Adsorptie, omzettingssnelheid en transport van carbendazim in twee bloembollengronden

Carbendazim is een fungicide dat diverse toepassingen kent in de bloembollenteelt en dat regelmatig in het oppervlaktewater wordt aangetroffen. Meer inzicht was nodig in de bijdrage van uitspoeling uit de bodem aan de emissie. De adsorptie van carbendazim aan twee bloembollengronden (humusarm zand) was matig. De omzetting bij 10 °C verliep verrassend snel, vermoedelijk door adaptatie van de micro-organismen in de gronden. Het gedrag van carbendazim in de bodem na toediening (begin december) van een restant ontsmettingsvloeistof aan twee bloembollenvelden werd gesimuleerd met het model PESTLA. De berekende concentraties in het drainagewater bleven ver beneden de bepalingsgrens van bijvoorbeeld 0,01 g/dm3. In scenario's met verhoogde bodembelasting, vertraging van de omzetting door een ander fungicide, slechts gedeeltelijke adaptatie, en een minder sterk gekromde adsorptie-isotherm bleef de berekende uitspoeling laag. Gezien de onzekerheden zijn enkele veldmetingen ter controle van de berekende resultaten gewenst. Extrapolatie naar gronden die niet regelmatig worden belast (minder adaptatie) is extra onzeker

PEARL model for pesticide behaviour and emissions in soil-plant systems : description of the processes in FOCUS PEARL v 1.1.1

The use of pesticides in agriculture presents risks to the environment, which are increasingly evaluated by using computation models. The new PEARL model simulates the behaviour of pesticides in soil-plant systems and their emissions to the environment. The pesticide model is used in combination with the hydrological model SWAP. Various agricultural situations and ways of applying the pesticides can be simulated. The model accounts for different sorption mechanisms, in equilibrium and non-equilibriumdomains of the soil. Pesticide transport in the liquid and gas phases is described by the convection-dispersion-diffusion type equation, which is supplemented with sink terms. Comprehensive reaction schemes are processed in matrix form. The rate in first-order transformation kinetics is dependent on temperature, soil moisture content and depth in the soil. Besides computing persistence and distribution of the pesticidal compounds in soil, the model computes volatilization into the air, lateral drainage to water courses and leaching to groundwater

Rehabilitation patients: undernourished and obese?

BACKGROUND: The aim of this study was to assess the prevalence of undernutrition in patients in Dutch rehabilitation centres and to measure the diagnostic accuracy of available screening tools. METHODS: This cross-sectional multicentre study was conducted in 11 rehabilitation centres in The Netherlands. Patient's nutritional status was determined by the amount of weight loss during the last 1, 3 and 6 months and body mass index (BMI). Diagnostic accuracy was assessed for 5 screening tools: Short Nutritional Assessment Questionnaire (SNAQ), Short Nutritional Assessment Questionnaire Residential Care (SNAQRC), SNAQ65+, Malnutrition Universal Screening Tool and Mini nutrition Assessment-short form. RESULTS: Twenty-eight percent of the patients were severely undernourished and 10% were moderately undernourished. In the undernourished group, 28% were overweight (BMI 25-30) and 19% were obese (BMI > 30). The SNAQ65+ is the recommended screening tool due to its high diagnostic accuracy (sensitivity 96%, specificity 77%, positive predictive value 62%, negative predictive value 90%) and quick and easy use. The MNA had the worst diagnostic accuracy, with a sensitivity of 44%. CONCLUSION: The prevalence of undernutrition in patients in Dutch rehabilitation centres is high. Almost half of the undernourished patients were overweight or obese. Therefore, it is important not only to screen for undernutrition, but also carefully to assess possible overweight/obesity in every undernourished rehabilitation patient

Embedded Stellar Populations towards Young Massive Star Formation Regions I. G305.2+0.2

We present deep, wide-field J, H and Ks images taken with IRIS2 on the Anglo Australian Telescope, towards the massive star formation region G305.2+0.2. Combined with 3.6, 4.5, 5.8 and 8.0 micron data from the GLIMPSE survey on the Spitzer Space Telescope, we investigate the properties of the embedded stellar populations. After removing contamination from foreground stars we separate the sources based on their IR colour. Strong extended emission in the GLIMPSE images hampers investigation of the most embedded sources towards the known sites of massive star formation. However, we find a sizeable population of IR excess sources in the surrounding region free from these completeness effects. Investigation reveals the recent star formation activity in the region is more widespread than previously known. Stellar density plots show the embedded cluster in the region, G305.24+0.204, is offset from the dust emission. We discuss the effect of this cluster on the surrounding area and argue it may have played a role in triggering sites of star formation within the region. Finally, we investigate the distribution of IR excess sources towards the cluster, in particular their apparent lack towards the centre compared with its immediate environs.Comment: 16 pages, 16 figures (significantly size reduced), 2 tables, accepted MNRA

