Dynamical universality of the contact process

The dynamical relaxation and scaling properties of three different variants of the contact process in two spatial dimensions are analysed. Dynamical contact processes capture a variety of contagious processes such as the spreading of diseases or opinions. The universality of both local and global two-time correlators of the particle-density and the associated linear responses are tested through several scaling relations of the non-equilibrium exponents and the shape of the associated scaling functions. In addition, the dynamical scaling of two-time global correlators can be used as a tool to improve on the determination of the location of critical points.Comment: 20 pages, 8 figure

Schlagspezifische N-Mineralisationsberechnungen als Teilinstrument einer internetgestützten Düngeplanung zu Winterweizen in Niedersachsen

Für ausgewählte Versuchsflächen und Schläge von Pilotbetrieben wurden schlagspezifische Berechnungen der Netto-N-Mineralisation als Bestandteil eines Online-Düngeplanungsprogramms für Winterweizen durchgeführt. Mit der berechneten N-Mineralisation sind unter Berücksichtigung der N-Aufnahme, N-Düngung und der N-Auswaschung schlagspezifische Hinweise zum Bodenvorrat an mineralischem Stickstoff im Frühjahr zur 2. N-Gabe möglich. Zur 3. N-Gabe wird die Mineralisation insbesondere für ungepflügte Flächen überschätzt. Hierfür soll eine Korrektur der Gleichungen mit Säulenversuchen im Freiland erfolgen. Für später ist geplant, dass nach Eingabe leicht verfügbarer Standort- und Bewirtschaftungsdaten die Berechnungen vollautomatisch ablaufen und der Landwirt online Düngehinweise erhält

High‐Purity Er3_{3}N@C80_{80} Films: Morphology, Spectroscopic Characterization, and Thermal Stability

Films comprising the endohedral fullerene Er3N@C80 are deposited onto highly oriented pyrolytic graphite (HOPG) substrates in high purity enabled by performing mass-selected low-energy deposition from a cation beam. In the initial stage, the growth on HOPG is dominated by spontaneous nucleation of small 2D islands both on intact terraces as well as the step edges. The island growth exhibits strong differences from lms comprising other fullerenes grown by the same method. This behavior can be explained by the surface-diffusion-mediated nucleation model presented in previous work: Dominant components in the behavioural differences are a high intercage dispersion interaction and a lower kinetic energy of cages migrating on the surface in comparison with previously deposited materials. When annealed, the lms undergo several competing processes: A small fraction desorbs in the temperature range 700–800 K, another fraction forms covalent intercage bonds instead of the previous purely dispersive bonding mode, and a third fraction probably decomposes to small fragments

Contribution of Particulate and Mineral-Associated Organic Matter to Potential Denitrification of Agricultural Soils

Water-extractable organic carbon (WEOC) is considered as the most important carbon (C) source for denitrifying organisms, but the contribution of individual organic matter (OM) fractions (i.e., particulate (POM) and mineral-associated (MOM)) to its release and, thus, to denitrification remains unresolved. Here we tested short-time effects of POM and MOM on potential denitrification and estimated the contribution of POM- and MOM-derived WEOC to denitrification and CO2 production of three agricultural topsoils. Suspensions of bulk soils with and without addition of soil-derived POM or MOM were incubated for 24 h under anoxic conditions. Acetylene inhibition was used to determine the potential denitrification and respective product ratio at constant nitrate supply. Normalized to added OC, effects of POM on CO2 production, total denitrification, and its product ratios were much stronger than those of MOM. While the addition of OM generally increased the (N2O + N2)-N/CO2-C ratio, the N2O/(N2O + N2) ratio changed differently depending on the soil. Gas emissions and the respective shares of initial WEOC were then used to estimate the contribution of POM and MOM-derived WEOC to total CO2, N2O, and N2O + N2 production. Water-extractable OC derived from POM accounted for 53–85% of total denitrification and WEOC released from MOM accounted for 15–47%. Total gas emissions from bulk soils were partly over- or underestimated, mainly due to nonproportional responses of denitrification to the addition of individual OM fractions. Our findings show that MOM plays a role in providing organic substrates during denitrification but is generally less dominant than POM. We conclude that the denitrification potential of soils is not predictable based on the C distribution over POM and MOM alone. Instead, the source strength of POM and MOM for WEOC plus the WEOC’s quality turned out as the most decisive determinants of potential denitrification

Influence of Dispersion Interactions on the Thermal Desorption of Nonplanar Polycyclic Aromatic Hydrocarbons on HOPG

