Does On-Farm quality Assurance Pay? A Cost-Benefit Analysis of the GrainSafe Program

Since the introduction of genetically modified (GM) crops, the commodity grain system has been under pressure to segregate GM and non-GM crops. Starting at the level of the grain handler, members of the grain supply chain have successfully used quality assurance and identity preservation programs to segregate non-GM crops. Producers delivering high value, identity preserved crops have become interested in implementing these quality management systems at the farm level. We conduct a cost-benefit analysis that shows that quality assurance program may be profitable for producers, depending on their farm size and equipment management strategy.on-farm quality assurance, identity preservation, cost-benefit analysis, @Risk

Genetic and Biochemical Characterization of COP1/SPA Funktion in Arabidopsis Photomorphogenesis

Plants as sessile organisms are dependent on a complex interaction with their environment. Light is one of the most important factors that affect multiple stages of plant growth and development. In concert with the four SPA proteins (SPA1-SPA4) the E3-ubiquitin ligase COP1 acts as a repressor of light signaling in darkness. COP1 and SPA proteins were also found to regulate processes like Determination of leaf size, stomata differentiation and Induktion of photoperiodic flowering. In this regard, COP1 targets transcription factors like HY5, HFR1 or CO for ubiquitination and subsequent 26S proteasome-dependent degradation. Furthermore, SPA proteins physically interact with the COP1 protein. In the present study I could show that SPA proteins can interact with each other in vitro and in planta, building homo- and heterodimers. This indicates the existence of larger COP1/SPA containing complexes in which every combination of SPA dimers is possible. Further, I could show that the N-terminus including the proteins’ coiled-coil domain mediates the interactions within the SPAs. Since SPA proteins carry out overlapping but also distinct functions throughout plant development and this cannot be solely explained by their mRNA and Protein expression patterns, there must be other mechanisms regulating COP1/SPA complex assembly and/or activity. Using antibodies against native SPA1 and SPA2 protein generated in this study, I could show that SPA1 and SPA2 Protein levels decrease in far-red light compared to darkness, whereas transcript levels remained unchanged, pointing to a post-translational mechanism regulating SPA Funktion. However, whether this is dependent on COP1 needs to be verified. COP1/SPA complexes most likely are involved in a broad spectrum of developmental processes. Thus, I analyzed the regulation of two new potential targets, PAP1 and PAP2, which are transcription factors involved in the regulation of light-dependent anthocyanin biosynthesis. I could show that PAP1 and PAP2 interact with the members of COP1/SPA complexes in yeast. Further, I could show that PAP1 and PAP2 proteins from overexpressing plants are stabilized by light and accumulate upon treatment with the proteasomal blocker MG132, indicating a post-translational regulation of PAP protein abundance. Analysis of RNAi mutants and PAP overexpressing plants in cop1-4 background revealed an effect of the cop1 Mutation on PAP-dependent anthocyanin biosynthesis. Furthermore, an initial Experiment showed, that PAP2 protein in 35S::HA-PAP2 cop1-4 overexpressing plants is further stabilized in darkness and light compared to overexpressing lines in wild-type background, supporting the hypothesis that COP1/SPA complexes regulate PAP protein levels under both conditions

Tenfold your photons -- a physically-sound approach to filtering-based variance reduction of Monte-Carlo-simulated dose distributions

X-ray dose constantly gains interest in the interventional suite. With dose being generally difficult to monitor reliably, fast computational methods are desirable. A major drawback of the gold standard based on Monte Carlo (MC) methods is its computational complexity. Besides common variance reduction techniques, filter approaches are often applied to achieve conclusive results within a fraction of time. Inspired by these methods, we propose a novel approach. We down-sample the target volume based on the fraction of mass, simulate the imaging situation, and then revert the down-sampling. To this end, the dose is weighted by the mass energy absorption, up-sampled, and distributed using a guided filter. Eventually, the weighting is inverted resulting in accurate high resolution dose distributions. The approach has the potential to considerably speed-up MC simulations since less photons and boundary checks are necessary. First experiments substantiate these assumptions. We achieve a median accuracy of 96.7 % to 97.4 % of the dose estimation with the proposed method and a down-sampling factor of 8 and 4, respectively. While maintaining a high accuracy, the proposed method provides for a tenfold speed-up. The overall findings suggest the conclusion that the proposed method has the potential to allow for further efficiency.Comment: 6 pages, 3 figures, Bildverarbeitung f\"ur die Medizin 202

