379 research outputs found
Lead toxicity to wildlife: Derivation of a critical blood concentration for wildlife monitoring based on literature data
No full textGeneric risk assessments of lead (Pb) toxicity to wildlife puts soil Pb limits below the natural background. The Tissue Residue Approach (TRA) is an alternative method by which the current risk of Pb to wildlife can be assessed and avoids uncertainties about Pb exposure routes or bioavailability of environmental Pb. About 80 toxicity studies were reviewed of which 19 experimental and 6 field studies with mammals and birds were selected. Blood lead concentration (Pb-B, mu g Pb/dL) was used as the index of exposure. The highest No Observed Effect Concentrations (NOECs) varied about 1600-fold among species and tests when expressed as external doses (mg Pb/kg body weight/day) whereas this range reduced to 50-fold when expressed as Pb-B. This illustrates that variation in Pb absorption from diet largely contributes to the variation in critical doses. A critical Pb-B concentration protecting mammals and birds from Pb toxicity was calculated with the HC(5) approach, i.e. the 5th percentile of species NOEC values with data of 15 different species and using growth, reproduction or hematology as endpoints. The HC(5) was significantly lower for mammals than that for birds (p <0.05), suggesting that the association between blood lead concentration and systemic toxicity was different between the two groups. The HC(5) was 18 mu g/dL for mammals and was 71 mu g/dL for birds. The dose-response relationship between hematological effects (hemoglobin concentration, hematocrit) and Pb-B was aggregated for different species. These relationships were highly significant and significantly different between mammals and birds. The relationships predict that the % inhibitions of hematological endpoints at the calculated HC(5) values are only 1.5% in mammals and 2% in birds. clearly within the natural variation. (C) 2009 Elsevier B.V. All rights reserved
Dike relocation Nijmegen-lent: example of adaptive water management?
No full textDike relocation Nijmegen-lent: example of adaptive water management? — TU Delft Research Portal Skip to main navigation Skip to search Skip to main content TU Delft Research Portal Logo Help & FAQ Home Researchers Research Units Research output Activities Datasets Press / Media Prizes Projects Search by expertise, name or affiliation Dike relocation Nijmegen-lent: example of adaptive water management? ME Cuppen, B Stalenberg, C Redeker Policy Analysis Hydraulic Structures and Flood Risk Research output: Chapter in Book/Conference proceedings/Edited volume › Conference contribution › Scientific › peer-review Overview Original language Undefined/Unknown Title of host publication Proceedings of NIG Workconference 2009 Editors Jurian Edelenbos et al. Place of Publication Leiden Publisher NIG Pages 1-22 Number of pages 22 Publication status Published - 2009 Event NIG Workconference …</p
Expected transport of cover layer material
No full textIn 1982 the Netherlands Marine Technological Research (MaTS) organization requested the Coastal Engineering Group of the Department of Civil Engineering at the Delft University of Technology to conduct research on the behaviour of pipelines instalied on a sandy sea bottom. This research project was split in the following subprojects. A - Study of the scour around pipelines on a sandy bottom, and the possible resulting self-burial. B - Stresses in the pipeline during the development of free spans. C - Forces exerted by groundwater pressures, when partly or completely burried. D - Stability of cover layers. This report is concerned with the last of these sub-projects. The design of a cover layer can be split into three parts: - The overall lay-out of the cover layer. - The dimensions of the top-layer material. - The filter construction.Hydraulic EngineeringCivil Engineering and Geoscience
Rhine Cities - Urban Flood Integration (UFI)
No full textWhile agglomerations along the Rhine are confronted with the uncertainties of an increasing flood risk due to climate change, different programs are claiming urban river front sites. Simultaneously, urban development, flood management, as well as navigation and environmental protection are negotiating the border between the river and the urban realm. This produces complex spatial constellations between the river system and the urban realm with a diverse set of interdependencies, where programs have to synergize while adapting to dynamic water levels. Based on an expanding area at risk and the reliance on flood levels to remain within an acceptable spectrum for adaptive measures to be effective Urban Flood Integration (UFI) involves border negotiations between the river and the urban realm where adaptation and mitigation ideally synergize. Instead of a scientific approach that reduces complexity in order to reach a verifiable question, a post-normal science approach is chosen as an