OLFAR a radio telescope based on nano satellites in moon orbit

It seems very likely that missions with nano-satellites in professional scientific or commercial applications will not be single-satellite missions. Well structured formations or less structured swarms of nano-satellites will be able to perform tasks that cannot be done in the “traditional” way. The Dutch space-born radio telescope project OLFAR, the Orbiting Low Frequency Array, is a good example of a typical “swarm task”. The OLFAR radio telescope will be composed of an antenna array based on nano-satellites orbiting the moon to shield the receiving nodes from terrestrial interference. The array will receive frequencies in a band from around 30 kHz to 30 MHz. This frequency band is scientifically very interesting, since it will be able to detect signals originating from the yet unseen “Dark Ages” ranging from the Big Bang until around 400 million year after. Another science driver is the LF activity from (exo) planets. In this paper the design parameters for the satellites and the swarm will be given and status of the OLFAR project will be reported. Details will be given about the antenna system, the LF-receiver and the signals that are expecte

Matching Queries to Frequently Asked Questions: Search Functionality for the MRSA Web-Portal

As part of the long-term EUREGIO MRSA-net project a system was developed which enables health care workers and the general public to quickly find answers to their questions regarding the MRSA pathogen. This paper focuses on how these questions can be answered using Information Retrieval (IR) and Natural Language Processing (NLP) techniques on a Frequently-Asked-Questions-style (FAQ) database

Behandeling, controle en metabole instelling van patiënten met diabetes mellitus type II en de prevalentie van late complicaties bij deze patiënten

Diabetes mellitus is een frequent voorkomende stofwisselingsaandoening, die in minstens twee afzonderlijke ziekten uiteenvalt. Dit zijn het type I diabetes mellitus, de insuline-afhankelijke vorm en het type ll diabetes mellitus, de niet primair insuline-afhankelijke vorm. Beide typen hebben gemeen dat zogenaamde late complicaties kunnen ontstaan. Dit zijn afwijkingen van de ogen, nieren, zenuwen, hart en bloedvaten, die zich in de loop van de ziekte diabetes mellitus kunnen ontwikkelen. Type 11 diabetes mellitus komt ook in Nederland veel voor; er wordt wel aangenomen dat er ongeveer 200.000 patiënten met type ll bekend zijn, tegenover ongeveer 50.000 patiënten met type I diabetes mellitus. De meeste patiënten met het type Il diabetes mellitus worden in Nederland door de huisarts behandeld en gecontroleerd. In zijn zogenaamde "Basistakenpakket" wordt de zorg voor de patiënt met type Il diabetes mellitus als zodanig expliciet genoemd. Er zijn echter weinig gegevens bekend over de populatie patiënten met type 11 diabetes mellitus. Met name ontbreken veel gegevens over de wijze van controle en behandelen, de mate van metabole instelling, de prevalentie van late complicaties en de vroege stadia van deze late complicaties

Nutrient Cycling and Retention Along a Littoral Gradient in a Dutch Shallow Lake in Relation to Water Level Regime

Littoral zones are characterized by gradients in depth and vegetation biomass, influencing nutrient retention capacity. A field experiment was conducted in a Phragmites australis dominated littoral zone to investigate nutrient retention and its effect on surface water quality. Measurements were done in mesocosms where water levels could be manipulated. Nutrient status was investigated along a gradient perpendicular to the shore during two growing seasons, one with a stable water level and one with a gradually decreasing water level. Nutrient concentrations in sediment, soil pore water and surface water were significantly lower in the vegetated than in the unvegetated zone. The negative correlations of nutrients in sediment and water, with nutrient contents of the vegetation suggest a direct effect of the vegetation. Nutrient uptake and biomass of the vegetation was higher in continuously flooded soils than in seasonally emerging sediments higher along the littoral gradient, probably due to the increased salinity in drained zones. Denitrification rate was highest in the unvegetated zone and was positively related to water level. Flooded littoral zones did result in a higher nutrient retention than drained zones. On small scale, for an optimal nutrient retention a fluctuating regime is not necessarily better suited than a stable water level, but on a larger scale it can substantially increase the width of the vegetated zone. It is important to optimize conditions for helophyte growth since the positive effect of vegetation on nutrient retention, at least at local scale, has been demonstrated in this study

Completeness of the cubic and quartic H\'enon-Heiles Hamiltonians

The quartic H\'enon-Heiles Hamiltonian $H = (P_1^2+P_2^2)/2+(\Omega_1 Q_1^2+\Omega_2 Q_2^2)/2 +C Q_1^4+ B Q_1^2 Q_2^2 + A Q_2^4 +(1/2)(\alpha/Q_1^2+\beta/Q_2^2) - \gamma Q_1$ passes the Painlev\'e test for only four sets of values of the constants. Only one of these, identical to the traveling wave reduction of the Manakov system, has been explicitly integrated (Wojciechowski, 1985), while the three others are not yet integrated in the generic case $(\alpha,\beta,\gamma)\not=(0,0,0)$. We integrate them by building a birational transformation to two fourth order first degree equations in the classification (Cosgrove, 2000) of such polynomial equations which possess the Painlev\'e property. This transformation involves the stationary reduction of various partial differential equations (PDEs). The result is the same as for the three cubic H\'enon-Heiles Hamiltonians, namely, in all four quartic cases, a general solution which is meromorphic and hyperelliptic with genus two. As a consequence, no additional autonomous term can be added to either the cubic or the quartic Hamiltonians without destroying the Painlev\'e integrability (completeness property).Comment: 10 pages, To appear, Theor.Math.Phys. Gallipoli, 34 June--3 July 200

