Spatio-temporal dynamics induced by competing instabilities in two asymmetrically coupled nonlinear evolution equations

Pattern formation often occurs in spatially extended physical, biological and chemical systems due to an instability of the homogeneous steady state. The type of the instability usually prescribes the resulting spatio-temporal patterns and their characteristic length scales. However, patterns resulting from the simultaneous occurrence of instabilities cannot be expected to be simple superposition of the patterns associated with the considered instabilities. To address this issue we design two simple models composed by two asymmetrically coupled equations of non-conserved (Swift-Hohenberg equations) or conserved (Cahn-Hilliard equations) order parameters with different characteristic wave lengths. The patterns arising in these systems range from coexisting static patterns of different wavelengths to traveling waves. A linear stability analysis allows to derive a two parameter phase diagram for the studied models, in particular revealing for the Swift-Hohenberg equations a co-dimension two bifurcation point of Turing and wave instability and a region of coexistence of stationary and traveling patterns. The nonlinear dynamics of the coupled evolution equations is investigated by performing accurate numerical simulations. These reveal more complex patterns, ranging from traveling waves with embedded Turing patterns domains to spatio-temporal chaos, and a wide hysteretic region, where waves or Turing patterns coexist. For the coupled Cahn-Hilliard equations the presence of an weak coupling is sufficient to arrest the coarsening process and to lead to the emergence of purely periodic patterns. The final states are characterized by domains with a characteristic length, which diverges logarithmically with the coupling amplitude.Comment: 9 pages, 10 figures, submitted to Chao

The role of octadecanoids and functional mimics in soybean defense responses

Oxylipins of the jasmonate pathway and synthetic functional analogs have been analyzed for their elicitor like activities in an assay based on the induced accumulation of glyceollins, the phytoalexins of soybean (Glycine max L.), in cell suspension cultures of this plant. Jasmonic acid (JA) and its methyl ester showed weak phytoalexininducing activity when compared to an early jasmonate biosynthetic precursor, 12-oxophytodienoic acid (OPDA), as well as to the bacterial phytotoxin coronatine and certain 6-substituted indanoylLisoleucine methyl esters, which all were highly active. Interestingly, different octadecanoids and indanoyl conjugates induced the accumulation of transcripts of various defenserelated genes to different degrees, indicating distinct induction competencies. Therefore, these signaling compounds and mimics were further analyzed for their effects on signal transduction elements, such as the transient enhancement of the cytosolic Ca2+ concentration and MAP kinase activation, which are known to be initiated by a soybean pathogenderived {[}beta]glucan elicitor. In contrast to the {[}beta]glucan elicitor, none of the other compounds tested triggered these early signaling elements. Moreover, endogenous levels of OPDA and JA in soybean cells were shown to be unaffected after treatment with {[}beta]glucans. Thus, OPDA and JA, which are functionally mimicked by coronatine and a variety of 6-substituted derivatives of indanoylLisoleucine methyl ester, represent highly efficient signaling compounds of a lipidbased pathway not deployed in the {[}beta]glucan elicitorinitiated signal transduction

Ermittlung der Vorfruchtwirkung unterschiedlicher Wintererbsengenotypen in Rein- und Gemengesaat

In organic farming the cultivation of leguminous crops is one of the most important sources of nitrogen (N). However, in the case of winter field peas, the amount of N fixed, N supply to the subsequent crop and N balance there are hardly any published data. Therefore, the pre-crop effect of six genotypes of winter pea (five regular leaf type, one semi-leafless cultivar) and one semi-leafless spring pea cultivar in single and mixed cropping (with rye spring barley respectively) was examined in three suc-cesive growing seasons (2003/04-2005/06). Immediately after harvest, a catch crop was sown and sampled during the first half of October to determine biomass dry matter and N uptake. In single cropping, N uptake by the catch crop was usually significantly higher after regular leaf type peas in two years, whereas in mixed cropping it was only in one (p<0.05). It is suggested that response of N uptake was - among other possible factors (like e.g. soil tillage after harvest) – due to the mineralized N content in soil at harvest as both correlated significantly (R² between 0.53* and 0.79***, with exception of semi-leafless winter pea (R²=0,19)). It is very important to protect the large N quantities after conventional leafed winter pea cultivars as a sole crop against leaching. Results for the third experimental season will be presented at the conference

Ecomat und Dammkultur – Alternative Bodenbearbeitungssysteme im Ökologischen Landbau – Erste Ergebnisse aus einem Exaktversuch

In the interdisciplinary research project a field experiment of alternative tillage systems in organic farming was installed. Ridge till system from Turiel-Major and Ecomat-system from Kverneland will be compared with conventional ploughing system. Within the project, located on the experimental farm of the University of Kassel, regular yearly workshops are led. Due to the regular contact with farmers, advisers, developers and scientists knowledge of practice will be carried into scientific research, the transfer of knowledge will be carried on. The change to the Ecomat-system is simple. Take notice that after very shallow till-age, like stubble cultivation (short stubble) or turning grass-clover, the following tillage has to be done a few cm deeper. In the year of implementing the Ecomat-system there were no decreases in yields. The mineralization of Nitrogen was the same as in the ploughing system. When changing to the ridge till system the width of the dams (90 cm) must fit to the track width, planting and harvesting equipment. After stubble cultivation in the ridge till system mineralization of N increased. This N was taken up by the catch crop. Leaching of N is not expected. Even in the first year after changing the tillage systems the alternative systems Eco-mat and ridge till showed higher saturated hydraulic conductivity than the conventional ploughing system. This leads to much lower susceptibility of soil erosion when using these soil layer conservation systems

Many-body localization phase in a spin-driven chiral multiferroic chain

Many-body localization (MBL) is an emergent phase in correlated quantum systems with promising applications, particularly in quantum information. Here, we unveil the existence and analyze this phase in a chiral multiferroic model system. Conventionally, MBL occurrence is traced via level statistics by implementing a standard finite-size scaling procedure. Here, we present an approach based on the full distribution of the ratio of adjacent energy spacings. We find a strong broadening of the histograms of counts of these level spacings directly at the transition point from MBL to the ergodic phase. The broadening signals reliably the transition point without relying on an averaging procedure. The fast convergence of the histograms even for relatively small systems allows monitoring the MBL dynamics with much less computational effort. Numerical results are presented for a chiral spin chain with a dynamical Dzyaloshinskii-Moriya interaction, an established model to describe the spin excitations in a single-phase spin-driven multiferroic system. The multiferroic MBL phase is uncovered and it is shown how to steer it via electric fields

Ermittlung der Futterqualität verschiedener Wintererbsengenotypen in Rein- und Gemengesaat zur Nutzung als nachwachsender Rohstoff, als Grünfutter und als Druschfrucht

Normalblättrige Wintererbsen sind in Reinsaat eine rohproteinreiche Winterzwischenfrucht für die Nutzung als Grünfutter oder als nachwachsender Rohstoff zur Energiegewinnung im Rahmen von Zweikulturnutzungssystemen. Zum Korndrusch im Gemengeanbau stellen sie bei mindestens vergleichbaren Kornerträgen und Qualitäten eine Alternative zu Sommererbsen dar. Dabei können Anbauprobleme von Sommererbsen besonders hinsichtlich der Unkrautregulierung reduziert werden