Fosfaatbebemesting landbouwgronden op andere leest schoeien

De fosfaatbelasting van oppervlaktewater moet omlaag. Naast regelgeving kan dat door draagvlak te creëren in de agrarische sector. De grondslag van de bemestingsadvisering voor fosfaat dient daarvoor te worden aangepast. Dat moet leiden tot een meer autonome realisatie van doelstellingen zoals in de Kaderrichtlijn Water, betogen de auteur

Predicting the potential of soils to supply phosphorus by integrating soil chemical processes and standard soil tests

In agriculture there is a growing need to use phosphorus (P) fertilizer more efficiently because of P related environmental problems and diminishing P reserves. A key factor to achieve this is an accurate prediction of the P supply potential of a soil. To improve the choice of soil tests and interpretation of the corresponding results a new methodology is proposed. The methodology is derived based on the continuous removal of P from soils using an artificial P sink (Fe oxide-impregnated paper) and linking the results to standard soil tests. To achieve this, the desorption results are modeled based on the adsorption characteristics of the P sink and a soil specific Langmuir desorption isotherm in which the parameters are calculated a priori from standard soil tests. To be able to make any prediction of the P supply potential a minimum of two parameters is needed: a measure for the reversibly adsorbed P (Q) and for the P concentration in solution (C). The best prediction is obtained when Q was approximated by P-Olsen, followed by PAL and Pox. The measure for C is an indication of the rate with which P can be removed from the soil and is approximated by P-CaCl2. The ratio Q over C is an indication of the capacity of the soil to buffer C, and thus the capacity to maintain the flux from the soil to a sink. The accuracy of this prediction increases for soils with high buffer power, i.e. with low P saturation of the reactive surface area associated with the readily desorbable P. In this case the Langmuir isotherm is linear. To increase the accuracy of this prediction for soils that do not have a high buffer power, and the Langmuir isotherm is thus nonlinear, a measure for the reactive surface area (e.g. Fe-ox and Al-ox) of the soil must also be taken into account. In addition, to be able to extend the prediction of the soil P supply potential to an amount of P exceeding the amount of readily desorbable P. a measure for the total desorbable P content must be included (e.g. P-ox). This total desorbable P content dictates the level at which C is highly buffered once the reversibly adsorbed P has been depleted. The methodology was verified in pot- and field experiments. Implementation of the methodology based on two parameters in a Dutch routine soil laboratory has resulted in a more accurate P fertilizer recommendation for grassland

Naar een betrouwbare schatting van de chemische beschikbaarheid van fosfaat in de bodem

Om eutrofiëring van oppervlaktewater te beperken is minimalisatie van uitspoeling en afspoeleing van fosfaat in de bodem geboden. Het nauwkeurig vaststellen van de biobeschikbaarheid van fosfaat in de bodem is dan ook van groot belang om agrarische en milieu doelstellingen te integreren. Er is nu een nieuwe methodiek bepaal

Speciation of Se and DOC in soil solution and their relation to Se bioavailability.

A 0.01 M CaCl2 extraction is often used to asses the bioavailability of plant nutrients in soils. However, almost no correlation was found between selenium (Se) in the soil extraction and Se content in grass. The recently developed anion Donnan membrane technique was used to analyze chemical speciation of Se in the 0.01 M CaCl2 extractions of grassland soils and fractionation of DOC (dissolved organic carbon). The results show that most of Se (67-86%) in the extractions (15 samples) are colloidal-sized Se. Only 13-34% of extractable Se are selenate, selenite and small organic Se

Deskstudie naar de mogelijkheden voor het aanwijzen van fosfaatarme gronden op basis van P-PAE

Het Bedrijfslaboratorium voor Grond- en Gewasonderzoek hanteert sinds twee jaar het onderzoekspakket Plant Available Elements (PAE). In dit pakket is fosfaat opgenomen (P-PAE). P-PAE is niet opgenomen in het protocol voor het aanwijzen van landbouwpercelen die in aanmerking komen voor een verhoogde fosfaatgebruiksnorm. Een deskstudie naar het opnemen van P-PAE als derde methode voor het aanwijzen van fosfaatarme gronden is uitgevoerd

Targeting Hypoxia, HIF-1, and Tumor Glucose Metabolism to Improve Radiotherapy Efficacy

