Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 50 / 174

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Relative Validity of the HELIUS Food Frequency Questionnaire for Measuring Dietary Intake in Older Adult Participants of the Longitudinal Aging Study Amsterdam
    Visser, Marjolein ; Elstgeest, Liset E.M. ; Winkens, Laura H.H. ; Brouwer, Ingeborg A. ; Nicolaou, Mary - \ 2020
    Nutrients 12 (2020)7. - ISSN 2072-6643
    24-hour recall - diet assessment - elderly - FFQ - validation

    The aim of this study was to determine the relative validity of the HEalthy LIfe in an Urban Setting (HELIUS) food frequency questionnaire (FFQ) in assessing the dietary intake of energy, nutrients, and food groups of Dutch older men and women. In 2014-2015, 88 participants of the Longitudinal Aging Study Amsterdam aged 71.9 (SD 8.6) years completed the 238-item HELIUS FFQ and three 24-hour dietary recalls. The mean group-level bias in the intakes of energy, nutrients, and food groups between the two methods was assessed, as well as Pearson's correlation coefficients and level of agreement using quintile distribution. For the intakes of energy and macronutrients, the group-level bias was ≤5%, Pearson's correlation coefficients were moderate to good (ranging from 0.26 for total fat to 0.72 for alcohol), and agreement was moderate to high (classification in same or adjacent quintile ranging from 63% for energy, protein, and carbohydrate to 91% for alcohol). For most micronutrients and food groups, the relative validity was moderate (Pearson's correlation coefficients between 0.3 and 0.5), with the lowest correlations for β-carotene (0.08), vitamin B1 (0.19), fish (0.14), and grains (0.24). In conclusion, for energy and macronutrients, most micronutrients, and most food groups, the relative validity of the HELIUS FFQ to assess dietary intake in Dutch older adults was acceptable to good.

    How to compare sampling designs for mapping?
    Wadoux, Alexandre M.J.C. ; Brus, Dick J. - \ 2020
    European Journal of Soil Science (2020). - ISSN 1351-0754
    Kriging - machine learning - pedometrics - random forest - soil sampling - validation

    If a map is constructed through prediction with a statistical or non-statistical model, the sampling design used for selecting the sample on which the model is fitted plays a key role in the final map accuracy. Several sampling designs are available for selecting these calibration samples. Commonly, sampling designs for mapping are compared in real-world case studies by selecting just one sample for each of the sampling designs under study. In this study, we show that sampling designs for mapping are better compared on the basis of the distribution of the map quality indices over repeated selection of the calibration sample. In practice this is only feasible by subsampling a large dataset representing the population of interest, or by selecting calibration samples from a map depicting the study variable. This is illustrated with two real-world case studies. In the first case study a quantitative variable, soil organic carbon, is mapped by kriging with an external drift in France, whereas in the second case a categorical variable, land cover, is mapped by random forest in a region in France. The performance of two sampling designs for mapping are compared: simple random sampling and conditioned Latin hypercube sampling, at various sample sizes. We show that in both case studies the sampling distributions of map quality indices obtained with the two sampling design types, for a given sample size, show large variation and largely overlap. This shows that when comparing sampling designs for mapping on the basis of a single sample selected per design, there is a serious risk of an incidental result. Highlights: We provide a method to compare sampling designs for mapping. Random designs for selecting calibration samples should be compared on the basis of the sampling distribution of the map quality indices.

    Simultaneous Analysis of Glucosinolates and Isothiocyanates by Reversed-Phase Ultra-High-Performance Liquid Chromatography-Electron Spray Ionization-Tandem Mass Spectrometry
    Andini, Silvia ; Araya-Cloutier, Carla ; Sanders, Mark ; Vincken, Jean Paul - \ 2020
    Journal of Agricultural and Food Chemistry 68 (2020)10. - ISSN 0021-8561 - p. 3121 - 3131.
    dithiocarbamate - glucosinolate breakdown product - LC-MS analysis - mustard - thioglucosidase - validation

    A new method to simultaneously analyze various glucosinolates (GSLs) and isothiocyanates (ITCs) by reversed-phase ultra-high-performance liquid chromatography-electron spray ionization-tandem mass spectrometry has been developed and validated for 14 GSLs and 15 ITCs. It involved derivatization of ITCs with N-acetyl-l-cysteine (NAC). The limits of detection were 0.4-1.6 μM for GSLs and 0.9-2.6 μM for NAC-ITCs. The analysis of Sinapis alba, Brassica napus, and Brassica juncea extracts spiked with 14 GSLs and 15 ITCs indicated that the method generally had good intraday (≤10% RSD) and interday precisions (≤16% RSD). Recovery of the method was unaffected by the extracts and within 71-110% for GSLs and 66-122% for NAC-ITCs. The method was able to monitor the enzymatic hydrolysis of standard GSLs to ITCs in mixtures. Furthermore, GSLs and ITCs were simultaneously determined in Brassicaceae plant extracts before and after myrosinase treatment. This method can be applied to further investigate the enzymatic conversion of GSLs to ITCs in complex mixtures.

    Field data of "Monitoring forest phenology and leaf area index with the autonomous, low-cost transmittance sensor PASTiS-57"
    Brede, Benjamin ; Gastellu-Etchegorry, Jean Philippe ; Lauret, Nicolas ; Baret, Frederic ; Clevers, Jan ; Verbesselt, Jan ; Herold, Martin - \ 2020
    Wageningen University & Research
    forest - ground-based - Land Surface Phenology - Leaf Area Index - validation
    Land Surface Phenology (LSP) and Leaf Area Index (LAI) are important variables that describe the photosynthetically active phase and capacity of vegetation. Both are derived on the global scale from optical satellite sensors and require robust validation based on in situ sensors at high temporal resolution. This study assesses the PAI Autonomous System from Transmittance Sensors at 57? (PASTiS-57) instrument as a low-cost transmittance sensor for simultaneous monitoring of LSP and LAI in forest ecosystems. In a field experiment, spring leaf flush and autumn senescence in a Dutch beech forest were observed with PASTiS-57 and illumination independent, multi-temporal Terrestrial Laser Scanning (TLS) measurements in five plots. Both time series agreed to less than a day in Start Of Season (SOS) and End Of Season (EOS). LAI magnitude was strongly correlated with a Pearson correlation coefficient of 0.98. PASTiS-57 summer and winter LAI were on average 0.41m2m-2 and 1.43m2m-2 lower than TLS. This can be explained by previously reported overestimation of TLS. Additionally, PASTiS-57 was implemented in the Discrete Anisotropic Radiative Transfer (DART) Radiative Transfer Model (RTM) model for sensitivity analysis. This confirmed the robustness of the retrieval with respect to non-structural canopy properties and illumination conditions. Generally, PASTiS-57 fulfilled the CEOS LPV requirement of 20% accuracy in LAI for a wide range of biochemical and illumination conditions for turbid medium canopies. However, canopy non-randomness in discrete tree models led to strong biases. Overall, PASTiS-57 demonstrated the potential of autonomous devices for monitoring of phenology and LAI at daily temporal resolution as required for validation of satellite products that can be derived from ESA Copernicus’ optical missions, Sentinel-2 and -3.
    Evaluating the ecological realism of plant species distribution models with ecological indicator values
    Hellegers, Marjon ; Ozinga, Wim A. ; Hinsberg, Arjen ; Huijbregts, Mark A.J. ; Hennekens, Stephan M. ; Schaminée, Joop H.J. ; Dengler, Jürgen ; Schipper, Aafke M. - \ 2020
    Ecography 43 (2020)1. - ISSN 0906-7590 - p. 161 - 170.
    BioScore - ecological niche model - Ellenberg indicator values - model selection - scale dependency - validation

    Species distribution models (SDMs) are routinely applied to assess current as well as future species distributions, for example to assess impacts of future environmental change on biodiversity or to underpin conservation planning. It has been repeatedly emphasized that SDMs should be evaluated based not only on their goodness of fit to the data, but also on the realism of the modeled ecological responses. However, possibilities for the latter are hampered by limited knowledge on the true responses as well as a lack of quantitative evaluation methods. Here we compared modeled niche optima obtained from European-scale SDMs of 1476 terrestrial vascular plant species with empirical ecological indicator values indicating the preferences of plant species for key environmental conditions. For each plant species we first fitted an ensemble SDM including three modeling techniques (GLM, GAM and BRT) and extracted niche optima for climate, soil, land use and nitrogen deposition variables with a large explanatory power for the occurrence of that species. We then compared these SDM-derived niche optima with the ecological indicator values by means of bivariate correlation analysis. We found weak to moderate correlations in the expected direction between the SDM-derived niche optima and ecological indicator values. The strongest correlation occurred between the modeled optima for growing degree days and the ecological indicator values for temperature. Correlations were weaker for SDM-derived niche optima with a more distal relationship to ecological indicator values (notably precipitation and soil moisture). Further, correlations were consistently highest for BRT, followed by GLM and GAM. Our method gives insight into the ecological realism of modeled niche optima and projected core habitats and can be used to improve SDMs by making a more informed selection of environmental variables and modeling techniques.

    Risk assessment of exotic disease incursion and spread
    Cabral, M. ; Taylor, R. ; Vos, C.J. de - \ 2019
    EFSA Journal 17 (2019)S2. - ISSN 1831-4732
    generic model - Import risk assessment - introduction risk - livestock disease - validation

    This Technical Report describes the activities developed in the scope of the EU-FORA Fellowship, within the work programme of risk assessment (RA) of exotic disease incursion and spread, developed at Wageningen Bioveterinary Research (WBVR). The programme focused on the work carried out in the Generic risk assessment for introduction of animal diseases (G-RAID) project, which brings together a number of different generic RA tools from multiple European partners. The aim of the fellowship was to gain understanding of veterinary import risk assessment by using different RA tools and to learn how different algorithms can be used to calculate disease incursion risks. G-RAID's tools cover a wide range of RA methodologies; from purely qualitative, to semi-quantitative and fully stochastic quantitative methods, which allowed the fellow to understand a variety of algorithms used to produce the final risk estimate. The fellowship programme provided the fellow with the chance to learn in detail about how generic RAs are performed across Europe, understanding how to deal with the uncertainty and variability involved in RAs and the potential problems of data availability and reliability. The fellow made an inventory of publicly available databases on disease occurrence and international trade that could be used for import RA and assessed their quality and usefulness for the different generic RA tools. The programme also provided the fellow the opportunity to perform several import risk assessments using the RA tools of G-RAID. She completed a RA on African swine fever using the MINTRISK model developed by WBVR. Furthermore, she assessed the risk of foot and mouth disease introduction using the Rapid Risk Assessment Tool (RRAT) model developed by WBVR and the COMPARE model developed by the Animal and Plant Health Agency (APHA). To this end, the fellow completed a short-term visit to APHA, enabling her to have additional training in quantitative RA and to expand her professional network in this area.

