Auswirkungen reduzierter Bodenbearbeitung und Vorfrucht auf die Unkrautvegetation

The reduction of soil tillage intensity is of special interest for organic farmers. To study the influence of reduced tillage on soil properties and weed vegetation field plots were set up in 1992 on the FAM Research farm in southern Germany. From 1999 till 2002 weed vegetation was recorded including soil seed bank, plant density, number of flowering plants and biomass. Reduced tillage intensity did not influence the weed population dymamics but did influence the species composition. Elymus repens, Apera spica-venti and Poa annua were promoted by a tillage regime that omitted deep ploughing in four of seven years. The cultivation of grass/ley mixtures plays an important role in crop rotations of organic farming systems e.g. as part of the weed management. In rotation after grass/ley mixture mechanical weeding in winterwheat led to a remarkable reduction of total weed density and flowering plants. Thus the input of fresh seeds to the seedbank is reduced

Whispering Gallery Mode Resonator Stabilized Narrow Linewidth Fiber Loop Laser

We demonstrate a narrow line, fiber loop laser using Erbium-doped fiber as the gain material, stabilized by using a microsphere as a transmissive frequency selective element. Stable lasing with a linewidth of 170 kHz is observed, limited by the experimental spectral resolution. A linear increase in output power and a red-shift of the lasing mode were also observed with increasing pump power. Its potential application is also discussed

Sub-kHz lasing of a CaF_2 Whispering Gallery Mode Resonator Stabilized Fiber Ring Laser

We utilize a high quality calcium fluoride whispering-gallery-mode resonator to stabilize a simple erbium doped fiber ring laser with an emission frequency of 196 THz (wavelenght 1530 nm) to a linewidth below 650 Hz. This corresponds to a relative stability of 3.3 x 10^(-12) over 16 \mus. In order to characterize the linewidth we use two identical self-built lasers and a commercial laser to determine the individual lasing linewidth via the three-cornered hat method.Comment: 4 pages, 3 figure

Validation of Kalman Filter alignment algorithm with cosmic-ray data using a CMS silicon strip tracker endcap

A Kalman Filter alignment algorithm has been applied to cosmic-ray data. We discuss the alignment algorithm and an experiment-independent implementation including outlier rejection and treatment of weakly determined parameters. Using this implementation, the algorithm has been applied to data recorded with one CMS silicon tracker endcap. Results are compared to both photogrammetry measurements and data obtained from a dedicated hardware alignment system, and good agreement is observed.Comment: 11 pages, 8 figures. CMS NOTE-2010/00

Polyclonal B-cell activation by a synthetic analogue of bacterial lipoprotein is functionally different from activation by bacterial lipopolysaccharide

The reactivity of 38 murine strains to a synthetic analogue of bacterial lipoprotein, tripalmitoyl-pentapeptide (TPP), was tested and compared with the reactivity to lipopolysaccharide (LPS). These strains include common laboratory mice and H-2 recombinant inbred lines, as well as some newly bred lines originating from animals recently captured in different regions of Europe. All animals analysed were reactive to TPP and polyclonally activated to proliferation and immunoglobulin synthesis. Large differences in mitogen reactivities of various H-2 recombinant inbred strains suggest that MHC or closely linked gene products influence the reactivity to the LPS and TPP mitogens. By analysing the frequencies of precursor cells reactive to TPP or LPS and the isotype patterns obtained after stimulation, we demonstrated that both mitogens activate individual B cells in different ways.Peer reviewe

Toughening mechanisms in novel nano-silica epoxy polymers

A crosslinked epoxy polymer has been modified by the addition of nano-silica particles. The particles were introduced via a sol-gel technique which gave a very well dispersed phase of nanosilica particles which were about 20 nm in diameter. The glass transition temperature was unchanged by the addition of the nano-particles, but both the modulus and toughness were increased. The fracture energy increased from 100 J/m2 for the unmodified epoxy to 460 J/m2 for the epoxy with 13 vol% of nano-silica. The microscopy studies showed evidence of debonding of the nano-particles and subsequent plastic void growth of the epoxy polymer. A theoretical model of plastic void growth was used to confirm this mechanism

Whispering gallery mode resonator based ultra-narrow linewidth external cavity semiconductor laser

We demonstrate a miniature self-injection locked DFB laser using resonant optical feedback from a high-Q crystalline whispering gallery mode resonator. The linewidth reduction factor is greater than 10,000, with resultant instantaneous linewidth less than 200 Hz. The minimal value of the Allan deviation for the laser frequency stability is 3x10^(-12) at the integration time of 20 us. The laser possesses excellent spectral purity and good long term stability.Comment: To be published in Optics Letter

Neutrino spin oscillations in gravitational fields

We study neutrino spin oscillations in black hole backgrounds. In the case of a charged black hole, the maximum frequency of oscillations is a monotonically increasing function of the charge. For a rotating black hole, the maximum frequency decreases with increasing the angular momentum. In both cases, the frequency of spin oscillations decreases as the distance from the black hole grows. As a phenomenological application of our results, we study simple bipolar neutrino system which is an interesting example of collective neutrino oscillations. We show that the precession frequency of the flavor pendulum as a function of the neutrino number density will be higher for a charged/non-rotating black hole compared with a neutral/rotating black hole respectively.Comment: Replaced with the version accepted for publication in Gravitation and Cosmology, Springer. 10 pages. 4 figure