Determination of tissue-level strains in trabecular structures with a 3-D digital image correlation technique

Poster 051

Runderbegrazing en erosiebestendigheid op primaire waterkeringen in de Hoeksche Waard en het Eiland van Dordrecht

Ter ondersteuning van het integraal beleid voor het behoud en beheer van waterkeringen is onderzoek verricht naar het effect van runderbegrazing op de erosiebestendigheid van dijkgraslanden. Het doel is om, met het oog op de gewenste dijkgraslandkwaliteit, runderbegrazing te heroverwegen, danwel de voorwaarden voor runderbegrazing aan te passen

Effects of PTH treatment on tibial bone of ovariectomized rats assessed by in vivo micro-CT

Summary: Using in vivo microcomputed tomography (micro-CT), we found in parathyroid hormone (PTH)-treated osteopenic rats linear increases in cortical and trabecular, due to increased trabecular thickness and number, bone mass. Bone was formed in cavities, leading to restoral of nearly cleaved trabeculae. For the first time, effects in PTH-treated rats were analyzed longitudinally. Introduction: Our aims were to over time (1) determine changes in trabecular thickness and number after PTH, (2) compare responses to PTH between the meta- and epiphysis, (3) determine effects of PTH on mineralization and mechanical properties, (4) determine locations of new bone formation due to PTH on a microlevel, and (5) determine the predictive value of bone structural properties for gain in bone mass after PTH. Methods: Adult rats were divided into ovariectomy (OVX; n = 8), SHAM-OVX (n = 8), and OVX and PTH treatment (n = 9). Between weeks 8 and 14, PTH rats received daily subcutaneous PTH injections (60 µg/kg/day). At weeks 0, 8, 10, 12, and 14, in vivo micro-CT scans were made of the proximal and diaphyseal tibia. After sacrifice, all tibiae were tested in three-point bending. Results: PTH increased bone volume fraction linearly over time in meta- and epiphysis, accompanied by increased trabecular thickness in both and increased trabecular number only in the latter one. CT-estimated mineralization increased in trabecular and remained constant in cortical bone. Ultimate load and energy were increased and ultimate displacement and stiffness unaltered compared to SHAM rats. For those trabeculae analyzed, bone was formed initially on places where it was most beneficial for increasing their strength and later on to all surfaces. © 2009 The Author(s)

Biodiversiteit op de Scheldeschorren

The tidal marshes along the Scheldt estuary are rather unique in Europe, because they still exist along the complete salinity gradient. Key ecological factors for the vegetation are salinity, tidal regime and current and historical management. A general portrait with the most characterising plant species as well as a succession scheme are presented for salt, brackish and fresh tidal marshes separately, because they have few plant species and vegetation types in common. Tidal regime changes as a combined effect of sea level rise and the channel deepening in the Westerscheldt. This affects the marsh vegetation. Biodiversity patterns and factors affecting the distribution of species on the tidal marshes are discussed for plants, gastropodes, arthropodes and birds. In general the number of species on the tidal marshes increases from salt to fresh water and from higher to lower inundation frequencies. However salt and brackish marshes accommodate relatively more specific, rare and vulnerable species. Faunal communities are much less known and understood as compared to vegetation and need more integrated monitoring

Inventarisatie erosiebestendigheid dijkgraslanden in de Krimpenerwaard

Met behulp van de Leidraad Toetsen op Veiligheid (TAW 1999) dienen de waterkeringen middels een vijfjaarlijkse veiligheidstoetsing te worden onderzocht op hun veiligheid tegen overstromen, zoals vastgelegd in de Wet op de waterkering. Een deel van deze toets betreft de bekleding van de dijk. Door het Hoogheemraadschap van de Krimpenerwaard zijn een aantal dijktrajecten geselecteerd, waar Alterra in 2003 de vegetatie heeft onderzocht door middel van een vegetatieopname, de bedekking heeft geschat en de doorworteling heeft gemeten. Met deze informatie is de erosiebestendigheid van dijkgrasland op de onderdelen vegetatie, bedekking en doorworteling getoetst