Gold surface with gold nitride–a surface enhanced Raman scattering active substrate

The nitration of gold surfaces is a nonpolluting method, which can lead to large scale production of substrates with remarkable properties and applications. We present a topographical study of the nanoscale structure of the gold nitride surfaces produced by radio frequency (rf) nitrogen plasma etching of thin gold films. Atomic force microscopy images taken after rf etching reveal the striking appearance of the cluster assembly with large clusters surrounded by small clusters (7.9±1.4 and 2.3±0.9 nm, respectively) appearing to exhibit an attractive interaction. We discuss the possible mechanism for this attraction based on a colloid model by Messina et al. [Phys. Rev. Lett. 85, 872 (2000) ]. This surface exhibits a notable surface enhanced Raman scattering effect demonstrated with L-alanine and rhodamine-6G. The significance of this work is that we found that this SERS active gold nitride surface can be prepared in just one step: by nitrogen plasma etching a thin gold film. Until now most SERS active gold cluster covered surfaces have been prepared in several steps very often requiring complex lithography

Impact of short-term storage on the quantity of extended-spectrum beta-lactamase–producing Escherichia coli in broiler litter under practical conditions

Applying broiler litter containing extended-spectrum beta-lactamase (ESBL)–producing Escherichia coli (E. coli) to arable land poses a potential risk for humans to get colonized by contact with contaminated soil or vegetables. Therefore, an inactivation of these bacteria before land application of litter is crucial. We performed 2 short-term litter storage trials (one in summer and winter, respectively), each covering a time span of 5 D to investigate the effectiveness of this method for inactivation of ESBL-producing E. coli in chicken litter. Surface and deep litter samples were taken from a stacked, ESBL-positive chicken litter heap in triplicates in close sampling intervals at the beginning and daily for the last 3 D of the experiments. Samples were analyzed quantitatively and qualitatively for ESBL-producing E. coli, total E. coli, and enterococci. Selected isolates were further characterized by whole-genome sequencing (WGS). In the depth of the heap ESBL-producing E. coli were detected quantitatively until 72 h and qualitatively until the end of the trial in winter. In summer detection was possible quantitatively up to 36 h and qualitatively until 72 h. For surface litter samples a qualitative detection of ESBL-producing E. coli was possible in all samples taken in both trials. In the deep samples a significant decrease in the bacterial counts of over 2 Log10 was observed for total E. coli in the winter and for total E. coli and enterococci in the summer. Genetic differences of the isolates analyzed by WGS did not correlate with survival advantage. In conclusion, short-term storage of chicken litter stacked in heaps is a useful tool for the reduction of bacterial counts including ESBL-producing E. coli. However, incomplete inactivation was observed at the surface of the heap and at low ambient temperatures. Therefore, an extension of the storage period in winter as well as turning of the heap to provide aerobic composting conditions should be considered if working and storage capacities are available on the farms

The pristine atomic structure of MoS2 monolayer protected from electron radiation damage by graphene

Materials can, in principle, be imaged at the level of individual atoms with aberration corrected transmission electron microscopy. However, such resolution can be attained only with very high electron doses. Consequently, radiation damage is often the limiting factor when characterizing sensitive materials. Here, we demonstrate a simple and effective method to increase the electron radiation tolerance of materials by using graphene as protective coating. This leads to an improvement of three orders of magnitude in the radiation tolerance of monolayer MoS2. Further on, we construct samples in different heterostructure configurations to separate the contributions of different radiation damage mechanisms

Particle-in-cell simulations of particle energization from low Mach number fast mode shocks

Astrophysical shocks are often studied in the high Mach number limit but weakly compressive fast shocks can occur in magnetic reconnection outflows and are considered to be a site of particle energization in solar flares. Here we study the microphysics of such perpendicular, low Mach number collisionless shocks using two-dimensional particle-in-cell (PIC) simulations with a reduced ion/electron mass ratio and employ a moving wall boundary method for initial generation of the shock. This moving wall method allows for more control of the shock speed, smaller simulation box sizes, and longer simulation times than the commonly used fixed wall, reflection method of shock formation. Our results, which are independent of the shock formation method, reveal the prevalence shock drift acceleration (SDA) of both electron and ions in a purely perpendicular shock with Alfv\'en Mach number $M_A=6.8$ and ratio of thermal to magnetic pressure $\beta=8$. We determine the respective minimum energies required for electrons and ions to incur SDA. We derive a theoretical electron distribution via SDA that compares to the simulation results. We also show that a modified two-stream instability due to the incoming and reflecting ions in the shock transition region acts as the mechanism to generate collisionless plasma turbulence that sustains the shock

Institutionelle Anreizfaktoren im deutschen Schulsystem: Status quo und Reformoptionen am Beispiel Nordrhein-Westfalens

Im vorliegenden Artikel argumentieren wir, dass eine alleinige Ausweitung der finanziellen Ressourcen für den primaren und sekundaren Bildungsbereich als Reaktion auf das schlechte Abschneiden deutscher Schüler bei internationalen Vergleichsstudien eine ineffiziente Verwendung öffentlicher Gelder darstellen würde. Die Anreizstrukturen im Status quo sind weit davon entfernt, den Interessen des entscheidenden Akteurs innerhalb des Bildungswesens zu dienen, d. h. denjenigen des Schülers bzw. der Schülerin. Bereits mit den gegebenen finanziellen Ressourcen könnte diesem Ziel deutlich näher gekommen werden, wenn das institutionelle Anreizumfeld für die im Schulsystem handelnden Akteure vor allem Lehrer, Schulleitungen und Schüler bzw. ihre Eltern entsprechend ausgerichtet würde. Mit Hilfe des Prinzipal-Agenten-Ansatzes stellen wir zunächst die unterschiedlichen Abhängigkeiten und Anreizstrukturen im Bildungswesen abstrakt vor. Daran anschließend zeigen wir auf, wie die existierenden schulpolitischen Reformvorschläge aus anreiztheoretischer Sicht zu bewerten sind. Am Beispiel Nordrhein-Westfalens wird schließlich konkretisiert, welche Vorteile die Gewährung von Schulautonomie, mehr Wahlfreiheit für Eltern und Wettbewerb zwischen den Schulen aufweisen, bzw. bei geeigneter Umsetzung aufweisen könnten. Im vorliegenden Artikel ist es nicht das Ziel, Schulqualität gemessen an den Indikatoren internationaler Vergleichsstudien bei gegebenem Ressourceneinsatz zu maximieren. Stattdessen sollen die Anreize so ausgerichtet werden, dass sie dem Schüler bzw. den entscheidungsbefugten Eltern zum Vorteil gereichen, und dass diese entscheiden können, was unter hoher Schulqualität zu verstehen ist