Prevention of vole damage in organic pomiculture

Vole damage is one of the most difficult phytosanitary problems to solve in organic pomiculture. A survey conducted in 2002 among German fruit growers showed that 90 % of the farms suffered from this damage. The water vole (A. terrestris) revealed to be the main pest in 80 % of the orchards. 61 % of the farmers announced a high interest in the development of new preventive and control methods. To stop immigration of voles into orchards a mechanical barrier system was developed and tested at two study sites in Baden-Wuerttemberg and Rhineland-Palatinate. At each location barrier systems with wire mesh (mesh size 10 mm) and polyolefine-foil were installed arround two 0.7 ha study plots. Two unprotected plots were used as a control. The barriers were anchored 20 cm deep into the soil. 30 cm of the material protruded over the surface. Automatic gates were installed for the entrance of vehicles. 4 persons needed approximately one day to install a barrier around a plot with the size of 1 ha. Not only was the wire mesh cheaper than the foil, it was permeable for wind, water and small beneficial organisms. After installing the barrier systems, voles were removed from all plots. Snap trap boxes were ranged along the outside of the barriers to catch migrating voles. A total of 33 water voles and 1263 common voles (M. arvalis) were captured on both study sites from October 2002 to November 2003. During the study period a total of 5 water voles immigrated into the first control plot and 6 settled into the other plot. Four water voles entered two of the barrier protected plots by using fresh mole galleries. The other protected plots stayed free from water voles. Simultaneous to the field studies, trials in two enclosures were carried out in Muenster. The barriers kept all water voles outside the protected plots. The results showed a high efficacy of the developed barrier system

How expensive is vole damage?

Vole species, especially Arvicola terrestris and Microtus arvalis cause significant economical damage in organic pomiculture by gnawing the root system of trees. The importance of voles as pest organisms is well known. Nevertheless, the estimation of financial loss caused by voles is difficult for German fruit growers. We conducted a survey among organic fruit growers to get data on kind and amount of annual damage. Using the available publications and official statistics we calculated economical values of organic apple trees for different types of orchard processing and tree ages. Furthermore we calculated the number of trees lost due to voles in one year

Calibration of thickness-dependent k-factors for germanium X-ray lines to improve energy-dispersive X-ray spectroscopy of SiGe layers in analytical transmission electron microscopy

We show that the accuracy of energy-dispersive X-ray spectroscopy can be improved by analysing and comparing multiple lines from the same element. For each line, an effective k-factor can be defined that varies as a function of the intensity ratio of multiple lines (e.g. K/L) from the same element. This basically performs an internal self-consistency check in the quantification using differently absorbed X-ray lines, which is in principle equivalent to an absorption correction as a function of specimen thickness but has the practical advantage that the specimen thickness itself does not actually need to be measured

Hydrogen adsorption in metal-organic frameworks: the role of nuclear quantum effects

The role of nuclear quantum effects on the adsorption of molecular hydrogen in metal-organic frameworks (MOFs) has been investigated on grounds of Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT) calculations. For this purpose, we have carefully validated classical H2 -host interaction potentials that are obtained by fitting Born-Oppenheimer ab initio reference data. The hydrogen adsorption has first been assessed classically using Liquid Density-Functional Theory (LDFT) and the Grand-Canonical Monte Carlo (GCMC) methods. The results have been compared against the semi-classical treatment of quantum effects by applying the Feynman-Hibbs correction to the Born-Oppenheimer-derived potentials, and by explicit treatment within the Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT). The results are compared with experimental data and indicate pronounced quantum and possibly many-particle effects. After validation calculations have been carried out for IRMOF-1 (MOF-5), GC-QLDFT is applied to study the adsorption of H2 in a series of MOFs, including IRMOF-4, -6, -8, -9, -10, -12, -14, -16, -18 and MOF-177. Finally, we discuss the evolution of the H2 quantum fluid with increasing pressure and lowering temperature

Grand-Canonical Quantized Liquid Density-Functional Theory in a Car-Parrinello Implementation

