The topic of this study is the portfolio that is being used in a teacher education institute as an instrument for stimulating reflection on their development as teachers by student teachers. This... Show moreThe topic of this study is the portfolio that is being used in a teacher education institute as an instrument for stimulating reflection on their development as teachers by student teachers. This reflection can be seen in the themes student teachers have written in their portfolios. The nature of reflection has been described by means of content analysis. The student teachers in this study mainly used their portfolios for examing what they had done and learned and much less for learning from these experiences. The results show that teacher education institutes must be very clear about what they aim at with reflection. Subsequently portfolio supervision and the use of the portfolio should be much better geared to this. Whether the portfolio is a suitable instrument for using in educating teachers should also be discussed. Show less
We consider choosing an estimator or model from a given class by cross validation consisting of holding a nonneglible fraction of the observations out as a test set. We derive bounds that show that... Show moreWe consider choosing an estimator or model from a given class by cross validation consisting of holding a nonneglible fraction of the observations out as a test set. We derive bounds that show that the risk of the resulting procedure is (up to a constant) smaller than the risk of an oracle plus an error which typically grows logarithmically with the number of estimators in the class. We extend the results to penalized cross validation in order to control unbounded loss functions. Applications include regression with squared and absolute deviation loss and classification under Tsybakov’s condition. Show less
This study is aimed at the molecular characterisation of solid organic (food) residues preserved in an assemblage of vessels recovered from an indigenous settlement dating back to the Iron Age and... Show moreThis study is aimed at the molecular characterisation of solid organic (food) residues preserved in an assemblage of vessels recovered from an indigenous settlement dating back to the Iron Age and Roman period at Uitgeest – Groot Dorregeest (The Netherlands). Analytical thermal-fragmentation techniques such as Curie-point pyrolysis Mass Spectrometry and Direct Temperature-resolved Mass Spectrometry gave information about a wide range of compound classes as diverse as lipids, waxes, polynuclear aromatic compounds, oligosaccharides, small peptides and protein fragments, and a variety of thermally stable (more or less condensed) polymeric char structures. Multivariate analysis identified different chemotypes: groups of residues with comparable chemical characteristics. The biomolecular origin of these chemotypes was identified by comparison with experimentally charred reference materials and the application of complementary analytical techniques such as FTIR and 13C CP/MAS NMR. The chemotypes A1 and A2 consist of charred residues identified as starch-rich foods (mixed with either animal or plant products), chemotype C consists of protein-rich charred animal products without starch, chemotype B contains smoke condensates from wood fires, and chemotype D consists of special protein-rich and lipid-free foods or non-food products. Although many molecular characteristics of the original foods have been lost as a result of extensive thermal degradation and interpretation remains limited to general food groups, the results give valuable direct evidence of ancient diet and vessel-use. Show less
Verdoes, M.; Florea, B.I.; Menendez-Benito, V.; Maynard, C.J.; Witte, M.D.; Linden, W.A. van der; ... ; Overkleeft, H.S. 2006
This thesis deals with the associations between parasitic snails and their mushroom coral hosts. Gittenberger has spent 800 hours under water and searched about 60,000 coral discs for these... Show moreThis thesis deals with the associations between parasitic snails and their mushroom coral hosts. Gittenberger has spent 800 hours under water and searched about 60,000 coral discs for these parasites. He dived in Egypt, the Maldives, Thailand, Malaysia, Japan, Palau, the Philippines, Indonesia and Australia. Places that are less popular with divers, like very deep or shallow sites, areas with strong currents, murky water, or sandy bottoms, received special attention. The greatest biodiversity was found off Sulawesi, a region that needs protection. Except for shell morphology, molecular, anatomical and ecological characters of the snails were studied. As a result it turned out that many more species exist than hitherto thought. Some dozens of unnamed cryptic ones were discovered. These can be distinguished most clearly by their DNA and their host specificity. The species of parasitic snails evolved most probably by bypassing the defence mechanism of one or a few coral species. Most of the data support a sympatric speciation model for these taxa. The molecular phylogenies of the parasites and their hosts were compared to investigate the amount of co-evolution. Show less