    Evaluation of Mycotoxin Screening Tests in a Verification Study Involving First Time Users
    Lattanzio, Veronica M.T. ; Holst, Christoph von; Lippolis, Vincenzo ; Girolamo, Annalisa De; Logrieco, Antonio F. ; Mol, Hans G.J. ; Pascale, Michelangelo - \ 2019
    Toxins 11 (2019)2. - ISSN 2072-6651 - 18 p.
    cereals - immunoassay - mass spectrometry - mycotoxins - screening - validation

    (AFB₁) in maize and wheat using LFD and LC-HRMS, respectively. The results of analyses were used to calculate intermediate precision (RSDip, covering the inter-analyst variability in preparing the analytical samples and the precision under repeatability conditions) cut-off values and false suspect rates. RSDip ranged from 6.5% to 30% for DON, and from 16% to 33% for AFB₁. The highest obtained variances were associated with the AFB₁ analyses due to working with much lower mass fractions. The rate of false suspect results were lower than 0.1% for all tested methods. All methods showed a fit-for-purpose method performance profile, which allowed a clear distinction of samples containing the analytes at the screening target concentration (STC) from negative control samples. Moreover, the first time users obtained method performances similar to those obtained for validation studies previously performed on the screening methods included in the training course.

    Pooling of genital swabs for detection by PCR of Taylorella equigenitalis, the cause of contagious equine metritis
    Mawhinney, I. ; Errington, J. ; Stamper, N. ; Torrens, N. ; Engelsma, M.Y. ; Roest, H.I.J. - \ 2019
    Equine Veterinary Journal 51 (2019)2. - ISSN 0425-1644 - p. 227 - 230.
    diagnosis - horse - infection - validation

    Background: Sets of genital swabs are routinely taken from horses to screen for the presence of Taylorella equigenitalis, the cause of contagious equine metritis. Typically, two to four different sites are swabbed at a time and tested by culture or PCR. Objectives: This study explored the feasibility of pooling these swabs for a single PCR test per animal instead of testing each swab individually. Study design: In vitro. Methods: PCR signal strengths (Ct values) from 149 historical PCR positive genital swabs, together with historical data on the number of swabs in a set expected to be positive, were used to assess the suitability of pooling for screening horses for T. equigenitalis infection in the population at large. Twenty-four sets of four equine genital swabs were tested. The sets were prepared in the laboratory using one or more swabs positive for T. equigenitalis from naturally infected cases. Positive and negative swabs were selected to reflect a typical range of PCR Ct values expected in field cases of T. equigenitalis infection. These pools were tested by an established PCR to assess the impact and suitability of a PCR test on pooled swabs compared to individual swab testing, by comparing the Ct values. Results: Pooling one positive swab with three negative swabs produced a small drop in Ct value but all pools were still clearly positive. Main limitations: Large numbers of field positive horses are not available, but the proof of concept approach with laboratory prepared pools shows the method is applicable to field cases. Conclusions: It was concluded that pooling of swabs would confer no appreciable drop in the ability to detect a positive animal compared to individual swab testing; pooling is therefore a suitable alternative to individual swab testing with reduced costs. The Summary is available in Spanish – see Supporting Information.

    Validation of a mathematical model of the bovine estrous cycle for cows with different estrous cycle characteristics
    Boer, H.M.T. ; Butler, S.T. ; Stötzel, C. ; Pas, M.F.W. te; Veerkamp, R.F. ; Woelders, H. - \ 2017
    Animal 11 (2017)11. - ISSN 1751-7311 - p. 1991 - 2001.
    bovine - estrous cycle - mathematical model - parameter identification - validation

    A recently developed mechanistic mathematical model of the bovine estrous cycle was parameterized to fit empirical data sets collected during one estrous cycle of 31 individual cows, with the main objective to further validate the model. The a priori criteria for validation were (1) the resulting model can simulate the measured data correctly (i.e. goodness of fit), and (2) this is achieved without needing extreme, probably non-physiological parameter values. We used a least squares optimization procedure to identify parameter configurations for the mathematical model to fit the empirical in vivo measurements of follicle and corpus luteum sizes, and the plasma concentrations of progesterone, estradiol, FSH and LH for each cow. The model was capable of accommodating normal variation in estrous cycle characteristics of individual cows. With the parameter sets estimated for the individual cows, the model behavior changed for 21 cows, with improved fit of the simulated output curves for 18 of these 21 cows. Moreover, the number of follicular waves was predicted correctly for 18 of the 25 two-wave and three-wave cows, without extreme parameter value changes. Estimation of specific parameters confirmed results of previous model simulations indicating that parameters involved in luteolytic signaling are very important for regulation of general estrous cycle characteristics, and are likely responsible for differences in estrous cycle characteristics between cows.

    Development and validation of the Axiom®Apple480K SNP genotyping array
    Bianco, Luca ; Cestaro, Alessandro ; Linsmith, Gareth ; Muranty, Hélène ; Denancé, Caroline ; Théron, Anthony ; Poncet, Charles ; Micheletti, Diego ; Kerschbamer, Emanuela ; Pierro, Erica A. Di; Larger, Simone ; Pindo, Massimo ; De Weg, Eric Van; Davassi, Alessandro ; Laurens, François ; Velasco, Riccardo ; Durel, Charles Eric ; Troggio, Michela - \ 2016
    The Plant Journal 86 (2016)1. - ISSN 0960-7412 - p. 62 - 74.
    genome-wide association study - genotyping - linkage mapping - Malus × domestica Borkh. - SNP chip - validation

    Cultivated apple (Malus × domestica Borkh.) is one of the most important fruit crops in temperate regions, and has great economic and cultural value. The apple genome is highly heterozygous and has undergone a recent duplication which, combined with a rapid linkage disequilibrium decay, makes it difficult to perform genome-wide association (GWA) studies. Single nucleotide polymorphism arrays offer highly multiplexed assays at a relatively low cost per data point and can be a valid tool for the identification of the markers associated with traits of interest. Here, we describe the development and validation of a 487K SNP Affymetrix Axiom® genotyping array for apple and discuss its potential applications. The array has been built from the high-depth resequencing of 63 different cultivars covering most of the genetic diversity in cultivated apple. The SNPs were chosen by applying a focal points approach to enrich genic regions, but also to reach a uniform coverage of non-genic regions. A total of 1324 apple accessions, including the 92 progenies of two mapping populations, have been genotyped with the Axiom®Apple480K to assess the effectiveness of the array. A large majority of SNPs (359 994 or 74%) fell in the stringent class of poly high resolution polymorphisms. We also devised a filtering procedure to identify a subset of 275K very robust markers that can be safely used for germplasm surveys in apple. The Axiom®Apple480K has now been commercially released both for public and proprietary use and will likely be a reference tool for GWA studies in apple.

