Towards a process-based understanding of Holocene polar climate change. Using glacier-fed lake sediments from Arctic Svalbard and Antarctic South Georgia

Earth`s polar regions are undergoing dramatic changes due to ongoing climate change as demonstrated by increasing temperatures, collapsing ice shelves, Arctic sea ice loss and rapid glacier retreat. Driving an accelerating rise in global sea level, this amplified regional response may have devastating global socio-economic consequences in the foreseeable future. Yet the causes and range of polar climate variability remain poorly understood as observational records are short and fragmentary, while climate proxy timeseries remain scarce and often lack resolution. More detailed and longer paleoclimate archives are urgently needed to allow assessment of the full envelope of natural polar climate variability. This would allow us to contextualise ongoing warming and help improve policy scenarios, in effect using the past as the key to both present and future. Glaciers are sensitive recorders of climate variability as demonstrated by their response to ongoing global change. In addition to changes in size, this response is also captured by variations in glacial erosion in alpine glacier systems. The finest constituent of this process, known as glacial flour, is suspended in meltwater streams and may be deposited in downstream lakes. Hence, the bottom sediments of such glacier-fed lakes are continuous archives of past glacier activity and thus represent prime targets for paleoclimate studies. In this thesis, the paleoclimatic potential of glacier-fed lake sediments is harnessed to improve our understanding of past polar climate change. To this end, sensitive sites on Arctic Svalbard and Antarctic South Georgia, in the pathways of major regional circulation patterns, were targeted. Emphasis is placed on the present Holocene interglacial as it is characterised by climatic boundary conditions that are similar to the present. A targeted multi-proxy approach, concentrating on geomorphological mapping, sediment fingerprinting, paleothermometry and advanced numerical techniques, was employed to enhance the potential of glacier-fed lakes as paleoclimate archives. Also, site-specific findings were contextualised through integration in a wider regional paleoclimate framework. This thesis presents the first full Holocene records of glacier variability and summer temperature on Svalbard, in addition to the first continuous reconstruction of Late Holocene glacier Equilibrium Line Altitude (ELA) in the sub-Antarctic. The reported findings indicate a dynamic Holocene climate history of Svalbard, characterised by 1) pervasive Early Holocene glacial meltwater cooling, delaying the Hypsithermal until ± 7 ka BP and culminating in a glacier maximum, 2) a two-stage inception of the Neoglacial between ± 7-5 ka BP, driven by the strengthening influence of Arctic water and sea-ice against a backdrop of decreasing summer insolation and 3) a changeable Neoglacial from 4 ka BP onwards, characterised by a mean cold climate state that was perturbed by centennial-scale temperature excursions and glacial advances that were driven by the interaction between oceanic (AMOC), atmospheric (NAO) and solar forcing. This study shows that Late Holocene climate on South Georgia responded intricate transient phase-dependent interactions between regional circulation patterns (SWW, SAM and ENSO). In addition to these regional forcings, the reconstructed bi-polar expression of the Little Ice Age (LIA) and observed response to recent warming demonstrate the imprint of global forcing(s). Notwithstanding limitations posed by e.g. closed-sum effects on proxy measurements as well as analytical and chronological uncertainties, this work advances our knowledge on Holocene polar climate variability, providing a reference to assess ongoing change. In addition to expanding the spatio-temporal coverage of high latitude proxy archives, future research should focus on 1) the integration of geomorphological mapping and sediment fingerprinting to constrain the signature of lake sedimentation, 2) the development of advanced ELA models in tandem with the application of paleothermometry to constrain the impact of atmosphere-driven shifts in hydroclimate and 3) the application of novel numerical tools to improve the robustness of glacier-fed lake-based paleoclimate studies. Prime examples include integration with model scenarios and instrumental calibration

Beobachtungen von Sternbedeckungen durch den Mond.

