The purpose of this research is to investigate the performace of a prototype detector for a neutrino telescope built in the Mediterranean Sea. The telescope consists of photomultiplier tubes which...Show moreThe purpose of this research is to investigate the performace of a prototype detector for a neutrino telescope built in the Mediterranean Sea. The telescope consists of photomultiplier tubes which record the position and time stamps of Cherenkov light created by charged particles form e.g. neutrino interactions. This investigation is done to find neutrino sources in the cosmos which could lead to a better understanding of active galactic nuclei, supernova remnants, micro-quasars and gammaray bursts. We used the data of a prototype where most of the signals stem from muons created in atmospheric interactions of cosmic rays. In the first part the properties of the detected signals are being investigated and we look for a lower limit to have a noise free signal when looking for Cherenkov light created by charged particles between multiple digital optical modules. The last part of this project is devoted to calibrating the observed data with the simulated data so that in future experiments it could be seen at which time a particle is detected with nanosecond precision and thus with an angular precision of a tenth of a degree the direction and path of particles could be constructed.Show less
In superconductor-ferromagnet hybrids the opposite-spin singlet Cooper-pairs are transformed to equal-spin triplet correlations. A magnetic non-collinearity at the SF interface is essential for...Show moreIn superconductor-ferromagnet hybrids the opposite-spin singlet Cooper-pairs are transformed to equal-spin triplet correlations. A magnetic non-collinearity at the SF interface is essential for this conversion. This can be achieved in systems where two ferromagnets have a misaligned magnetization with respect to each other. The optimal system for triplet generation is then investigated with the help of micromagnetic simulations. Out of the various systems studied, a disk geometry consisting of nickel and cobalt layers proved to be the most promising. This system was fabricated and subsequently measured. Although the existence of triplet correlations are yet to be verified, a fully proximized junction was observed. In addition, an attempt is made to realise current induced magnetization switching by utilising 100% spin-polarized current from half-metallic CrO2. We expect the required current density to be significantly reduced, thus minimizing the energy dissipation, which is currently the greatest obstacle in fabricating fully functional spintronic devices.Show less
The study of ocular diseases has traditionally been hampered by low SNR and image resolution. Improvements in SNR of ocular images can be achieved by using higher field strength and RF surface...Show moreThe study of ocular diseases has traditionally been hampered by low SNR and image resolution. Improvements in SNR of ocular images can be achieved by using higher field strength and RF surface receive coils specifically designed for proton imaging of the eye. In this project a surface array coil consisting of two orthogonally placed receive-only coils was constructed for proton ocular imaging at 7T. Clear improvements in image quality were achieved in comparison to ocular images acquired using a head coil at 3T, providing a more accurate diagnostic tool.Show less
Dielectric pads have been used successfully to improve the homogeneity of the B1+ field in MRI imaging yet some issues remain in their implementation. The dielectric materials currently used in...Show moreDielectric pads have been used successfully to improve the homogeneity of the B1+ field in MRI imaging yet some issues remain in their implementation. The dielectric materials currently used in dielectric pads have a tendency to drop out of suspension within a few weeks after construction of the pads. The limited space available during neuroimaging prevents the simultaneous utilization of headphones and dielectric pads. In this thesis methods will be examined to improve upon these issues. The aim of this project is to produce dielectric pads that offer optimum B1+ homogeneity improvement as well as longevity and can be integrated in to the sound system of an MRI scanner. The appropriate mixing rule for suspensions of barium titanate, calcium titanate and mixture of barium and calcium titanate will be determined to allow for the production of dielectric pads with a broad range of permittivities. Several materials will be added to the suspension matrix with the aim of improving the stability of the suspension while minimally impacting the permittivity and conductivity of the suspension. The efficacy of pads over a range of permittivities will be examined in simulations as well as the impact of the creation of a hole in the pad, which is needed to integrate the communication system of the MRI scanner.Show less
One of the most commonly used methods of creating entangled photon states is by means of parametric down-conversion, and it is therefore of interest to thoroughly understand the light produced by...Show moreOne of the most commonly used methods of creating entangled photon states is by means of parametric down-conversion, and it is therefore of interest to thoroughly understand the light produced by this process. In this thesis, we investigate the far-field distribution of SPDC photons produced by a 2 mm long periodically pooled potassium titanyl phosphate (PPKTP) crystal, at various crystal temperatures. We look both at the distribution itself and at the spatial correlations between the produced photons. Also, we present a novel way of approximating the theoretical far-field intensity which facilitates fitting the model to the data. Aggregating the data obtained over 81 experiments, we find the dependence of the phase matching angle ϕ of the crystal under consideration on the crystal temperature. Also, we find correlations between photon momenta indicating the presence of spatially entangled photon pairs as well as higher photon tuples.Show less
