Pancreatic cancer is an aggressive cancer associated with a poor prognosis as a large proportion of these patients have locally advanced disease or metastases at the time of diagnosis. Currently... Show morePancreatic cancer is an aggressive cancer associated with a poor prognosis as a large proportion of these patients have locally advanced disease or metastases at the time of diagnosis. Currently onlypatients with localized pancreatic tumors can undergo surgery, which is the cornerstone in thetreatment of pancreatic cancer, whether or not preceded by neoadjuvant (chemo/radio)therapy. To establish the diagnosis, imaging techniques are used, tumor tissue must be obtained, and certain tumor markers can be determined in the blood. During surgery, the tumor must be removed in its entirety to prevent early recurrence. This thesis describes the potential role of tumor markers, which can be determined in the blood, and several experimental optical imaging techniques applied to pancreatic cancer. Show less
In this thesis new methodologies are developed for the detection and systematic study of radio sources in the early universe. This allows us to gain a deeper understanding of the formation and... Show moreIn this thesis new methodologies are developed for the detection and systematic study of radio sources in the early universe. This allows us to gain a deeper understanding of the formation and evolution of galaxies, the activity of supermassive black holes, and the final phase transition of our universe: the epoch of reionization. Using the Low Frequency Array (LOFAR) telescope, this thesis systematically investigates the low radio frequency properties of quasars, the brightest non-variable objects in our cosmos, in the first billion years after the Big Bang. Through the discovery of new radio quasars in the early universe and subsequent studies, this thesis shows the diversity within the quasar population and highlights the importance of multi-wavelength observations for our comprehension of the formation and evolution of active supermassive black holes and their impact on the surrounding environment. Show less
Gold nanoparticles show surprisingly strong interactions with light in the visible range, which can be divided into scattering, absorption, and photoluminescence. When a nanoparticle absorbs light,... Show moreGold nanoparticles show surprisingly strong interactions with light in the visible range, which can be divided into scattering, absorption, and photoluminescence. When a nanoparticle absorbs light, the corresponding energy is converted to heat, which can affect the environment of the (hot) nanoparticle. This thesis uses scattering and photoluminescence to study the behaviour of optically heated single gold nanoparticles: it discusses the behaviour of single plasmonic vapour nanobubbles, which occur around highly heated nanoparticles immersed in a liquid, the detection of chirality in nano-objects through their absorption and the photothermal effect, the behaviour of gold nanoparticles under sub-picosecond pulsed excitation, and the temperature dependence of pulse-excited photoluminescence of such particles. Show less
The prevalence of obesity, defined as a body mass index (BMI) > 30 kg/m2, is increasing to epidemic proportions. In 2014, 11% of men and 15% of women worldwide were obese. Thus, more than... Show moreThe prevalence of obesity, defined as a body mass index (BMI) > 30 kg/m2, is increasing to epidemic proportions. In 2014, 11% of men and 15% of women worldwide were obese. Thus, more than half a billion adults worldwide are classed as obese. The fundamental cause of obesity is an imbalance between energy intake (excessive intake of energy-dense foods) and energy expenditure (reduced physical activity). People with obesity are at risk for a range of chronic conditions including cardiovascular disease (CVD) and nonalcoholic fatty liver disease (NAFLD). Furthermore, obesity is a major risk factor for the development of type 2 diabetes, which is one of the most common chronic diseases in nearly all countries. According to the World Health Organization, the global prevalence of diabetes in 2014 was estimated to be 9%, of which 90% was comprised of type 2 diabetes. This thesis focuses on cardiovascular and cerebral dimensions and function in people with obesity and type 2 diabetes. State-of-the-art imaging techniques are used to investigate links between the heart, liver, abdominal fat, and brain to elucidate parts of the complex relationships between these organs. Show less
DNA-hosted silver clusters (Ag:DNAs) have attracted a lot of attention due to their small size (~20 atoms), wide range of applications in chemistry and biology, and sequence-dependent optical... Show moreDNA-hosted silver clusters (Ag:DNAs) have attracted a lot of attention due to their small size (~20 atoms), wide range of applications in chemistry and biology, and sequence-dependent optical tunability. Most of the previous studies are focused on the ensemble of emitters in solution. However, little is known about the optical properties of individual emitters, which is a crucial step towards understanding of their real nature, otherwise lost in ensemble averaging. We show that the excitation and emission spectra of individual emitters are broad even at 1.7 K (FWHM ~25 nm). Also, polarization measurements indicate that the excitation is not strongly dependent on the polarization of excitation light, whereas the emission is highly linearly polarized. Furthermore, from time-resolved measurements, we can conclude that the emission of single emitters can be fitted with single exponential decay curve, whereas the emitters organized with nanometer precision on the DNA scaffolds show double–exponential decay. This indicates the interaction between densely packed Ag:DNAs. Finally, we show that the DNA tubes can be used as a nano-contact glue between the colloidal particles functionalized with short DNA strands. Show less
Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) can play a key role in understanding neurobiological mechanisms of diseases that affect the human brain. The specific changes that occur... Show moreDiffusion-weighted magnetic resonance spectroscopy (DW-MRS) can play a key role in understanding neurobiological mechanisms of diseases that affect the human brain. The specific changes that occur within neurons can be reflected as changes in the diffusivity of tNAA, whereas the changes in glial cells can cause pronounced changes in the diffusivities of tCr and tCho. This information combined with that obtained from diffusion tensor imaging (DTI) and other MRI tools can help elucidate various disease processes in the future. The main purposes of this thesis are (i) to investigate neuroanatomy in vivo with DW-MRS, (ii) to develop methodology to enable future clinical applications of the technique in human brain in vivo, and (iii) to characterize the microstructural deficit in neuropsychiatric systemic lupus erythematous (NPSLE) with DW-MRS and other microstructural tools such as DTI and magnetization transfer imaging. The studies presented in this thesis show the robustness and clinical relevance of microstructural information obtained via DW-MRS. The contributions of this thesis such as the optimized acquisition protocols for single volume DW-MRS, the robust DW-CSI and DW-MRS post-processing pipelines that comprise information from DTI, will all facilitate the applications of DW-MRS both for basic neuroscience research and clinical research studies. Show less
Versluis, M.J.; Grond, J. van der; Buchem, M.A. van; Zijl, P. van; Webb, A.G. 2012
Mid-infrared (mid-IR) astronomical observations show that molecules freeze out on interstellar grains to form interstellar ices. These ices play an important role in the chemical evolution of... Show moreMid-infrared (mid-IR) astronomical observations show that molecules freeze out on interstellar grains to form interstellar ices. These ices play an important role in the chemical evolution of molecules in space. Understanding the physical interactions and chemical reactions that take place in these ices gives us important clues to how the ices are formed and which role they play in the formation of complex molecules. The physical interactions in H2O:CO binary ices and in CH3OH and NH3 containing ices are studied both in the laboratory and in space by means of mid-IR spectroscopy, resulting in the unambiguous detection of NH3 in a low-mass protostar. Additionally, mid-IR and near-UV/VIS spectroscopic measurements on the ultraviolet induced photochemistry of large molecules, Polycyclic Aromatic Hydrocarbons (PAHs), trapped in ices are described. These molecules are known to be abundantly present in space, but their influence on the chemical evolution of interstellar ices has never been studied in detail. The experiments indicate that the processes are important in the formation of complex and charged molecules and that new astrochemical models should take the role of PAHs in ice into account. Show less
The aim of the thesis was to provide more insight into the influence of myocardial steatosis on left ventricular function in healthy volunteers and in patients with type 2 diabetes mellitus.... Show moreThe aim of the thesis was to provide more insight into the influence of myocardial steatosis on left ventricular function in healthy volunteers and in patients with type 2 diabetes mellitus. Therefore we developed a reproducible proton magnetic resonance (MR) spectroscopic technique with respiratory motion compensation to study myocardial steatosis. Using these technique, combined with MR imaging to study myocardial function, correlations between myocardial steatosis and left ventricular function were shown in several (patho)physiological conditions. Furthermore, we showed that myocardial triglyceride content is increased in patients with type 2 diabetes mellitus and is an independent predictor of left ventricular diastolic dysfunction. In addition, differential, tissue-specific partitioning of triglycerides and/or fatty acids among non-adipose organs during various diets was shown. Given the obesity and type 2 diabetes mellitus pandemic and the increasing evidence indicating that lipid oversupply to cardiomyocytes plays a role in the development of diabetic cardiomyopathy, therapeutic strategies that target reduction of cardiac lipid overexposure might be beneficial to prevent diabetic cardiomyopathy. Show less
Al voordat het grote publiek kennismaakte met nanotechnologie, besteedde de wetenschap aandacht aan steeds kleinere objecten. Sinds 15 jaar is het bijvoorbeeld mogelijk om met speciale microscopen... Show moreAl voordat het grote publiek kennismaakte met nanotechnologie, besteedde de wetenschap aandacht aan steeds kleinere objecten. Sinds 15 jaar is het bijvoorbeeld mogelijk om met speciale microscopen naar individuele moleculen te kijken! Deze techniek hebben we nu gebruikt om halfgeleider nanokristallen te bestuderen. Halfgeleiders zijn materialen die worden gebruikt in computers. Afhankelijk van hun bewerking en toepassing kunnen zij stroom goed of slecht geleiden. Maar deze nanokristallen zijn zo klein, slechts 5 nanometer (1 miljoen nm = 1 mm) en dus veel kleiner dan de golflengte van licht, dat ze zich heel anders gedragen. Ze kunnen bijvoorbeeld licht absorberen en uitzenden (fluoresceren), maar omdat ze zo klein zijn altijd slechts __n lichtdeeltje (foton) tegelijk, net als een molecuul. Ook het ritme (de statistiek) waarmee dit gebeurt, is heel bijzonder en vergelijkbaar met de statistiek waarmee aardbevingen voorkomen. De pauze tussen het uitzenden van twee fotonen varieert bijvoorbeeld zo sterk, dat we de gemiddelde pauze niet kunnen uitrekenen! Dankzij diverse wiskundige trucs kunnen we dit ritme nu toch beschrijven. Deze wiskunde is ook handig om verschillende experimenten te kunnen vergelijken, zowel voor nanokristallen als voor moleculen. Vervolgens hebben we een model opgesteld dat beschrijft wat er in nanokristallen gebeurt, als een foton wordt geabsorbeerd of uitgezonden. Show less