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New image analysis of large food particles can discriminate experimentally suppressed mastication

Objective parameters that could provide a basis for food texture selection for elderly or dysphagic patients have not been established. We, therefore, aimed to develop a precise method of measuring large particles (>2 mm in diameter) in a bolus and an analytical method to provide a scientific rationale for food selection under masticatory dysfunction conditions. We developed a new illumination system to evaluate the ability of twenty female participants (mean age, 23·4 ± 4·3 years) to masticate carrots, peanuts and beef with full, half and one quarter of the number of masticatory strokes. We also evaluated mastication under suppressed force, regulated by 20% electromyographic of the masseter muscle. The intercept and inclination of the regression line for the distribution of large particles were adopted as coefficients for the discrimination of masticatory efficiency. Single set of coefficient thresholds of 0·10 for the intercept and 1·62 for the inclination showed excellent discrimination of masticatory conditions for all three test foods with high specificity and sensitivity. These results suggested that our method of analysing the distribution of particles >2 mm in diameter might provide the basis for the appropriate selection of food texture for masticatory dysfunction patients from the standpoint of comminution

Interview met Daphne Smeets -Rijksvoorlichtingsdienst-

Na politicologie gestudeerd te hebben in Leiden, met als oriëntatie de internationale richting, is Daphne Smeets vorig jaar afgestudeerd in vergelijkende politicologie. Tegenwoordig is ze volop actief in de landelijke politiek, bij de Afdeling Informatievoorziening onder de Directie Voorlichting bij de RVD

Secreção salivar e mastigação: efeitos estimulantes de alimento artificial e natural

The aim of the present study was to determine the relationship between the flow rate of saliva and characteristics of the food. Therefore, we determined the rate of saliva secretion in 16 healthy subjects in rest and while chewing natural and artificial foods (toast with and without margarine, three sizes of breakfast cake, and Parafilm). We also determined the chewing rate, number of chewing cycles until swallowing, and time until swallowing. The physical characteristics of the foods were quantified from force-deformation experiments. The results showed that the average at which mechanical failure occurred (yield force) was 1.86 &plusmn; 0.24 N for the breakfast cake and 16.3 &plusmn; 1.3 N for the melba toast. The flow rates obtained without stimulation and with Parafilm were significantly lower (P < 0.001) than the flow rates obtained from chewing food. No differences in flow rate occurred between the natural foods. The flow rates of the saliva as obtained without stimulation, with Parafilm stimulation, and with chewing on the various foods were significantly correlated (P < 0.05). There were no significant differences in chewing rate among the foods. The number of chewing cycles and the time until swallowing significantly depended on the type or volume of the food.O objetivo deste estudo foi determinar a relação entre o fluxo salivar e características de diferentes alimentos. Avaliou-se a taxa de secreção salivar em 16 indivíduos saudáveis, sem estimulação, na estimulação com Parafilm e na mastigação de alimentos naturais (torrada com e sem margarina e 3 volumes de bolo industrial). Determinou-se também a velocidade, o tempo de mastigação, o número de ciclos mastigatórios até o limiar da deglutição. As características físicas dos alimentos foram quantificadas através da experimentação força-deformação. Os resultados mostraram que a média em que a falha mecânica ocorreu foi 1,86 &plusmn; 0,24 N para o bolo industrial e 16,3 &plusmn; 1,3 N para a torrada. Os fluxos salivares obtidos sem estimulação e com a estimulação pelo Parafilm foram significativamente menores (P < 0,001) que os fluxos salivares obtidos na mastigação dos alimentos naturais. Não houve diferença significativa no fluxo salivar entre os alimentos naturais. Os fluxos salivares obtidos sem estimulação, com estimulação pelo Parafilm e na mastigação dos vários alimentos foram significantemente correlacionados (P < 0,05). Não houve diferença significativa na velocidade da mastigação entre os alimentos. O número de ciclos mastigatórios e o tempo de mastigação até o limiar da deglutição dependeram do tipo e do volume do alimento

ICT: hoe en wat?

Informatie- en communicatietechnologie (ICT)I is-voor veel studenten een nieuw begrip. Het is een meer en meer gehoorde term de laatste jaren, ook in het openbaar bestuur. Van het begrip ICT bestaat geen eenduidige definitie. Een brede omschrijving zou kunnen zijn: activiteiten, producten en processen op het gebied van multimedia, simulaties, teleleren en telewerken die op efficiënte wijze voorzien in de informatiebehoefte van gebruikers. Tegenwoordig wordt wel gesproken van een ICT revolutie: ontwikkelingen volgen elkaar in hoog tempo op, zowel wat betreft innovaties als wat betreft verspreiding binnen de maatschappij. Wat houdt de ontwikkeling nu eigenlijk in en wat is de stand van zaken binnen de overheid