Resonant enhancement of second harmonic generation in the mid-infrared using localized surface phonon polaritons in sub-diffractional nanostructures

We report on strong enhancement of mid-infrared second harmonic generation (SHG) from SiC nanopillars due to the resonant excitation of localized surface phonon-polaritons within the Reststrahlen band. The magnitude of the SHG peak at the monopole mode experiences a strong dependence on the resonant frequency beyond that described by the field localization degree and the dispersion of linear and nonlinear-optical SiC properties. Comparing the results for the identical nanostructures made of 4H and 6H SiC polytypes, we demonstrate the interplay of localized surface phonon polaritons with zone-folded weak phonon modes of the anisotropic crystal. Tuning the monopole mode in and out of the region where the zone-folded phonon is excited in 6H-SiC, we observe a prominent increase of the already monopole-enhanced SHG output when the two modes are coupled. Envisioning this interplay as one of the showcase features of mid-infrared nonlinear nanophononics, we discuss its prospects for the effective engineering of nonlinear-optical materials with desired properties in the infrared spectral range.Comment: 16 pages, 3 figure

Spherical nanoindentation – advancements and prospects towards its application as a multifunctional testing technique

With the development of modern high-performance materials and components, cases increase where conventional testing techniques used for the mechanical characterization miss their target. Material fabrication at a bench scale, miniaturization and not least cost-effectiveness yearn for a highly reliable, fast and highly automatable testing technique. Even though uniaxial micromechanical tests on micro-pillars or -tensile samples are well suitable for the extraction of flow curves, they face the problem of elaborate specimen manufacturing. Spherical nanoindentation could be a candidate technique to overcome the mentioned drawbacks, since time needed for sample preparation is tremendously reduced. The present study will outline solutions of existing problems, which may lay the foundation for spherical nanoindentation to become a widely-used testing technique. Main objections concerning tip imperfections will be resolved by modifying the calibration procedure, and validated on a broad spectrum of materials independent of the indenter tip radius. Once the actual tip shape is available, displacement-time profiles can be designed to guarantee constant strain-rates during testing and thus permit the determination of the strain-rate sensitivity for rate-dependent materials. Finally, the comparison between nanoindentation flow curves and uniaxial tests will evidence that spherical indentation is a highly reliable technique for the extensive mechanical characterization of modern high-performance materials and show its high potential as a multifunctional standard testing technique. Please click Additional Files below to see the full abstract

Tailoring and enhancing spontaneous two-photon emission processes using resonant plasmonic nanostructures

The rate of spontaneous emission is known to depend on the environment of a light source, and the enhancement of one-photon emission in a resonant cavity is known as the Purcell effect. Here we develop a theory of spontaneous two-photon emission for a general electromagnetic environment including inhomogeneous dispersive and absorptive media. This theory is used to evaluate the two-photon Purcell enhancement in the vicinity of metallic nanoparticles and it is demonstrated that the surface plasmon resonances supported by these particles can enhance the emission rate by more than two orders of magnitude. The control over two-photon Purcell enhancement given by tailored nanostructured environments could provide an emitter with any desired spectral response and may serve as an ultimate route for designing light sources with novel properties

