XML-driven exploitation of combined scalability in scalable H.264/AVC bitstreams

The heterogeneity in the contemporary multimedia environments requires a format-agnostic adaptation framework for the consumption of digital video content. Scalable bitstreams can be used in order to satisfy as many circumstances as possible. In this paper, the scalable extension on the H.264/AVC specification is used to obtain the parent bitstreams. The adaptation along the combined scalability axis of the bitstreams is done in a format-independent manner. Therefore, an abstraction layer of the bitstream is needed. In this paper, XML descriptions are used representing the high-level structure of the bitstreams by relying on the MPEG-21 Bitstream Syntax Description Language standard. The exploitation of the combined scalability is executed in the XML domain by implementing the adaptation process in a Streaming Transformation for XML (STX) stylesheet. The algorithm used in the transformation of the XML description is discussed in detail in this paper. From the performance measurements, one can conclude that the STX transformation in the XML domain and the generation of the corresponding adapted bitstream can be realized in real time

Concise report : teenage sexting on the rise? Results of a cohort study using a weighted sample of adolescents

Background: The vast differences in sampling techniques, cultural contexts between international studies, the differences in age groups of the samples and various definitions used to measure sexting make it hard to compare how sexting behaviour has evolved over the past years. This exploratory study aims to address this critical gap in the research by using two datasets of a biennial study on adolescents' media use. The first aim of this study is to compare the sexting prevalence and correlates (i.e. age, gender and smartphone ownership) of youth in 2015 and 2017. The second aim is to investigate the risk mitigation behaviours of youth who engage in sexting and to assess how their behaviours differ between the two time points. Methods: The data for cohort 1 were collected in October and November 2015 and comprise of 2663 students from 11 secondary schools in the Dutch-speaking community of Belgium. For the second cohort, the data were collected in October and November 2017 and comprise of 2681 students from 10 secondary schools. A weighing factor was implemented on the dataset. Results: The results show sexting behaviour has significantly increased between cohorts, with 8.3% of the respondents having sent a sext in the first cohort, compared with 12.1% in the second cohort. The sexting prevalence rates also significantly increased between cohorts when taking into account students who owned a smartphone. Furthermore, engagement in sexting was associated with being older, and no gender differences were found. In the second cohort, 36.8% of youth who had sent a sext were identifiable in those images. There were no differences between cohorts. Conclusion: The results indicate that other factors next to smartphone ownership may be associated with an increase in sexting prevalence. The findings also highlight the need for the development of age-appropriate sexting educational materials

Kosten en baten van bodemmaatregelen : Grondbewerking, organische stofaanvoer en Tagetes patula als aaltjesvanggewas

Bodemstructuur, organische stof en bodemgezondheid zijn belangrijke aandachtspunten in de akkerbouw. In langjarige systeemproeven op verschillende grondsoorten is onderzoek gedaan naar verschillende grondbewerkingsmethoden, organische stofstrategieën en aaltjesvanggewassen. In deze kosten-batenanalyse zijn de resultaten van de proeven geëvalueerd. De onderzochte maatregelen laten economisch vaak relatief kleine verschillen zien met de referentie. In een aantal gevallen is er wel een groter verschil, vooral als de opbrengst van hoogsalderende gewassen door de maatregel verandert. Dat is soms positief (hogere lelie-opbrengst door Tagetes patula als aaltjesvanggewas), soms negatief (lagere peen-opbrengst door NKG op klei)

Verduurzaming samenwerking akkerbouw-veehouderij in Drenthe : Expertbeoordeling en advies

Samenwerking tussen akkerbouw- en melkveebedrijven komt veel voor in Drenthe, met name in de vorm van grondruil. De provincie heeft Wageningen UR gevraagd om een expertbeoordeling voor de volgende vraag: is deze huidige vorm van samenwerking duurzaam en waar is nog winst te halen? Daarbij werd specifiek aandacht gevraagd voor organische stof, nutriëntenefficiëntie, bodemgezondheid en de inzet van gewasbeschermingsmiddelen. Uit de beoordeling blijkt dat de huidige vorm van samenwerking qua duurzaamheid niet of nauwelijks afwijkt van de situatie zonder samenwerking. Op de verschillende duurzaamheidsthema’s is nog wel winst te behalen. Het is daarvoor nodig dat de samenwerkende bedrijven gezamenlijk een teelt- en bodemplan maken

