Avalanche‐Discharge‐Induced Electrical Forming in Tantalum Oxide‐Based Metal–Insulator–Metal Structures

Oxide‐based metal–insulator–metal structures are of special interest for future resistive random‐access memories. In such cells, redox processes on the nanoscale occur during resistive switching, which are initiated by the reversible movement of native donors, such as oxygen vacancies. The formation of these filaments is mainly attributed to an enhanced oxygen diffusion due to Joule heating in an electric field or due to electrical breakdown. Here, the development of a dendrite‐like structure, which is induced by an avalanche discharge between the top electrode and the Ta₂O_5‐x layer, is presented, which occurs instead of a local breakdown between top and bottom electrode. The dendrite‐like structure evolves primarily at structures with a pronounced interface adsorbate layer. Furthermore, local conductive atomic force microscopy reveals that the entire dendrite region becomes conductive. Via spectromicroscopy it is demonstrated that the subsequent switching is caused by a valence change between Ta⁴⁺ and Ta⁵⁺, which takes place over the entire former Pt/Ta₂O_5‐x interface of the dendrite‐like structure.     

Uranium sorption on various forms of titanium dioxide--influence of surface area, surface charge, and impurities

Titanium dioxide (TiO(2)) has often served as a model substrate for experimental sorption studies of environmental contaminants. However, various forms of Ti-oxide have been used, and the different sorption properties of these materials have not been thoroughly studied. We investigated uranium sorption on some thoroughly characterized TiO(2) surfaces with particular attention to the influence of surface area, surface charge, and impurities. The sorption of U(VI) differed significantly between samples. Aggressive pretreatment of one material to remove impurities significantly altered the isoelectric point, determined by an electroacoustic method, but did not significantly impact U sorption. Differences in sorption properties between the various TiO(2) materials were related to the crystallographic form, morphology, surface area, and grain size, rather than to surface impurities or surface charge. In-situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopic studies showed that the spectra of the surface species of the TiO(2) samples are not significantly different, suggesting the formation of similar surface complexes. The data provide insights into the effect of different source materials and surface properties on radionuclide sorption.     

Antibiotic resistance in bacteria isolated from vegetables with regards to the marketing stage (farm vs. supermarket)

The aim of this study was to elucidate whether and to what extent fresh produce from Germany plays a role as a carrier and reservoir of antibiotic resistant bacteria. For this purpose, 1001 vegetables (fruit, root, bulbous vegetables, salads and cereals) were collected from 13 farms and 11 supermarkets in Germany and examined bacteriologically. Phenotypic resistance of Enterobacter cloacae (n = 172); Enterobacter gergoviae (n = 92); Pantoea agglomerans (n = 96); Pseudomonas aeruginosa (n = 295); Pseudomonas putida (n = 106) and Enterococcus faecalis (n = 100) against up to 30 antibiotics was determined by using the microdilution method. Resistance to ß-lactams was most frequently expressed by P. agglomerans and E. gergoviae against cefaclor (41% and 29%). Relatively high resistance rates were also observed for doxycycline (23%), erythromycin (21%) and rifampicin (65%) in E. faecalis, for spectinomycin (28%) and mezlocillin (12%) in E. cloacae, as well as for streptomycin (19%) in P. putida. In P. aeruginosa, relatively low resistance rates were observed for the aminoglycosides amikacin, apramicin, gentamicin, neomycin, netilmicin and tobramycin (< 4%); 11% was resistant to streptomycin. No glycopeptide-resistant enterococci were observed. Resistance rates of bacteria isolated from farm samples were higher than those of the retail markets whenever significant differences were observed. This suggests that expressing resistance is at the expense of bacterial viability, since vegetables purchased directly at the farm are probably fresher than at the supermarket, and they have not been exposed to stress factors. However, this should not keep the customer from buying directly at the farm, since the overall resistance rates were not higher than observed in bacteria from human or animal origin. Instead, peeling or washing vegetables before eating them raw is highly recommended, since it reduces not only the risk of contact with pathogens, but also that of ingesting and spreading antibiotic resistant bacteria.     

