explores Low Temperature-Proton Exchange Membrane Fuel Cell (LT-PEMFC) hybrid energy systems as a potential solution to reduce shipping emissions. Emphasizing the operational zero-emission capability of PEMFC fueled by hydrogen, the research scrutinizes the emission intensity from hydrogen production and the impact of component degradation on hybrid system efficiency and hydrogen consumption.The research pivots around optimizing the design and operation of ship hybrid energy systems to minimize costs while considering well-to-wake (WTW) emissions and component lifetime. It investigates two hybrid configurations: PEMFC/Li-ion battery (LIB) and Diesel Generator (DG)/PEMFC/LIB. Employing a Mixed Integer Linear Programming approach for component modeling, the study conducts a two-stage analysis: design optimization considering various hydrogen sources and plant lifetime estimation focusing on PEMFC and battery degradation.Initial findings reveal that system design costs do not significantly differ across hydrogen grades. The DG/PEMFC/LIB configuration emerges as cost-effective, reducing CAPEX by 62.8% compared to the PEMFC/LIB setup. Carbon Capture and Storage (CCS) hydrogen grades strike a balance between cost and emission reduction, notably cutting emissions by up to 85% in the PEMFC/LIB configuration at a 27% OPEX increase.Lifetime estimation highlights the effectiveness of a hierarchical optimization method in mitigating PEMFC voltage loss and extending component lifespan, albeit with increased battery cycling aging. The study underscores the importance of selecting the appropriate hydrogen grade and operational strategies to enhance the sustainability and economic viability of maritime hybrid energy systems, aligning with IMO’s emission reduction goals.Mechanical Engineerin
Autonomic responses to pressure sensitivity of head, face and neck: Heart rate and skin conductance
No full textSubjective scales are frequently used in the design process of head-related products to assess pressure discomfort. Nevertheless, some users lack fundamental cognitive and motor abilities (e.g., paralyzed patients). Therefore, it is vital to find non-verbal measurements of pressure discomfort and pressure pain. This study gathered the autonomic response data (heart rate and skin conductance) of 30 landmarks in head, neck and face from 31 participants experiencing pressure discomfort and pressure pain. The results indicate that pressure stimulation can change heart rate (HR) and skin conductance (SC). SC can be more useful in assessing pressure discomfort than HR for specific landmarks, and SC also possesses a faster arousal rate than HR. Moreover, HR decreased in response to pressure stimulation, while SC decreased followed by an increase. In comparisons between genders, the subjective pressure discomfort threshold (PDT) and pressure pain threshold (PPT) of women were lower than those of men, but men's autonomic responses (HR and SC) were more intense. Furthermore, there was no linear correlation between subjective pressure thresholds (PDT and PPT) and autonomic response intensity. This study has significant implications for resolving ergonomic issues (pressure discomfort and pain) associated with head-related products.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Human-Centered DesignApplied Ergonomics and Desig
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