Relativity, correlation and core electron spectra

Het ontwerpen van nieuwe (multi)functionele materialen is voor een groot deel gebaseerd op kennis van de microscopische eigenschappen van deze materialen. Deze worden voor een groot deel bepaald door de elektronische structuur, d.w.z. de elektronische energieniveaus en bijbehorende elektronenverdelingen. Spectroscopie van binnenschilelektronen is een waardevolle techniek om de elektronische structuur van verschillende systemen, zoals atomen, moleculen en vaste stoffen, te achterhalen. De benodigde straling bevindt zich in het röntgengebied, vaak aangeduid als X-rays. De verschillende vormen van deze techniek kunnen worden ingedeeld in twee categorieën, namelijk X-ray foto-elektron spectroscopie (XPS) en X-ray absorptie spectroscopie (XAS). Bij XPS worden elektronen uit de binnenschil van het systeem gestoten met behulp van röntgenstraling. De kinetische energie en aantal van die elektronen wordt gemeten als een spectrum. Bij XAS wordt gebruik gemaakt van röntgenstraling om een elektron van de binnenschil naar een valentieschil te brengen. De röntgenstraling met een energie gelijk aan de overgangsenergie wordt geabsorbeerd, wat ook gemeten wordt als een spectrum. De resulterende spectra leveren informatie over de gehele elektronische structuur van het systeem, door de interacties met de andere elektronen. Hierdoor is de interpretatie van de spectra echter wel ingewikkeld. Door middel van kwantummechanische berekeningen kunnen we het XPS/XAS proces nauwkeurig beschrijven en de spectra beter interpreteren. In dit proefschrift beschrijven we een kwantummechanische methode om XPS/XAS spectra te berekenen, waarbij de effecten van relativiteit en elektron-correlatie gebalanceerd worden meegenomen. Resultaten van het uranium atoom, titanium clusters en ytterbium fosfide laten goede overeenstemming zien met experimentele spectra

Severe hypokalaemic paralysis and rhabdomyolysis due to ingestion of liquorice

Chronic ingestion of liquorice induces a syndrome with findings similar to those in primary hyperaldosteronism. We describe a patient who, with a plasma K+ of 1.8 mmol/l, showed a paralysis and severe rhabdomyolysis after the habitual consumption of natural liquorice. Liquorice has become widely available as a flavouring agent in foods and drugs. It is important for physicians to keep liquorice consumption in mind as a cause for hypokalaemic paralysis and rhabdomyolysis

A three-layer MRI-based head phantom for experimental validation of tES simulations

Transcranial electric stimulation (tES) is being investigated for the relief of seizures in medically refractory epilepsy patients. In a quest to optimize the electrode placement and current for improvement of the outcome, we are investigating the exploitation of the pre-stimulation planning using finite element simulations based on individual anatomy from MRI [RM1] scans. A crucial step is validating the stimulation modeling accuracy, but commercial setups for validation do not exist.Hereto, we developed a three-layer head phantom, consisting of skin, skull, and brain tissue, that captures the crucial anatomical features and provides a convenient way of verifying the induced electric fields. It also enables systematic characterization of the uncertainties and variations in conductivity and anatomy. Experiments on the three-layer phantom bridge the gap between simulations and clinical practice since they also allow for using clinical hardware and electrodes.The developed phantom consists of an agar and salt brain layer, a graphite-doped polyurethane skull, and a skin layer made from agar gel with a different conductivity. In this way the solid skull separates the two gel layers, preventing possible ion drift over the layers. The anatomy is based on the ICBM 152 linear model, an average of 152 MRI scans, which enables us to intuitively link measurements and simulations. To perform the systematic characterization experiments, hardware and software were designed in-house. This allows for stimulations and measurements on the phantom in a cheap and modular way. The designed hardware consists of a PID-controlled tES stimulator, which can deliver 4 mA with a frequency up to 100 Hz, and a four-channel differential sensing board based on the OpenBCI Ganglion board.A realistic and modular phantom expands the possibilities of preclinical tES research by providing a tool to validate electric field simulations as well as experiment with clinical hardware and anatomical variations

