Newest publications
Influence of self-compaction on the airflow resistance of grain bulks
(2020) Ramaj, Iris; Schock, Steffen; Karaj, Shkelqim; Müller, Joachim
Aeration practices have been widely employed to force conditioned air through in-storage grain bulks to guarantee quality preservation and safe storage. Despite the attention given in the last decades as a principal grain management technique, many obstacles have been encountered in reducing the deteriorative effects of high moisture content and temperature throughout the in-storage bulk. This was attributed to the misestimation of the resistance of stored grains to the airflow, which led to deficiencies in bulk aeration. This resistance is complex and strongly dependent on airflow and grain properties. In this study, the airflow resistance of wheat grains (Pioneer A DSV AG, 12.37 % w.b moisture content) during storage was investigated. A cylindrical, stationary bed (0.5 m diameter and 3.6 m height) was used as an experimental basis. A coherent set of airflow velocities ranging from 0.01 to 0.15 m·s-1 and storage times ranging from 1 to 236 h at four grain depth levels were applied accordingly. The relationship between pressure drop and velocity was assessed experimentally and modeled theoretically with an overall goodness of fit of R2=0.99, RMSE=25.7, and MAPE=10.4%. Results demonstrated an increase of the airflow resistance throughout the depth of the grain bulk and storage time. This behavior was ascribed to the self-compaction of the bulk material arising from the burden pressures imposed by the dead weight of the bulk. The self-compaction decreased the porosity significantly, increased the bulk density, enlarged the airflow resistance and consequently, considerably increased the pressure drop. Hence, extra power supplies for aeration are prerequisites to overcome the resistance caused by self-compaction. The spatial and temporal effects of self-compaction in stored grain bulks should be accommodated in the design and analysis of aeration systems.
Untangling the actual infection status: detection of avian haemosporidian parasites of three Malagasy bird species using microscopy, multiplex PCR, and nested PCR methods
(2022) Musa, Sandrine; Mackenstedt, Ute; Woog, Friederike; Dinkel, Anke
The development of new molecular methods has significantly improved the detection and identification of avian haemosporidian parasites ( Plasmodium , Haemoproteus and Leucocytozoon ) compared to microscopic examination. Very large numbers of previously hidden Haemosporida species of a wide range of avian hosts have thus been discovered in the last two decades. However, test parameters of the various detection methods remain largely unevaluated. In this study, the merits of microscopy, multiplex PCR, and nested PCR were compared to identify the infection status of three Malagasy bird species. A total of 414 blood samples of Hypsipetes madagascariensis , Foudia omissa and F. madagascariensis , as well as 147 blood smears, were examined for haemosporidian infection. Thirty-four lineages of haemosporidian parasites could be identified, of which six have been detected for the first time. Microscopy, multiplex and nested PCR showed differences in detection rate, most likely due to low parasitemia of chronically infected birds. The combination of both PCR methods yielded the best results. In particular, detection of multiple infections could be greatly improved and will enable more precise prevalence estimates of individual haemosporidian species in wild birds in the future.
Negotiation systems and studies
(2022) Schoop, Mareike; Vetschera, Rudolf
Contrasting yield responses at varying levels of shade suggest different suitability of crops for dual land-use systems: a meta-analysis
(2022) Laub, Moritz; Pataczek, Lisa; Feuerbacher, Arndt; Zikeli, Sabine; Högy, Petra
Despite the large body of research surrounding crop growth parameters, there is still a lack of systematic assessments on how harvestable yields of different crop types respond to varying levels of shading. However, with the advent of agrivoltaic systems, a technology that combines energy and food production, shade tolerance of cropping systems is becoming increasingly important. To address this research gap, a meta-analysis with data from two experimental approaches (intercropping and artificial shading with cloths, nets or solar panels) was performed. The aim was to quantitatively assess the susceptibility of different temperate crop types to increasing levels of shading. Crop type specific yield response curves were developed as a function of reduction in solar radiation, estimating relative crop yields compared to the unshaded controls. Only studies that reported reduction in solar radiation and crop yield per area in temperate and subtropical areas were included. The results suggested a nonlinear relationship between achieved crop yields and reduction in solar radiation for all crop types. Most crops tolerate reduced solar radiation up to 15%, showing a less than proportional yield decline. However, significant differences between the response curves of the following crop types existed: Berries, fruits and fruity vegetables benefited from reduction in solar radiation up to 30%. Forages, leafy vegetables, tubers/root crops, and C3 cereals initially showed less than proportional crop yield loss. In contrast, maize and grain legumes experienced strong crop yield losses even at low shade levels. The results provide a set of initial indicators that may be used in assessing the suitability of crop types for shade systems, and thus for agrivoltaic or other dual land-use systems. Detailed yield response curves, as provided by this study, are valuable tools in optimizing the output of annual crop components in these systems.
Online hyphenation of centrifugal partition chromatography with countercurrent chromatography (CPC-CCC) and its application to the separation of saturated alkylresorcinols
(2022) Hammerschick, Tim; Vetter, Walter
Centrifugal partition chromatography (CPC) and countercurrent chromatography (CCC) are two preparative techniques mainly used for the isolation and purification of natural products. While CPC benefits from a larger sample capacity, CCC typically provides better peak resolutions and hereby higher purities. In this study, we aimed to combine both advantages by the direct linking of CPC and CCC which was achieved by installation of switching valves and connection tube. The hyphenated CPC-CCC setup was tested with major alkylresorcinols which were obtained from a transesterified and hydrogenated rye extract. Injections of 1- and 5-g samples into the individual CCC system confirmed the limited sample capacity because of immediate flooding with the 5-g sample (total loss of stationary phase). In comparison, the CPC system was stable with 5- and 10-g samples but the peak resolution with 1-g sample was poorer than with the CCC system. Injections of 5- and 10-g samples into the CPC-CCC system were successful. However, a sample load of 10 g resulted in lower purities of the alkylresorcinols (80% or less) due to peak tailing. By contrast, injection of 5-g sample provided high amounts of ~ 1.2 g alkylresorcinols with purities of > 95%.