University of Groningen Digital Archive
Not a member yet
80723 research outputs found
Sort by
It's now or never
No full textFrank Brokken is security manager bij het CIT. Met het instellen van deze functie probeert de RUG het ‘security bewustzijn’ bij de gebruikers van de universitaire ICT-voorzieningen te bevorderen. In zijn column houdt Frank ons op de hoogte van de stand van zaken met betrekking tot zijn missie.
Faculteit Intermenselijke Wetenschappen. E-mailverkeer
No full textde Faculteit Intermenselijke Wetenschappen voert zelf een security awareness-campagne...
Realtime Multiscale Visualization of Flight Data
No full textIn this thesis we present a set of multi-scale visualization techniques, with implementation, for air traffic data. The goal of our visualizations is showing attributes of spatio-temporal data for multiple levels of detail both in geographical and temporal space, which can help with finding anomalies in air traffic and optimizing flight paths. We allow continuous transitions between the visualization of instantaneous flight positions and visually aggregated data for multiple days. We use animation, bundling and density map to reduce clutter and achieve visual scalability. Implementing our algorithms on the GPU allows us to visualize thousands of trails with millions of datapoints at interactive framerates.
Pathophysiological aspects of lifestyle and the kidney
No full textDit proefschrift onderzoekt de rol van verschillende leefstijlfactoren in het ontstaan, progressie en behandeling van nierschade. Lichaamsbeweging, conditie en voeding zijn terug te vinden in lichaamssamenstelling (spiermassa, vetmassa). We onderzochten daarom de rol van spiermassa, vetmassa en een centrale vetverdeling - waarbij het vet rondom de buik gelokaliseerd is: de “appelvorm” - als renale risicofactoren. Een lage spiermassa in nierpatiënten met suikerziekte bleek gepaard te gaan met een verhoogd risico op overlijden. We pleiten daarom voor aandacht voor conditieverbetering bij de begeleiding van deze patienten. Voorts bleek een “appelvorm” gepaard te gaan met een verhoogde druk in de kleine bloedvaatjes in de nier, vooral als er ook sprake is van overgewicht. We vonden bovendien dat een hogere bloeddruk in de kleine nierbloedvaatjes bijdraagt aan nierschade op de lange termijn bij de mens: dit verband werd reeds lang vermoed, maar was bij de mens nog nooit bewezen. Op grond hiervan pleiten we voor meer aandacht voor een gezond gewicht bij de begeleiding van de nierpatiënt. Tenslotte deden we aan aantal studies naar de rol van zoutbeperking bij nierschade. Hoewel aanbevolen bij nierpatienten, was het effect bij nierpatienten met suikerziekte tot dusverre niet onderzocht. Wij vonden dat een lichte zoutbeperking uitgesproken gunstige effecten heeft op bloeddruk, cholesterol en urine-eiwit bij deze patiënten. Ook bij suikerziekte is zoutbeperking dus gunstig. Bovendien vermindert het ontsteking en bindweefselvorming in patiënten met chronische nierziekte. We concluderen dat lichaamsbeweging, een gezond gewicht, en zoutbeperking van belang zijn voor de nierpatient en dat leefstijl-management een integraal onderdeel zou moeten zijn van de begeleiding van deze patienten.
The general aim of this thesis was to explore the role of lifestyle factors in the establishment, progression and treatment of chronic kidney disease. Physical exercise, condition and nutritional intake are reflected by one’s body composition (muscle mass and fat mass). We investigated the role of muscle mass, fat mass, as well as body fat distribution – so-called ‘apple shaped body’ – as renal risk factors. We found that lower muscle was independently associated with higher risk of mortality mass in diabetes patients with renal disease. We therefore state that improvement of physical condition is an important treatment goal for these patients. We furthermore found that subjects with obesity or a central body fat distribution have an increased blood pressure in the small renal arteries which contributes to long-term renal damage. This is the first human evidence of an association between renal blood pressure and renal outcome. To test whether intervention in lifestyle can intervene in renal disease progression, we studied the effect of sodium restriction. We found that sodium reduction had a pronounced effect on blood pressure and urinary protein loss, as well as on inflammation/fibrosis and blood cholesterol in renal patients. Taken together, we conclude that lifestyle intervention is a feasible and elegant measure to treat disease progression in renal patients.
Vibrational energy relaxation of the OH-stretch in methanol and HOD
No full textThe vibrational dynamics of the OH-stretch vibration are investigated by a combined theoretical and experimental approach. We try to develop a model for the OH-stretch relaxation by use of the surface hopping method. Most attention is being paid to the relaxation in diluted HOD in D2O. We look for signatures of the 'hot ground state' in the 2D spectrum, a result of local heating upon relaxation. Our findings indicate that this is in principle possible in this system with a surface hopping model, but the simple model in this work turns out to insufficient. The outcome is compared with 2D-spectra obtained by real-life experiments on this system. Furthermore the temperature dependent linear spectra and vibrational relaxation of the same mode in diluted methanol in partly deuterated methanol (CH3OD) is studied by the use of pump-probe experiments. We find blueshift of 0.7 cm-1K-1 of the OH-stretch peak in the first experiment, and a relaxation time of 0.6 ps in the pump-probe measurements.