    Monitoring forest cover loss using multiple data streams, a case study of a tropical dry forest in Bolivia
    Dutrieux, L.P. ; Verbesselt, J. ; Kooistra, L. ; Herold, M. - \ 2015
    ISPRS Journal of Photogrammetry and Remote Sensing 107 (2015). - ISSN 0924-2716 - p. 112 - 125.
    landsat time-series - structural-change - vegetation indexes - rainfall products - detecting trends - east-africa - amazon - disturbance - validation - modis
    Automatically detecting forest disturbances as they occur can be extremely challenging for certain types of environments, particularly those presenting strong natural variations. Here, we use a generic structural break detection framework (BFAST) to improve the monitoring of forest cover loss by combining multiple data streams. Forest change monitoring is performed using Landsat data in combination with MODIS or rainfall data to further improve the modelling and monitoring. We tested the use of the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) with varying spatial aggregation window sizes as well as a rainfall derived index as external regressors. The method was evaluated on a dry tropical forest area in lowland Bolivia where forest cover loss is known to occur, and we validated the results against a set of ground truth samples manually interpreted using the TimeSync environment. We found that the addition of an external regressor allows to take advantage of the difference in spatial extent between human induced and naturally induced variations and only detect the processes of interest. Of all configurations, we found the 13 by 13 km MODIS NDVI window to be the most successful, with an overall accuracy of 87%. Compared with a single pixel approach, the proposed method produced better time-series model fits resulting in increases of overall accuracy (from 82% to 87%), and decrease in omission and commission errors (from 33% to 24% and from 3% to 0% respectively). The presented approach seems particularly relevant for areas with high inter-annual natural variability, such as forests regularly experiencing exceptional drought events.
    Evaluation of Satellite Rainfall Estimates for Drought and Flood Monitoring in Mozambique
    Tote, C. ; Patricio, D. ; Boogaard, H.L. ; Wijngaart, R. van der; Tarnavsky, E. ; Funk, C. - \ 2015
    Remote Sensing 7 (2015)2. - ISSN 2072-4292 - p. 1758 - 1776.
    west-africa - precipitation - validation - products - microwave - climate - dataset - gages - sahel - trmm
    Satellite derived rainfall products are useful for drought and flood early warning and overcome the problem of sparse, unevenly distributed and erratic rain gauge observations, provided their accuracy is well known. Mozambique is highly vulnerable to extreme weather events such as major droughts and floods and thus, an understanding of the strengths and weaknesses of different rainfall products is valuable. Three dekadal (10-day) gridded satellite rainfall products (TAMSAT African Rainfall Climatology And Time-series (TARCAT) v2.0, Famine Early Warning System NETwork (FEWS NET) Rainfall Estimate (RFE) v2.0, and Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS)) are compared to independent gauge data (2001–2012). This is done using pairwise comparison statistics to evaluate the performance in estimating rainfall amounts and categorical statistics to assess rain-detection capabilities. The analysis was performed for different rainfall categories, over the seasonal cycle and for regions dominated by different weather systems. Overall, satellite products overestimate low and underestimate high dekadal rainfall values. The RFE and CHIRPS products perform as good, generally outperforming TARCAT on the majority of statistical measures of skill. TARCAT detects best the relative frequency of rainfall events, while RFE underestimates and CHIRPS overestimates the rainfall events frequency. Differences in products performance disappear with higher rainfall and all products achieve better results during the wet season. During the cyclone season, CHIRPS shows the best results, while RFE outperforms the other products for lower dekadal rainfall. Products blending thermal infrared and passive microwave imagery perform better than infrared only products and particularly when meteorological patterns are more complex, such as over the coastal, central and south regions of Mozambique, where precipitation is influenced by frontal systems.
    Loss of Olfactory Function and Nutritional Status in Vital Older Adults and Geriatric Patients
    Toussaint, N. ; Roon, M. de; Campen, J.P.C.M. van; Kremer, S. ; Boesveldt, S. - \ 2015
    Chemical Senses 40 (2015)3. - ISSN 0379-864X - p. 197 - 203.
    mild cognitive impairment - odor identification - normative data - taste - malnutrition - smell - discrimination - dysfunction - prevalence - validation
    The aim of this cross-sectional study was to assess the association of olfactory function and nutritional status in vital older adults and geriatric patients. Three hundred forty-five vital (mean age 67.1 years) and 138 geriatric older adults (mean age 80.9 years) were included. Nutritional status was assessed using the mini nutritional assessment-short form. The Sniffin’ Sticks was used to measure olfactory function. Eleven percentage of the vital older adults were at risk of malnutrition, whereas 60% of the geriatric participants were malnourished or at risk. Only 2% of the vital older adults were anosmic, compared with 46% of the geriatric participants. Linear regression demonstrated a significant association (P = 0.015) between olfactory function and nutritional status in the geriatric subjects. However, this association became insignificant after adjustment for confounders. Both crude and adjusted analysis in the vital older adults did not show a significant association. The results indicate that, in both groups of elderly, there is no direct relation between olfactory function and nutritional status. We suggest that a decline in olfactory function may still be considered as one of the risk-factors for malnutrition in geriatric patients—once co-occurring with other mental and/or physical problems that are more likely to occur in those patients experience.
    Surface water risk assessment of pesticides in Ethiopia
    Teklu, B.M. ; Adriaanse, P.I. ; Horst, M.M.S. ter; Deneer, J.W. ; Brink, P.J. van den - \ 2015
    Science of the Total Environment 508 (2015). - ISSN 0048-9697 - p. 566 - 574.
    predict insecticide concentrations - models fail - field - validation - exposure
    Scenarios for future use in the pesticide registration procedure in Ethiopia were designed for 3 separate Ethiopian locations, which are aimed to be protective for the whole of Ethiopia. The scenarios estimate concentrations in surface water resulting from agricultural use of pesticides for a small stream and for two types of small ponds. Seven selected pesticides were selected since they were estimated to bear the highest risk to humans on the basis of volume of use, application rate and acute and chronic human toxicity, assuming exposure as a result of the consumption of surface water. Potential ecotoxicological risks were not considered as a selection criterion at this stage. Estimates of exposure concentrations in surface water were established using modelling software also applied in the EU registration procedure (PRZM and TOXSWA). Input variables included physico-chemical properties, and data such as crop calendars, irrigation schedules, meteorological information and detailed application data which were specifically tailored to the Ethiopian situation. The results indicate that for all the pesticides investigated the acute human risk resulting from the consumption of surface water is low to negligible, whereas agricultural use of chlorothalonil, deltamethrin, endosulfan and malathion in some crops may result in medium to high risk to aquatic species. The predicted environmental concentration estimates are based on procedures similar to procedures used at the EU level and in the USA. Addition of aquatic macrophytes as an ecotoxicological endpoint may constitute a welcome future addition to the risk assessment procedure. Implementation of the methods used for risk characterization constitutes a good step forward in the pesticide registration procedure in Ethiopia. KEYWORDS: Aquatic ecosystems; Drinking water; Ecological risk assessment; Ethiopia; Exposure modelling; Pesticides; Tropics
    Probabilistic networks of blood metabolites in healthy subjects as indicators of latent cardiovascular risk
    Saccenti, E. ; Suarez Diez, M. ; Luchinat, C. ; Santucci, C. ; Tenori, L. - \ 2015
    Journal of Proteome Research 14 (2015)2. - ISSN 1535-3893 - p. 1101 - 1111.
    l-arginine supplementation - gene-coexpression network - insulin-resistance - metabolomic networks - disease - obesity - expression - cholesterol - association - validation
    The complex nature of the mechanisms behind cardiovascular diseases prevents the detection of latent early risk conditions. Network representations are ideally suited to investigate the complex interconnections between the individual components of a biological system underlying complex diseases. Here we investigate the patterns of correlations of an array of 29 metabolites identified and quantified in the plasma of 864 healthy blood donors and use a systems biology approach to define metabolite probabilistic networks specific for low and high latent cardiovascular risk. We adapted methods based on the likelihood of correlation and methods from information theory and combined them with resampling techniques. Our results show that plasma metabolite networks can be defined that associate with latent cardiovascular disease risk. The analysis of the networks supports our previous finding of a possible association between cardiovascular risk and impaired mitochondrial activity and highlights post-translational modifications (glycosilation and oxidation) of lipoproteins as a possible target-mechanism for early detection of latent cardiovascular risk.
    Multi-model radiometric slope correction of SAR images of complex terrain using a two-stage semi-empirical approach
    Hoekman, D.H. ; Reiche, J. - \ 2015
    Remote Sensing of Environment 156 (2015). - ISSN 0034-4257 - p. 1 - 10.
    radar imagery - topography - forest - classification - backscatter - validation
    Practical approaches for the implementation of terrain type dependent radiometric slope correction for SAR data are introduced. Radiometric slope effects are modelled as the products of two models. The first is a simple physical model based on the assumption of a uniform opaque layer of isotropic scatterers, which is independent of terrain type, frequency and polarization. It accounts for the slope-induced variation in the number of scatterers per resolution cell. The second is a semi-empirical model, which accounts for the variation in scattering mechanisms, dependent on terrain type, frequency and polarization. PALSAR FBD (L-band, HH- and HV-polarization) data are used at two test sites in Brazil and Fiji. Results for the Brazilian area, which has slopes up to 25°, show that remaining slope effects for the multi-model case are much smaller than 0.1 dB, for all land cover types. This is much better than the best single-model approach where remaining slope effects can be very small for forests but be as large as 1.77 dB for woodland in HH-polarization. Results for the Fiji area, which has different vegetation types, are very similar. The potential large improvement, using this multi-model approach, in the accuracy of biomass estimation for transparent or open canopies is discussed. It is also shown that biomass change on slopes can be systematically under- or overestimated because of associated change in scattering mechanism.
    Comparison of approaches to correct intake-health association for FFQ measurement eroor using a duplicate recovery biomarker and a duplicate 24h dietary recall as reference method
    Geelen, A. ; Souverein, O.W. ; Busstra, M.C. ; Vries, J.H.M. de; Veer, P. van 't - \ 2015
    Public Health Nutrition 18 (2015)2. - ISSN 1368-9800 - p. 226 - 233.
    episodically consumed foods - european centers - urinary nitrogen - potassium intake - validation - cancer - nutrition - protein - questionnaires - individuals