A combination of low energy ion beam deposition and mass resolved thermal desorption spectroscopy is applied to analyze the binding behavior of two nonplanar polycyclic aromatic hydrocarbons (PAHs) to highly oriented pyrolytic graphite (HOPG) surfaces—also concerning their lateral dispersion interactions. In particular, the fullerene precursor C60H30 (FPC) and rubrene C42H28 are studied. Due to their smaller contact areas, both molecules exhibit significantly weaker binding energies to the HOPG surface compared to planar PAHs of similar size: C60H30 is bound to the surface by 3.04 eV, which is 0.6 eV lower than for a fully planar homologue. For rubrene, an isolated molecule–substrate binding energy of 1.59 eV is found, which is about 1 eV less than that of the corresponding planar homologue hexabenzocoronene C42H18. In contrast to FPC, rubrene shows a significant (intermolecular) lateral dispersion contribution to the binding energy as the submonolayer coverage increases

Sterols in soil organic matter of sandy arable soils: Quantification using mass spectrometry and their relation to mineralizability of soil organic N

Lately, a significant negative correlation between proportions of the compound class of sterols from pyrolysis-field ionization mass spectrometry (Py-FIMS) and net N mineralizability of soil organic N was found. However, main plant sterols (?-Sitosterol, Stigmasterol, and Campesterol) cannot be clearly verified and quantified with Py-FIMS, and there are only very few studies on measuring concentrations in soils. Thus, the objective was the extraction, identification and quantification of typical plant sterols and their relation to net N mineralization rates. The three sterols were identified and quantified in lipid extracts (Soxhlet procedure) using gas chromatography - mass spectrometry (GC-MS). Concentrations were similar to few other available studies, but concentrations of the three sterols were not significantly correlated with net N mineralizability. As quantification was difficult due to co-elution, further optimization of the methodology is necessary. In addition, the underlying mechanisms also need to be clarified

Potential denitrification stimulated by water-soluble organic carbon from plant residues during initial decomposition

Denitrification usually takes place under anoxic conditions and over short periods of time, and depends on readily available nitrate and carbon sources. Variations in CO2 and N2O emissions associated with plant residues have mainly been explained by differences in their decomposability. A factor rarely considered so far is water-extractable organic matter (WEOM) released to the soil during residue decomposition. Here, we examined the potential effect of plant residues on denitrification with special emphasis on WEOM. A range of fresh and leached plant residues was characterized by elemental analyses, 13C-NMR spectroscopy, and extraction with ultrapure water. The obtained solutions were analyzed for the concentrations of organic carbon (OC) and organic nitrogen (ON), and by UV-VIS spectroscopy. To test the potential denitrification induced by plant residues or three different OM solutions, these carbon sources were added to soil suspensions and incubated for 24 h at 20 °C in the dark under anoxic conditions; KNO3 was added to ensure unlimited nitrate supply. Evolving N2O and CO2 were analyzed by gas chromatography, and acetylene inhibition was used to determine denitrification and its product ratio. The production of all gases, as well as the molar (N2O + N2)–N/CO2–C ratio, was directly related to the water-extractable OC (WEOC) content of the plant residues, and the WEOC increased with carboxylic/carbonyl C and decreasing OC/ON ratio of the plant residues. Incubation of OM solutions revealed that the molar (N2O + N2)–N/CO2–C ratio and share of N2O are influenced by the WEOM's chemical composition. In conclusion, our results emphasize the potential of WEOM in largely undecomposed plant residues to support short-term denitrification activity in a typical ˈhot spot–hot momentˈ situation

Effect of high frequency subsurface drip fertigation on plant growth and agronomic nitrogen use efficiency of red cabbage

High emissions of nitrogen to the environment are one of the major drawbacks of modern agriculture. Subsurface drip fertigation (SDF) is a technology to apply fertilizer in small amounts continuously and directly into the root zone with the potential of mitigating deep percolation losses when accurately managed. Our study was established to analyze possible benefits of SDF, i.e. nitrate losses reduction without decrease in yield, as alternative to the conventional application of nitrogen fertilizer. In this five-year field study, effects of SDF on red cabbage (Brassica oleracea) growth, yield, root distribution and nitrogen uptake were evaluated. The experiments took place in northern Germany. Application of fertilizer in a solution with water was managed to match the needs of crops and placed directly in the root zone through permanently buried driplines. The outcomes of crop growth under SDF were compared with a control crop receiving fertilizer at one or two dates by surface broadcasting. Yield and agronomic nitrogen use efficiency were higher for crops grown under SDF. Total dry mass increase was especially high under dry conditions (34%) but as well under wet conditions with efficient management (20%). Head dry mass of crops grown under SDF had a stronger reaction to the available nitrogen than crops under conventional application, with values of 0.19 and 0.1 Mg ha-1 per kg N ha-1 respectively. Moreover, SDF treatment resulted on average ca. 14 kg ha−1 higher nitrogen uptake. In SDF plots, yield formation and nitrogen uptake was higher for plants grown directly above drip lines. Effect of the distance to nitrogen source was supported with numerical simulations. The root structure showed different distributions for the two treatments, particularly in years with low rainfall. Overall, the results showed the potential of SDF to effectively control nitrogen supply, thereby increasing yield formation of marketable plant organs