An extensive and autonomous deep space navigation system using radio pulsars

Interstellar navigation poses significant challenges in all aspects of a spacecraft. One of them is reliable, low-cost, real-time navigation, especially when there is a considerable distance between Earth and the spacecraft in question. In this paper, a complete system for navigation using pulsar radio emissions is described and analysed. The system uses a pulsar‟s emissions in the radio spectrum to create a novel system capable of fully autonomous navigation. The system is roughly divided into two parts, the front - end and the back - end, as well as their subdivisions. The front - end performs initial signal reception and pre-processing. It applies time-based coherent de-dispersion to allow for low-power on-board processing, and uses a very wide bandwidth to limit the required antenna size. As a result, the electronics required performing the processing is complex, but the system is well limited in both size and power consumption

Cell-wall polysaccharides play an important role in decay resistance of Sphagnum and actively depressed decomposition in vitro

Sphagnum-dominated peatlands head the list of ecosystems with the largest known reservoirs of organic carbon (C). The bulk of this C is stored in decomposition-resistant litter of one bryophyte genus: Sphagnum. Understanding how Sphagnum litter chemistry controls C mineralization is essential for understanding potential interactions between environmental changes and C mineralization in peatlands. We aimed to separate the effects of phenolics from structural polysaccharides on decay of Sphagnum. Wemeasured aerobic microbial respiration of different moss litter types in a lab. We used chemical treatments to step-wise remove the chemical compounds thought to be important in decay-resistance in three taxonomically distant moss genera. We also focused on the effect of Sphagnum-specific cell-wall pectin-like polysaccharides (sphagnan) on C and N mineralization. Removing polymeric lignin-like phenolics had only negligible effects on C mineralization of Sphagnum litter, but increased mineralization of two other bryophyte genera, suggesting a minor role of these phenolics in decay resistance of Sphagnum but a major role of cell-wall polysaccharides. Carboxyl groups of pectin-like polysaccharides represented a C-source in non-Sphagnum litters but resisted decay in Sphagnum. Finally, isolated sphagnan did not serve as C-source but inhibited C and N mineralization instead, reminiscent of the effects reported for phenolics in other ecosystems. Our results emphasize the role of polysaccharides in resistance to, and active inhibition of, microbial mineralization in Sphagnum-dominated litter. As the polysaccharides displayed decay-inhibiting properties hitherto associated with phenolics (lignin, polyphenols), it raises the question if polysaccharide- dominated litter also shares similar environmental controls on decomposition, such as temperature or nutrient and water availabilit

On reductions of some KdV-type systems and their link to the quartic He'non-Heiles Hamiltonian

A few 2+1-dimensional equations belonging to the KP and modified KP hierarchies are shown to be sufficient to provide a unified picture of all the integrable cases of the cubic and quartic H\'enon-Heiles Hamiltonians.Comment: 12 pages, 3 figures, NATO ARW, 15-19 september 2002, Elb

Over vlugge spraak en vluchtige sjwa’s De relatie tussen spreektempo en de duur van Nederlandse svarabhaktivocalen

This study investigates the relationship between speech tempo and the duration of epentheticschwa in Dutch. The speech materials consisted of the spontaneous speech of 160 teachers of Dutch: these speakers were equally distributed over four different regions in Belgium and the Netherlands. There were an equal number of men and women. The research focus was on 750words which contained a consonant cluster with ras the first element and a non-alveolar consonant or nas the second element. These words consisted of two or three syllables after schwa insertion (e.g., werk‘work’ > [wɛrək], werken‘to work’ > [wɛrəkən]). The speech rate of these words was calculated and the duration of any inserted schwa was measured. As predicted, the results show a clear relationship between speech rate and the duration of schwa: faster speech yields shorter schwas. Besides this general trend a statistically significant effect was found of geographical region, the number of syllables, the place of articulation of rand the second element of the consonant cluster. In addition, there was a significant interaction between speech tempo and the schwa duration in men and women: women produce shorter schwas in faster speech, while their shwas in slower speech are longer thanthose in men. As such the durational differences in schwa are more outspoken in women thanin men. This can be accounted for by the general trend that vowels are generally longer in women’s speech. The shorter schwa durations in women’s fast speech may have to do with the fact that it is easier for women to bridge articulatory distances as a result of smaller oral cavity volume