We worked on a new ”ultimate” patchy particle. Silica colloids are coated with a lipid bilayer composed of a mixture of saturated and unsaturated, charged and zwitterionic lipids. The lipids are...Show moreWe worked on a new ”ultimate” patchy particle. Silica colloids are coated with a lipid bilayer composed of a mixture of saturated and unsaturated, charged and zwitterionic lipids. The lipids are shown to be mobile on these colloids and phase separation is induced using the right lipid mixture. DNA attached to cholesterol partitioned to one of the phases is used as a linker, creating specific interaction on patches. Giant unilamellar vesicles are used as a model system to study phase separation in a lipid bilayer and the partitioning of the DNA attached to cholesterol.Show less
Carbon Nanomembranes (CNMs) are two-dimensional materials made by cross-linking (interconnecting) the molecules of a Self Assembled Monolayer (SAM). CNMs can be chemically tailored on one or both...Show moreCarbon Nanomembranes (CNMs) are two-dimensional materials made by cross-linking (interconnecting) the molecules of a Self Assembled Monolayer (SAM). CNMs can be chemically tailored on one or both sides leading to a variety of possible properties (e.g. mechanical, conductive, chemical, etc.). Once these properties are understood and controlled, CNMs might be a candidate for (among other things) functional devices based on molecules. In this thesis, it is described how to create laterally patterned CNMs by cross-linking aromatic based self assembled monolayers. Cross-linking is done by in situ low-energy electron irradiation with low energy electron microscopy (LEEM). This novel method allows for new types of experiments giving a brand new perspective. We show that a new structure (possibly CNM) was created after electron irradiation of SAM followed by annealing, furthermore, we have learned that our SAMs show an electron irradiation induced effect. This effect is most accurately described as a front shaped like the irradiated area, slowly shrinking in size until its disappearance. This effect was observed right after irradiation if certain conditions on the illumination time and electron energy were met. This phenomenon was imaged live and down to micrometer scale. These measurements have brought us to the conclusion that this front is not shrinking with a constant speed but is accelerating just before its disappearance. Furthermore, our measurements hint for a connection between the parameters illumination time & electron energy and the visibility and speed of a front.Show less
Spontaneous synchronization of coupled oscillators is ubiquitous in biological and physical systems. Among the many attempts to model such behavior, the Kuramoto model has proven to be mathematical...Show moreSpontaneous synchronization of coupled oscillators is ubiquitous in biological and physical systems. Among the many attempts to model such behavior, the Kuramoto model has proven to be mathematical tractable yet sufficiently rich to capture this phenomenology. In the past three decades, numerous extensive studies have been devoted to the model. The first aim of this thesis is to review these works. In particular, we discuss the rich phenomenology of the Kuramoto model defined on complex networks, which has mainly been studied in the statistical physics literature. Moreover, we consider several rigorous results obtained in the mathematical literature concerning the synchronization behavior of the Kuramoto model with a mean-field coupling. As a second aim, we investigate a Kuramoto-like model defined on the hierarchical lattice. To this end, we provide a preliminary analysis for a renormalization program in order to rigorously describe the behavior of this model.Show less
Diffuse interstellar bands are broad absorption features detected in diffuse interstellar clouds, first discovered almost a century ago. The carriers of these bands have not yet been identified, it...Show moreDiffuse interstellar bands are broad absorption features detected in diffuse interstellar clouds, first discovered almost a century ago. The carriers of these bands have not yet been identified, it is suspected that they are carbon chain radicals or polycyclic aromatic hydrocarbons. This thesis reports on laboratory spectra of C6H, the hexatriynyl radical, and their analysis. It concerns two vibronic bands of the B2Pi-X2Pi electronic transition, the Omega = 3/2 component of the origin band and an unidentified band, for both 12C6H and 13C6H. Molecular parameters for the origin band components and the centres of the unidentified bands' Q branches are determined. All four features are compared to catalogues of known diffuse interstellar bands, none of them matches.Show less
There has been tried to develop a suitable experimental setup to study the ordering of anisotropic colloidal clusters at liquid-liquid interfaces. PMMA colloids and glycerol - CHB-decalin...Show moreThere has been tried to develop a suitable experimental setup to study the ordering of anisotropic colloidal clusters at liquid-liquid interfaces. PMMA colloids and glycerol - CHB-decalin interfaces have been used for this system. Different configurations of interfaces have been made and analyzed. A suitable tracking code has been developed to analyze the ordering of anisotropic colloidal clusters as well. This code can track colloidal clusters in two and three dimensional space.Show less
We seek to create close packed tetrahedral clusters. Our method uses a glue particle to which cluster particles attach. We expand on previous methods by allowing the cluster particles to remain...Show moreWe seek to create close packed tetrahedral clusters. Our method uses a glue particle to which cluster particles attach. We expand on previous methods by allowing the cluster particles to remain mobile during clustering. We do this by using unpolymerised TPM droplets as glue particles and use lipid biotin linkers which diffuse over the surface of this droplet. NeutrAvidin coated polystyrene beads are used as the cluster particles. We describe the protocol for creating these clusters and verify the mobility of the cluster particles.Show less
