Optimizing substrate surface and catalyst conditions for high yield chemical vapor deposition grown epitaxially aligned single-walled carbon nanotubes

Single-crystal stable-temperature (ST)-cut quartz substrates, which have a (0 1 1 1) crystallographic plane with their surface normal lying close to 38° from the y axis ([0 1 0]), were annealed in air prior to use as a support for aligned carbon nanotube growth by chemical vapor deposition. Very smooth substrate surfaces were obtained with annealing times in the vicinity of 15 h at a temperature of 750 °C. These smooth surfaces are ideal for the growth of horizontally aligned SWCNTs with high spatial density, while less dense SWCNTs were obtained with less smooth surfaces. Under optimized growth conditions, only SWCNT are observed and they can grow to lengths in excess of 100 μm. Our findings suggest structural defects interfere with the growth process. A binary Fe/Co catalyst was employed to grow the nanotubes. No obvious dependence on the Fe:Co ratio is observed.     

Basic model for membrane electrode assembly design for direct methanol fuel cells

This research proposes a model that predicts the effect of the anode diffusion layer and membrane properties on the electrochemical performance and methanol crossover of a direct methanol fuel cell (DMFC) membrane electrode assembly (MEA). It is an easily extensible, lumped DMFC model. Parameters used in this design model are experimentally obtainable, and some of the parameters are indicative of material characteristics. The quantification of these material parameters builds up a material database. Model parameters for various membranes and diffusion layers are determined by using various techniques such as polarization, mass balance, electrochemical impedance spectroscopy (EIS), and interpretation of the response of the cell to step changes in current. Since the investigation techniques cover different response times of the DMFC, processes in the cell such as transport, reaction and charge processes can be investigated separately. Properties of single layers of the MEA are systematically varied, and subsequent analysis enables identification of the influence of the layer's properties on the electrochemical performance and methanol crossover. Finally, a case study indicates that the use of a membrane with lower methanol diffusivity and a thicker anode micro-porous layer (MPL) yields MEAs with lower methanol crossover but similar power density.     

A rigorous small area modelling-study for the helicobacter pylori epidemiology

This paper presents an investigation into spatial risk differences over small distances for the Helicobacter pylori infection in the city of Leipzig, Germany and two rural districts. A model, using Bayesian inference, was developed that adjusts the risk for individual-specific factors, and for spatial or individual over-dispersion, respectively. Additionally, the model takes into account conditional spatial autocorrelation. We found a significant positive association to the H. pylori infection risk for: “more than three children live in the household” (OR = 2.4, p = 0.001), “more persons live per sq.m than average” (OR = 1.4, p = 0.03), “home situated at main road” (OR = 1.4, p = 0.04) and “using well water” (OR = 2.3, p = 0.05). A protective effect was identified for “travelled to low prevalence region” (OR = 0.4, p < 0.0001) and “born in Germany” (OR = 0.2, p < 0.0001). Three administrative areas with significantly increased spatial risk were identified: one in the rural district and two in the city of Leipzig. The model explained 24.9% of the total deviance. Contrary to expectations, the largest part of deviance of the data was not explained by the identified significant risk factors, but by individual-specific heterogeneities. We conclude that further - so far not discussed - factors influence the risk and the spatial variation of the H.pylori infection. Furthermore, from the results we speculate about a possible impact of long-time air pollution and surface water.     

Thesen und Trends &#x0096; Mit funktionalen Oberflächen in die Zukunft

Propositions and Trends &#x0096; With Functional Surfaces into the Future Functional surfaces are the key to innovative products. Already today the properties, lifetime, and costs for most industrial and consumer products are determined by functionalised surfaces. Three Fraunhofer Institutes supported by the BMBF investigated the actual state of the art of production technology regarding functional surfaces, their future perspectives and the research and development demand. The results are published in the study “Production technology for the generation of functional surfaces” available at info@ist.‐ fraunhofer.de and the essentials are summarised in this article.     