DNA self-assembled filaments for micro- and nanoscale propulsion

Auf der Mikroebene nutzen viele prokaryotische Mikroorganismen die Rotation helikaler Filamente, sogenannter Flagellen, um sich fortzubewegen. Die Nachahmung dieser hoch entwickelten Strukturen eröffnet einen vielversprechender Ansatz für die Konstruktion künstlich angetriebener Mikro- und Nanoroboter. Die Realisierung künstlicher Flagellen bedarf einer Methode, welche die komplexe Proteinarchitektur dieser Filamente möglichst genau imitieren kann. Neben ihrer Hauptfunktion als Träger der Erbinformation hat sich die Desoxyribonukleinsäure (DNA) in den letzten Jahren als vielseitiger Baustein im Bereich der molekularen Selbstassemblierung etabliert. In vorliegender Dissertation werden auf DNA Selbstassemblierung beruhende Filamente vorgestellt, welche als künstliche Flagellen für den Antrieb von Mikro- und Nanoschwimmern sorgen. Mikrometer lange, helikale DNA Nanotubes, welche in Form und Größe bakteriellen Flagellen gleichen, wurden unter Zuhilfenahme des „DNA tile assembly“ realisiert. Das Einfügen und/oder Entfernen von Basenpaaren ermöglichte es uns die helikale Struktur der Nanotubes auf der Nanoebene zu kontrollieren. Nanotubes mit Mikrometer großen helikalen Durchmessern und definierter Chiralität wurden anhand einer neuartigen Design Technik, dem “tile shifting”, konstruiert. Durch das Anbinden der helikalen Strukturen an magnetische Mikropartikel konzipierten wir eine neue Klasse von biokompatiblen Mikroschwimmern. Diese hybriden Strukturen lassen sich durch ein externes Magnetfeld antreiben, steuern und bewegen sich mittels eines Flagellenbündels, ähnlich wie Bakterien, fort. Mithilfe der DNA Origami Technik waren wir zudem in der Lage, DNA Nanoflagellen mit definierter Form zu konstruieren und an magnetische Nanopartikel anzubinden. Die daraus resultierenden Nanoschwimmer wurden magnetisch angeregt und zeigten eine leichte Erhöhung ihrer Diffusion gegenüber einer reinen Brownschen Molekularbewegung. Eine solch erhöhte Diffusion kann für die Fortbewegung von Nanorobotern von Vorteil sein, falls eine gerichtete Bewegung durch thermische Kräfte verhindert wird. Abschließend konstruierten wir einen Prototyp eines sich autonom fortbewegenden DNA-basierten Mikroschwimmers, indem wir den molekularen Motor F – ATPase zwischen DNA Flagellum und Mikropartikel integrierten. Nach Bereitstellung des Motortreibstoffes ATP lösten sich jedoch die künstlichen Flagellen von den Partikeln, wodurch ein Antrieb der Schwimmer verhindert wurde. Die erfolgreiche Anbindung der DNA Flagellen und die Aktivität der integrierten ATPase stellen dennoch wichtige Schritte für die Realisierung autonomer Mikroschwimmer dar. Die in dieser Dissertation gewonnen Erkenntnisse zeigen, dass DNA basierte molekulare Selbstassemblierung ein ausgezeichnetes Instrument für die Konstruktion von biokompatiblen künstlichen Filamenten ist, welche als Antriebsmechanismus künftiger Generationen von Mikro- und Nanorobotern Verwendung finden können.The rotation of helically shaped filaments, so-called flagella, is one major strategy used by many motile microorganisms to achieve propulsion. Mimicking these highly evolved structures can be a promising approach for the construction of artificially propelled micro- and nanorobots. Realizing artificial flagella, however, requires a technique, which can precisely copy the complex architecture of these protein filaments. Besides its fundamental function as carrier of the genetic information, DNA has proven to be a versatile building block in molecular self-assembly. In this dissertation, DNA-self assembled filaments are presented, which function as artificial flagella for the propulsion of micro- and nanoswimmers. Micrometer-long helically shaped DNA nanotubes, which closely resemble bacterial flagella, were constructed by applying the DNA tile assembly technique. Through the insertion and/or deletion of base pairs, we generated bending and twisting in the DNA nanotubes, which allowed us to control the tubes’ helical shape in the nanoscale regime. Nanotubes with microscale helical diameters and defined chirality were constructed by introducing a new design technique, the so-called tile shifting. By coupling the helical filaments to magnetic microparticles, we constructed a new class of fully biocompatible artificial microswimmers. The hybrid structures were actuated and steered by an external magnetic field and propelled by means of a flagellar bundle similar to motile bacteria. The DNA origami technique further allowed us to realize nanometer-sized artificial DNA flagella with defined shape and to attach them onto magnetic nanoparticles. The resulting nanoswimmers were actuated by a magnetic field and exhibited a slight enhancement of their diffusivity, in comparison to a mere Brownian motion. Such an enhanced diffusion can be of advantage for the locomotion of nanorobots if a directed motion is unfeasible due to strong thermal forces. Finally, we constructed a prototype of an autonomously propelling DNA-based microswimmer by incorporating the molecular motor F-ATPase between DNA flagella and magnetic microparticle. Unfortunately, we observed a detachment of the artificial flagella upon addition of the “motor fuel” ATP, which inhibited the propulsion of the swimmer. The successful coupling of the artificial flagella and the activity of the incorporated ATPase, nevertheless, constitute important steps towards the realization of autonomous microswimmers. The insights gained in this dissertation illustrate that DNA molecular self-assembly is an excellent tool for constructing fully biocompatible artificial flagella, which can provide future micro- and nanorobotic devices with an effective propulsion mechanism