Effectgerichte maatregelen voor het herstel en beheer van stuifzanden

Onderzoek naar het functioneren van stuifzanden onder gewijzigde abiotische condities en naar beheer en herstel van klein- en grootschalige stuifzandlandschappen. Waarin bijdragen: Bosschap, Stichting Bargerveen, Radboud Universiteit, Universiteit Amsterdam, SOVON, Vlinderstichting, Alterra en Stichting Geomofologie en Landschap. Het is een vervolg op Preadvies stuifzanden (Bakker, 2003)

Contextual uncertainty determines early attentional orienting in visual selection

Our attention can be inadvertently captured by irrelevant or distracting stimuli. Past work has shown that knowledge about the search context in which targets and distractors occur, such as where distractors often occur, can greatly reduce attentional capture. In this study, we set out to show that uncertainty about this context (or contextual variability) is another critical determinant of attentional capture by physically salient distractors. Specifically, in three (preregistered) capture-probe experiments (n =288, n = 114, n = 114), we manipulated singleton distractor location and context uncertainty separately from set size. We found that rendering the distractor location less variable did not affect attentional capture. However, when contextual uncertainty was reduced, by keeping parts of the search display fixed across trials or by exposing participants to a restricted set of search configurations, attentional capture disappeared. Our findings support the notion that contextual uncertainty is a critical factor determining whether salient distractors capture attention.</p

POSA: Perl Objects for DNA Sequencing Data Analysis

BACKGROUND: Capillary DNA sequencing machines allow the generation of vast amounts of data with little hands-on time. With this expansion of data generation, there is a growing need for automated data processing. Most available software solutions, however, still require user intervention or provide modules that need advanced informatics skills to allow implementation in pipelines. RESULTS: Here we present POSA, a pair of new perl objects that describe DNA sequence traces and Phrap contig assemblies in detail. Methods included in POSA include basecalling with quality scores (by Phred), contig assembly (by Phrap), generation of primer3 input and automated SNP annotation (by PolyPhred). Although easily implemented by users with only limited programming experience, these objects considerabily reduce hands-on analysis time compared to using the Staden package for extracting sequence information from raw sequencing files and for SNP discovery. CONCLUSIONS: The POSA objects allow a flexible and easy design, implementation and usage of perl-based pipelines to handle and analyze DNA sequencing data, while requiring only minor programming skills

Gully cut- and- fill cycles as related to agromanagement : a historical curve number simulation in the Tigray Highlands

Gully cut-and-fill dynamics are often thought to be driven by climate and/or deforestation related to population pressure. However, in this case-study of nine representative catchments in the Northern Ethiopian Highlands, we find that neither climate changes nor deforestation can explain gully morphology changes over the twentieth century. Firstly, by using a Monte Carlo simulation to estimate historical catchment-wide curve numbers, we show that the landscape was already heavily degraded in the nineteenth and early twentieth century – a period with low population density. The mean catchment-wide curve number (> 80) one century ago was, under the regional climatic conditions, already resulting in considerable simulated historical runoff responses. Secondly, twentieth century land-cover and runoff coefficient changes were confronted with twentieth century changing gully morphologies. As the results show, large-scale land-cover changes and deforestation cannot explain the observed processes. The study therefore invokes interactions between authigenic factors, small-scale plot boundary changes, cropland management and sociopolitical forces to explain the gully cut processes. Finally, semi-structured interviews and sedistratigraphic analysis of three filled gullies confirm the dominant impact of (crop)land management (tillage, check dams in gullies and channel diversions) on gully cut-and-fill processes. Since agricultural land management – including land tenure and land distribution – has been commonly neglected in earlier related research, we argue therefore that it can be a very strong driver of twentieth century gully morphodynamics

Single and combined effects of αvβ3- and α5β1-integrins on capillary tube formation in a human fibrinous matrix

The fibrinous exudate of a wound or tumor stroma facilitates angiogenesis. We studied the involvement of RGD-binding integrins during tube formation in human plasma-derived fibrin clots and human purified fibrin matrices. Capillary-like tube formation by human microvascular endothelial cells in a 3D plasma-derived fibrinous matrix was induced by FGF-2 and TNF-α and depended largely on cell-bound u-PA and plasmin activities. While tube formation was minimally affected by the addition of either the αvβ3-integrin inhibiting mAb LM609 or the α5-integrin inhibiting mAb IIA1, the general RGD-antagonist echistatin completely inhibited this process. Remarkably, when αvβ3- and α5β1-integrins were inhibited simultaneously, tube formation was reduced by 78%. It was accompanied by a 44% reduction of u-PA antigen accumulation and 41% less production of fibrin degradation products. αvβ5-integrin-blocking antibodies further enhanced the inhibition by mAb LM609 and mAb IIA1 to 94%, but had no effect by themselves. αv-specific cRGD only inhibited angiogenesis when α5β1-integrin was simultaneously blocked. Endostatin mimicked the effect of α5β1-integrin and inhibited tube formation only in the presence of LM609 or cRGD (73 and 80%, respectively). Comparable results were obtained when purified fibrin matrices were used instead of the plasma-derived fibrinous matrices. These data show that blocking of tube formation in a fibrinous exudate requires the simultaneous inhibition of αvβ3- and α5β1-integrins. This may bear impact on attempts to influence angiogenesis in a fibrinous environment

Comparative analysis of models for design of infiltration basins in unpaved roads

Unpaved roads are of great importance for the economic and social development of a country. Water erosion provoked by the concentration of runoff along the road is a principle cause of its degradation. The construction of infiltration basins for runoff retention on unpaved roads is a usually alternative for the problem solution. The use of more coherent methodologies for designing infiltration basins is fundamental for the appropriate road degradation processes control. Therefore, the objective of this work was to perform a comparative analysis of a methodology for the design of infiltration basins that consider an intense rainfall associated to a determined return period, with a methodology that use all events of a determined precipitation series, and overlapping effects of their respective runoff volumes. According to the obtained results, it was found that the volume calculated for the infiltration basin by the model which considers all events of the precipitation series is greater when the rate of water infiltration into the soil at the basin bottom is lowest.Estradas não pavimentadas são imprescindíveis para o desenvolvimento econômico e social de um país. A erosão provocada pela concentração do escoamento superficial ao longo da estrada é a principal causa da sua degradação. A construção de bacias de infiltração para reter o volume do escoamento superficial proveniente das estradas não pavimentadas, consiste em uma alternativa comumente empregada para a solução do problema. O uso de metodologias mais coerentes para o dimensionamento de bacias de infiltração é fundamental para controlar, de forma mais adequada, o processo de degradação das estradas. Assim, o objetivo deste trabalho foi a realização de uma análise comparativa de uma metodologia para o dimensionamento de bacias de infiltração, que considera uma chuva intensa associada a determinado período de retorno, com uma metodologia que pondera uma série histórica de eventos de precipitação. Evidenciou-se, de acordo com os resultados obtidos, que o volume da bacia de infiltração calculado pelo modelo que leva em consideração todos os eventos da série de precipitação, é maior quando a taxa de infiltração da água no solo no fundo da bacia é menor