Friction stir welding of API X70 steel incorporating Ti-dioxide

In the present work, the microstructural evolution and hardness of HSLA X70 joined by friction stir welding were investigated. The FSW was applied to HSLA X70 with and without the addition of titanium dioxide (TiO₂) powders. To evaluate the microstructural features and hardness of different weld zones, optical microscopy and Vickers microhardness measurements were applied. The results show that the distribution of TiO₂ powders is strongly dependent on the applied friction stir processing, which in turn changed significantly the microstructure and hardness profile. In this regard, the optimum stirring action resulted in a homogeneous and fine dispersion of particles leading to the domination of an acicular ferrite phase with a hardness of 370 HV. On the other hand, the lower stirring action resulted in coarse particles as well as the development of the polygonal ferrite structure with a hardness of ～185 HV.     

Multivariate process trajectories for molecular description of MF thermal curing and correlation with hydrolytic stability

During curing of thermosetting resins the technologically relevant properties of binders and coatings develop. However, curing is difficult to monitor due to the multitude of chemical and physical processes taking place. Precise prediction of specific technological properties based on molecular properties is very difficult. In this study, the potential of principal component analysis (PCA) and principal component regression (PCR) in the analysis of Fourier transform infrared (FTIR) spectra is demonstrated using the example of melamine-formaldehyde (MF) resin curing in solid state. FTIR/PCA-based reaction trajectories are used to visualize the influence of temperature on isothermal cure. An FTIR/PCR model for predicting the hydrolysis resistance of cured MF resin from their spectral fingerprints is presented which illustrates the advantages of FTIR/PCR compared to the combination differential scanning calorimetry/isoconversional kinetic analysis. The presented methodology is transferable to the curing reactions of any thermosetting resin and can be applied to model other technologically relevant final properties as well.     

Discovery of the Tiancilactone Antibiotics by Genome Mining of Atypical Bacterial Type II Diterpene Synthases

Although genome mining has advanced the identification, discovery, and study of microbial natural products, the discovery of bacterial diterpenoids continues to lag behind. Herein, we report the identification of 66 putative producers of novel bacterial diterpenoids, and the discovery of the tiancilactone (TNL) family of antibiotics, by genome mining of type II diterpene synthases that do not possess the canonical DXDD motif. The TNLs, which are broad‐spectrum antibiotics with moderate activities, are produced by both Streptomyces sp. CB03234 and Streptomyces sp. CB03238 and feature a highly functionalized diterpenoid skeleton that is further decorated with chloroanthranilate and γ‐butyrolactone moieties. Genetic manipulation of the tnl gene cluster resulted in TNL congeners, which provided insights into their biosynthesis and structure–activity relationships. This work highlights the biosynthetic potential that bacteria possess to produce diterpenoids and should inspire continued efforts to discover terpenoid natural products from bacteria.     

Graphite Oxide and Aromatic Amines: Size Matters

Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molecules prefer to covalently connect to the graphene oxide matrix via chemical grafting, while napthalene amine molecules bind with the graphene oxide surface through π–π interactions. The presence of intercalated aromatic molecules between the graphene oxide layers is demonstrated by X‐ray diffraction, while the type of interaction between graphene oxide and polycyclic organic molecules is elucidated by X‐ray photoelectron spectroscopy. Combined quantum mechanical and molecular mechanical calculations describe the intercalation mechanism and the aniline grafting, rationalizing the experimental data. The present work opens new perspectives for the interaction of various aromatic molecules with graphite oxide and the so‐called “intercalation chemistry”.     

Development and optimisation of a defined high cell density yeast medium

Saccharomyces cerevisiae cells grown in a small volume of chemically defined media neither reach the desired cell density nor grow at a fast enough rate to scale down the volume and increase the sample number of classical biochemical assays, as the detection limit of the readout often requires a high number of cells as an input. To ameliorate this problem, we developed and optimised a new high cell density (HCD) medium for S. cerevisiae. Starting from a widely used synthetic medium composition, we systematically varied the concentrations of all components without the addition of other compounds. We used response surface methodology to develop and optimise the five components of the medium: glucose, yeast nitrogen base, amino acids, monosodium glutamate, and inositol. We monitored growth, cell number, and cell size to ensure that the optimisation was towards a greater density of cells rather than just towards an increase in biomass (i.e., larger cells). Cells grown in the final medium, HCD, exhibit growth more similar to the complex medium yeast extract peptone dextrose (YPD) than to the synthetic defined (SD) medium. Whereas the final cell density of HCD prior to the diauxic shift is increased compared with YPD and SD about threefold and tenfold, respectively. We found normal cell-cycle behaviour throughout the growth phases by monitoring DNA content and protein expression using fluorescent reporters. We also ensured that HCD media could be used with a variety of strains and that they allow selection for all common yeast auxotrophic markers.     

