Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Strong and weak family ties revisited: reconsidering European family structures from a network perspective.
Mönkediek, B. ; Bras, H. - \ 2014
The History of the Family 19 (2014)2. - ISSN 1081-602X - p. 235 - 259.
western-europe - household - fertility - attitudes - kinship - bonds - loneliness - behavior - germany - support
Family systems appear to be an important factor framing people's individual behavior. Thus far, family systems have been primarily addressed on a macro regional level with indirect measures. Revisiting Reher (1998) and the family ties criterion, the main question of this paper is to examine to what extent we perceive family structures differently in Europe by taking direct measures of the structures of people's broader social networks into consideration. Based on the Survey of Health, Ageing and Retirement in Europe (SHARE), we derived two indicators of family regimes based on individual-level data regarding the density of ego social networks: contact frequency and geographic proximity among network members. We aggregated these data and mapped them on the NUTS 2 level regions for various locations in Europe. The results of our analyses exhibit that, based on these two network indicators, significant differences in family structures between European regions exist. These results confirm the classification of strong family Southern and comparatively weaker family Northern European regions to a large extent, though substantial regional differences in and between countries are also revealed. Our findings demonstrate that the classification of European regions largely depends on which indicator of network density we consider. This is particularly obvious in the Eastern European regions where the classification markedly differs according to the type of network indicator. Intriguingly, social networks in Central European regions can be characterized as rather loose, often even looser than the ‘traditional’ weak ties in Scandinavia. Family regimes can, therefore, be regarded as a construct of multiple dimensions of which one dimension may be classified as weak while the other can be strong at the same time.
Relationship between redox potential and the emergence of three submerged macrophytes
Zuidam, B.G. van; Cazemier, M. ; Geest, G.J. van; Roijackers, R.M.M. ; Peeters, E.T.H.M. - \ 2014
Aquatic Botany 113 (2014). - ISSN 0304-3770 - p. 56 - 62.
seed banks - sediment load - zannichellia-palustris - hydrogen-sulfide - lake-sediments - western-europe - shallow lake - germination - burial - impact
Sedimentation may have large negative effects on aquatic vegetation as burial of propagules can reduce emergence. Burial changes the redox potential around the propagules and this might be the mechanism that causes the observed burial effects. We conducted a laboratory experiment to evaluate the effect of redox potential on the emergence of three aquatic macrophytes from their propagules. Different redox potential treatments were applied by burying propagules of Potamogeton pusillus and Chara cf. contraria at three different depths and with two different sediments (loamy mud and sand). Propagules of Zannichellia palustris were also buried at three depths, but only with sand. Emergence of P. pusillus and Z. palustris decreased with increasing burial depth, while burial up to 5 cm depth had almost no effect on Chara cf. contraria. Burial with sand reduced emergence of P. pusillus more than burial with loamy mud, while composition of the burial sediment did not affect Chara cf. contraria. The redox potential treatments explained emergence of P. pusillus better than burial depth or composition of the burial sediment separately. There was a strong relationship between mean emergence of P. pusillus per treatment and redox potential of the treatment. Burial caused high mortality of the non-emerged propagules of P. pusillus and Z. palustris within a relatively short period of time. Our results show that redox potential could be an important factor in causing the effect of burial on emergence. On longer time scale, sedimentation has species-specific consequences potentially leading to changes in vegetation species composition.
Structural and diffusion effects in the Dutch fertility transition, 1870-1940
Bras, H. - \ 2014
Demographic Research 30 (2014). - ISSN 1435-9871 - p. 151 - 186.