    Objective To illustrate the impact of intake-related bias in FFQ and 24 h recall (24hR), and correlated errors between these methods, on intake–health associations. Design Dietary intake was assessed by a 180-item semi-quantitative FFQ and two 24hR. Urinary N and urinary K were estimated from two 24 h urine samples. We compared four scenarios to correct associations for errors in an FFQ estimating protein and K intakes. Setting Wageningen, The Netherlands. Subjects Fifty-nine men and fifty-eight women aged 45–65 years. Results For this FFQ, measurement error weakened a true relative risk of 2·0 to 1·4 for protein and 1·5 for K. As compared with calibration to duplicate recovery biomarkers (i.e. the preferred scenario 1), estimating a validity coefficient using this duplicate biomarker resulted in overcorrected associations, caused by intake-related bias in the FFQ (scenario 2). The correction factor based on a triad using biomarkers and 24hR was hampered by this intake-related bias and by correlated errors between FFQ and 24hR, and in this population resulted in a nearly perfect correction for protein but an overcorrection for K (scenario 3). When the 24hR was used for calibration, only a small correction was done, due to correlated errors between the methods and intake-related bias in the 24hR (scenario 4). Conclusions Calibration to a gold standard reference method is the preferred approach to correct intake–health associations for FFQ measurement error. If it is not possible to do so, using the 24hR as reference method only partly removes the errors, but may result in improved intake–health associations.
    Moisture transport in swelling media modelled with a Lattice Boltzmann scheme having a deforming lattice
    Sman, R.G.M. van der - \ 2014
    Journal of Food Engineering 124 (2014). - ISSN 0260-8774 - p. 54 - 63.
    non-brownian suspensions - diffusion lattice - water transport - flow - simulations - profiles - kinetics - food - gels - validation
    In this paper we present a novel numerical scheme for simulating the one-dimensional deformation of hydrogel material due to drying or rehydration. The scheme is based on the versatile Lattice Boltzmann method, which has been extended such that the computational grid (lattice) deforms due to shrinkage or swelling. This property of a deforming grid is new to the lattice Boltzmann method, and a detailed description of this new method is given. Via simulations we show that self-similar moisture concentration profiles occur in two periods in both drying and swelling processes: the penetration period and the regular regime. Given the property of self-similarity, we have been able to formulate a reduced-order model for the regular regime of swelling.
    The Wageningen Lowland Runoff Simulator (WALRUS): application to the Hupsel Brook catchement and Cabauw polder
    Brauer, C.C. ; Torfs, P.J.J.F. ; Teuling, A.J. ; Uijlenhoet, R. - \ 2014
    Hydrology and Earth System Sciences 18 (2014). - ISSN 1027-5606 - p. 4007 - 4028.
    surface parameterization schemes - distributed hydrological model - flow route contributions - land-surface - groundwater interactions - spatial variability - rainfall - scale - netherlands - validation
    The Wageningen Lowland Runoff Simulator (WALRUS) is a new parametric (conceptual) rainfall–runoff model which accounts explicitly for processes that are important in lowland areas, such as groundwater-unsaturated zone coupling, wetness-dependent flowroutes, groundwater–surface water feedbacks, and seepage and surface water supply (see companion paper by Brauer et al., 2014). Lowland catchments can be divided into slightly sloping, freely draining catchments and flat polders with controlled water levels. Here, we apply WALRUS to two contrasting Dutch catchments: the Hupsel Brook catchment and the Cabauw polder. In both catchments, WALRUS performs well: Nash–Sutcliffe efficiencies obtained after calibration on 1 year of discharge observations are 0.87 for the Hupsel Brook catchment and 0.83 for the Cabauw polder, with values of 0.74 and 0.76 for validation. The model also performs well during floods and droughts and can forecast the effect of control operations. Through the dynamic division between quick and slow flowroutes controlled by a wetness index, temporal and spatial variability in groundwater depths can be accounted for, which results in adequate simulation of discharge peaks as well as low flows. The performance of WALRUS is most sensitive to the parameter controlling the wetness index and the groundwater reservoir constant, and to a lesser extent to the quickflow reservoir constant. The effects of these three parameters can be identified in the discharge time series, which indicates that the model is not overparameterised (parsimonious). Forcing uncertainty was found to have a larger effect on modelled discharge than parameter uncertainty and uncertainty in initial conditions.
    Status quo and future research challenges on organic food quality determination with focus on laboratory methods
    Kahl, J. ; Bodroza-Solarov, M. ; Busscher, N. ; Hajslova, J. ; Kneifel, W. ; Kokornaczyk, M.O. ; Ruth, S.M. van; Schulzova, V. ; Stolz, P. - \ 2014
    Journal of the Science of Food and Agriculture 94 (2014)13. - ISSN 0022-5142 - p. 2595 - 2599.
    wheat-grain leakages - grown winter-wheat - nutritional quality - crystallization patterns - samples - standardization - authentication - definition - validation - products
    Organic food quality determination needs multi-dimensional evaluation tools. The main focus is on the authentication as an analytical verification of the certification process. New fingerprinting approaches such as ultra-performance liquid chromatography–mass spectrometry, gas chromatography–mass spectrometry, direct analysis in real time–high-resolution mass spectrometry as well as crystallization with and without the presence of additives seem to be promising methods in terms of time of analysis and detecting organic system-related parameters. For further methodological development, a system approach is recommended, which also takes into account food structure aspects. Furthermore, the authentication of processed organic samples needs more consciousness, hence most of organic food is complex and processed.
    Fast and nondestructive method for leaf level chlorophyll estimation using hyperspectral LiDAR
    Nevalainen, O. ; Hakala, T. ; Suomalainen, J.M. ; Mäkipää, R. ; Peltoniemi, M. ; Krooks, A. ; Kaasalainen, S. - \ 2014
    Agricultural and Forest Meteorology 198-199 (2014). - ISSN 0168-1923 - p. 250 - 258.
    supercontinuum laser source - vegetation indexes - reflectance spectra - precision agriculture - canopy reflectance - red edge - airborne - model - spectroscopy - validation
    We propose an empirical method for nondestructive estimation of chlorophyll in tree canopies. The first prototype of a full waveform hyperspectral LiDAR instrument has been developed by the Finnish Geodetic Institute (FGI). The instrument efficiently combines the benefits of passive and active remote sensing sensors. It is able to produce 3D point clouds with spectral information included for every point, which offers great potential in the field of environmental remote sensing. The investigation was conducted by using chlorophyll sensitive vegetation indices applied to hyperspectral LiDAR data and testing their performance in chlorophyll estimation. The amount of chlorophyll in vegetation is an important indicator of photosynthetic capacity and stress, and thus important for monitoring of forest condition and carbon sequestration on Earth. Performance of chlorophyll estimation was evaluated for 27 published vegetation indices applied to waveform LiDAR collected from ten Scots pine shoots. Reference data were collected by laboratory chlorophyll concentration analysis. The performance of the indices in chlorophyll estimation was determined by linear regression and leave-one-out cross-validation. The chlorophyll estimates derived from hyperspectral LiDAR linearly correlate with the laboratory analyzed chlorophyll concentrations, and they are able to represent a range of chlorophyll concentrations in Scots pine shoots (R2 = 0.88, RMSE = 0.10 mg/g). Furthermore, they are insensitive to measurement scale as nearly the same values of vegetation indices were measured in natural setting while scanning the whole canopy and from clipped shoots re-measured with hyperspectral LiDAR in laboratory. The results indicate that the hyperspectral LiDAR instrument has the potential to estimate vegetation biochemical parameters such as the chlorophyll concentration. The instrument holds much potential in various environmental applications and provides a significant improvement over single wavelength LiDAR or passive optical systems for environmental remote sensing.
    Genomic prediction based on data from three layer lines using non-linear regression models
    Huang, H. ; Windig, J.J. ; Vereijken, A. ; Calus, M.P.L. - \ 2014
    Genetics, Selection, Evolution 46 (2014). - ISSN 0999-193X - 11 p.
    dairy-cattle breeds - dimensionality reduction - gaussian kernel - accuracy - traits - values - validation - selection - pedigree - plant
    Background - Most studies on genomic prediction with reference populations that include multiple lines or breeds have used linear models. Data heterogeneity due to using multiple populations may conflict with model assumptions used in linear regression methods. Methods - In an attempt to alleviate potential discrepancies between assumptions of linear models and multi-population data, two types of alternative models were used: (1) a multi-trait genomic best linear unbiased prediction (GBLUP) model that modelled trait by line combinations as separate but correlated traits and (2) non-linear models based on kernel learning. These models were compared to conventional linear models for genomic prediction for two lines of brown layer hens (B1 and B2) and one line of white hens (W1). The three lines each had 1004 to 1023 training and 238 to 240 validation animals. Prediction accuracy was evaluated by estimating the correlation between observed phenotypes and predicted breeding values. Results - When the training dataset included only data from the evaluated line, non-linear models yielded at best a similar accuracy as linear models. In some cases, when adding a distantly related line, the linear models showed a slight decrease in performance, while non-linear models generally showed no change in accuracy. When only information from a closely related line was used for training, linear models and non-linear radial basis function (RBF) kernel models performed similarly. The multi-trait GBLUP model took advantage of the estimated genetic correlations between the lines. Combining linear and non-linear models improved the accuracy of multi-line genomic prediction. Conclusions - Linear models and non-linear RBF models performed very similarly for genomic prediction, despite the expectation that non-linear models could deal better with the heterogeneous multi-population data. This heterogeneity of the data can be overcome by modelling trait by line combinations as separate but correlated traits, which avoids the occasional occurrence of large negative accuracies when the evaluated line was not included in the training dataset. Furthermore, when using a multi-line training dataset, non-linear models provided information on the genotype data that was complementary to the linear models, which indicates that the underlying data distributions of the three studied lines were indeed heterogeneous.
    Fusion of pan-tropical biomass maps using weighted averaging and regional calibration data
    Ge, Y. ; Avitabile, V. ; Heuvelink, G.B.M. ; Wang, J. ; Herold, M. - \ 2014
    International Journal of applied Earth Observation and Geoinformation 31 (2014). - ISSN 0303-2434 - p. 13 - 24.
    remotely-sensed imagery - land-cover datasets - multisensor data - forest biomass - carbon-dioxide - sensing data - soil maps - classification - deforestation - validation
    Biomass is a key environmental variable that influences many biosphere–atmosphere interactions. Recently, a number of biomass maps at national, regional and global scales have been produced using different approaches with a variety of input data, such as from field observations, remotely sensed imagery and other spatial datasets. However, the accuracy of these maps varies regionally and is largely unknown. This research proposes a fusion method to increase the accuracy of regional biomass estimates by using higher-quality calibration data. In this fusion method, the biases in the source maps were first adjusted to correct for over- and underestimation by comparison with the calibration data. Next, the biomass maps were combined linearly using weights derived from the variance–covariance matrix associated with the accuracies of the source maps. Because each map may have different biases and accuracies for different land use types, the biases and fusion weights were computed for each of the main land cover types separately. The conceptual arguments are substantiated by a case study conducted in East Africa. Evaluation analysis shows that fusing multiple source biomass maps may produce a more accurate map than when only one biomass map or unweighted averaging is used.
    Nutrient-rich foods, cardiovascular diseases and all-cause mortality: the Rotterdam study
    Streppel, M.T. ; Sluik, D. ; Yperen, J. van; Geelen, A. ; Hofman, A. ; Franco, O.H. ; Witteman, J.C.M. ; Feskens, E.J.M. - \ 2014
    European Journal of Clinical Nutrition 68 (2014). - ISSN 0954-3007 - p. 741 - 747.