Composition of a protein-like fluorophore of dissolved organic matter in coastal wetland and estuarine ecosystems

This study demonstrates the compositional heterogeneity of a protein-like fluorescence emission signal (T-peak; excitation/emission maximum at 280/325 nm) of dissolved organic matter (DOM) samples collected from subtropical river and estuarine environments. Natural water samples were collected from the Florida Coastal Everglades ecosystem. The samples were ultrafiltered and excitation-emission fluorescence matrices were obtained. The T-peak intensity correlated positively with N concentration of the ultrafiltered DOM solution (UDON), although, the low correlation coefficient (r(2)=0.140, p<0.05) suggested the coexistence of proteins with other classes of compounds in the T-peak. As such, the T-peak was unbundled on size exclusion chromatography. The elution curves showed that the T-peak was composed of two compounds with distinct molecular weights (MW) with nominal MWs of about >5 x 10(4) (T(1)) and approximately 7.6 x 10(3) (T(2)) and with varying relative abundance among samples. The T(1)-peak intensity correlated strongly with [UDON] (r(2)=0.516, p<0.001), while T(2)-peak did not, which suggested that the T-peak is composed of a mixture of compounds with different chemical structures and ecological roles, namely proteinaceous materials and presumably phenolic moieties in humic-like substances. Natural source of the latter may include polyphenols leached from senescent plant materials, which are important precursors of humic substances. This idea is supported by the fact that polyphenols, such as gallic acid, an important constituent of hydrolysable tannins, and condensed tannins extracted from red mangrove (Rhizophora mangle) leaves exhibited the fluorescence peak in the close vicinity of the T-peak (260/346 and 275/313 nm, respectively). Based on this study the application of the T-peak as a proxy for [DON] in natural waters may have limitations in coastal zones with significant terrestrial DOM input.     

Function-analysis and valuation as a tool to assess land use conflicts in planning for sustainable, multi-functional landscapes

In order to reconcile landscape conservation with changing demands on land use and natural resources, it is essential that the ecological, socio-cultural and economic values of the landscape be fully taken into account in planning and decision-making.This paper presents a comprehensive framework for integrated assessment of ecological services and socio-economic benefits of natural and semi-natural ecosystems and landscapes. The framework can be applied at different scale levels to different ecosystems or landscape-units and basically consists of three steps: (1) Function-analysis: translates ecological complexity into a limited number of ecosystem (or landscape) functions, which, in turn, provide a range of goods and services; (2) Function valuation: includes ecological, socio-cultural and economic valuation methods; and (3) Conflict analysis: to facilitate the application of function-analysis and valuation at different scale levels, it is important to integrate analytical valuation methods with stakeholder participation techniques.The framework presented in this paper facilitates the structured assessment of the (total) value of the goods and services provided by a specific area (landscape) and to analyze the costs and benefits involved in trade-offs between various land use options. The last section of this paper gives some conclusions and recommendations for application-possibilities of function-analysis and valuation to achieve more sustainable landscape use and maintenance of our “natural capital”.     

Bedeutung des Speichersystems Lohsa II für die wasserhaushaltliche Sanierung im Spreegebiet

Within the framework of the mining remidiation the residual holes of the former brown coal opencast mines “Lohsa”, “Dreiweibern” and “Burghammer” will be connected with each other in order to form the retaining system “Lohsa II”. Including the neighbouring residual hole “Bärwalde” they will provide a storage capacity of more than 90 millions m ³ (118.421 millions cu yards). Considering the water economy the project is expected to be completely ready for operation in the year 2005. Up to 13 m ³ /s (16.9 cu yards per second) of water are to be supplied during dry spells. This will sustain the draining function of the river Spree which has been damaged by lignite mining. At the same time the ecological requirements of the biosphere reserve “Spreewald” and the demands of the conurbation Berlin – concerning its water supply and water storage – will be fulfilled     

Studying sulfur functional groups in Norway spruce year rings using S L-edge total electron yield spectroscopy

Profiles of the major sulfur functional groups in mature Norway spruce wood tissue have been established for the first time. The big challenge was the development of a method suitable for sulfur speciation in samples with very low sulfur content (<100 ppm). This became possible by synchrotron X-ray absorption spectroscopy at the sulfur L-edge in total electron yield (TEY) detection mode with thin gold-coated wood slices. Functional groups were identified using sulfur compound spectra as fingerprints. Latewood of single year rings revealed metabolic plausible sulfur forms, particularly inorganic sulfide, organic disulfide, methylthiol, and highly oxidized sulfur. Form-specific profiles with Norway spruces from three different Swiss forest sites revealed high, but hitherto little-noticed, sulfur intensities attributable to natural heartwood formation and a common, but physiologically unexpected maximum around year ring 1986 with trees from the industrialized Swiss Plateau. It is hypothesized whether it may have resulted from the huge reduction in sulfur emissions after 1980 due to Swiss policy. Comparison with total S content profiles from optical emission spectroscopy underlined the more accurate and temporally better resolved TEY data with single wood year rings and it opened novel insights into the wood cell chemistry.