Homocysteine is a risk factor for venous thrombosis. Elevated concentrations can be treated with folic acid, vitamin B6 and vitamin B12. The main study (chapter 9) in this thesis is a randomized... Show moreHomocysteine is a risk factor for venous thrombosis. Elevated concentrations can be treated with folic acid, vitamin B6 and vitamin B12. The main study (chapter 9) in this thesis is a randomized placebo-controlled trial in which patients with a first event of deep-vein thrombosis or pulmonary embolism are treated with above mentioned vitamins or a placebo. There was no effect of vitamin treatment on recurrent thrombosis. A case-control study is described whichs shows that elevated homocysteine concentrations are a risk factor for venous thrombosis and pulmonary embolism in elderly patients (chapter 7). Two studies deal with acidic citrate as an anticoagulant in blood collection tubes. We show that acidic citrate stabilizes homocysteine concentrations at room temperature (chapter 3) and that the homocysteine concentrations measured in blood collection tubes with acidic citrate as anticoagulant correlate well with the concentrations measured in blood tubes with EDTA as anticoagulant (chapter 4). One study compared patients on and off anticoagulant therapy. There was no influence of coumarin derivatives on plasma homocysteine concentrations (chapter 5). The endogeous thrombin potential is not different in patients with high homocysteine concentrations in comparison to patients with low homocysteine concentrations (chapter 6). Show less
A spectrometer for Electron Paramagnetic Resonance (EPR), operating at the very high microwave frequency of 275 GHz in both continuous wave (cw) and pulsed mode, is described and its capabilities... Show moreA spectrometer for Electron Paramagnetic Resonance (EPR), operating at the very high microwave frequency of 275 GHz in both continuous wave (cw) and pulsed mode, is described and its capabilities are illustrated. A superconducting magnet provides the magnetic field up to 12 Tesla and experiments are possible between room temperature and 5 K. The system utilizes pseudo-optical techniques to minimize microwave losses and a single-mode resonator is used to maximize the microwave field at the sample position. The material under study can also be subjected to a radiofrequency radiation field to enable Electron Nuclear Double Resonance (ENDOR) experiments. Technical details of the design and the operation are presented. First results are discussed which demonstrate the increased sensitivity and resolution compared to experiments at lower microwave frequencies. These concern various materials, ranging from semi-conductors to proteins, including an aqueous solution of a proxyl radical at room temperature. ENDOR performance is illustrated with data from a sample of zinc-germanium-phosphide (ZnGeP2) doped with Manganese (Mn). Separate chapters cover experiments on the organic semiconductor P3HT and the observation of Dynamic Nuclear Polarization (DNP) in zinc oxide (ZnO). Show less
This work covers the evolution of satellite based Aeronautical Public Correspondence and the operational environment in which services are being offered. Followed by an examination of applicable... Show moreThis work covers the evolution of satellite based Aeronautical Public Correspondence and the operational environment in which services are being offered. Followed by an examination of applicable rules, including the relevant institutions from which they emanate, attention is devoted to questions on liability and the effect of State Sovereignty, applicable in territorial airspace, the Arctic, Antarctica, and the High Seas as well as, to activities such as telecommunications, air transport, copyright protection and trade in services. Particular attention is given to the ITU Radio Regulations; ITU Sector Recommendations; ICAO Council Regulations; International Copyright Laws; National Operational Procedures and Statutes. Show less
Differentiated thyroid carcinoma (DTC) has favorable prognosis with high cure rate under treatment of thyroidectomy followed by radiotherapy. However, therapeutic efficiency decreases when... Show moreDifferentiated thyroid carcinoma (DTC) has favorable prognosis with high cure rate under treatment of thyroidectomy followed by radiotherapy. However, therapeutic efficiency decreases when dedifferentiation occurs. One of the purposes in this study is to use pharmaceuticals intervention to promote therapeutic responsiveness in thyroid carcinomas. Lithium compound and retinoid derivatives have been applied in thyroid cancer patients and in normal and thyroid cancer cell lines. The results indicate that Lithium compound doesn__t influence either iodine uptake in vivo and in vitro conditions or iodine efflux in cell lines observed. Retinoid, Bexarotene, slightly increases iodine uptake in thyroid cancer patients but does not reach the therapeutic level. In attempt to find efficient diagnostic markers, 156 patient samples including subsets of thyroid carcinomas and benign thyroid disorders have been investigated using immunohistochemistry in tissue micro-array sections. The results indicate that combination of protein expression of NIS, FN and Gal-3 may distinguish benign tumors from malignant thyroid carcinomas with high accuracy. As thyroid cancer patients have high survival rate, efficient and sensitive screening tool is crucial for follow up in DTC. In this study, thyroglobulin (Tg) of over 600 patients has been studies at unicenter with uniformed treatment. The results prove that multiple tests of Tg at fix time points may predict DTC prognosis and death. Show less