evaluation and working method applied within this research. The working method relies on literature studies, semi-structured interviews and empirical research through repeated site visits. The general heterogeneity of the case studies regarding their planning structure, status and time scales, data availability and the willingness by the agencies involved to provide usable information shapes the formal research structure. Part I serves as a narrative for the case study analysis and for the final conclusions and recommendations in Part II. It is made up of three chapters, where Urban Flood Integration is framed historically theoretically and strategically within the specific geographic context of the navigable Rhine: Anthropogenic transformations of the Rhine flood plains in the 19th and 20th century have turned formerly wide, often meandering or bifurcating river beds into urbanized embankments along straight, channelled rivers. The perception of the river changed from being dynamic to being controllable. This produced the spatial backdrop for modernist and therefore sectoral developments based on a dialectical relationship between the urban realm and the (river) landscape. Yet, as conversions of former harbours are turning sites outside the flood defence into inner city living quarters, as retention polders are positioned in flood plains with enough damage potential to threaten regional economies, and flood mitigating measures are more viable/effective on site in the middle of the city than in a rural area, site specific negotiations between simultaneous programmatic claims are producing new urban typologies/ecologies that demand and rely on a new methodological approach. Within this research design is considered not only a spatial, but also a strategic tool capable of not only linking different programs, but also different disciplines. Flood Risk Management along the Rhine today combines river expanding measures and adaptive strategies with the existing defensive system to cope with the risk increase as a consequence of previous interventions and developments and fluctuations in water levels due to climate change. Differences in landscapes and urgencies and differences in planning cultures between the Upper and Lower Rhine and the Delta have also led to different strategic approaches. Within this research the innovative capacity of the adaptive and anticipatory water-based approach in the Netherlands provides lessons to be learned specifically regarding spatial quality as a strategic component of water related projects. In Part II, the investigation of two Dutch and two German urbanized water front developments along different river segments of the Rhine according to their synergetic potential, but also regarding the temporal and spatial interdependencies between the river system as a whole, the regional context as well as the actual water front as the project site, aims to examine the following questions: Between adaptive and mitigative strategies, what is the spectrum of spatial constellations between urban development and flood management within the constraints set by navigation and a (partial) restoration of the dynamic river landscape? How are temporal and spatial interdependencies shaping these projects? Relational diagrams show the reciprocations between urban development and river dynamics of each investigated case study and the respective agencies and processes involved. The case study analysis serves as a basis for recommendations for the architectural and programmatic scope of flood-resilient projects dealing with expansive flood management strategies and respectively a strategic design approach addressing multiple scales and programs. Embedded in an exemplary atlas of the respective typology along the different Rhine segments, the four case studies from south to north are: Karlsruhe Rappenwört, a steered retention polder along the meandering Upper Rhine Mainz Zollhafen, a port conversion with flood adaptive housing along the bifurcating Upper Rhine Nijmegen Lent, a bypass and urban extension based on a dike set back along the Waal Dordrecht Stadswerven, an urban development outside the dikes in the DeltaUrban Theory and MethodsArchitecture and The Built Environmen
HLA A2 restricted cytotoxic T lymphocyte responses to multiple hepatitis B surface antigen epitopes during hepatitis B virus infection