Two 2MASS-Selected Young Stellar Clusters: Photometry, Spectroscopy, and the IMF

We present near-infrared J, H, and K_s images and K-band spectroscopy of two newly discovered stellar clusters at different stages of evolution. Our spectra suggest the presence of massive YSOs in the heavily embedded cluster in the star-forming region near radio source G353.4-0.4 and an O5-O6V star in the cluster near radio source G305+00.2. We determine a K-band luminosity function (KLF) for both clusters and an initial mass function (IMF) for the cluster near G305+00.2. The derived IMF slope is -1.5 if the KLF is used to derive the IMF and is -0.98 if the color-magnitude diagram and spectra are used. The more reliable CMD-based slope is flatter than the Salpeter value usually found for stellar clusters. We find that using the KLF alone to derive an IMF is likely to produce an overly steep slope in stellar clusters subject to variable extinction.Comment: 16 pages, 18 figures, accepted to A

Estimating input data for computations on the volatilisation of pesticides from plant canopies and competing processes

Volatilisation of pesticides from the crop can be an important emission pathway to the environment. A computation module was developed for making estimates on this emission. However, various input data for this module are not measured directly in registration procedures, so they have to be estimated from theory or from a diversity of experimental data. Vapour pressure is the most important property in volatilisation, which needs a critical evaluation in case of conflicting data. Diffusion coefficients for transport in a laminar boundary layer are estimated from theory. Penetration of pesticides into the leaves is highly affected by substances in the formulation and by environmental conditions. Pesticide deposit is often vulnerable to washoff by rainfall. Often, no directly measured rates are available for photochemical transformation on plant surfaces, so these have to be estimated from a variety of experimental results. In critical cases, comprehensive experiments with micro-agro-ecosystems and/or in the field are needed

Effect of soil moisture condition on the conversion rate of oxamyl.

The decomposition of oxamyl in four soils under moist conditions was measured in incubation experiments at 15 deg C. Half-lives of oxamyl in soils with moisture tensions of approx. -9.8 X 103 Pa were 13 days in a clay loam, 14 days in a loamy sand, 34 days in a peaty sand and 39 days in a humic loamy sand. The rate of oxamyl decomposition in the clay loam decreased with decreasing soil moisture content down to values for below wilting point. Oxamyl decomposition in the humic loamy sand decreased with decreasing soil moisture content, but increased sharply in the very dry range. (Abstract retrieved from CAB Abstracts by CABI’s permission

Diffusion and adsorption of the nematicide 1,3-dichloropropene in soil

After soil fumigation the concentration of the nematicidal compounds cis and trans 1,3-dichloropropene at various depths in the soil was estimated by electron-capture gas-chromatography. The coefficients for the distribution of the compounds over the phases in soil under various conditions were also measured. Differential equations were derived for the events during fumigation in the field. Combinations of analytical starting solutions and numerical solutions of these equations were used. With the computation models the dose patterns in soil under various conditions could be calculated. Of the weather related factors, soil moisture had the greatest influence on efficiency of fumigation. Large clods in the plough layer caused a shade effect in the dose patterns and a rough soil surface also decreased effectiveness. After careful application differences in effectivity for various types of fumigator were small. Most of the undesirable side-effects that appear after the waiting period can be prevented by fumigating in the favourable soil moisture range and by tilling to plough depth. Estimates were made of the relative importance of disappearance by volatilization, leaching and decomposition

A multi-wavelength census of stellar contents in the young cluster NGC 1624

We present a comprehensive multi-wavelength analysis of the young cluster NGC 1624 associated with the H II region Sh2-212 using optical UBVRI photometry, optical spectroscopy and GMRT radio continuum mapping along with the near-infrared (NIR) JHK archival data. Reddening E(B-V) and distance to the cluster are estimated to be 0.76 - 1.00 mag and 6.0 +/- 0.8 kpc, respectively. Present analysis yields a spectral class of O6.5V for the main ionizing source of the region. The distribution of YSOs in (J-H)/ (H-K) NIR colour-colour diagram shows that a majority of them have A_V $\le$ 4 mag. Based on the NIR excess characteristics, we identified 120 probable candidate YSOs in this region which yield a disk frequency of ~ 20%. These YSOs are found to have an age spread of ~ 5 Myr with a median age of ~ 2-3 Myr and a mass range of ~ 0.1 - 3.0 $M_\odot$. A significant number of YSOs are located close to the cluster centre and we detect an enhanced density of reddened YSOs located/projected close to the molecular clumps at the periphery of NGC 1624. This indicates that the YSOs located within the cluster core are relatively older in comparison to those located/projected near the clumps. From the radio continuum flux, spectral class of the ionizing source of the ultra-compact H II region at the periphery of Sh2-212 is estimated to be ~ B0.5V. From optical data, slope of the mass function (MF) $\Gamma$, in the mass range $1.2 \le M/M_{\odot}<27$ can be represented by a single power law with a slope -1.18 +/- 0.10, whereas the NIR data in the mass range $0.65 \le M/M_{\odot}<27$ yields $\Gamma$ = -1.31 +/- 0.15. The slope of the K-band luminosity function (KLF) for the cluster is found to be 0.30 +/- 0.06 which is in agreement with the values obtained for other young clusters.Comment: Accepted for publication in MNRA

Moorden door Pubers

Elke tienermoord schokt de samenleving. Maar het beeld dat het ‘steeds erger’ wordt, klopt niet. Hun aandeel is opvallend stabiel.Security and Global Affair