The mathematics of french fries

Although the act of cutting a single potato (Solanum tuberosum) into french fries may appear to be trivial, the questions concerning the efficiency of this process on an industrial scale are quite daunting. Therefore, many producers are looking for a rigorous method to evaluate the market potential of a given potato crop by predicting the number and parameters of the fries that can be cut from it. Applying the methods of geometry and numerical analysis our group was able to propose several algorithms that can be directly incorporated into the existing production process. Keywords: French fries, geometry, cutting, Finite Fry Method, simulations, histogram

Automatic radiographic quantification of hand osteoarthritis; accuracy and sensitivity to change in joint space width in a phantom and cadaver study

This is the final version of the article. Available from Springer Verlag via the DOI in this record.OBJECTIVE: To validate a newly developed quantification method that automatically detects and quantifies the joint space width (JSW) in hand radiographs. Repeatability, accuracy and sensitivity to changes in JSW were determined. The influence of joint location and joint shape on the measurements was tested. METHODS: A mechanical micrometer set-up was developed to define and adjust the true JSW in an acrylic phantom joint and in human cadaver-derived phalangeal joints. Radiographic measurements of the JSW were compared to the true JSW. Repeatability, systematic error (accuracy) and sensitivity (defined as the smallest detectable difference (SDD)) were determined. The influence of joint position on the JSW measurement was assessed by varying the location of the acrylic phantom on the X-ray detector with respect to the X-ray beam and the influence of joint shape was determined by using morphologically different human cadaver joints. RESULTS: The mean systematic error was 0.052 mm in the phantom joint and 0.210 mm in the cadaver experiment. In the phantom experiments, the repeatability was high (SDD = 0.028 mm), but differed slightly between joint locations (p = 0.046), and a change in JSW of 0.037 mm could be detected. Dependent of the joint shape in the cadaver hand, a change in JSW between 0.018 and 0.047 mm could be detected. CONCLUSIONS: The automatic quantification method is sensitive to small changes in JSW. Considering the published data of JSW decline in the normal and osteoarthritic population, the first signs of OA progression with this method can be detected within 1 or 2 years.This work was funded by the Dutch Arthritis Association (Reumafonds). The study sponsor had no involvement in study design, data collection, data analysis, or interpretation of the results

Quantitative cross-species extrapolation between humans and fish: The case of the anti-depressant fluoxetine

This article has been made available through the Brunel Open Access Publishing Fund.Fish are an important model for the pharmacological and toxicological characterization of human pharmaceuticals in drug discovery, drug safety assessment and environmental toxicology. However, do fish respond to pharmaceuticals as humans do? To address this question, we provide a novel quantitative cross-species extrapolation approach (qCSE) based on the hypothesis that similar plasma concentrations of pharmaceuticals cause comparable target-mediated effects in both humans and fish at similar level of biological organization (Read-Across Hypothesis). To validate this hypothesis, the behavioural effects of the anti-depressant drug fluoxetine on the fish model fathead minnow (Pimephales promelas) were used as test case. Fish were exposed for 28 days to a range of measured water concentrations of fluoxetine (0.1, 1.0, 8.0, 16, 32, 64 μg/L) to produce plasma concentrations below, equal and above the range of Human Therapeutic Plasma Concentrations (HTPCs). Fluoxetine and its metabolite, norfluoxetine, were quantified in the plasma of individual fish and linked to behavioural anxiety-related endpoints. The minimum drug plasma concentrations that elicited anxiolytic responses in fish were above the upper value of the HTPC range, whereas no effects were observed at plasma concentrations below the HTPCs. In vivo metabolism of fluoxetine in humans and fish was similar, and displayed bi-phasic concentration-dependent kinetics driven by the auto-inhibitory dynamics and saturation of the enzymes that convert fluoxetine into norfluoxetine. The sensitivity of fish to fluoxetine was not so dissimilar from that of patients affected by general anxiety disorders. These results represent the first direct evidence of measured internal dose response effect of a pharmaceutical in fish, hence validating the Read-Across hypothesis applied to fluoxetine. Overall, this study demonstrates that the qCSE approach, anchored to internal drug concentrations, is a powerful tool to guide the assessment of the sensitivity of fish to pharmaceuticals, and strengthens the translational power of the cross-species extrapolation