    nutritional quality index - physical-activity - dietary pattern - elderly-people - women - risk - questionnaire - validation - cohort
    Background/Objectives: The nutrient-rich food (NRF) index assesses nutrient quality of individual food items by ranking them according to their nutrient composition. The index reflects the nutrient density of the overall diet. We examined the associations between the NRF9.3 index—a score on the basis of nine beneficial nutrients (protein, fiber, vitamins and minerals) and three nutrients to limit (saturated fat, sugar and sodium)—incidence of cardiovascular disease (CVD) events and all-cause mortality. Subjects/Methods: A total of 4969 persons aged 55 and older from the Rotterdam Study, a prospective cohort study in the Netherlands, were studied. First, all foods were scored on the basis of their nutrient composition, resulting in an NRF9.3 score on food item level. Subsequently, they were converted into individual weighted scores on the basis of the amount of calories of each food item consumed by the subjects and the total energy intake. The hazard ratios (HRs) of the NRF9.3 index score were adjusted for age, gender, body mass index, smoking history, doctor-prescribed diet, alcohol consumption and education. Results: Food groups that contributed most to the NRF9.3 index score were vegetables, milk and milk products, fruit, bread and potatoes. A high NRF9.3 index score was inversely associated with all-cause mortality (HR Q4 versus Q1: 0.84 (95% confidence interval: 0.74, 0.96)). Associations were stronger in women than in men. The NRF9.3 index score was not associated with incidence of CVD. Conclusion: Elderly with a higher NRF9.3 index score, indicating more beneficial components and/or less limiting components, had a lower risk of all-cause mortality. Consuming a nutrient-dense diet may improve survival
    Rapid analysis of Delta-9-tetrahydrocannabinol in hair using direct analysis in real time ambient ionization orbitrap mass spectrometry
    Duvivier, W.F. ; Beek, T.A. van; Pennings, E.J.M. ; Nielen, M.W.F. - \ 2014
    Rapid Communications in Mass Spectrometry 28 (2014)7. - ISSN 0951-4198 - p. 682 - 690.
    synthetic cannabinoids - cocaine - drugs - identification - capabilities - metabolites - validation - samples - abuse
    RATIONALE - Forensic hair analysis methods are laborious, time-consuming and provide only a rough retrospective estimate of the time of drug intake. Recently, hair imaging methods using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) were reported, but these methods require the application of MALDI matrix and are performed under vacuum. Direct analysis of entire locks of hair without any sample pretreatment and with improved spatial resolution would thus address a need. METHODS - Hair samples were attached to stainless steel mesh screens and scanned in the X-direction using direct analysis in real time (DART) ambient ionization orbitrap MS. The DART gas temperature and the accuracy of the probed hair zone were optimized using ¿-9-tetrahydrocannabinol (THC) as a model compound. Since external contamination is a major issue in forensic hair analysis, sub-samples were measured before and after dichloromethane decontamination. RESULTS - The relative intensity of the THC signal in spiked blank hair versus that of quinine as the internal standard showed good reproducibility (26% RSD) and linearity of the method (R2¿=¿0.991). With the DART hair scan THC could be detected in hair samples from different chronic cannabis users. The presence of THC was confirmed by quantitative liquid chromatography/tandem mass spectrometry. Zones with different THC content could be clearly distinguished, indicating that the method might be used for retrospective timeline assessments. Detection of THC in decontaminated drug user hair showed that the DART hair scan not only probes THC on the surface of hair, but penetrates deeply enough to measure incorporated THC. CONCLUSIONS - A new approach in forensic hair analysis has been developed by probing complete locks of hair using DART-MS. Longitudinal scanning enables detection of incorporated compounds and can be used as pre-screening for THC without sample preparation. The method could also be adjusted for the analysis of other drugs of abuse.
    Evaluation of preformance of Predictive Models for Deoxynivalenol in Wheat
    Fels, H.J. van der - \ 2014
    Risk Analysis 34 (2014)2. - ISSN 0272-4332 - p. 380 - 390.
    fusarium mycotoxins - winter-wheat - validation
    The aim of this study was to evaluate the performance of two predictive models for deoxynivalenol contamination of wheat at harvest in the Netherlands, including the use of weather forecast data and external model validation. Data were collected in a different year and from different wheat fields than data used for model development. The two models were run for six preset scenarios, varying in the period for which weather forecast data were used, from zero-day (historical data only) to a 13-day period around wheat flowering. Model predictions using forecast weather data were compared to those using historical data. Furthermore, model predictions using historical weather data were evaluated against observed deoxynivalenol contamination of the wheat fields. Results showed that the use of weather forecast data rather than observed data only slightly influenced model predictions. The percent of correct model predictions, given a threshold of 1,250 µg/kg (legal limit in European Union), was about 95% for the two models. However, only three samples had a deoxynivalenol concentration above this threshold, and the models were not able to predict these samples correctly. It was concluded that two- week weather forecast data can reliable be used in descriptive models for deoxynivalenol contamination of wheat, resulting in more timely model predictions. The two models are able to predict lower deoxynivalenol contamination correctly, but model performance in situations with high deoxynivalenol contamination needs to be further validated. This will need years with conducive environmental conditions for deoxynivalenol contamination of wheat.
    A high-throughput method for GMO multi-detection using a microfluidic dynamic array
    Brod, F.C.A. ; Dijk, J.P. van; Voorhuijzen, M.M. ; Dinon, A.Z. ; Guimarães, L.H.S. ; Scholtens, I.M.J. ; Arisi, A.C.M. ; Kok, E.J. - \ 2014
    Analytical and Bioanalytical Chemistry 406 (2014)5. - ISSN 1618-2642 - p. 1397 - 1410.
    genetically-modified maize - real-time pcr - polymerase-chain-reaction - modified organisms - reference molecules - quantitative pcr - screening-assay - digital pcr - zea-mays - validation
    The ever-increasing production of genetically modified crops generates a demand for high-throughput DNAbased methods for the enforcement of genetically modified organisms (GMO) labelling requirements. The application of standard real-time PCR will become increasingly costly with the growth of the number of GMOs that is potentially present in an individual sample. The present work presents the results of an innovative approach in genetically modified crops analysis byDNA basedmethods, which is the use of a microfluidic dynamic array as a high throughput multi-detection system. In order to evaluate the system, six test samples with an increasing degree of complexity were prepared, preamplified and subsequently analysed in the Fluidigm system. Twenty-eight assays targeting different DNA elements, GM events and species-specific reference genes were used in the experiment. The large majority of the assays tested presented expected results. The power of low level detection was assessed and elements present at concentrations as low as 0.06 % were successfully detected. The approach proposed in this work presents the Fluidigm system as a suitable and promising platform for GMO multi-detection.
    Global water resources affected by human interventionss and climate change
    Haddeland, I. ; Heinke, J. ; Biemans, H. ; Eisner, S. ; Florke, M.F. ; Hanasaki, N. ; Konzmann, M. ; Ludwig, F. - \ 2014
    Proceedings of the National Academy of Sciences of the United States of America 111 (2014)9. - ISSN 0027-8424 - p. 3251 - 3256.
    integrated model - bias correction - surface-water - validation - fluxes - scheme
    Humans directly change the dynamics of the water cycle through dams constructed for water storage, and through water withdrawals for industrial, agricultural, or domestic purposes. Climate change is expected to additionally affect water supply and demand. Here, analyses of climate change and direct human impacts on the terrestrial water cycle are presented and compared using a multimodel approach. Seven global hydrological models have been forced with multiple climate projections, and with and without taking into account impacts of human interventions such as dams and water withdrawals on the hydrological cycle. Model results are analyzed for different levels of global warming, allowing for analyses in line with temperature targets for climate change mitigation. The results indicate that direct human impacts on the water cycle in some regions, e.g., parts of Asia and in the western United States, are of the same order of magnitude, or even exceed impacts to be expected for moderate levels of global warming (+2 K). Despite some spread in model projections, irrigation water consumption is generally projected to increase with higher global mean temperatures. Irrigation water scarcity is particularly large in parts of southern and eastern Asia, and is expected to become even larger in the future.
    Skill of a global seasonal streamflow forecasting system, relative roles of initial conditions and meteorological forcing
    Yossef, N.C. ; Winsemius, H. ; Weerts, A.H. ; Beek, R. van; Bierkens, M.F.P. - \ 2013
    Water Resources Research 49 (2013)8. - ISSN 0043-1397 - p. 4687 - 4699.
    united-states - hydrological model - water-resources - climate-change - discharge - predictability - availability - prediction - validation - balances
    We investigate the relative contributions of initial conditions (ICs) and meteorological forcing (MF) to the skill of the global seasonal streamflow forecasting system FEWS-World, using the global hydrological model PCRaster Global Water Balance. Potential improvement in forecasting skill through better climate prediction or by better estimation of ICs through data assimilation depends on the relative importance of these sources of uncertainty. We use the Ensemble Streamflow Prediction (ESP) and reverse ESP (revESP) procedure to explore the impact of both sources of uncertainty at 78 stations on large global basins for lead times upto 6 months. We compare the ESP and revESP forecast ensembles with retrospective model simulations driven by meteorological observations. For each location, we determine the critical lead time after which the importance of ICs is surpassed by that of MF. We analyze these results in the context of prevailing hydroclimatic conditions for larger basins. This analysis suggests that in some basins forecast skill may be improved by better estimation of initial hydrologic states through data assimilation; whereas in others skill improvement depends on better climate prediction. For arctic and snowfed rivers, forecasts of high flows may benefit from assimilation of snow and ice data. In some snowfed basins where the onset of melting is highly sensitive to temperature changes, forecast skill depends on better climate prediction. In monsoonal basins, the variability of the monsoon dominates forecasting skill, except for those where snow and ice contribute to streamflow. In large basins, initial surface water and groundwater states are important sources of skill.
    Making Sense of Agrobiodiversity, Diet, and Intensification of Smallholder Family Farming in the Highland Andes of Ecuador
    Oyarzun, P.J. ; Borja, R.M. ; Sherwood, S. ; Parra, V. - \ 2013
    Ecology of Food and Nutrition 52 (2013)6. - ISSN 0367-0244 - p. 515 - 541.
    nutrition - biodiversity - food - agriculture - validation - diversity - stability - recall - health - crops
    Methods are needed for helping researchers and farmers to interactively describe and analyze local practices in search of opportunities for improving health, environment, and economy. The authors worked with smallholder family farmers in five Andean villages in Ecuador to apply participatory four-cell analysis (PFCA) in characterizing agrobiodiversity. Margelef and Shannon indices examined ecological richness and evenness, and a simplified 24-hour dietary recall characterized food consumption. Cross-analysis tested interactions among agrobiodiversity, farm size, and diet. Overall trends appeared to work against sustainable intensification, with notable heterogeneity and positive deviance found in the practices of relatively smaller enterprises, representing a potential resource for sustainable intensification. The suite of methods was determined useful for initiating researcher-farmer explorations of promising innovation pathways.