Bioluminescent Optogenetics: A Novel Experimental Therapy to Promote Axon Regeneration after Peripheral Nerve Injury

Functional recovery after peripheral nerve injury (PNI) is poor, mainly due to the slow and incomplete regeneration of injured axons. Experimental therapies that increase the excitability of the injured axons have proven remarkably successful in promoting regeneration, but their clinical applicability has been limited. Bioluminescent optogenetics (BL-OG) uses luminopsins, fusion proteins of light-generating luciferase and light-sensing ion channels that could be used to increase neuronal excitability if exposed to a suitable substrate. Excitatory luminopsins were expressed in motoneurons of transgenic mice and in wildtype mice transduced with adeno-associated viral vectors. Intraperitoneal administration of coelenterazine (CTZ), a known luciferase substrate, generated intense bioluminescence in peripheral axons. This bioluminescence increased motoneuron excitability. A single administration of CTZ immediately after sciatic nerve transection and repair markedly enhanced motor axon regeneration. Compound muscle action potentials were 3–4 times larger than controls by 4 weeks after injury. The results observed with transgenic mice were comparable to those of mice in which the luminopsin was expressed using viral vectors. Significantly more motoneurons had successfully reinnervated muscle targets four weeks after nerve injury in BL-OG treated mice than in controls. Bioluminescent optogenetics is a promising therapeutic approach to enhancing axon regeneration after PNI.     

A comparative analysis of EIA practice for wastewater treatment plants in great Britain and Germany

This article reports the findings of an investigation of the practice of environmental impact assessment (EIA) for wastewater treatment plants in the United Kingdom and Germany. It demonstrates that both EIA systems have a number of common deficiencies but that the differences between the practice of EIA in Britain and Germany are considerable. These indicate that one of the objectives of the European Directive—to harmonize environmental controls—has not been met. The differences can be explained by examining: (1) the context in which EIAs for wastewater treatment plants take place in both countries; (2) the ways in which EIA procedures are implemented in both countries; and (3) the attitudes of the competent authorities in both countries to EIA.     

Trends in the production and storage of fresh meat – the holistic approach to bacteriological meat quality

The aim of this review paper is to introduce readers to the modern approach to meat production as recommended by public authorities. No part of the food chain can be regarded alone but has to be seen as part of the whole. A holistic approach to fresh meat storage and retailing must therefore start with the living animal and cannot end with the sale of the meat. It must also include the consumers. One of the highest priority issues for consumers, producers and governments is food safety, and with it, consumer safety. Here we briefly describe the possibilities of keeping initial amounts of bacteria in meat low and modern storage of fresh meat. In future, the consumer must be incorporated in the meat food chain.     

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Quantitative determination of combustion intermediates with cavity ring-down spectroscopy: systematic study in propene flames near the soot-formation limit

Cavity ring-down spectroscopy (CRDS) was applied in several fuel-rich, one-dimensional, premixed C3H6/O2/Ar flames at 50 mbars (37.5 torr) to measure absolute OH, HCO, and 1CH2 concentration as well as temperature as a function of stoichiometry. Although these flames near the sooting limit present a complex chemical environment, significant spectral interferences were found to be absent. Specific aspects of the CRDS technique for measurement of temperature and radical concentration profiles are discussed; and the results are analyzed in comparison with flame model simulations.     

Osteogenic differentiation of mesenchymal progenitor cells in computer designed fibrin-polymer-ceramic scaffolds manufactured by fused deposition modeling

Biomimetic scaffolds offer great potentials in the development of bone analogs for tissue engineering. The studies presented in this paper focus specifically on the osteogenic potential of the novel PCL/CaP matrices and its degradation behavior. Biodegradable Polymer-ceramic Scaffolds were fabricated using the solid free form fabrication technology: Fused Deposition Modeling (FDM). The scaffold architecture was characterized by a honeycomb-like design and a complete interconnectivity of the pores. Human mesenchymal stem cells (MSCs) were seeded together with fibrin glue into PCL/CaP scaffolds and cultured in vitro for periods of up to eight weeks. Cellular adhesion, proliferation and osteogenic differentiation were assessed in these constructs using a range of histological and microscopic techniques. In additional experiments, degradation was assessed by measuring mass loss, diameter change, molecular weight change and by scanning electron micrographs. MSCs were able to adhere, migrate, and differentiate along the osteogenic lineage with in these scaffolds. The PCL/CaP scaffolds showed up to 27 fold increased degradation of compared to PCL scaffolds.