This thesis contributes to a better understanding of the roles of apoCI, LPL, and CETP in lipoprotein metabolism. Our data illustrate that the activity of LPL, and thereby the level of plasma TG,... Show moreThis thesis contributes to a better understanding of the roles of apoCI, LPL, and CETP in lipoprotein metabolism. Our data illustrate that the activity of LPL, and thereby the level of plasma TG, is crucially determined by the relative abundance of apolipoproteins. In addition, we showed that LPL is an important determinant in remnant-particle clearance in the absence of the three main apoE-recognizing receptors. Finally, we demonstrated that CETP presents a pro-atherogenic factor in mice resembling a human lipid distribution over lipoproteins and that atorvastatin and fenofibrate treatment influence HDL-metabolism via inhibition of CETP, which may thus add to their therapeutic benefit. Since there were initial concerns that inhibition of CETP would reduce the flux of cholesteryl esters from the periphery back to the liver, thereby possibly increasing the risk for atherosclerosis, it is of interest that we found that fenofibrate-mediated inhibition of CETP did not hamper the total flux of HDL-cholesteryl esters. This holds promise for therapies based on CETP inhibition. Show less
Everybody still knows the images of hunger and drought in the dry zones of Africa (the Sahel). These last years the situation for the millions of people living there has stabilised due to the fact... Show moreEverybody still knows the images of hunger and drought in the dry zones of Africa (the Sahel). These last years the situation for the millions of people living there has stabilised due to the fact that rainfall has not failed. But what about the future? The population is still growing rapidly, and industries to absorb these numbers does not exist. The future of the Sahel depends on the investments of the farmers to improve the productivity of their arable land. But the people are poor, there are no good markets to trade new agricultural products, and there is still some bushland available where new fields may be made if the old fields are exhausted. The dissertation deals with this bushland in the Sahel. In the bush, we find trees, grass and bushes, which are used for cattle, wood supply, medicines and may other functions, such as fallow and hunting. Is it possible to estimate the value of this land? Will all of this bushland be lost in the near future, converted to arable land to feed the ever higher population? After studying these questions in a specific area in Cameroon, Wassouni concludes that it is unwise to wait till all bushland is used up. Active protection of the bush, by the government but also by local people, is necessary to stimulate the farmers to invest in their land before they have become so poor that they no longer can. Show less
The initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To... Show moreThe initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To be able to distinguish phenomena unique for configuration from phenomena also present in conventional resonators, i.e., roughness-induced scattering and aberrations, the performance of a conventional stable resonator is investigated first. Roughness-induced scattering turns out to affect the cavity finesse as well as the average power throughput and produces mode coupling close to frequency-degenerate points. We demonstrate, furthermore, a method to accurately determine aberrations by measuring the Gouy phase of subsequent higher-order modes around frequency-degeneracy. The bifocal mirror is not fabricated by traditional grinding and polishing, but by diamond-machining. The eigenmodes of a resonator with one diamond-machined bifocal mirror turn out to be Laguerre-Gaussian. We demonstrate furthermore, the coupling of two resonators based on transmission spectra and patterns, and report on the ability of the configuration to fulfill the basic requirements to obtain chaos. Show less
This thesis comprises elementary work on the evolution of ageing. The issue of ageing, and especially of starvation resistance, has been approached from both the environmental and the genetic sides... Show moreThis thesis comprises elementary work on the evolution of ageing. The issue of ageing, and especially of starvation resistance, has been approached from both the environmental and the genetic sides that are of relevance to the issue. Therewith, this study has a broad orientation, varying from ecophysiology to selection experiments, mutant analysis and sate of the art microarray gene expression analysis. All this work was performed on Drosophila melnogaster, the fruit fly, and was put in an integrative context with human ageing. Show less
Osteoarthritis (OA) refers to a heterogeneous group of conditions. This thesis focuses on OA with a hereditary background; Familial OA at multiple joint sites and radiological hand OA at middle age... Show moreOsteoarthritis (OA) refers to a heterogeneous group of conditions. This thesis focuses on OA with a hereditary background; Familial OA at multiple joint sites and radiological hand OA at middle age. The main objective is to identify risk factors that play a role in the development of OA in order to gain further insight in the aetiology of OA. The secondary objective is to investigate factors that determine the outcome in OA. This thesis provides evidence that familial clustering of symptomatic OA is most prominent for hand and hip OA. In search for genetic risk factors, we present data suggesting that a proportion of the genetic susceptibility for OA at multiple sites is encoded by variation in innate cytokine activity. Further, we find HLA-DR antigens to be associated with radiological hand OA. In addition to genetic risk factors, this thesis demonstrates that other systemic risk factors such as hormonal status and local factors, to be important in the susceptibility of familial OA at multiple sites, underscoring the multicausal etioliology of this phenotype. Finally, this thesis addresses the resulting disability from OA. Using the International Classification of Functioning, Disability and Health as framework, we show illness perceptions and mental health to be important modifying factors in OA in the hands and lower extremities. Show less