Effect of the finish rolling and cooling conditions on the properties of microalloyed plate steels

The processing parameters of finish rolling and cooling of three HSLA steels were varied in a wide range applying the plane strain hot compression simulation test on the hot deformation simulator (Wumsi). Evaluating the flow curves of the deformation steps, some metallurgical phenomena in austenite during hot deformation could be determined. The results of material testing after the simulation experiments exhibit a strong correlation between the finish rolling and cooling conditions and the final mechanical properties of the steels tested. As a way to increase strength, lowering finishing temperatures and/or accelerating cooling after finish rolling proved to be most effective. To improve notch toughness, on the other hand, a high total finishing strain should be applied as well as low finishing temperatures, however, above A_r3.     

Dielectric and lattice-dynamical properties of III-nitrides

First-principles calculations are performed to investigate dynamical and dielectric properties of group-III-nitrides. We focus on vibrational frequencies, dynamical charges, and the phonon density of states of cubic AlN, GaN, and InN. Chemical trends are derived and discussed. The first ab initio calculations of phonon branches and density of states are presented for an ordered In_xGa_1−xN structure.     

Active Site Mapping of Human Cathepsin F with Dipeptide Nitrile Inhibitors

Cleavage of the invariant chain is the key event in the trafficking pathway of major histocompatibility complex class II. Cathepsin S is the major processing enzyme of the invariant chain, but cathepsin F acts in macrophages as its functional synergist which is as potent as cathepsin S in invariant chain cleavage. Dedicated low‐molecular‐weight inhibitors for cathepsin F have not yet been developed. An active site mapping with 52 dipeptide nitriles, reacting as covalent–reversible inhibitors, was performed to draw structure–activity relationships for the non‐primed binding region of human cathepsin F. In a stepwise process, new compounds with optimized fragment combinations were designed and synthesized. These dipeptide nitriles were evaluated on human cysteine cathepsins F, B, L, K and S. Compounds 10 (N‐(4‐phenylbenzoyl)‐leucylglycine nitrile) and 12 (N‐(4‐phenylbenzoyl)leucylmethionine nitrile) were found to be potent inhibitors of human cathepsin F, with K_i values <10 nM . With all dipeptide nitriles from our study, a 3D activity landscape was generated to visualize structure–activity relationships for this series of cathepsin F inhibitors.     

Correlation of Structure and Photoelastic Response in Tin Phosphate Glass

Recently an empirical model was established to predict the photoelastic response of a glass based on its composition and the crystalline structure of its constituents. In the present work the model was tested in detail by comparing the local structure assessed by a combination of nuclear magnetic resonance and Mössbauer spectroscopy with the model predictions and the measured photoelastic response. The system investigated was (SnO)_x(P₂O₅)_1−x. It was found that while the original simple model based on data on the pure components predicted the composition of the zero stress-optic glass to within about 15 mol%, inclusion of data on mixed systems, more reflective of the true glass structure, gave substantial improvement of the prediction. This finding further confirms the relation of local bonding structure to the photoelastic response of glass.     

Activation of Polycyclic Aromatic Compounds by cDNA-Expressed Phase I and Phase II Enzymes

A large number of human and other mammalian xenobiotic-metabolizing enzymes have been expressed in target cells of standard mutagenicity tests, such as Ames's Salmonella typhimurium strains and Chinese hamster V79 cells. These recombinant cells are useful for determining the ability of individual enzymes to activate (or inactivate) a given compound. In contrast to standard S9-mediated test systems, they also allow the detection of mutagenic metabolites that do not penetrate cell membranes--a situation often found with reactive phase II metabolites. We present mutagenicity data for benzo[ a ]pyrene and dibenzo[ a,l ]pyrene in V79-derived cells expressing human cytochrome P450 (CYP) 1A1, 1A2, and 1B1, and for 1-hydroxymethylpyrene, R - and S -1-( f -hydroxyethyl) pyrene, 4-hydroxycyclopenta[ def ]chrysene and N -hydroxy-2-acetylaminofluorene in V79-derived cells and/or Salmonella strains expressing the 11 human sulfotransferases (SULTs) identified. In some cases, allelic variants and orthologous enzymes from other mammalian species were also investigated. The data indicate that mutagenicity of many compounds is detected in the appropriate recombinant systems at extremely low substrate concentrations, that the activation of various promutagens is mediated with high specificity by only one or few enzyme forms, and that substantial differences may occur between alloenzymes from the same species and orthologous enzymes from different species. Such information could be important for understanding differences in susceptibility between tissues, species, individual genetic traits, and physiological states.