Microcavity-integrated graphene photodetector

There is an increasing interest in using graphene (1, 2) for optoelectronic applications. (3-19) However, because graphene is an inherently weak optical absorber (only ≈2.3% absorption), novel concepts need to be developed to increase the absorption and take full advantage of its unique optical properties. We demonstrate that by monolithically integrating graphene with a Fabry-Pérot microcavity, the optical absorption is 26-fold enhanced, reaching values >60%. We present a graphene-based microcavity photodetector with responsivity of 21 mA/W. Our approach can be applied to a variety of other graphene devices, such as electro-absorption modulators, variable optical attenuators, or light emitters, and provides a new route to graphene photonics with the potential for applications in communications, security, sensing and spectroscopy.     

Formal Translation of Bytecode into BoogiePL

Many modern program verifiers translate the program to be verified and its specification into a simple intermediate representation and then compute verification conditions on this representation. Using an intermediate language improves the interoperability of tools and facilitates the computation of small verification conditions. Even though the translation into an intermediate representation is critical for the soundness of a verifier, this step has not been formally verified. In this paper, we formalize the translation of a small subset of Java bytecode into an imperative intermediate language similar to BoogiePL. We prove soundness of the translation by showing that each bytecode method whose BoogiePL translation can be verified, can also be verified in a logic that operates directly on bytecode.     

Rückblicke und Ausblicke auf die Konstitutionsaufklärung der Cellulose

Ohne Zusammenfassung Mitteilung über makromolekulare Verbindungen 582. Mitt. vgl. Makromolekulare Chem. Bd.10 (1955), H. 2; zugl. 113, Mitt. über Cellulose.     

Polarographische Untersuchungen an 1,3-Thiazinthionen

Polarographic Investigations of 1,3-Thiazinthiones 1,3-Thiazine-6-thiones are stepwise reduced in aprotic media to the corresponding radical anions and dianions. In the case of the 2,4-diphenyl derivative ( 1a ) the radical anion is stable in dimethylformamide, whereas the dianion reacts further to yield the bithiazinylidene ( 4 ) among other products. The effect of substituents on the reduction potentials is discussed.     

Development of organosilicone–polyurethanes as stone preservation and consolidation materials

Two organosilicone-modified polyurethanes are investigated as potential materials for the conservation and consolidation of natural stones. The materials are low molecular weight oligomers at the application stage and react with the humidity of the air to give polymers, forming continuous microlayers. The two differ in the length of the organosilicone chain, resulting in pronounced differences in their physical state: one forms a brittle glassy material (T_g ≈ 70°C). and the other, a soft rubbery material (T_g ≈ −100°C). The rate of the polymerization of the prepolymers was investigated at different conditions, showing a strong dependence on the presence of a catalyst and air humidity. Both these favorable conditions exist probably in the natural stone pores, enhancing the formation of the protective hydrophobic internal microlayer. © 1996 John Wiley & Sons, Inc.     

Flavine und Zimtsäurederivat im Zusammenhang mit der lichtinduzierten Blattöffnung bei Albizia julibrissin

Flavins and Chinamoyl Derivatives in Relation to the Light-induced Leaf Opening in Albizia julibrissin In search of blue-light photoreceptors for light-induced leaf opening we isolated from the aqueous extract of Albizia julibrissin Durazz. two flavins by adsorption on XAD-4 and separation with HPLC. One sample was identified as riboflavin 1a. In the hydrolysate of the second flavin fraction we found another dimethylisoalloxazine with a C₅-side chain. Furthermore we isolated the cinnamoyl derivatives 3-O-(4-hydroxy-trans-cinnamoyl) quinic acid 2 and 3-O-(3,4-dihydroxy-trans-cinnamoyl)-4-O-malonyl-quinic acid 3 which formed charge transfer complexes with the flavins in the XAD-fraction. As a model complex we examined the absorption behaviour of the complex between riboflavin and chlorogenic acid. Using the association constant, we calculated the absorption spectrum and could show that a complex between a flavin and a phenolic compound is a possible blue-light photoreceptor for the light-induced leaf opening in Albizia julibrissin.     