This research project will focus on further developing a method for successful X-ray Photoelectron Spectroscopy under high pressure gas conditions, using a new method that no other group has used....Show moreThis research project will focus on further developing a method for successful X-ray Photoelectron Spectroscopy under high pressure gas conditions, using a new method that no other group has used. To do this we will develop coated ’smart’ STM tips for better accuracy as described by Shirato et al. (2014) [1], covered with an insulating layer and a shield layer to prevent charging of the insulating layer. On top of this, we will make simple tips coated with different kinds of polymer as alternative to the ’smart’ tips. We were not completely successful in creating these ’smart’ tips, but did manage to gain a lot of knowledge and experience that will surely help in further research in this topic.Show less
Increasing effort into parallel single molecule force experiments has led to the development of acoustic force spectroscopy (AFS). Acoustic standing waves of MHz frequencies are able to exert...Show moreIncreasing effort into parallel single molecule force experiments has led to the development of acoustic force spectroscopy (AFS). Acoustic standing waves of MHz frequencies are able to exert forces on microspheres, which can be used for the manipulation of single bio-molecules. The performance of acoustic tweezers is greatly dependent on setup design and the proper driving frequency. The need for AFS flow cell design modeling software is apparent. In this thesis we present a physical model for calculating the acoustic frequency response of a flow cell. We have found that an oil immersion objective lowers AFS performance drastically as opposed to an air objective and that the optimal driving frequency lies around 10.3 MHz for our prototype flow cell. Limited by the 10 MHz cap of our AC driver and problems with flow cell assembly yields, we were not able to demonstrate an acoustic pulling force. We need to switch to an air objective and, in order to make AFS work in our laboratory, either a new AC generator needs to be implemented or a piezoelectric transducer with a thickness mode within 8-10 MHz needs to be included.Show less
Several pathologies, such as Alzheimer's disease and Huntington's disease are associated with iron deposits in brain tissue. Ferritin is the protein that is responsible for the iron homoeostasis in...Show moreSeveral pathologies, such as Alzheimer's disease and Huntington's disease are associated with iron deposits in brain tissue. Ferritin is the protein that is responsible for the iron homoeostasis in the human body. Its peculiar magnetic properties make the protein a valuable target for a possible Magnetic Resonance Force Microscopy (MFRM) study. MRFM is considered to be one of the best possible ways to image biological nanostructures with atomic resolution in three dimensions. The detection of a magnetic signal of nanoparticles even with Magnetic Force Microscopy (MFM) has not been fully explored. Therefore we investigate ferritin with MFM at room temperature to get a more realistic view of the feasibility of studying ferritin with MRFM. We will show how to overcome the problem of clustered nanoparticles in biological samples. We found that no external magnetic field is required to observe magnetic interactions between a ferromagnetic probe and super-paramagnetic nanoparticles in MFM. The field generated by the magnetic probe is sufficiently large. By comparison to a non-magnetic nanoparticle, simulations and literature we conclude that MFM can detect magnetic properties of a single nanoparticle. This is the starting point for further investigation of ferritin with MRFM.Show less
In this thesis we will investigate the Hopf map, a differentiable map from the three-sphere to the two-sphere. Its fibres, the inverse images of points on the sphere, are circles that are all...Show moreIn this thesis we will investigate the Hopf map, a differentiable map from the three-sphere to the two-sphere. Its fibres, the inverse images of points on the sphere, are circles that are all linked with every other fibre. Based on the Hopf map we will construct divergenceless vector fields that have a physical interpretation as the magnetic field in the theory of magnetohydrodynamics. The concept of linking relates to helicity in this theory, a quantity that will be used to exhibit self-stable configurations of plasma.Show less
We studied sequential shape change in mechanical metamaterials. We designed transformers using a hierarchical tessellation of squares, creating a structure with two scales. Using biaxial loading,...Show moreWe studied sequential shape change in mechanical metamaterials. We designed transformers using a hierarchical tessellation of squares, creating a structure with two scales. Using biaxial loading, we reported shape change triggered by mechanical deformation. By designing the bending, buckling and self contact interactions, we were able to obtain either a random collapse or a sequential twofold shape change. We found a well defined sequence of geometric patters for the twofold shape change, which we characterised using wallpaper groups. We further evidenced that the shape change observed can be characterized by the mechanics and geometry of the transformers.Show less
In the development and maintenance of multicellular organisms, cell migration is an essential process. It is therefore important to study the migration of cells. The analysis of the position of the...Show moreIn the development and maintenance of multicellular organisms, cell migration is an essential process. It is therefore important to study the migration of cells. The analysis of the position of the cell during migration is often done by tracking the center of mass of the cell in the case that it's impossible to track the position of the nucleus. This tracking point is not ideal since the formation of protrusions and retractions lead to a fluctuation in the position of this tracking point while the body may not actually be moving. By using the medial axis of the binary object corresponding to the cell, we found an alternative tracking point, which is a slight improvement over the center of mass as the tracking point. We succeeded in tracking and analyzing the protrusions formed by the cell. These findings open up the possibility to characterize different cell types by the behavior of their protrusions and to obtain a quantitative description of the molecules contributing to the formation and dynamics of protrusions.Show less