western-europe - demographic-transition - 19th-century flanders - decline - population - decisions - patterns - siblings - time - ties
Background: Ever since the Princeton European Fertility Project, structural and diffusion effects on fertility behavior have been juxtaposed. However, we still hardly know what the relative effects were of shifting socio-economic conditions and shifts in sociability in explaining the historical fertility decline. Objective: To what extent and how did structural and diffusion effects play a role in the adoption of fertility control in the Dutch historical fertility transition? Methods: A national data set was used with more than 3,000 maternity histories of married Dutch women aged 15-50, whose reproductive careers took place between 1870 and 1940. Apart from husbands' occupations, characteristics of the set of couples' marriage witnesses were included to measure their social networks. Cox regression analyses of age at last birth and negative binomial regressions of net family size were conducted. Results: Results indicate that unskilled laborers and farm laborers were laggards in the practice of fertility control during the Dutch fertility transition. Besides SES differentials, differences in couples' social networks were important in explaining fertility behavior. Those who had networks consisting of lateral kin, age peers, and people of urban background stopped childbearing earlier and had smaller families than other couples did. Particularly the presence of lateral kin of the bride and of female witnesses was strongly associated with smaller family size. Conclusions: The evidence lends support for so-called "blended diffusion models" and suggests that the fertility transition must be understood as much from the viewpoint of changed cost-benefit calculations related to structural changes, as from shifting patterns of sociability associated with the decline of patriarchy and the increasing lateralization and age homophily of people's social networks.
Newcastle disease virus outbreaks: Vaccine mismatch or inadequate appication?
Dortmans, J.C.F.M. ; Peeters, B.P.H. ; Koch, G. - \ 2012
Veterinary Microbiology 160 (2012)1-2. - ISSN 0378-1135 - p. 17 - 22.
shedding following vaccination - fusion protein - genotype vii - phylogenetic-relationships - molecular epidemiology - paramyxovirus type-1 - western-europe - china - chickens - strains
Newcastle disease (ND) is one of the most important diseases of poultry, and may cause devastating losses in the poultry industry worldwide. Its causative agent is Newcastle disease virus (NDV), also known as avian paramyxovirus type 1. Many countries maintain a stringent vaccination policy against ND, but there are indications that ND outbreaks can still occur despite intensive vaccination. It has been argued that this may be due to antigenic divergence between the vaccine strains and circulating field strains. Here we present the complete genome sequence of a highly virulent genotype VII virus (NL/93) obtained from vaccinated poultry during an outbreak of ND in the Netherlands in 1992–1993. Using this strain, we investigated whether the identified genetic evolution of NDV is accompanied by antigenic evolution. In this study we show that a live vaccine that is antigenically adapted to match the genotype VII NL/93 outbreak strain does not provide increased protection compared to a classic genotype II live vaccine. When challenged with the NL/93 strain, chickens vaccinated with a classic vaccine were completely protected against clinical disease and mortality and virus shedding was significantly reduced, even with a supposedly suboptimal vaccine dose. These results suggest that it is not antigenic variation but rather poor flock immunity due to inadequate vaccination practices that may be responsible for outbreaks and spreading of virulent NDV field strains.
Skill and uncertainty of a regional air quality model ensemble
Vautard, R. ; Schaap, M. ; Bergström, R. ; Bessagnet, B. ; Brandt, J. ; Builtjes, P.J.H. ; Krol, M.C. - \ 2009
Atmospheric Environment 43 (2009)31. - ISSN 1352-2310 - p. 4822 - 4832.
2003 heat-wave - climate-change - pollution model - western-europe - surface ozone - aerosol - simulations - summer - validation - transport
Recently several regional air quality projects were carried out to support the negotiation under the Clean Air For Europe (CAFE) programme by predicting the impact of emission control policies with an ensemble of models. Within these projects, CITYDELTA and EURODELTA, the fate of air quality at the scale of European cities or that of the European continent was studied using several models. In this article we focus on the results of EURODELTA. The predictive skill of the ensemble of models is described for ozone, nitrogen dioxide and secondary inorganic compounds, and the uncertainty in air quality modelling is examined through the model ensemble spread of concentrations. For ozone daily maxima the ensemble spread origin differs from one region to another. In the neighbourhood of cities or in mountainous areas the spread of predicted values does not span the range of observed data, due to poorly resolved emissions or complex-terrain meteorology. By contrast in Atlantic and North Sea coastal areas the spread of predicted values is found to be larger than the observations. This is attributed to large differences in the boundary conditions used in the different models. For NO2 daily averages the ensemble spread is generally too small compared with observations. This is because models miss highest values occurring in stagnant meteorology in stable boundary layers near cities. For secondary particulate matter compounds the simulated concentration spread is more balanced, observations falling nearly equiprobably within the ensemble, and the spread originates both from meteorology and aerosol chemistry and thermodynamics
Evaluation of long-term ozone simulations from seven regional air quality models and their ensemble
Loon, M. van; Vautard, R. ; Schaap, M. ; Bergström, R. ; Bessagnet, B. ; Brandt, J. ; Krol, M.C. - \ 2007
Atmospheric Environment 41 (2007)10. - ISSN 1352-2310 - p. 2083 - 2097.