Determination of Glyphosate and Its Metabolite AMPA (Aminomethylphosphonic Acid) in Cereals After Derivatization by Isotope Dilution and UPLC-MS/MS”

A straightforward analytical method has been developed for the determination of glyphosate and aminomethylphosphonic acid (AMPA), its major metabolite in cereals. This method entails a rapid extraction and derivatization with 9-fluorenylmethyl chloroformate followed by separation with a conventional reversed-phase rapid chromatography used in daily routine analysis and detection by electrospray ionization tandem mass spectrometry. To overcome matrix effects and compensate for any analyte losses during sample treatment, an isotopic dilution approach was used. Since 2010, the monitoring of cereals for the widely used herbicide glyphosate is obligatory to all European Union (EU)-member states, laid down in Commission Regulation (EC) No. 1213/2008. Hence, there is definitively a need for a reliable and easy-to-handle analytical method for monitoring of this compound. The proposed method can be run without having to make time-consuming changes on the equipment used for daily routine analysis. The analytical performance of the method was evaluated according to SANCO/10684/2009 criteria and demonstrated that this method is rugged and cost-effective, therefore suitable for monitoring purposes as well as legislative enforcements within the EU. The apparent recoveries of both analytes were between 97% and 113% with relative standard deviations less than 20%. The limits of quantification of glyphosate and AMPA were 0.02 mg/kg in cereal matrices. Finally, the accuracy of the method was assessed by analyzing a proficiency test material which was available from a previous round (EUPT-C4).     

Cloning of the bile salt hydrolase (bsh) gene from Enterococcus faecium FAIR-E 345 and chromosomal location of bsh genes in food enterococci

Enterococcus faecium strain FAIR-E 345 isolated from food was shown to possess bile salt hydrolase (Bsh) activity in a plate screening assay and by high-performance liquid chromatography analysis. The bsh gene was cloned and sequenced. DNA sequence analysis revealed that it encoded a protein of 324 amino acids, with pI 4.877. A bsh gene probe was prepared from the cloned bsh gene and was used for probing plasmid and total genomic DNA of Bsh-positive enterococci isolated from food to determine the genomic location of their bsh genes. This probe was able to detect the bsh gene among total genomic DNA preparations but not from plasmid preparations of 10 plasmid-bearing Enterococcus strains. However, the probe could detect the bsh gene from total genomic DNA preparations of 12 Enterococcus strains that did not contain detectable plasmid DNA. In no cases did the probe hybridize with plasmid DNA preparations, suggesting that the bsh gene among enterococci is probably generally chromosomally encoded. This presumptive chromosomal location of bsh genes among food enterococci suggests that transfer of this trait by conjugative plasmids is unlikely.     

Influence of Methanol on Prion Reduction during High Temperature and High Pressure Oleochemical Processes

Prion‐reduction in standard biodiesel processes is caused by acidic and alkaline conditions. In the alternative RepCat biodiesel process, efficient prion‐reduction can be achieved by high‐temperature/pressure. However, a possible increase in thermostability of prions in the presence of methanol during these conditions has not previously been investigated, and is verified in this work. Samples are spiked with prions, treated with methanol, and incubated at 220 °C at 80 bar for 30 min. No traces of protease‐resistant prion protein (as proxy for prions) are detected in tallow or glycerine (as the final by‐product) after treatment. Serial dilutions of spiked prions show at least 6 log₁₀ prion reduction. More importantly, similar effects are detected using milder conditions of 200 °C at 70 bar for 15 min, representing the worst‐case conditions of the process. In conclusion, this study shows that methanol does not increase the thermostability of prions and the RepCat process can efficiently eliminate prions and is therefore safe for the usage of category 1 tallow. Practical Applications: The study further supports the applicability of RepCat process in reducing prion‐contamination in the presence of methanol. Furthermore, the conditions leads to a considerable reduction of prions in glycerine obtained as by‐product.