The Tully-Fisher relations of early-type spiral and S0 galaxies

We demonstrate that the comparison of Tully-Fisher relations (TFRs) derived from global HI line widths to TFRs derived from the circular velocity profiles of dynamical models (or stellar kinematic observations corrected for asymmetric drift) is vulnerable to systematic and uncertain biases introduced by the different measures of rotation used. We therefore argue that to constrain the relative locations of the TFRs of spiral and S0 galaxies, the same tracer and measure must be used for both samples. Using detailed near-infrared imaging and the circular velocities of axisymmetric Jeans models of 14 nearby edge-on Sa-Sb spirals and 14 nearby edge-on S0s drawn from a range of environments, we find that S0s lie on a TFR with the same slope as the spirals, but are on average 0.53+/-0.15 mag fainter at Ks-band at a given rotational velocity. This is a significantly smaller offset than that measured in earlier studies of the S0 TFR, which we attribute to our elimination of the bias associated with using different rotation measures and our use of earlier type spirals as a reference. Since our measurement of the offset avoids systematic biases, it should be preferred to previous estimates. A spiral stellar population in which star formation is truncated would take ~1 Gyr to fade by 0.53 mag at Ks-band. If S0s are the products of a simple truncation of star formation in spirals, then this finding is difficult to reconcile with the observed evolution of the spiral/S0 fraction with redshift. Recent star formation could explain the observed lack of fading in S0s, but the offset of the S0 TFR persists as a function of both stellar and dynamical mass. We show that the offset of the S0 TFR could therefore be explained by a systematic difference between the total mass distributions of S0s and spirals, in the sense that S0s need to be smaller or more concentrated than spirals.Comment: Accepted for publication in MNRAS; 17 pages; v2 incorporates minor proof corrections and updated reference

Cultureel-archeologisch en ecologisch onderzoek van twee vroegmiddeleeuwse waterputten uit Nijlen: landschap en landgebruik

Bij opgravingen op de terreinen van de verkaveling Mussenpad, niet ver van de kerk van Nijlen, kwamen onder meer twee goed bewaarde eikenhouten vroegmiddeleeuwse waterputten aan het licht. Na de opgravingen werd beslist om op artefacten en ecologisch materiaal uit deze twee waterputten verdere natuurwetenschappelijke analyses en detailstudies uit te voeren. Het doel van dit vervolgonderzoek was het lokale landschap en het landgebruik zo goed als mogelijk te reconstrueren. De verschillende vondstencategorieën geven samen een coherent beeld van de vroegere omgeving. Het archeologisch onderzoek in Nijlen-Mussenpad documenteert bovendien ook vroegmiddeleeuwse metaalverwerking in ruraal gebied. Dit is een voor Vlaanderen weinig beschreven gegeven. Deze artisanale onderneming werd klaarblijkelijk op enige afstand van de behuizing georganiseerd. Het gaat hier over een productie die de plaatselijke noden van een kleine gemeenschap oversteeg en die dus een wijder afzetgebied moet gekend hebben

Long-wavelength observations of debris discs around sun-like stars

[Abridged] We present two deep surveys of circumstellar discs around solar-type stars at different ages carried out at 350 micron with the CSO and at 1.2 mm with the IRAM 30-m telescope. The aim of this study is to understand the evolution timescale of circumstellar debris discs, and the physical mechanisms responsible for such evolution around solar-type stars. In addition, we perform a detailed characterisation of the detected debris discs. Theoretically, the mass of the disc is expected to decrease with time. In order to test this hypothesis, we performed the generalised Kendall's tau correlation and three different two-sample tests. A characterisation of the detected debris discs has been obtained by computing the collision and Poynting-Robertson timescales and by modelling the spectral energy distribution. The Kendall's tau correlation yields a probability of 76% that the mass of debris discs and their age are correlated. Similarly, the three two-sample tests give a probability between 70 and 83% that younger and older debris systems belong to different parent populations in terms of dust mass. We detected submillimetre/millimetre emission from six debris discs, enabling a detailed SED modelling. Our results on the correlation and evolution of dust mass as a function of age are conditioned by the sensitivity limit of our survey. Deeper millimetre observations are needed to confirm the evolution of debris material around solar-like stars. In the case of the detected discs, the comparison between collision and Poynting-Robertson timescales supports the hypothesis that these discs are collision dominated. All detected debris disc systems show the inner part evacuated from small micron-sized grains.Comment: Accepted by A&