Screening and Xylanase Production by Streptomyces sp. Grown on Lignocellulosic Wastes

Xylanases have raised interest because of their potential applications in various industrial fields, including the pulp and paper industries, bioethanol production, and the feed industry. In bioethanol production from lignocellulosic compounds, xylanase can improve the hydrolysis of cellulose into fermentable sugars, since the xylan restricts the cellulases from acting efficiently. In this work, a new thermophilic Streptomyces sp. was selected for its ability to produce xylanase. Carbon source selection is an important factor in the production of hemicellulases. The highest activity was obtained when Streptomyces sp. I3 was grown in the presence of wheat bran. Xylanase activity was partially characterized concerning the effect of pH and temperature on activity and thermostability, and the effects of different metal ions were also tested. The pH and temperature profile showed optimal activity at pH 6.0/70 °C. Zymogram analysis showed multiple xylanases (39, 21, 18, and 17 kDa). Xylanases studied in this work are thermophilic, thermostable, and active in a wide pH range; they have potential to be used in the development of new processes of biotechnological interest.     

A variational approach to image registration in dynamic contrast-enhanced MRI of the human kidney

Kidney function can be accessed by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) measurements which yield spatially resolved maps of physiological parameters like perfusion or filtration. The motion of the kidneys during the scan is a dominant limitation of the measurement quality, and image registration is necessary for accurate quantification. We analyzed the feasibility of applying an algorithm, originally developed for multimodal registration, to kidney perfusion time series. The algorithm uses a variational calculation scheme to align the images. In four out of five data sets, kidney motion could be reduced to below the spatial resolution of the images of 1.6 mm while preserving the enhancement pattern of kidney perfusion. Fitting a pharmacokinetic model to the data showed an average reduction of the Akaike fit error of 10% for the registered data, suggesting more stable parameters. We conclude that this image registration algorithm is feasible for correcting kidney motion in renal DCE-MRI.     

Zur Untersuchung der Butter

Ohne Zusammenfassung     

The holomorphic solutions of the generalized Dhombres functional equation

We study holomorphic solutions f of the generalized Dhombres equation f(zf(z))=φ(f(z)), z∈C, where φ is in the class E of entire functions. We show, that there is a nowhere dense set E₀⊂E such that for every φ∈E?E₀, any solution f vanishes at 0 and hence, satisfies the conditions for local analytic solutions with fixed point 0 from our recent paper. Consequently, we are able to provide a characterization of solutions in the typical case where φ∈E?E₀. We also show that for polynomial φ any holomorphic solution on C?{0} can be extended to the whole of C. Using this, in special cases like φ(z)=zk+1, k∈N, we can provide a characterization of the analytic solutions in C.     

Synthetische Versuche in der Topasreihe

Ohne ZusammenfassungIch erfülle zum Schlusse die angenehme Pflicht, Herrn Prof. Arzruni von der technischen Hochschule in Aachen, der die krystallographischen Bestimmungen in ausserordentlich liebenswürdiger Weise übernommen und durchgeführt hat, hier an dieser Stelle herzlichst zu danken.Weiterhin sei es mir gestattet, meinem hochverehrten Lehrer, Herrn Prof. Weidel, unter dessen Leitung die Arbeit durchgeführt wurde, für die vielfachen Unterstützungen meinen wärmsten Dank auszusprechen.     

A DFT study of H adsorption on Pt(111) and Pt-Ru(111) surfaces

In this work a comparative analysis between different Pt-Ru(111) surface models and pure Pt(111) surface is presented. Some aspects of the electronic structure of the surfaces and hydrogen adsorption are analysed based on density functional theory calculations. The hydrogen adsorption energy is significantly reduced when Ru is present on the surface. The substitution of Pt atoms by Ru atoms reinforce the Pt-H bond while the metal-metal bond is strongly modified, making the system less stable.     

Potentiometrische Analyse

Ohne Zusammenfassung