    Factors influencing assessment quality in higher vocational education
    Baartman, L. ; Gulikers, J.T.M. ; Dijkstra, A. - \ 2013
    Assessment & Evaluation in Higher Education 38 (2013)8. - ISSN 0260-2938 - p. 978 - 997.
    assessing professional competence - argument-based approach - validity - validation - performance
    The development of assessments that are fit to assess professional competence in higher vocational education requires a reconsideration of assessment methods, quality criteria and (self)evaluation. This article examines the self-evaluations of nine courses of a large higher vocational education institute. Per course, 4–11 teachers and 3–10 students participated. The purpose of this article is to critically examine the quality of assessment in higher vocational education, to identify critical factors influencing assessment quality and to study whether self-evaluation leads to concrete points for improvement. Results show that strong points are fitness for purpose, comparability and fairness. Weak points are reproducibility of decisions and development of self-regulated learning. Critical factors are the translation of competences into assessment criteria to be used in daily lessons and the involvement of the work field. The self-evaluations generated many points for improvement, but not all were translated into actions. Altogether, this article provides a rich picture of assessment quality in higher education and identifies quality aspects that need improvement, (partly) confirming other research on current assessment methods.
    Application of gas chromatography–(triple quadrupole) massspectrometry with atmospheric pressure chemical ionization for thedetermination of multiclass pesticides in fruits and vegetables
    Cherta, L. ; Portoles, T. ; Beltran, J. ; Pitarch, E. ; Mol, J.G.J. ; Hernandez, F. - \ 2013
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1314 (2013). - ISSN 0021-9673 - p. 224 - 240.
    solid-phase extraction - residue analysis - multiresidue method - organic pollutants - quechers method - gc-ms - validation - ms/ms - water
    A multi-residue method for the determination of 142 pesticide residues in fruits and vegetables has been developed using a new atmospheric pressure chemical ionization (APCI) source for coupling gas chromatography (GC) to tandem mass spectrometry (MS). Selected reaction monitoring (SRM) mode has been applied, acquiring three transitions for each compound. In contrast to the extensive fragmentation typically obtained in classical electron ionization (EI), the soft APCI ionization allowed the selection of highly abundant protonated molecules ([M+H](+)) as precursor ions for most compounds. This was favorable for both sensitivity and selectivity. Validation of the method was performed in which both quantitative and qualitative parameters were assessed using orange, tomato and carrot samples spiked at two levels, 0.01 and 0.1mg/kg. The QuEChERS method was used for sample preparation, followed by a 10-fold dilution of the final acetonitrile extract with a mixture of hexane and acetone. Recovery and precision were satisfactory in the three matrices, at both concentration levels. Very low limits of detection (down 0.01µg/kg for the most sensitive compounds) were achieved. Ion ratios were consistent and identification according to EU criteria was possible in 80% (0.01mg/kg) to 96% (0.1mg/kg) of the pesticide/matrix combinations. The method was applied to the analysis of various fruits and vegetables from the Mediterranean region of Spa
    Identification of drug metabolites in human plasma or serum integrating metabolite prediction, LC–HRMS and untargeted data processing.
    Jacobs, P.L. ; Ridder, L.O. ; Ruijken, M. ; Rosing, H. ; Jager, N.G.L. ; Beijnen, J.H. ; Bas, R.R. ; Dongen, W.D. van - \ 2013
    Bioanalysis 5 (2013)17. - ISSN 1757-6180 - p. 2115 - 2128.
    ionization mass-spectrometry - preclinical safety - major metabolite - in-vivo - disposition - excretion - pharmacokinetics - inhibitor - annotation - validation
    Background: Comprehensive identification of human drug metabolites in first-in-man studies is crucial to avoid delays in later stages of drug development. We developed an efficient workflow for systematic identification of human metabolites in plasma or serum that combines metabolite prediction, high-resolution accurate mass LC–MS and MS vendor independent data processing. Retrospective evaluation of predictions for 14 14C-ADME studies published in the period 2007–January 2012 indicates that on average 90% of the major metabolites in human plasma can be identified by searching for accurate masses of predicted metabolites. Furthermore, the workflow can identify unexpected metabolites in the same processing run, by differential analysis of samples of drug-dosed subjects and (placebo-dosed, pre-dose or otherwise blank) control samples. To demonstrate the utility of the workflow we applied it to identify tamoxifen metabolites in serum of a breast cancer patient treated with tamoxifen. Results & Conclusion: Previously published metabolites were confirmed in this study and additional metabolites were identified, two of which are discussed to illustrate the advantages of the workflow.
    Sensitivity analysis and calibration of the Modified Universal Soil Loss Equation (MUSLE) for the upper Malewa Catchment, Kenya
    Odongo, V.O. ; Onyando, J.O. ; Mutua, B.M. ; Oel, P.R. van; Becht, R. - \ 2013
    International Journal of Sediment Research 28 (2013)3. - ISSN 1001-6279 - p. 368 - 383.
    sediment rating curves - uncertainty analysis - hydrologic-models - river catchment - erosion - yield - delivery - runoff - validation - greece
    Simulation models are widely used for studying physical processes such as surface runoff, sediment transport and sediment yield in catchments. Most models need case-specific empirical data for parameterization before being applied especially in regions other than the ones they have been developed. Sensitivity analysis is usually performed to determine the most influential factors of a model so that they can be prioritized for optimization. In this way uncertainties in model outputs can be reduced considerably. This study evaluates the commonly used modified universal soil loss equation (MUSLE) model used for sediment yield simulation for the case of the upper Malewa catchment in Kenya. The conceptual factors of the model are assessed relative to the hydrological factors in the model. Also, the sensitivity of the model to the choice of the objective function in calibration is tested. The Sobol' sensitivity analysis method was used for evaluating the degree of sensitivity of the conceptual and hydrological factors for sediment yield simulations using the MUSLE model. Nash-Sutcliffe Efficiency (NSE) and the modified Nash-Sutcliffe Efficiency (NSEm) are used to test the sensitivity of the model to the choice of the objective function and robustness of model performance with sediment data measured from upper Malewa catchment, Kenya. The results indicate that the conceptual factors are the most sensitive factors of the MUSLE model contributing about 66% of the variability in the output sediment yield. Increased variability of sediment yield output was also observed. This was attributed to interactions of input factors. For the upper Malewa catchment calibration of the MUSLE model indicates that the use of NSEm as an objective function provides stable results, which indicates that the model can satisfactorily be applied for sediment yield simulations.
    Receptor-based high-throughput screening and identification of estrogens in dietary supplements using bioaffinity liquid-chromatography ion mobility mass spectrometry
    Aqai, P. ; Gómez Blesa, N. ; Major, H. ; Pedotti, P. ; Varani, L. ; Ferrero, V.E.V. ; Haasnoot, W. ; Nielen, M.W.F. - \ 2013
    Analytical and Bioanalytical Chemistry 405 (2013)29. - ISSN 1618-2642 - p. 9427 - 9436.
    ms-binding assays - multi-residue method - anabolic-steroids - lc-ms - nutritional supplements - chemical derivatization - native marker - contamination - transporter - validation
    A high-throughput bioaffinity liquid chromatography-mass spectrometry (BioMS) approach was developed and applied for the screening and identification of recombinant human estrogen receptor a (ERa) ligands in dietary supplements. For screening, a semi-automated mass spectrometric ligand binding assay was developed applying 13C2,15¿N-tamoxifen as non-radioactive label and fast ultra-high-performance–liquid chromatography–electrospray ionisation–triple-quadrupole-MS (UPLC-QqQ-MS), operated in the single reaction monitoring mode, as a readout system. Binding of the label to ERa-coated paramagnetic microbeads was inhibited by competing estrogens in the sample extract yielding decreased levels of the label in UPLC-QqQ-MS. The label showed high ionisation efficiency in positive electrospray ionisation (ESI) mode, so the developed BioMS approach is able to screen for estrogens in dietary supplements despite their poor ionisation efficiency in both positive and negative ESI modes. The assay was performed in a 96-well plate, and all these wells could be measured within 3 h. Estrogens in suspect extracts were identified by full-scan accurate mass and collision-cross section (CCS) values from a UPLC-ion mobility-Q-time-of-flight-MS (UPLC-IM-Q-ToF-MS) equipped with a novel atmospheric pressure ionisation source. Thanks to the novel ion source, this instrument provided picogram sensitivity for estrogens in the negative ion mode and an additional identification point (experimental CCS values) next to retention time, accurate mass and tandem mass spectrometry data. The developed combination of bioaffinity screening with UPLC-QqQ-MS and identification with UPLC-IM-Q-ToF-MS provides an extremely powerful analytical tool for early warning of ERa bioactive compounds in dietary supplements as demonstrated by analysis of selected dietary supplements in which different estrogens were identified.
    Evaluation of food and nutrient intake assessment using concentration biomarkers in European adolescents from the Healthy Lifestyle in Europe by Nutrition in Adolescence study
    Vandevijvere, S. ; Geelen, A. ; Gonzalez-Gross, M. ; Veer, P. van 't; Dallongeville, J. ; Mouratidu, T. ; Dekkers, A. ; Börnhorst, C. ; Breidenassel, C. - \ 2013
    The British journal of nutrition 109 (2013)4. - ISSN 0007-1145 - p. 736 - 747.
    serum cholesteryl esters - n-3 fatty-acids - dietary-intake - energy-intake - additional measurements - micronutrient intake - biochemical markers - adipose-tissue - vitamin-c - validation
    Accurate food and nutrient intake assessment is essential for investigating diet–disease relationships. In the present study, food and nutrient intake assessment among European adolescents using 24 h recalls (mean of two recalls) and a FFQ (separately and the combination of both) were evaluated using concentration biomarkers. Biomarkers included were vitamin C, ß-carotene, DHA+EPA, vitamin B12 (cobalamin and holo-transcobalamin) and folate (erythrocyte folate and plasma folate). For the evaluation of the food intake assessment 390 adolescents were included, while 697 were included for the nutrient intake assessment evaluation. Spearman rank and Pearson correlations, and validity coefficients, which are correlations between intake estimated and habitual true intake, were calculated. Correlations were higher between frequency of food consumption (from the FFQ) and concentration biomarkers than between mean food intake (from the recalls) and concentration biomarkers, especially for DHA+EPA (r 0·35 v. r 0·27). Most correlations were higher among girls than boys. For boys, the highest validity coefficients were found for frequency of fruit consumption (0·88) and for DHA+EPA biomarker (0·71). In girls, the highest validity coefficients were found for fruit consumption frequency (0·76), vegetable consumption frequency (0·74), mean fruit intake (0·90) and DHA+EPA biomarker (0·69). After exclusion of underreporters, correlations slightly improved. Correlations between usual food intakes, adjusted for food consumption frequency, and concentration biomarkers were higher than correlations between mean food intakes and concentration biomarkers. In conclusion, two non-consecutive 24 h recalls in combination with a FFQ seem to be appropriate to rank subjects according to their usual food intake
    Practical Experiences with an Extended Screening Strategy for Genetically Modified Organisms (GMOs) in Real-Life Samples
    Scholtens-Toma, I.M.J. ; Laurensse, E. ; Molenaar, B. ; Zaaijer, S. ; Gaballo, H.M.S. ; Boleij, P.A. ; Bak, A. ; Kok, E.J. - \ 2013
    Journal of Agricultural and Food Chemistry 61 (2013)38. - ISSN 0021-8561 - p. 9097 - 9109.
    modified maize - reference molecules - quantitation - validation