No full textInasmuch as the hepatitis B virus (HBV) is not directly cytopathic for the infected hepatocyte, it is generally presumed that viral clearance and liver cell injury during viral hepatitis are due to a CTL response to HBV encoded Ag presented by HLA class I molecules. We have previously examined the peripheral blood CTL response to two HBV nucleocapsid epitopes in patients with acute and chronic viral hepatitis, one of which is restricted by HLA-A2, whereas the other is dually restricted by HLA-A31 and Aw68. In this study, we defined the HLA-A2-restricted CTL response to the hepatitis B surface Ag (HBsAg) by using a panel of HBsAg-derived synthetic peptides containing the ideal HLA-A2.1 binding motif (-L------V). Several novel aspects of HBV immunobiology and pathogenesis are evident from this study. First, the peripheral blood CTL response to HBV-encoded Ag is remarkably polyclonal and multispecific in most patients with acute hepatitis. Indeed, HLA-A2-restricted CTL specific for as many as four envelope epitopes and one nucleocapsid epitope were found to be present simultaneously in individual patients with acute viral hepatitis. Second, HBV-specific CTL are not detectable in the peripheral blood in a minority of patients with acute hepatitis, nor have we detected a CTL response in any of the patients with chronic hepatitis that we have studied thus far. Although the cellular and molecular basis for CTL nonresponse remains to be determined, the data suggest that it may contribute to viral persistence. Third, the diversity and the specificity of the CTL response is determined in part by the coding sequence of the viral genome present in each infected patient. Indeed, the apparent nonresponse of some acutely infected patients to at least one HBsAg-specific CTL epitope actually reflects infection by a viral variant that contains a critical substitution in one of the anchor residues within the epitope. Finally, at a fundamental level, the data suggest that the presence of the HLA-A2.1-binding motif in a peptide may not be sufficient for binding; and the capacity of a peptide to bind the class I molecule does not guarantee that it will be immunogenic
Half-sandwich complexes of titanium and zirconium with the (diisopropylaminoethyl)cyclopentadienyl ligand - Molecular structure of [((C5H4CH2CH2NCH)(i)Pr-2)ZnCl3](+)Cl-.2CH(3)OH
No full textJutzi P, Redeker T, Neumann B, Stammler H-G. Half-sandwich complexes of titanium and zirconium with the (diisopropylaminoethyl)cyclopentadienyl ligand - Molecular structure of [((C5H4CH2CH2NCH)(i)Pr-2)ZnCl3](+)Cl-.2CH(3)OH. JOURNAL OF ORGANOMETALLIC CHEMISTRY. 1997;533(1-2):237-245.The synthesis of titanium and zirconium complexes with the donor functionalized 2-(N,N-diisopropylaminoethyl)cyclopentadienyl (CpN) ligand is described. The reaction of TiCl4 with ((C5H4CH2CH2NPr2)-Pr-i)Li leads to the formation of the highly moisture-sensitive half-sandwich complex ((C5H4CH2CH2NPr2)-Pr-1)TiCl3 (1), which easily forms a coordination polymer. Complex 1 reacts with one equivalent of HCl under protonation of the amino group to give the monomeric hydrochloride [(C5H4CH2CH2N(H)Pr-i(2))TiCl3]Cl-+(-) (2), which shows excellent solubility in polar solvents. The compound ((C5H4CH2CH2NPr2)-Pr-i)Ti(NMe2)(3) (3) is prepared by the reaction of Ti(NMe,), with one equivalent of (C5H5CH2CH2NPr2)-Pr-i ((CpH)-H-N). Reaction of 3 with three equivalents of isopropanol affords the isopropoxy derivative ((C5H4CH2CH2NPr2)-Pr-i)Ti((OPr)-Pr-i), (4) in quantitative yield. The reaction of ((C5H4CH2C2NPr2)-Pr-i)Li with Me3SiCl leads to the formation of the Cp-N-transfer reagent ((C5H4CH2CN2NPr2)-Pr-i)SiMe3 (5). The polymeric zirconium compound [((C5H4CH2CH2NPr2)-Pr-i)ZrCl3](x) (6) is synthesized by the reaction of 5 with ZrCl4. 6 reacts with one equivalent of HCl under protonation of the amino group to give the monomeric air- and moisture-stable hydrochloride [(C5H4CH2CH2N(H)Pr-i(2))ZrCl3]Cl-+(-).2CH(2)OH (7). The structure of 7 has been determined by single-crystal X-ray diffractometry. The reaction of 7 with water leads under exchange of the donor ligands to the formation of the air- and water-stable hydrochloride [(C5H4CH2CH2N(H)Pr-i(2))ZrCl3]Cl-+(-).2H(2)O (8). The compound ((C5H4CH2CH2NPr2)-Pr-i)Zr(NMe2)(3) (9) is prepared by the reaction of Zr(NMe2)(4) with one equivalent of (C5H5CH2CH2NPr2)-Pr-i in nearly quantitative yield
SYNTHESIS, STRUCTURE AND PROPERTIES OF GRIGNARD COMPOUNDS WITH N,N-DIMETHYLAMINOETHYL-SUBSTITUTED CYCLOPENTADIENYL SYSTEMS
No full textJutzi P, KLEIMEIER J, REDEKER T, Stammler H-G, NEUMANN B. SYNTHESIS, STRUCTURE AND PROPERTIES OF GRIGNARD COMPOUNDS WITH N,N-DIMETHYLAMINOETHYL-SUBSTITUTED CYCLOPENTADIENYL SYSTEMS. JOURNAL OF ORGANOMETALLIC CHEMISTRY. 1995;498(1):85-89.Synthesis, structure and properties of the Grignard compounds [(Me(2)NCH(2)CH(2))C5H4MgBr](2) (1), [(Me(2)NCH(2)CH(2))C(5)Me(4) MgBr](2) (2), [(Me(2)NCH(2)CH(2))C(5)Me(4)MgCl](2) (3) and (Me(2)NCH(2)CH(2))C(5)Me(4)MgBr . THF (4) containing chelating dimethylaminoethyl-cyclopentadienyl ligands are described. Complexes 1-4 are stable in CH2Cl2 and CHCl3 solution; 1 undergoes slow protonation in CHCl3. Complexes 1-3 form halogen-bridged dimeric units; in the monomeric 4a the tetrahydrofuran molecule completes the ligand sphere at the magnesium centre. The crystal structures of 2 and 4 are discussed. The unit cell of 2 contains two different dimeric molecules; species 2a shows symmetric Mg-Br-Mg bridges with Mg-Br distances of 2.57 Angstrom, and in species 2b the Mg-Br-Mg bridges are asymmetric with Mg-Br distances of 2.55 Angstrom and 2.62 Angstrom
