An average case analysis of the minimum spanning tree heuristic for the range assignment problem

We present an average case analysis of the minimum spanning tree heuristic for the range assignment problem on a graph with power weighted edges. It is well-known that the worst-case approximation ratio of this heuristic is 2. Our analysis yields the following results: (1) In the one dimensional case ($d = 1$), where the weights of the edges are 1 with probability $p$ and 0 otherwise, the average-case approximation ratio is bounded from above by $2-p$. (2) When $d =1$ and the distance between neighboring vertices is drawn from a uniform $[0,1]$-distribution, the average approximation ratio is bounded from above by $2-2^{-\alpha}$ where $\alpha$ denotes the distance power radient. (3) In Euclidean 2-dimensional space, with distance power gradient $\alpha = 2$, the average performance ratio is bounded from above by $1 + \log 2$

Tetragonal zirconia: Wet chemical preparation, mechanical and electrical properties

Yttria-stabilized zirconia powders were prepared in the composition range of 3 to 13 at% yttria. The hydrolysis-gel precipitation technique was used, starting from metal alkoxides or chlorides. In the composition range between 5 and 10 at% yttria, the materials sintered at 1250°C have a fully tetragonal structure. The density was higher than 95% and the grain sizes can be varied between 0.1 and 0.5μm depending on the preparation conditions. The fracture toughness KIC amounts 6 to 11 MPam but is not dependent on the composition. The transformation toughening mechanism and the properties of the tetragonal phase itself play an important role in the increase of KIC compared with cubic materials. The magnitude of the oxygen-ion conductivity value is comparable with that for cubic materials

Annual Report Ant Smelt 2010: A changing role for smelt Osmerus eperlanus in the Lake IJsselmeer and Lake Markermeer foodweb? Climate- and nutrient-induced changes in ecoystem functioning

The smelt project is part of a larger research project that aims at generating, exploring and testing different possible explanations for the observed Autonomous Negative Trends (ANT) in water fowl in Lake Markermeer and Lake IJsselmeer. The smelt populations in both lakes have been in severe decline since 1990. These declines have a large impact on the conservation of water birds relying on smelt as their prey and the fishery both on smelt and on piscivorous fish relying on smelt. In winter time the Lake IJsselmeer area is home to the largest population of waterfowl in Western Europe. The area is therefore considered to be an important Natura-2000 area. Identification of the causes of the observed negative trends will help managers (RWS) to take the appropriate restoration measures and thereby improve the these lakes as habitat for waterfowl

Effects of retro-nasal aroma release on satiation

It is suggested that the brain response of a food odour sensed retro-nasally is related to satiation. The extent of retro-nasal aroma release during consumption depends on the physical structure of a food, i.e. solid foods generate a longer, more pronounced retro-nasal aroma release than liquid foods. The aim of this study was to investigate if a beverage becomes more satiating when the retro-nasal aroma release profile coincides with the profile of a (soft) solid food. In a double-blind placebo-controlled randomised cross-over full factorial design, twenty-seven healthy subjects (fourteen males and thirteen females; aged 16-65 years; BMI 19-37 kg/m(2) were administered aroma profiles by a computer-controlled stimulator based on air dilution olfactometry. Profile A consisted of a profile that is obtained during consumption of normal beverages. Profile B is normally observed during consumption of (soft) solids. The two profiles were produced with strawberry aroma and administered in a retro-nasal fashion, while the subjects consumed a sweetened milk drink. Before, during and after the sensory stimulation, appetite profile measurements were performed. Subjects felt significantly more satiated if they were aroma stimulated with profile B (P = 0.04). After stimulation with sweet strawberry aroma, there was a significant decrease in desire to eat sweet products (P = 0.0001). In conclusion, perceived satiation was increased by altering the extent of retro-nasal aroma release

Recreatieve visserij onder de loep

Hoeveel recreatieve vissers zijn er in Nederland en hoeveel vis vangen deze vissers? Deze op het eerste gezicht simpele vraag is volgens IMARES onderzoeker Martin de Graaf in de praktijk niet eenvoudig te beantwoorden. Vooral het nauwkeurig schatten van het aantal sportvissers en hun vangsten is vaak een lastige opgave

Report on the eel stock and eel fishery in the Netherlands in 2010

Onderliggend rapport bevat het overzicht van de toestand van de aalstand in Nederland dat in de zomer van 2011 is opgesteld. De tijdreeksen in dit rapport lopen tot en met 2010, met uitzondering van de glasaalintrek waarvoor gegevens tot en met het voorjaar van 2011 beschikbaar zijn

SCIAMACHY Absorbing Aerosol Index ? calibration issues and global results from 2002?2004

International audienceThe validity of the Absorbing Aerosol Index (AAI) product from the SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY (SCIAMACHY) is discussed. The operational SCIAMACHY AAI product suffers from calibration errors in the reflectance as measured by SCIAMACHY and neglect of polarisation effects in the AAI computational algorithm. Therefore, the AAI product was recalculated, compensating for the errors, with reflectance data from the start of measurements of SCIAMACHY until December 2004. Appropriate correction factors were determined for the UV to correct for the radiometric error in the SCIAMACHY reflectances. The algorithm was provided with LookUp Tables in which a good representation of polarisation effects was incorporated, as opposed to the LookUp Tables of the operational product, in which polarisation effects were not accounted for. The results are presented, their validity discussed, and compared to the operational product and independent AAI data from the Total Ozone Mapping Spectrometer (TOMS). The AAI is very sensitive to calibration errors and can be used to monitor calibration errors and changes. The AAI is sensitive to sunglint and a correction flag used for the AAI is presented. From 2004 onwards, the new SCIAMACHY AAI is suitable to add to the continuation of the long-term AAI record. Important changes in the long-term AAI record due to instrument and algorithm changes are highlighted. Recommendations are given for improvement of the operational AAI product

Stability of additive-free water-in-oil emulsions

We calculate ion distributions near a planar oil-water interface within non-linear Poisson-Boltzmann theory, taking into account the Born self-energy of the ions in the two media. For unequal self-energies of cations and anions, a spontaneous charge separation is found such that the water and oil phase become oppositely charged, in slabs with a typical thickness of the Debye screening length in the two media. From the analytical solutions, the corresponding interfacial charge density and the contribution to the interfacial tension is derived, together with an estimate for the Yukawa-potential between two spherical water droplets in oil. The parameter regime is explored where the plasma coupling parameter exceeds the crystallization threshold, i.e. where the droplets are expected to form crystalline structures due to a strong Yukawa repulsion, as recently observed experimentally. Extensions of the theory that we discuss briefly include numerical calculations on spherical water droplets in oil, and analytical calculations of the linear PB-equation for a finite oil-water interfacial width.Comment: 9 pages, 4 figures, accepted by JPCM for proceedings of LMC