Periodic review and continuous ordering
No full textThere exist many inventory control studies that consider either continuous review & continuous ordering, or periodic review & periodic ordering. Mixtures of the two are hardly ever studied. However, the model with periodic review and continuous ordering is highly relevant in practice, as information on the actual inventory level is not always up to date while making ordering decisions. This paper will therefore consider this case of periodic review and continuous ordering. Assuming zero fixed ordering costs, and allowing for a non-negative lead time and a general demand process, we first consider a one-period decision problem with no salvage cost for inventory remaining at the end of the period. In this setting we derive a base-line optimal order path, which is described by a simple newsvendor solution with safety stocks increasing towards the end of a review period. We then show that for the general, multi-period problem, the optimal policy in a period is to first arrive at this path by not ordering until the excess buffer stock from the previous review period is depleted, then follow the path for some time by continuous ordering, and stop ordering towards the end to limit excess stocks for the next review period. An important managerial insight is that, typically and possibly counterintuitively, no order should be placed at a review moment, although this may seem intuitive and is also the standard assumption in periodic review models. We illustrate for Normally distributed demand that adhering to the optimal ordering path instead can lead to cost reductions of 30% to 60% compared to periodic ordering, i.e. ordering exclusively at review moments.
Photopharmacology: Beyond Proof of Principle
No full textPharmacotherapy is often severely hindered by issues related to poor drug selectivity, including side effects, environmental toxicity, and the emergence of resistance. Lack of selectivity is caused by the inability to control drug activity in time and space. Photopharmacology aims at solving this issue by incorporating photoswitchable groups into the molecular structure of bioactive compounds. These switching units allow for the use of light as an external control element for pharmacological activity, which can be delivered with very high spatiotemporal precision. This Perspective presents the reader with the current state and outlook on photopharmacology. In particular, the principles behind photoregulation of bioactivity, the challenges of molecular design, and the possible therapeutic scenarios are discussed.
Computationally designed libraries for rapid enzyme stabilization
No full textThe ability to engineer enzymes and other proteins to any desired stability would have wide-ranging applications. Here, we demonstrate that computational design of a library with chemically diverse stabilizing mutations allows the engineering of drastically stabilized and fully functional variants of the mesostable enzyme limonene epoxide hydrolase. First, point mutations were selected if they significantly improved the predicted free energy of protein folding. Disulfide bonds were designed using sampling of backbone conformational space, which tripled the number of experimentally stabilizing disulfide bridges. Next, orthogonal in silico screening steps were used to remove chemically unreasonable mutations and mutations that are predicted to increase protein flexibility. The resulting library of 64 variants was experimentally screened, which revealed 21 (pairs of) stabilizing mutations located both in relatively rigid and in flexible areas of the enzyme. Finally, combining 10–12 of these confirmed mutations resulted in multi-site mutants with an increase in apparent melting temperature from 50 to 85°C, enhanced catalytic activity, preserved regioselectivity and a >250-fold longer half-life. The developed Framework for Rapid Enzyme Stabilization by Computational libraries (FRESCO) requires far less screening than conventional directed evolution.
A comparative study of the molecular structure, lipophilicity, solubility, acidity, absorption and polar surface area of coumarinic anticoagulants and direct thrombin inhibitors
No full textEssay: The effects of physical exercise on neurodegeneration and cognitive decline. Which molecular pathways are involved?
No full textIt is well known that physical exercise reduces the risk of cardiovascular disease, metabolic syndrome and obesity. Several studies have now shown that physical exercise also has a beneficial effect on cognitive impairment and dementia due to ageing and neurodegenerative diseases. However, exercise is a very broad term and most research that has been done focuses on different aspects of exercise. Since it is impossible to cover all these aspects in this thesis, I will focus on the effect of physical exercise in improving cognition and neuroprotection in elderly and in particular which molecular pathways are affected. Animal and human research show that by regulating the expression of several growth factors, including IGF-1, BDNF, VEGF and NGF, neurotransmitters and anti-inflammatory cytokines, exercise is capable of improving cognitive functions. However, the effect of exercise depends on duration, the sort of exercise that is performed and age. Also, not all cognitive processes improve to the same extent. Since most elderly are not capable of performing physical exercise, recent research has shifted towards the effects of whole body vibration on improving cognition as an alternative for physical exercise.