    Nowadays most animal feed products imported into Europe have a GMO (genetically modified organism) label. This means that they contain European Union (EU)-authorized GMOs. For enforcement of these labeling requirements, it is necessary, with the rising number of EU-authorized GMOs, to perform an increasing number of analyses. In addition to this, it is necessary to test products for the potential presence of EU-unauthorized GMOs. Analysis for EU-authorized and -unauthorized GMOs in animal feed has thus become laborious and expensive. Initial screening steps may reduce the number of GMO identification methods that need to be applied, but with the increasing diversity also screening with GMO elements has become more complex. For the present study, the application of an informative detailed 24-element screening and subsequent identification strategy was applied in 50 animal feed samples. Almost all feed samples were labeled as containing GMO-derived materials. The main goal of the study was therefore to investigate if a detailed screening strategy would reduce the number of subsequent identification analyses. An additional goal was to test the samples in this way for the potential presence of EU-unauthorized GMOs. Finally, to test the robustness of the approach, eight of the samples were tested in a concise interlaboratory study. No significant differences were found between the results of the two laboratories.
    Measuring fast-temporal sediment fluxes with an analogue acoustic sensor: a wind tunnel study
    Poortinga, A. ; Minnen, J. van; Keijsers, J.G.S. ; Riksen, M.J.P.M. ; Goossens, D. ; Seeger, K.M. - \ 2013
    PLoS ONE 8 (2013)9. - ISSN 1932-6203
    eolische processen - sediment - windtunnels - meettechnieken - aeolian processes - sediment - wind tunnels - measurement techniques - inland drift-sand - aeolian transport - erosion - velocity - cloud - soil - validation - efficiency - intensity - saltation
    In aeolian research, field measurements are important for studying complex wind-driven processes for land management evaluation and model validation. Consequently, there have been many devices developed, tested, and applied to investigate a range of aeolian-based phenomena. However, determining the most effective application and data analysis techniques is widely debated in the literature. Here we investigate the effectiveness of two different sediment traps (the BEST trap and the MWAC catcher) in measuring vertical sediment flux. The study was performed in a wind tunnel with sediment fluxes characterized using saltiphones. Contrary to most studies, we used the analogue output of five saltiphones mounted on top of each other to determine the total kinetic energy, which was then used to calculate aeolian sediment budgets. Absolute sediment losses during the experiments were determined using a balance located beneath the test tray. Test runs were conducted with different sand sizes and at different wind speeds. The efficiency of the two traps did not vary with the wind speed or sediment size but was affected by both the experimental setup (position of the lowest trap above the surface and number of traps in the saltation layer) and the technique used to calculate the sediment flux. Despite this, good agreement was found between sediment losses calculated from the saltiphone and those measured using the balance. The results of this study provide a framework for measuring sediment fluxes at small time resolution (seconds to milliseconds) in the field.
    In aeolian research, field measurements are important for studying complex wind-driven processes for land management evaluation and model validation. Consequently, there have been many devices developed, tested, and applied to investigate a range of aeolian-based phenomena. However, determining the most effective application and data analysis techniques is widely debated in the literature. Here we investigate the effectiveness of two different sediment traps (the BEST trap and the MWAC catcher) in measuring vertical sediment flux. The study was performed in a wind tunnel with sediment fluxes characterized using saltiphones. Contrary to most studies, we used the analogue output of five saltiphones mounted on top of each other to determine the total kinetic energy, which was then used to calculate aeolian sediment budgets. Absolute sediment losses during the experiments were determined using a balance located beneath the test tray. Test runs were conducted with different sand sizes and at different wind speeds. The efficiency of the two traps did not vary with the wind speed or sediment size but was affected by both the experimental setup (position of the lowest trap above the surface and number of traps in the saltation layer) and the technique used to calculate the sediment flux. Despite this, good agreement was found between sediment losses calculated from the saltiphone and those measured using the balance. The results of this study provide a framework for measuring sediment fluxes at small time resolution (seconds to milliseconds) in the field.
    An evaluation of WRF's ability to reproduce the surface wind over complex terrain based on typical circulation patterns.
    Jiménez, P.A. ; Dudhia, J. ; González-Rouco, J.F. ; Montávez, J.P. ; Garcia-Bustamante, E. ; Navarro, J. ; Vilà-Guerau de Arellano, J. ; Munoz-Roldán, A. - \ 2013
    Journal of Geophysical Research: Atmospheres 118 (2013)14. - ISSN 2169-897X - p. 7651 - 7669.
    regional climate model - cluster-analysis - quality-assurance - mesoscale model - united-states - variability - validation - reanalysis - classification - simulation
    [1] The performance of the Weather Research and Forecasting (WRF) model to reproduce the surface wind circulations over complex terrain is examined. The atmospheric evolution is simulated using two versions of the WRF model during an over 13¿year period (1992 to 2005) over a complex terrain region located in the northeast of the Iberian Peninsula. A high horizontal resolution of 2km is used to provide an accurate representation of the terrain features. The multiyear evaluation focuses on the analysis of the accuracy displayed by the WRF simulations to reproduce the wind field of the six typical wind patterns (WPs) identified over the area in a previous observational work. Each pattern contains a high number of days which allows one to reach solid conclusions regarding the model performance. The accuracy of the simulations to reproduce the wind field under representative synoptic situations, or pressure patterns (PPs), of the Iberian Peninsula is also inspected in order to diagnose errors as a function of the large-scale situation. The evaluation is accomplished using daily averages in order to inspect the ability of WRF to reproduce the surface flow as a result of the interaction between the synoptic scale and the regional topography. Results indicate that model errors can originate from problems in the initial and lateral boundary conditions, misrepresentations at the synoptic scale, or the realism of the topographic features.
    Lipids from yeasts and fungi: Tomorrow's source of Biodiesel?
    Meeuwse, P. ; Sanders, J.P.M. ; Tramper, J. ; Rinzema, A. - \ 2013
    Biofuels Bioproducts and Biorefining 7 (2013)5. - ISSN 1932-104X - p. 512 - 524.
    solid-state fermentation - fatty-acid production - gamma-linolenic acid - sugar-beet pulp - mortierella-isabellina - oleaginous fungi - chemostat model - scale-up - validation - cultures
    In the search for new transport fuels from renewable resources, biodiesel from microbial lipids comes into view. We have evaluated the lipid yield and energy use of a process for production of biodiesel from agricultural waste using lipid-accumulating yeast and fungi. We included different bioreactors for submerged and solid-state fermentation in our evaluation. Using existing kinetic models, we predict lipid yields on substrate between 5% and 19% (w/w), depending on the culture system. According to the same models, improvement of the yield to 25–30% (w/w) is possible, for example by genetic modifi cation of the micro-organisms. The net energy ratio of the non-optimized systems varies between 0.8 and 2.5 MJ produced per MJ used; energy use for pre-treatment and for oxygen transfer are most important. For the optimized systems, the net energy ratio increases to 2.9–5.5 MJ produced per MJ used, which can compete very well with other biofuels such as bioethanol or algal biodiesel. This shows that, although quite some work still has to be done, microbial lipids have the potential to be tomorrow’s source of biodiesel. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd
    Assessing spatial uncertainties of land allocation using a scenario approach and sensitivity analysis: A study for land use in Europe
    Verburg, P.H. ; Tabeau, A.A. ; Hatna, E. - \ 2013
    Journal of Environmental Management 127 (2013)suppl.. - ISSN 0301-4797 - p. S132 - S144.
    climate-change - global change - cover data - future - models - projections - validation - impact - eu
    Land change model outcomes are vulnerable to multiple types of uncertainty, including uncertainty in input data, structural uncertainties in the model and uncertainties in model parameters. In coupled model systems the uncertainties propagate between the models. This paper assesses uncertainty of changes in future spatial allocation of agricultural land in Europe as they arise from a general equilibrium model coupled to a spatial land use allocation model. Two contrasting scenarios are used to capture some of the uncertainty in the development of typical combinations of economic, demographic and policy variables. The scenario storylines include different measurable assumptions concerning scenario specific drivers (variables) and parameters. Many of these assumptions are estimations and thus include a certain level of uncertainty regarding their true values. This leads to uncertainty within the scenario outcomes. In this study we have explored how uncertainty in national-level assumptions within the contrasting scenario assumptions translates into uncertainty in the location of changes in agricultural land use in Europe. The results indicate that uncertainty in coarse-scale assumptions does not translate into a homogeneous spread of the uncertainty within Europe. Some regions are more certain than others in facing specific land change trajectories irrespective of the uncertainty in the macro-level assumptions. The spatial spread of certain and more uncertain locations of land change is dependent on location conditions as well as on the overall scenario conditions. Translating macro-level uncertainties to uncertainties in spatial patterns of land change makes it possible to better understand and visualize the land change consequences of uncertainties in model input variables.
    Selected Reaction Monitoring method to determine the species origin of blood-based binding agents in meats: a collaborative study
    Grundy, H. ; Read, W.A. ; Macarthur, R. ; Alewijn, M. - \ 2013
    Food Chemistry 141 (2013)4. - ISSN 0308-8146 - p. 3531 - 3536.
    quadrupole mass-spectrometry - liquid-chromatography - products - validation
    Binding products or food ‘glues’ are used throughout the food industry to increase the meat use rate or to augment economic efficiency. Some of these binders contain thrombin from bovine and porcine blood. The European parliament has recently banned thrombin-based additives and labelling legislation governs their use in the US. A mass spectrometry screening method is available to detect the addition of thrombin agents to foods as there is a need to protect consumers and to avoid misleading trade practices. We report the details of an inter-laboratory trial to determine the transferability of this method to operators in various food testing laboratories, each using a different triple quadrupole mass spectrometer design. The trial was successful with the species origin of the binding agent contained in each of the forty three test materials being correctly reported by the participants. This is consistent with a false positive and false negative rate of zero percent. This is the first collaborative study, as far as we are aware, which involves a liquid chromatography mass spectrometry (LC-MS/MS) application to approach a food authenticity issue.
    Relative validity of the food frequency questionnaire used to assess dietary intake in the Leiden Longevity Study
    Streppel, M.T. ; Vries, J.H.M. de; Meyboom, S. ; Beekman, M. ; Craen, A.J.M. ; Slagboom, P.E. ; Feskens, E.J.M. - \ 2013
    Nutrition Journal 12 (2013). - ISSN 1475-2891 - 8 p.
    basal metabolic-rate - energy-intake - goldberg cutoff - limitations - validation - markers - design