This study is part of an interdisciplinary project dealing with the Palaeolithic occupation phases of northern Europe. In order to give feedback on the time control over the scattered Palaeolithic... Show moreThis study is part of an interdisciplinary project dealing with the Palaeolithic occupation phases of northern Europe. In order to give feedback on the time control over the scattered Palaeolithic evidence, the thesis is focused on the (chrono)stratigraphy of the terrestrial Middle Pleistocene succession, spanning the period from approximately 780,000 to 130,000 years ago. Its record, including the Palaeolithic archeological record, is fragmentary and heterogeneous both in time and space. Interpretation of a chronological sequence from sedimentary units into glacials and interglacials has never been documented in a satisfactory way. Different approaches supplementary to the traditional climatostratigraphical procedure have been assessed. Local multidisciplinary data from the type regions in Northwest and Central Europe has been integrated into a large-scale framework using unconformity-bounded and genetic sequence stratigraphical principles. From the genetic depositional sequences within this framework palaeoclimatic events have been interpreted comprising reflections of climate-forcing of different origin, type and scale order. They are arranged into a relative chronology on the basis of superposition, correlation of unconformity-bounded and biostratigraphical markers and independent dates. In the synthesis, the widespread terrestrial sequences and events have been matched with the marine isotope stages (MIS). At least two lower boundary levels can be placed at relevant MIS-transitions: - the lower boundary of the late Middle Pleistocene corresponding to the deglaciation interval of MIS 12/11 at about 400,000 years ago, representing the transition of the Elsterian cold Stage to the Holsteinian warm Stage - a boundary level corresponding to the deglaciation of MIS 16/15 at about 600,000 years ago, subdividing the Cromerian part of the early Middle Pleistocene into a part A and a part B. From the stratigraphical analysis in this thesis it is concluded that the lower boundary of Palaeolithic occupation in the study area has to be set at about 600,000 years ago. Show less
The studies present in this thesis fall into two broad areas: the first focusing on filarial infection, Ig (immunoglobulin)E levels and risk factors for infection, while the second deals with the... Show moreThe studies present in this thesis fall into two broad areas: the first focusing on filarial infection, Ig (immunoglobulin)E levels and risk factors for infection, while the second deals with the possible associations between nematode infection and allergy. Compared to ELISA, RAST is superior in detecting filarial specific IgE in endemic area of Brugia malayi. Levels of filaria-specific IgE and IgG4 in children up to 10 years correlated with maternal antibody levels. Genetic factors had a more pronounced effect in children than in adults. The use of objective measurements, such as skin prick test (SPT) and IgE levels are required when conducting epidemiological studies of allergic diseases in Indonesia. Study on risk factors of allergy in Indonesia showed that nutritional status of children in the high socioeconomic school negatively associate with SPT and IgE positivity but we did not show a statistically significant role for helminths in inhibiting SPT responses. In endemic area of lymphatic filariasis, genetic factors contribute significantly to both total and allergen-specific IgE, whereas environmental factors influence the clustering of SPT positivity. By using several TLR ligands it was demonstrated that the dynamics of cytokine production following the innate immune stimulation can differ according to helminth infection status. Show less
In this thesis we focused on the causes and consequences of hepatic steatosis. Epidemiological studies in humans, as well as experimental studies in animal models, have shown an association between... Show moreIn this thesis we focused on the causes and consequences of hepatic steatosis. Epidemiological studies in humans, as well as experimental studies in animal models, have shown an association between visceral obesity and dyslipidemia, insulin resistance and type 2 diabetes mellitus. The mechanism underlying this association remains unclear. Recently, attention has focused on the role of excessive accumulation of triglycerides (TG) in the liver (hepatic steatosis) in this association. Hepatic steatosis was considered a benign condition until it was discovered that a nonalcoholic fatty liver is associated with many cardiovascular risk factors. Subsequently, many studies have shown a strong association between hepatic TG content and hepatic insulin resistance. The studies in this thesis show that hepatic steatosis is actively and passively involved in the metabolic disturbances in the glucose and lipid metabolism. The prevalence of hepatic steatosis in western countries is high and will certainly increase with the epidemics of obesity and diabetes. This will put an increasing number of subjects at risk for disturbances in the glucose and lipid metabolism and concomitantly for cardiovascular disease. Show less