Quantized Liquid Density-Functional Theory [Phys. Rev. E 2009, 80, 031603], a method developed to assess the adsorption of gas molecules in porous nanomaterials, is reformulated within the grand canonical ensemble. With the grand potential it is possible to compare directly external and internal thermodynamic quantities. In our new implementation, the grand potential is minimized utilizing the Car-Parrinello approach and gives, in particular for low temperature simulations, a significant computational advantage over the original canonical approaches. The method is validated against original QLDFT, and applied to model potentials and graphite slit pores.Comment: 19 pages, 5 figure

3D simulations of self-propelled, reconstructed jellyfish using vortex methods

We present simulations of the vortex dynamics associated with the self-propelled motion of jellyfish. The geometry is obtained from image segmentation of video recordings from live jellyfish. The numerical simulations are performed using three-dimensional viscous, vortex particle methods with Brinkman penalization to impose the kinematics of the jellyfish motion. We study two types of strokes recorded in the experiment1. The first type (stroke A) produces two vortex rings during the stroke: one outside the bell during the power stroke and one inside the bell during the recovery stroke. The second type (stroke B) produces three vortex rings: one ring during the power stroke and two vortex rings during the recovery stroke. Both strokes propel the jellyfish, with stroke B producing the highest velocity. The speed of the jellyfish scales with the square root of the Reynolds number. The simulations are visualized in a fluid dynamics video.Comment: 1 page, 1 figur

Post-genomic characterization of metabolic pathways in Sulfolobus solfataricus

The physiological functions and mode of actions of different biomolecules are of continuous interest and a prerequisite to fully understand and appreciate the potential of Archaea and their molecules. We chose to study Sulfolobus solfataricus for its stable (heat-resistant) enzymes and specific metabolic potential, the ease of cultivation of this organism, and the relative large amount of knowledge about this heat-loving acidophilic organism. We selected a systems approach to study the behaviour of this organism trying to make steps forward into the unknown, whenever possible trying to link exploration to exploitation. The cultivation of S.solfataricus is an essential element in all systems approaches that link genotype to phenotype. Hence, specific attention is given to the advanced culturing systems for this extremophile that have been used in all experimental studies described here (Chapters 3-6). Systems analysis includes the integration of all available omics data and is increasingly used in the analysis of Archaea (Chapters 3 and 4). However, most attention has been given to archaeal transcriptome analysis and hence the most important literature on heat-loving Archaea is summarized (Chapter 2). In the experimental chapters (Chapters 3-6) various systems approaches are applied to gain understanding of metabolic pathways in Sulfolobus. Chapter 3 describes the study of the central carbon pathways, consisting of the (non-) phosphorilated Entner-Douderoff (ED) pathway and the citric acid cycle. Different functional genomic approaches were applied on the model organism Sulfolobus solfataricus to study the response of growth on different carbon sources, D-Glucose vs. Tryptone and Yeast Extract. The complete transcriptome was studied using PCR-based microarrays. In addition the proteome was studied using 2D-electrophoresis map in combination with 13N- labelling technique to determine protein fluctuations. Despite the large difference in medium, very few significant differences on protein or RNA level were observed for the two conditions. Therefore regulation of these pathways does in all probability not occur through changes in protein abundance but presumably rather by direct changes in enzyme activity. This is unlike two thermophilic Euryarchaea: Thermococcus kodaaraensis (Kanai, Akerboom et al. 2007)and Pyrococcus furiosus (Schut, Brehm et al. 2003)where extensive regulation of glycolytic genes was observed in a similar situation. Chapter 4describes the study of the degradation of D-arabinose through a similar approach as was described in chapter 3. S. solfataricus was grown on either D-arabinose or D-glucose and a comprehensive transcriptome and proteome study was carried out. The result of these studies was not only elucidation of the D-arabinose degradation route, but also a general prokaryotic pentose, hexaric acids and hydroxyproline degradation route, which supports the theory of metabolic pathway genesis by enzyme recruitment. Also this study predicted a cis-regulatory element to induce the arabinose degrading pathway when needed. The enzymes involved in the proposed pathway were cloned, expressed and their function was biochemically measured. This showed that using these enzymes, D-arabinose can be degraded to 2-oxogluterate, one of the metabolites that are part of the citric acid cycle. Chapter 5reports on the effects of different oxygen concentrations on the behaviour of Sulfolobus solfataricus. The oxygen amount can be controlled relatively easily in a bioreactor, which is crucial for rapid and reproducible growth. Based on growth experiments in microcosms, different types of behaviour could be seen. At 35% (v/v gas phase) the cultures did not grow, indicating that S. solfa-taricus experiences a lethal dose of oxygen. At 26-32% growth was impaired, suggesting a moderate toxicity compared to the reference (21%). In the ranges 16-24% of oxygen, standard growth was observed, suggesting that S. solfataricus is comfortable in these oxygen ranges. For the lower amounts of oxygen (1.5-15%), the growth was comparable to the reference, but the respiratoryefficiency was increased. To get some more insight into this behaviour, we looked at the transcriptome. It showed differential expression of several genes, including genes encoding terminal oxidases, indicating that the organism adapts to lower oxygen concentrations by adapting its respiratory machinery. Chapter 6 describes the zeaxanthin pathway in the Sulfolobus species. Zeaxanthin is a colorant and of vital importance for the function of the human eye. In this chapter the genes responsible for zeaxanthin production are presented. For this, DNA microarrays, bioinformatics as well as molecular genetics techniques were used. A crtx-like gene is operational in most of the known Sulfolobus species that is able to attach sugar-like molecules to zeaxanthin, which improves its solubility in water, which is very important in many food uses. We have cloned this crtx-like gene of S. solfataricus, S. shibatae, and S. acidocaldarius in a zeaxanthin overproducing E. coli strain. It has been demonstrated that the gene products of S. shibatae and S. acidocaldarius were responsible for attaching sugar-like molecules to zeaxanthin. The ctrx-like gene of S. solfataricus was not operating in E. coli. This is probably due to the fact that the gene is truncated. This chapter has further improved the understanding of archaeal carotenoid pathways and it has shown that the Sulfolobus species are able to modify zeaxanthin, although each species produces different zeaxanthin modifications. </p