    Background - Invalid information on dietary intake may lead to false diet-disease associations. This study was conducted to examine the relative validity of the food frequency questionnaire (FFQ) used to assess dietary intake in the Leiden Longevity Study. Methods - A total of 128 men and women participating in the Leiden Longevity Study were included in the present validation study. The performance of the FFQ was evaluated using the mean of three 24-hour recalls as the reference method. Evaluation in estimating dietary intake at the group level was done by paired t-tests. The relative validity of the individual energy adjusted level of intake was assessed with correlation analyses (Pearson’s), with correction for measurement error. Results - On group level, the FFQ overestimated as well as underestimated absolute intake of various nutrients and foods. The Bland and Altman plot for total energy intake showed that the agreement between the FFQ and the 24-hour recalls was dependent of intake level. Pearson correlation coefficients ranged from 0.21 (alpha linolenic acid) to 0.78 (ethanol) for nutrients and from -0.02 (legumes, non-significant) to 0.78 (alcoholic beverages) for foods. Adjustment for energy intake slightly lowered the correlation coefficients for nutrients (mean coefficient: 0.48 versus 0.50), while adjustment for within-subject variation in the 24-h recalls resulted in higher correlation coefficients for both nutrients and foods (mean coefficient: 0.69 for nutrients and 0.65 for foods). Conclusions - For most nutrients and foods, the ability of the FFQ to rank subjects was acceptable to good.
    Comparison of satellite-derived land surface temperature and air temperature from meteorological stations on the Pan-Arctic scale
    Urban, M. ; Eberle, J. ; Hüttich, C. ; Schmullius, C. ; Herold, M. - \ 2013
    Remote Sensing 5 (2013)5. - ISSN 2072-4292 - p. 2348 - 2367.
    recent climate-change - modis products - orbital drift - data set - avhrr - emissivity - dynamics - models - lst - validation
    Satellite-based temperature measurements are an important indicator for global climate change studies over large areas. Records from Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Very High Resolution Radiometer (AVHRR) and (Advanced) Along Track Scanning Radiometer ((A)ATSR) are providing long-term time series information. Assessing the quality of remote sensing-based temperature measurements provides feedback to the climate modeling community and other users by identifying agreements and discrepancies when compared to temperature records from meteorological stations. This paper presents a comparison of state-of-the-art remote sensing-based land surface temperature data with air temperature measurements from meteorological stations on a pan-arctic scale (north of 60° latitude). Within this study, we compared land surface temperature products from (A)ATSR, MODIS and AVHRR with an in situ air temperature (Tair) database provided by the National Climate Data Center (NCDC). Despite analyzing the whole acquisition time period of each land surface temperature product, we focused on the inter-annual variability comparing land surface temperature (LST) and air temperature for the overlapping time period of the remote sensing data (2000–2005). In addition, land cover information was included in the evaluation approach by using GLC2000. MODIS has been identified as having the highest agreement in comparison to air temperature records. The time series of (A)ATSR is highly variable, whereas inconsistencies in land surface temperature data from AVHRR have been found.
    The costs of complex model optimization
    Rubingh, C.M. ; Martens, H. ; Voet, H. van der; Smilde, A.K. - \ 2013
    Chemometrics and Intelligent Laboratory Systems 125 (2013). - ISSN 0169-7439 - p. 139 - 146.
    partial least-squares - metabolomics data - validation - selection - freedom
    Each data-driven action in data modelling consumes degrees of freedom, whether it concerns estimation of parameters, estimation of meta-parameters or selecting variables. By using a double cross validation approach for degrees of freedom calculation the costs for meta-parameter estimation and variable selection can be determined explicitly. The only assumptions are independent and identically distributed errors, which make the approach applicable to many predictive modelling techniques
    Development of an immunochromatographic assay based on carbon nanoparticles for the determination of the phytoregulator forchlorfenuron
    Suaréz-Pantaleón, C. ; Wichers, J.H. ; Abad-Somovilla, A. ; Amerongen, A. van - \ 2013
    Biosensors and Bioelectronics 42 (2013). - ISSN 0956-5663 - p. 170 - 176.
    lateral flow immunoassay - antibody-based immunoassay - computer image-analysis - rapid detection - sensitive detection - dipstick assay - water samples - strip test - validation - biosensor
    Rapid analytical methods enabling the determination of diverse targets are essential in a number of research areas, from clinical diagnostics to feed and food quality and safety. Herein, the development of a quantitative immunochromatographic assay for the detection of the synthetic phytoregulator forchlorfenuron (CPPU) is described. The competitive lateral flow immunoassay (LFIA) was based on the immobilization onto a nitrocellulose membrane of an ovalbumin–CPPU conjugate (test line) and on the use of an immunodetection ligand consisting of carbon nanoparticles labeled with an anti-CPPU monoclonal antibody through interaction with a secondary antibody. The presence of CPPU in horticultural samples was visually interpreted by the decrease in the black signal intensity of the test line, according to the competitive character of the format. The quantitative determination of the analyte was easily performed by a two-step procedure consisting of flatbed scanning of the strips followed by computer-based image analysis of the pixel gray volumes of the test lines. Under optimized conditions, the immunochromatographic test afforded a limit of quantification in buffer of 89 ng/L. The accuracy of the strip test was assessed by the analysis of fruit samples with incurred residues, and the obtained results were compared with those derived from two reference methods, ELISA and HPLC. The LOQ of the CPPU-specific LFIA in kiwifruits and grapes was established at 33.4 µg/kg. The excellent analytical performance of the developed strip test demonstrates the potential of immunochromatographic assays for the quantitative monitoring of small organic molecules in complex matrices.
    Sensitivity and uncertainty of analytical footprint models according to a combined natural tracer and ensemble approach
    Boer, A. van de; Moene, A.F. ; Schüttemeyer, D. ; Graf, A. - \ 2013
    Agricultural and Forest Meteorology 169 (2013). - ISSN 0168-1923 - p. 1 - 11.
    flux measurements - sonic anemometer - carbon-dioxide - surface-layer - water-vapor - exchange - heat - validation - efflux - fetch
    Evaluations of analytical footprint models using data from several stations located in different land use types are still scarce, but valuable for defining the spatial context of the measurements. Therefore, we evaluated two analytical footprint models by applying a ‘forward’ and an ‘inversion’ method. We used eddy covariance measurements from a flat agricultural landscape in western Germany in the summer of 2009, with seven eddy covariance systems over three different land use types with contrasting sensible heat fluxes. We found that the model of Hsieh et al. (2000. Adv. Water Resour. 23, 765–772) and of Kormann and Meixner (2001. Boundary Layer Meteorol. 99, 207–224) are both overestimating the distance of the peak contribution of the footprint. In our evaluation, the former model performs slightly better, independent of whether the crosswind dispersion was used from the latter model, or from the proposed model by Detto et al. (2006. Water Resour. Res. 42, 1–16).
    European ring trial to evaluate ELISAs for the diagnosis of infection with Rift Valley fever virus
    Kortekaas, J.A. ; Kant, J. ; Vloet, R.P.M. ; Cêtre-Sossah, C. ; Marianneau, P. ; Lacote, S. ; Banyard, A.C. ; Jeffries, C. ; Eiden, M. ; Groschup, M. ; Jäckel, S. ; Hevia, E. ; Brun, A. - \ 2013
    Journal of Virological Methods 187 (2013)1. - ISSN 0166-0934 - p. 177 - 181.
    linked-immunosorbent-assay - reverse transcription-pcr - nucleocapsid protein - domestic ruminants - capture elisa - igg antibody - validation - sandwich - humans - sheep
    A ring trial was organized to evaluate Rift Valley fever virus (RVFV) ELISAs by European laboratories. A total of five ELISAs, two of which specific for IgM antibodies, were evaluated by six participants. Sera were derived from cattle or sheep and originated from either a RVFV endemic area, a RVFV-free area or from experimental infection studies. Cohen's kappa analysis showed higher than 90% agreement of two commercially available ELISAs with the virus neutralization test, suggesting that primary screening as well as serological confirmation using these ELISAs is feasible. More extensive validations with sera of known IgM status are, however, required to determine agreement between IgM ELISAs.
    Evaluation of the variation in semantic contents of class sets on modelling dynamics of land-use changes
    Jansen, L.J.M. ; Veldkamp, T.A. - \ 2012
    International Journal of Geographical Information Science 26 (2012)4. - ISSN 1365-8816 - p. 717 - 746.
    use change scenarios - central-america - igbp discover - multiscale - population - database - environment - validation - accuracy - patterns
    Understanding the scale of interaction and the scale of different environmental and social processes is of paramount importance to define and explain the interaction of human-environment systems. There are three dimensions of scale: space, time and the organisational hierarchy as constructed by the observer. The latter is synonymous with the variation in semantic contents of data expressed as differences in categorisation. This dimension of scale has received little attention. In this article the relationship between the semantic contents of data and modelling dynamics is explored using two land-cover data sets for Romania, one based on the Land-Cover Classification System and the other as used in the EURURALIS study. Three levels of semantic contents of the LCCS data and the single semantic level present in the EURURALIS data are used to establish empirical relations between the land-cover class and its explaining factors. The analysis results show that the variations in semantic contents of data within one data set and between two data sets lead to different sets of spatial determinants for land cover. We did not recognise patterns when establishing the organisational hierarchy. Future policy and decision-making depend to a great extent on which organisational hierarchy is present in the data set used to formulate a policy or to make an informed decision. This would mean that if the same results would be found in other data sets using different models not only multi-scale but also multi-semantic analysis are needed in order to make meaningful predictions of spatially explicit land change.
    Comparing optimized CO emission estimates using MOPITT or NOAA surface network observations
    Hooghiemstra, P.B. ; Krol, M.C. ; Bergamaschi, P. ; Laat, A.T.J. de; Werf, G.R. van der; Novelli, P.C. ; Deeter, M.N. ; Aben, I. ; Rockmann, T. - \ 2012
    Journal of Geophysical Research: Atmospheres 117 (2012). - ISSN 2169-897X - 23 p.
    variational data assimilation - zoom model tm5 - carbon-monoxide - tropospheric chemistry - inversion - validation - sciamachy - algorithm - pollution - aircraft
    This paper compares two global inversions to estimate carbon monoxide (CO) emissions for 2004. Either surface flask observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) or CO total columns from the Measurement of Pollution in the Troposphere (MOPITT) instrument are assimilated in a 4D-Var framework. Inferred emission estimates from the two inversions are consistent over the Northern Hemisphere (NH). For example, both inversions increase anthropogenic CO emissions over Europe (from 46 to 94 Tg CO/yr) and Asia (from 222 to 420 Tg CO/yr). In the Southern Hemisphere (SH), three important findings are reported. First, due to their different vertical sensitivity, the stations-only inversion increases SH biomass burning emissions by 108 Tg CO/yr more than the MOPITT-only inversion. Conversely, the MOPITT-only inversion results in SH natural emissions (mainly CO from oxidation of NMVOCs) that are 185 Tg CO/yr higher compared to the stations-only inversion. Second, MOPITT-only derived biomass burning emissions are reduced with respect to the prior which is in contrast to previous (inverse) modeling studies. Finally, MOPITT derived total emissions are significantly higher for South America and Africa compared to the stations-only inversion. This is likely due to a positive bias in the MOPITT V4 product. This bias is also apparent from validation with surface stations and ground-truth FTIR columns. Our results show that a combined inversion is promising in the NH. However, implementation of a satellite bias correction scheme is essential to combine both observational data sets in the SH.
    Check title to add to marked list
    << previous | next >>

    Show 20 50 100 records per page

     
    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.