HLA-A31- and HLA-Aw68-restricted cytotoxic T cell responses to a single hepatitis B virus nucleocapsid epitope during acute viral hepatitis
No full textWe have recently developed the technology to identify and characterize the human histocompatibility leukocyte antigen (HLA) class I-restricted, CD8+ cytotoxic T lymphocyte (CTL) response to hepatitis B virus (HBV)-encoded antigens in patients with acute viral hepatitis. CTL are expanded in vitro by stimulation with HBV-derived synthetic peptides and selected by restimulation with a panel of HLA-matched stable transfectants that express the corresponding HBV protein. We have recently reported the existence of an HLA-A2-restricted, CD8+ CTL response to an epitope located between residues 18 and 27 of the HBV nucleocapsid core antigen (HBcAg). We now report the discovery of a CTL epitope located between HBcAg residues 141 and 151 that completely overlaps a critical domain in the viral nucleocapsid protein that is essential for its nuclear localization and genome packaging functions as well as processing of the precore protein. The CTL response to this epitope is dually restricted by the HLA-A31 and HLA-Aw68 alleles, which, unexpectedly, appear to use a common binding motif based on the results of alanine substitution and competition analysis, and the binding properties of these two alleles predicted from their known primary sequence, and from the three-dimensional structure of HLA-Aw68. We have also demonstrated that the HBV-specific CTL response to this epitope is polyclonal during acute viral hepatitis, since these two restriction elements can present the HBcAg 141-151 epitope to independent CTL clones derived from a single patient; and that the CTL response is multispecific, since HLA-A2-restricted and HLA-Aw68-restricted CTL responses to HBcAg 18-27 and HBcAg 141-151, respectively, have been identified to coexist in another patient. The foregoing argue against the emergence of CTL escape mutants as a significant problem during HBV infection, especially at this locus, where mutations might be incompatible with viral replication. Finally, our data suggest an association between the HBV-specific CTL response and viral clearance, and they have implications for the design of immunotherapeutic strategies to terminate HBV infection in chronically infected patients
Probabilistische kustlijnberekeningen: Met behulp van kustlijn simulatie model COSIM
No full textIn het vakgebied van de kust waterbouwkunde wordt o.a. studie verricht naar de beweging van de kustlijn als gevolg van zandtransporten in het gebied rond de kustlijn. Daarin zijn te onderscheiden, transport loodrecht op de kust(dwarstransport) en transport parallel aan de kust(langstransport). Zandtransport wordt globaal veroorzaakt door de interaktie tussen golven, stroom, bodemsediment en kustverdedigingskonstrukties. De interaktie tussen deze verschijnselen is zeer komplex en kan op vele schalen worden bestudeerd variërend van mikroskopische fysische schaal tot makroscopische schaal zoals bijvoorbeeld de invloed op de kustverandering van een eventuele stijging van het gemiddelde zeenivo. Om de ontwikkeling van de kustlijn op deze verschillende schalen te kunnen beschrijven zijn inmiddels evenzovele computermodellen ontwikkeld (variërend in kwaliteit van beschrijving van het proces op mikroskopische schaal tot op makroskopische schaal). AVECO ontwikkelde in 1986 het kustontwikkelingsmodel Coastline Simulation Model. Hoofdzakelijk voor praktisch ingenieursgebruik opgesteld, is COSIM een model dat alleen de voornaamste fysische processen van de kustlijnontwikkeling beschrijft. Dit nivo van beschrijven van de werkelijkheid is ingegeven door de beperkte hoeveelheid relevante kennis van de fysische processen in dit vakgebied en de mogelijke onnauwkeurigheid van de invoer waarden. Binnen AVECO is onderzoek gedaan naar de toepassingen van probabilistische kustlijnvoorspellingen. Dit zijn berekeningen waarmee de kansen en risiko's van kustlijnveranderingen bepaald kunnen worden. Voor het inzicht in de probabilistische mogelijkheden van het simuleren van kustlijnontwikkeling met COSIM is studie verricht naar: - de modelbeperkingen en voordelen van het één-lijnmodel; - de betrouwbaarheid van COSIM als één-lijn kustontwikkelingsprogramma; - de geschikte probabilistische methoden; - de door deskundigen tot nog toe opgedane ervaring met spreidingen voor invoervariabelen van de kustontwikkelingsmodellen COSIM blijkt als één-lijnmodel uitstekend te voldoen. De afwijkingen ten opzichte van analytische oplossingen zijn te verwaarlozen klein, zeker in vergelijking met de verschillen in resultaten bereikt met modellen gebaseerd op andere aannamen dan het lineaire één-lijnmodel. Zonder vergelijking met de werkelijkheid kan over de werkelijke modelonzekerheid van COSIM uiteraard niets worden gezegd.Hydraulic EngineeringCivil Engineering and Geoscience
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