tropospheric ozone - pollution model - european cities - western-europe - impact - variability - citydelta - summer
Long-term ozone simulations from seven regional air quality models, the Unified EMEP model, LOTOS-EUROS, CHIMERE, RCG, MATCH, DEHM and TM5, are intercompared and compared to ozone measurements within the framework of the EuroDelta experiment, designed to assess air quality improvement at the European scale in response to emission reduction scenarios for 2020. Modelled ozone concentrations for the year 2001 are evaluated. The models reproduce the main features of the ozone diurnal cycle, but generally overestimate daytime ozone. LOTOS-EUROS and RCG have a more pronounced diurnal cycle variation than observations, while the reverse occurs for TM5. CHIMERE has a large positive bias, which can be explained by a systematic bias in boundary conditions. The other models and the ¿ensemble model¿, whose concentrations are by definition averaged over all models, represent accurately the diurnal cycle. The ability of the models to simulate day-to-day daily ozone average or maxima variability is examined by means of percentiles, root mean square errors and correlations. In general, daily maxima are better simulated than daily averages, and summertime concentrations are better simulated than wintertime concentrations. Summertime correlations range between 0.5 and 0.7 for daily averages and 0.6 and 0.8 for daily maxima. Two health-related indicators are used, the number of days of exceedance of the threshold for the daily maximal 8-h ozone concentration and the SOMO35. Both are well reproduced in terms of frequency, but the simultaneity of occurrence of exceedance days between observations and simulations is not well captured. The advantage of using an ensemble of models instead of a single model for the assessment of air quality is demonstrated. The ensemble average concentrations almost always exhibit a closer proximity to observations than any of the models. We also show that the spread of the model ensemble is fairly representative of the uncertainty in the simulations.
Is regional air quality model diversity representative of uncertainty for ozone simulation?
Vautard, R. ; Loon, M. van; Schaap, M. ; Bergstrom, R. ; Bessagnet, B. ; Brandt, J. ; Builtjes, P.J.H. ; Christensen, J.H. ; Cuvelier, C. ; Graff, A. ; Jonson, J.E. ; Krol, M.C. ; Langner, J. ; Roberts, P. ; Rouil, L. ; Stern, R. ; Tarrason, L. ; Thunis, P. ; Vignati, E. ; White, L. ; Wind, P. - \ 2006
Geophysical Research Letters 33 (2006). - ISSN 0094-8276 - 5 p.
pollution model - western-europe - ensemble
We examine whether seven state-of-the-art European regional air quality models provide daily ensembles of predicted ozone maxima that encompass observations. Using tools borrowed from the evaluation of ensemble weather forecasting, we analyze statistics of simulated ensembles of ozone daily maxima over an entire summer season. Although the model ensemble overestimates ozone, the distribution of simulated concentrations is representative of the uncertainty. The spread of simulations is due to random fluctuations resulting from differences in model formulations and input data, but also to the spread between individual model systematic biases. The ensemble average skill increases as the spread decreases. The skill of the ensemble in giving probabilistic predictions of threshold exceedances is also demonstrated. These results allow for optimism about the ability of this ensemble to simulate the uncertainty of the impact of emission control scenarios.
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