Achtergrond: Cognitieve klachten komen in alle leeftijdsgroepen voor, maar het is nog onduidelijk hoe deze subjectieve cognitieve klachten samenhangen met objectieve cognitieve prestatie. Deze...Show moreAchtergrond: Cognitieve klachten komen in alle leeftijdsgroepen voor, maar het is nog onduidelijk hoe deze subjectieve cognitieve klachten samenhangen met objectieve cognitieve prestatie. Deze studie onderzocht de relatie tussen subjectieve cognitieve klachten, leeftijd en werkgeheugenprestatie bij volwassenen. Doel: Het doel van dit onderzoek was om een beter begrip te krijgen van de relatie tussen subjectieve en objectieve cognitie bij verschillende leeftijdsgroepen. Methode: Deelnemers (N = 134) variërend in leeftijd van 18 tot 67 jaar voltooiden online de Cognitive Failure Questionnaire en de Operation Span Task om subjectieve en objectieve cognitie te meten. Resultaten: De resultaten toonden aan dat er geen verband is tussen subjectieve en objectieve cognitie (β = -.013, p = .892) en dat leeftijd geen modererend effect heeft op deze relatie (β = .011, p = .206). Leeftijd bleek ook geen significante voorspeller van werkgeheugenprestatie (β = -.057, p = .510). Bovendien werd een lineaire relatie gevonden tussen leeftijd en subjectieve cognitieve klachten, waarbij deze klachten afnemen naarmate de leeftijd toeneemt. Discussie: De bevindingen dragen bij aan ons begrip van cognitie en benadrukken de noodzaak om zowel subjectieve als objectieve metingen voor cognitie in onderzoek te gebruiken.Show less
Abstract Working memory performance declines naturally in people as they get older. However, much variation exists between people in the degree to which their working memory deteriorates. Knowing...Show moreAbstract Working memory performance declines naturally in people as they get older. However, much variation exists between people in the degree to which their working memory deteriorates. Knowing the risk-factors associated with higher or lower working memory performance could help mitigate some of the negative effects that are experienced by people as such. There are many known predictors for lower working memory performance identified by the literature, such as age, education, cigarette smoking, alcohol consumption, and history of concussion. The aim of this study is to investigate the relationship of these predictors with working memory performance to identify which of these variables most strongly predict performance on a working memory test. Identifying the most prominent risk-factors associated with lower working memory performance can aid the development of specific tools and treatments for counteracting working memory deterioration as people get older. We included 132 subjects from the general population and measured working memory performance using a computerized OSPAN test. The predictors were measured using different self-report questionnaires, regarding demographics and general health. Linear regression models were then used to test each variable as a predictor of working memory performance. The total sample consisted of 49 males and 83 females with a median age of 44.5, and a mean education level of 4.97 years of education. Our analysis demonstrated that education level was positively associated with working memory performance (p = 0.008, F(1, 129) = 7.23, adjusted R2 = 0.05 ), whereas the other variables did not show a relationship with working memory. This result shows education level to be a significant determiner of higher or lower performance of working memory. However, the small effect size (0.05) makes it difficult to say whether education level makes much difference when generalizing to the general population. Furthermore, the influence of age, alcohol consumption, cigarette smoking, and history of concussion on working memory performance was not confirmed in this sample. The influence of these variables on working memory performance may only appear under different conditions, such as only in older participants or in participants that smoke or drink more frequently.Show less
Objective: Multiple Sclerosis (MS) is a chronic neurological disorder characterized by a wide range of symptoms, of which physical and cognitive impairments are prominent. Cognitive functioning in...Show moreObjective: Multiple Sclerosis (MS) is a chronic neurological disorder characterized by a wide range of symptoms, of which physical and cognitive impairments are prominent. Cognitive functioning in MS has received increasing attention due to its significant impact on quality of life. However, the exact relationship between physical functioning and cognitive functioning in people with MS (PwMS) remains insufficiently understood. This study aimed to explore the predictive value of physical outcome measures on cognitive functioning. Furthermore, the influence of disease severity and anxiety and depression on the relationship between physical outcome measures and cognitive functioning is explored. Methods: Conducted