Item does not contain fulltextRadiotherapy, an important treatment modality in oncology, kills cells through induction of oxidative stress. However, malignant tumors vary in their response to irradiation as a consequence of resistance mechanisms taking place at the molecular level. It is important to understand these mechanisms of radioresistance, as counteracting them may improve the efficacy of radiotherapy. In this review, we describe how the hypoxia-inducible factor 1 (HIF-1) pathway has a profound effect on the response to radiotherapy. The main focus will be on HIF-1-controlled protection of the vasculature postirradiation and on HIF-1 regulation of glycolysis and the pentose phosphate pathway. This aberrant cellular metabolism increases the antioxidant capacity of tumors, thereby countering the oxidative stress caused by irradiation. From the results of translational studies and the first clinical phase I/II trials, it can be concluded that targeting HIF-1 and tumor glucose metabolism at several levels reduces the antioxidant capacity of tumors, affects the tumor microenvironment, and sensitizes various solid tumors to irradiation. Clin Cancer Res; 18(20); 5585-94. (c)2012 AACR

Stereotactic radiotherapy boost after definite chemoradiation for non-responding locally advanced NSCLC based on early response monitoring 18F-FDG-PET/CT

Background and purpose: Prognosis of locally advanced non-small cell lung cancer remains poor despite chemoradiation. This planning study evaluated a stereotactic boost after concurrent chemoradiotherapy (30 × 2 Gy) to improve local control. The maximum achievable boost directed to radioresistant primary tumor subvolumes based on pre-treatment fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) (pre-treatment-PET) and on early response monitoring 18F-FDG-PET/CT (ERM-PET) was compared. Materials and methods: For ten patients, a stereotactic boost (VMAT) was planned on ERM-PET (PTVboost;ERM) and on pre-treatment-PET (PTVboost;pre-treatment), using a 70% SUVmax threshold with 7 mm margin to segmentate radioresistant subvolumes. Dose was escalated till organ at risk (OAR) constraints were met, aiming to plan at least 18 Gy in 3 fractions (EQD2 84 Gy/BED 100.8 Gy). Results: In five patients, PTVboost;ERM was 9–40% smaller relative to PTVboost;pre-treatment. Overlap of PTVboost;ERM with OARs decreased also compared to overlap of PTVboost;pre-treatment with OARs. However, any overlap with OAR remained in 4/5 patients resulting in minimal differences between planned dose before and during treatment. Median dose (EQD2) covering 99% and 95% of PTVboost;ERM were 15 Gy and 18 Gy respectively. Median boost volume receiving a physical dose of  ≥ 18 Gy (V18) was 88%. V18 was ≥ 80% for PTVboost in six patients. Conclusions: A significant stereotactic boost to volumes with high initial or persistent 18F-FDG-uptake could be planned above 60 Gy chemoradiation. Differences between planned dose before and during treatment were minimal. However, as an ERM-PET also monitors changes in tumor position, we recommend to plan the boost on the ERM-PET. Keywords: Non-small cell lung cancer, Early response monitoring fluorine 18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET), Stereotactic radiation boos

The influence of the exclusion of central necrosis on [¹⁸F]FDG PET radiomic analysis

Background: Central necrosis can be detected on [18F]FDG PET/CT as a region with little to no tracer uptake. Currently, there is no consensus regarding the inclusion of regions of central necrosis during volume of interest (VOI) delineation for radiomic analysis. The aim of this study was to assess how central necrosis affects radiomic analysis in PET. Methods: Forty-three patients, either with non-small cell lung carcinomas (NSCLC, n = 12) or with pheochromocytomas or paragangliomas (PPGL, n = 31), were included retrospectively. VOIs were delineated with and without central necrosis. From all VOIs, 105 radiomic features were extracted. Differences in radiomic features between delineation methods were assessed using a paired t-test with Benjamini-Hochberg multiple testing correction. In the PPGL cohort, performances of the radiomic models to predict the noradrenergic biochemical profile were assessed by comparing the areas under the receiver operating characteristic curve (AUC) for both delineation methods. Results: At least 65% of the features showed significant differences between VOIvital-tumour and VOIgross-tumour (65%, 79% and 82% for the NSCLC, PPGL and combined cohort, respectively). The AUCs of the radiomic models were not significantly different between delineation methods. Conclusion: In both tumour types, almost two-third of the features were affected, demonstrating that the impact of whether or not to include central necrosis in the VOI on the radiomic feature values is significant. Nevertheless, predictive performances of both delineation methods were comparable. We recommend that radiomic studies should report whether or not central necrosis was included during delineation.Biomechanical Engineerin