Ein Speicher-Durchfluss-Modell für die Abflussbildung im Oberjura-Karst der Schwäbischen Alb

Upper Jurassic karstified limestones in southern Germany are characterized by a dual-porosity system. Here we present a new model that describes the basic processes from recharge to discharge. While recharge is distributed to both main conduits and fractures, only minor amounts of the total runoff reach the karst system directly (direct runoff) while most water infiltrates into the fractured matrix. This mechanism expels pre-event water from the fissured matrix and into karst conduits. Additionally, matrix storage exponentially decreases during baseflow conditions. Altogether, direct runoff, pre-event water and baseflow fill the karst system and make up the spring discharge. Based on a time series of 40 years of recharge data, the model simulates daily changes of groundwater volumes within the two storage systems. Prerequisites are recession coefficients for baseflow and conduits. A distribution coefficient calculates the amount of direct runoff and a second coefficient the amount of pre-event water. Calculated discharges were in good agreement with the spring hydrograph.     

Antagonistic Interactions Mediated by Marine Bacteria: The Role of Small Molecules

Marine bacteria are known to produce a wide variety of structurally diverse and biologically active secondary metabolites. Considerably less is known about the ecological functions of these compounds, in part due to methodological challenges associated with this field of research. Here, we review the antagonistic activities mediated by marine bacteria with a focus on activities linked to structurally defined secondary metabolites. Bacterial antagonism has been documented against other marine bacteria as well as eukaryotes, and includes antibiosis, the inhibition of quorum sensing, larval settlement deterrence, and defense against predation. These compounds likely play important ecological roles that ultimately affect ecosystem structure and function, however, much remains to be learned before these roles can be fully appreciated. Recent technological advances coupled with a better understanding of the diverse processes mediated by secondary metabolites provide new opportunities to expand our understanding of the chemical ecology of bacterial antagonism in the marine environment.     

Ultrafast laser processing: New options for three-dimensional photonic structures

Abstract

Using tightly focused ultrashort laser pulses allows the direct writing of three-dimensional photonic structures in different glasses and also crystalline media. One of the main drawbacks of this technology is, however, the limited writing speed achieved so far. In this paper we shall review our recent advances in the direct writing of three-dimensional integrated-optical devices and discuss a new approach using a fibre-based femtosecond laser system producing 300 fs pulses with pulse energies of 0.6 μJ at 2 MHz repetition rate. Using this laser system we fabricated low-loss waveguides (less than 0.5 dBcm^?1) at writing speeds of 100 mms^?1 for the first time. The influence of the writing speed on the produced structures as well as their optical properties will be discussed in detail.     

Scope and Limitations of the Intermolecular Furan‐Yne Cyclization

Different types of alkynes were reacted with 2,5‐disubstituted furans in order to evaluate the scope of the intermolecular furan‐yne reaction. With ethynyl aryl ethers as starting materials, 2‐phenoxy phenols were accessible in moderate to good yields. A different reaction mode was observed for alkynes bearing electron‐withdrawing substituents. For these starting materials a cis‐selective hydroarylation took place in an anti‐Markovnikov fashion in excellent yields. 1,2‐Diynes turned out to be suitable starting materials as well. Due to the second alkynyl moiety, after an initial phenol synthesis, a subsequent hydro‐alkoxylation by the newly formed phenolic oxygen gives access to benzofurans in a tandem process.