as part of the ‘Don’t be late!’ project, this study included 23 PwMS (Mean age = 46.63, SD = 11.13; 60.9 % female). Physical functioning was assessed using balance, walking speed, grip strength, dexterity and endurance. Furthermore, cognitive functioning was assessed using the Minimal Assessment of Cognitive Functions in MS and disease severity and anxiety and depression were measured using the Expanded Disability Status Scale and the Hospital Anxiety and Depression Scale, respectively. Multiple regression analyses were performed to determine the predictive value of physical functioning on cognitive functioning. Mediation analyses were performed with disease severity and anxiety and depression as mediating factors. Results: No significant model for the predictive value of physical outcome measures on cognitive functioning was found (p = .117). Furthermore, the study found no significant mediating effects of disease severity (p = .979) or anxiety and depression (p = .633) on this relationship. Due to missing values on the Paced Auditory Serial Addition Test (PASAT), a post-hoc analysis was conducted. Significant effects were found for the predictive value of balance (p = .016), dexterity (p = .045) and walking speed (p = .008) on cognitive functioning. Conclusion: The study identified significant links between balance, dexterity, walking speed, and cognitive functioning in PwMS. It faced limitations including a small sample size and its cross-sectional nature. Despite these limitations, this study suggests that the interplay between physical and cognitive domains in MS is multifaceted and warrants more nuance investigation.Show less
Cognitieve vaardigheden zijn essentieel voor iemands dagelijks functioneren en voor iemands welzijn. Het is bekend dat stress zorgt voor een verslechtering van de cognitieve functies, in het...Show moreCognitieve vaardigheden zijn essentieel voor iemands dagelijks functioneren en voor iemands welzijn. Het is bekend dat stress zorgt voor een verslechtering van de cognitieve functies, in het bijzonder het geheugen en het executief functioneren. Hoewel informatie verwerkingssnelheid valt onder de cognitieve vaardigheden, ontbreekt literatuur die expliciet gaat over de invloed van stress op de verwerkingssnelheid. In deze studie wordt daarom de vraag behandeld wat het verband is tussen stress en informatie verwerkingssnelheid bij volwassenen. In de huidige studie zijn 25 deelnemers onderzocht (M = 33.24 jaar, SD = 16.03; 14 vrouwen, 11 mannen) in het kader van het bachelor-project. De deelnemers hebben de ‘Perceived Stress Scale’ ingevuld om stress te meten en de ‘Symbol Digit Modalities Test’ voltooid om informatie verwerkingssnelheid te bepalen. Naast de hoofdvraag is er ook gekeken of er verschillen zijn tussen jongeren en ouderen, tussen vrouwen en mannen, en tussen gestreste en niet-gestreste deelnemers als het gaat om de relatie tussen stress en informatieverwerkingssnelheid. Correlatieanalyses hebben geen verband gevonden tussen stress en informatie verwerkingssnelheid of verschillen in dit verband tussen de verschillende groepen (p > 0.05). Mogelijke verklaringen voor deze niet-significante resultaten kunnen te maken hebben met lage stressniveaus, het niet meten van acute versus chronische stress en een te kleine steekproef. Toekomstig onderzoek kan zich daarom richten op een grotere en diverse steekproef, en het gebruik van experimentele opzet, waarbij bijvoorbeeld stressniveaus in een laboratorium gemanipuleerd kunnen worden.Show less
Psychological resilience and cognitive functioning have both been studied in their relationship with quality of life in patients, yet, only a few studies have assessed their relationship in the...Show morePsychological resilience and cognitive functioning have both been studied in their relationship with quality of life in patients, yet, only a few studies have assessed their relationship in the working healthy adult population. As such, this study investigated the relationship between resilience and cognitive functioning in employed healthy adults. Resilience was measured using the 10-item Connor-Davidson Resilience Scale (CD-RISC-10), while objective cognitive functioning was measured by means of a composite score combining information on information processing speed (Symbol digit modalities test), verbal memory (California Verbal Learning Test-II), and visuo-spatial memory (Spatial recall test). In total, 30 participants aged were included in this study, of which 16 were female (53.3%) and 14 were male (46.7%). The age of the participants ranged between 19 and 59 years old. No significant correlation between resilience and cognitive functioning was found (N = 24, τ = .196 p = .193). A post-hoc analysis showed that there was a positive relationship present between resilience and cognitive functioning, when the correlation was calculated for females only (N = 14, r = .719, p = .004). No such relationship was found when the correlation was calculated for males only. It is recommended that future research investigates whether there are indeed differences between sexes on the relationship between psychological resilience and cognitive functioning, like the one reported here. In addition, this study encourages the further analysis of resilience and its relationship with cognition as well as its subdomains in healthy adults, to get a clearer picture if and how the two are related to one another, so that health programs could make potential use of psychological resilience, as to improve a person’s overall quality of life.Show less