Intensity-intensity correlations as a probe of interferences - under conditions of none in the intensity

The different behaviour of first order interferences and second order correlations are investigated for the case of two coherently excited atoms. For intensity measurements this problem is equivalent to Young's double slit experiment and was investigated in an experiment by Eichmann et al. [Phys. Rev. Lett. 70, 2359 (1993)] and later analyzed in detail by Itano et al. [Phys. Rev. A 57, 4176 (1998)]. Our results show that in cases where the intensity interferences disappear the intensity-intensity correlations can display an interference pattern with a visibility of up to 100%. The contrast depends on the polarization selected for the detection and is independent of the strength of the driving field. The nonclassical nature of the calculated intensity-intensity correlations is also discussed.Comment: 14 pages, 2 figure

Introducing the Spatial Conflict Dynamics indicator of political violence

Modern armed conflicts have a tendency to cluster together and spread geographically. However, the geography of most conflicts remains under-studied. To fill this gap, this article presents a new indicator that measures two key geographical properties of subnational political violence: the conflict intensity within a region on the one hand, and the spatial distribution of conflict within a region on the other. We demonstrate the indicator in North and West Africa between 1997 to 2019 to show that it can clarify how conflicts can spread from place to place and how the geography of conflict changes over time

Formation of Low Threshold Voltage Microlasers

Vertical cavity surface emitting lasers (VCSELs) with threshold voltages of 1.7V have been fabricated. The resistance-area product in these new vertical cavity lasers is comparable to that of edge-emitting lasers, and threshold currents as low as 3 mA have been measured. Molecular beam epitaxy was used to grow n-type mirrors, a quantum well active region, and a heavily Be-doped p-contact. After contact definition and alloying, passive high-reflectivity mirrors were deposited by reactive sputter deposition of SiO2/Si3N4 to complete the laser cavity