Current imaging is crucial to condensed matter physics, materials research and industry. State-of-the-art current imaging setups revolve around SQUID-on-tip (SOT) probes, that scan over a sample to...Show moreCurrent imaging is crucial to condensed matter physics, materials research and industry. State-of-the-art current imaging setups revolve around SQUID-on-tip (SOT) probes, that scan over a sample to locally measure magnetic fields and temperature. The resolution of such systems is presently limited by the lack of a robust method to control the probe-sample distance. In this thesis, we develop probes for hybrid microscopy that combine SOT with STM. We theoretically investigate interesting systems, and find that our approach would considerably improve on past magnetic investigations of vortex matter. We use focused-ion-beam milling to fabricate SOT probes on top of a commercial AFM-cantilever, and show these to be very sensitive to changes in applied magnetic field and temperature. We develop a novel readout scheme to simultaneously measure a magnetic and a tunneling signal. We present a proof-of-concept STMSOT probe that displays magnetic sensitivity inside a cryogenic STM setup, and use it as an STM probe to see the topography of a NbSe$_2$ crystal. Our approach will culminate in the development of a STMSOT setup in the near future.Show less
In order to curb the growing energy demand and environmental impact of data centers, breakthrough technologies bringing increased energy efficiency are required. Superconducting computing promises...Show moreIn order to curb the growing energy demand and environmental impact of data centers, breakthrough technologies bringing increased energy efficiency are required. Superconducting computing promises massive energy savings through near-dissipationless operation. So far, multiple designs for superconducting memory are proposed, but none meets all requirements for an implementable device. To this end, we propose a novel design of superconducting memory (SCM) device, using two stable magnetic spin textures in a single-layer elliptical SFS Josephson junction. We observe a change in critical current between the two states by a factor of five at remanence. Using a novel technique to quantify the effects of stray fields using micromagnetic simulations, we conclude that the shift in critical current is caused by a large contrast in stray field strength between the two magnetic states. Furthermore, we verify that the switching process is deterministic and unambiguous during read-out. Future pathways to scale up this memory device are proposed.Show less
SQUIDs, or Superconducting QUantum Interference Devices, are some of the most sensitive types of magnetometers known to date. The production of SQUIDs, which is typically a multi-step lithographic...Show moreSQUIDs, or Superconducting QUantum Interference Devices, are some of the most sensitive types of magnetometers known to date. The production of SQUIDs, which is typically a multi-step lithographic process, has limited the application of SQUIDs in non-planar and fragile systems. Recently, it was demonstrated that SQUIDs can be printed using a direct-write technique known as Electron Beam Induced Deposition (EBID), as was shown by van den Berg. The SQUIDs produced by van den Berg are a proof of principle, however, such SQUID devices are not yet suitable for real magnetometry measurements. This thesis aims to develop miniaturised EBID SQUIDs, where the flux can be electrically tuned. Hence, the SQUIDs can perform magnetometry measurements in real applications.Show less
One of the largest challenges in creating spin-driven electronic devices is manipulating the spin texture of a sample using a current, rather than a magnetic field. La0.7Sr0.3MnO3 (LSMO) nanowires...Show moreOne of the largest challenges in creating spin-driven electronic devices is manipulating the spin texture of a sample using a current, rather than a magnetic field. La0.7Sr0.3MnO3 (LSMO) nanowires are of particular interest for creating such devices, because they allow for the creation of currents carrying a net spin due to the spin-polarised nature of LSMO. If two regions of opposite magnetisation, separated by a domain wall, are created in such a nanowire, it should be possible to move said domain wall using a spin-polarised current. In this thesis, a candidate geometry for a LSMO nanowire that allows for the creation of a domain wall and subsequent manipulation by current of that domain wall is determined using micromagnetic simulations. Different geometries and strain axes were investigated using field sweeps. Both a transverse and a vortex domain wall were identified from these field sweeps and were then tested by applying current. It was determined that a continuous current density applied along the easy axis of the nanowire with a 20 nm thickness to a vortex domain wall, with a 7 mT external field along the same axis resulted in the domain wall being pushed past the notch. If reproduced experimentally, this would bring us one step closer to creating magnetic spin-based logic and storage devices.Show less
Focused electron-beam induced deposition (FEBID) is a non-destructive, relatively fast and cheap method with applications in AFM, plasmonics and nanomagnetics amongst others. In this thesis, three...Show moreFocused electron-beam induced deposition (FEBID) is a non-destructive, relatively fast and cheap method with applications in AFM, plasmonics and nanomagnetics amongst others. In this thesis, three dimensional superconducting arches were fabricated using this technique with the help of a computer aided design (CAD) program. Magnetic field sweeps were performed at low temperatures (∼2-5 K) to characterize these arches. With a few improvements, more complex 3D structures can be fabricated, paving the way towards the numerous applications people now can only dream of.Show less
Superconducting QUantum Interference Devices (SQUIDs) play a central role in numerous applications, ranging from cancer treatment to magnetic imaging of nanoparticles. Conventional fabrication...Show moreSuperconducting QUantum Interference Devices (SQUIDs) play a central role in numerous applications, ranging from cancer treatment to magnetic imaging of nanoparticles. Conventional fabrication methods revolve around a multi-step lithography process that encompasses etching, heating, chemical cleansing and coating, thereby limiting these techniques in practice. In this thesis we present a non-destructive alternative approach that does not entail pre- or post processing, namely, a direct-write printed SQUID patterned under 20 minutes using Focus Electron Beam Induced Deposition (FEBID). The Josephson behaviour of these devices is confirmed by performing out-of-plane magnetic field sweeps and measuring the corresponding oscillations in critical current. Our endeavours pave the way for printing sophisticated quantum systems and three dimensional superconducting sensors.Show less
The family of rare-earth nickelates (RNiO3. R = La, Pr, ..., Lu) show a sharp metal-insulator transition from a paramagnetic metal to an anti-ferromagnetic insulator. The only exception is LaNiO3...Show moreThe family of rare-earth nickelates (RNiO3. R = La, Pr, ..., Lu) show a sharp metal-insulator transition from a paramagnetic metal to an anti-ferromagnetic insulator. The only exception is LaNiO3 which is a paramagnetic metal even at low temperatures. Thin films of LaNiO3 do show a metal-insulator transition when reducing the film thickness to only a few unit cells. In this study we track the electronic structure of (001) oriented LaNiO3 thin films as they go from a metallic to an insulating state. We observe this transition occurring at a thickness of 4 unit cells. The very high resolution of our ARPES set-up allows us to resolve the inelastic mean free path changing with film thickness. We find that the mean free path mimics the reported resistivity behaviour. We also find a pseudogap opening in the insulating state.Show less
The search for topological insulators has intensified over the last couple of years. One of the candidates theorized to be a topological insulator are bilayers of bismuthene, the bismuth analogue...Show moreThe search for topological insulators has intensified over the last couple of years. One of the candidates theorized to be a topological insulator are bilayers of bismuthene, the bismuth analogue of graphene. During the bachelor project, multiple thin films of Bismuth were grown and their quality under the influence of underlying substrates of NaCl(001) and BaF2(111) has been investigated. Growth was achieved in a high vacuum Thermal Evaporator. The topography of substrates and grown films were analyzed using Atomic Force Microscopy. A large part of the project was focused on restoring a UHV system in which thin films could be grown and analyzed. This system will help improve the quality of the films and therefore improves the chances of producing a sufficiently large sample for electronic measurements. The cleaved barium-fluoride produces ultra-flat plateaus optimal for growth. The grains grown on the barium-fluoride substrates were larger in two-dimensional sizes than the grains grown on sodium-chloride. Further research is required to obtain the crystalline configuration of these grains.Show less
