Apparatus for steady-state kinetic measurements of the catalytic reduction of nitric oxide by ammonia on iron oxide

The reduction of nitric oxide with ammonia on an unsupported iron oxide catalyst has been studied in a continuous-flow recycle reactor using simulated flue gas. The responses of the employed reactor system to step and pulse inputs of tracer indicate that the system could be regarded as a continuous stirred tank reactor (CSTR). Preliminary tests were carried out to determine the effect of temperature and particle size on the measured reaction rates. Additional experiments were performed in order to study the influence of oxygen and water concentration on these rates. A gas chromatographic system has been developed to analyze the gas components NO, N₂O, NO₂, NH₃, H₂O, O₂, CO₂ and N₂. In addition, the concentrations of NO and NO₂ were measured with a nondisperse infrared (NDUV/NDIR) analyzer.     

Reasoning with graph constraints

Graph constraints were introduced in the area of graph transformation, in connection with the notion of (negative) application conditions, as a form to limit the applicability of transformation rules. However, we believe that graph constraints may also play a significant role in the area of visual software modelling or in the specification and verification of semi-structured documents or websites (i.e. HTML or XML sets of documents). In this sense, after some discussion on these application areas, we concentrate on the problem of how to prove the consistency of specifications based on this kind of constraints. In particular, we present proof rules for two classes of graph constraints and show that our proof rules are sound and (refutationally) complete for each class. In addition, we study clause subsumption in this context as a form to speed up refutation.     

Discrete retardance second harmonic generation ellipsometry

A new instrument was constructed to perform discrete retardance nonlinear optical ellipsometry (DR-NOE). The focus of the design was to perform second harmonic generation NOE while maximizing sample and application flexibility and minimizing data acquisition time. The discrete retardance configuration results in relatively simple computational algorithms for performing nonlinear optical ellipsometric analysis. NOE analysis of a disperse red 19 monolayer yielded results that were consistent with previously reported values for the same surface system, but with significantly reduced acquisition times.     

Identification of barramundi (Lates calcarifer) and tilapia (Oreochromis spp.) fillets by DNA- and protein-analytical methods

Fish and fillet of barramundi (Lates calcarifer) and tilapia (Oreochromis species) obtained from wholesale and retail trade were assigned to species by sequencing of PCR products. Two segments (358 and 464?bp) of the cytochrome b gene (cytb) were amplified using universal primers. The amplicons gave characteristic patterns in SSCP-analysis (single strand conformation polymorphism) suitable for differentiation of Lates calcarifer from Lates niloticus and Lateolabrax japonicus. Intra-specific variation of sequences and SSCP patterns were observed for barramundi. In case of tilapia species, it was found to be difficult to identify samples by BLAST due to the high similarity of cytb sequences of O. niloticus, O. mossambicus, O. aureus and Sarotherodon galileus. Four different patterns of single strand DNA (ssDNA) were obtained by SSCP analysis of the 464?bp amplicon of tilapia. Different patterns of ssDNA matched to variations in sequences. Protein profiles obtained by IEF (isoelectric focusing) of water-soluble proteins from raw fillet were found to be suitable for rapid differentiation of Lates calcarifer from Lateolabrax japonicus, but the three different Oreochromis species expressed only minor differences in protein patterns. The patterns of the tilapia and barramundi species showed a number of acidic, heat-stable proteins, presumably representing parvalbumin.     

Mikromethode zur quantitativen Bestimmung von Coffein

Zusammenfassung Zur quantitativen Bestimmung von Coffein in biologischem Material wird ein kombiniertes Verfahren aus Dünnschichtchromatographie und Densitometrie beschrieben. Das Verfahren läßt Bestimmungen im Nanogramm-Bereich zu. Das Probenvolumen liegt unter 100 l.Die Proben — Capillarblut — werden zunächst mit dem gleichen Volumen Chloroform extrahiert. Anschließend wird das Coffein mittels Dünnschichtchromatographie von Begleitstoffen und störenden Substanzen abgetrennt. Es werden Kieselgel-60-Fertigplatten und Chlorofom/Aceton (9 + 1; v/v) als Fließmittel verwendet, dabei beträgt die Laufzeit 30 min.Die quantitative densitometrische Auswertung erfolgt durch Remissionsmessung bei 273 nm. Im Bereich von 10–60 ng Coffein/Fleck verläuft die Eichkurve linear. 1 mg/I Coffein kann noch sicher quantitativ erfaßt werden. Die Nachweisgrenze liegt bei 0,1 mg/1.

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A quantitative micromethod for the caffeine determination

Summary A combined procedure with thin-layer-chromatography and densitometry is described for the quantitative estimation of caffeine in biological material. This method ist applicable in the nanogram range. Test samples of less than 100 l may be used. The samples (capillary-blood) are extracted with the same volume of chloroform. Caffeine is separated from interfering compounds by thin-layer-chromatography. Commercial silica-60-plates with chloroform/acetone (9 + 1; v/v) as solvent are used. The running time is about 30 min. The quantitative densitometric determinations are performed in the remission mode at 273 nm. In the range from 10 to 60 ng/spot the calibration curve is linear. Accurate quantitative data will be obtained even at concentrations of 1 mg/1 caffeine. The detection limit is at about 0.1 mg/1.

     

Charakterisierung niedermolekularer Zinkspezies in handelsüblichen pflanzlichen Lebensmitteln

In six different ordinary vegetables, namely kohlrabi, Chinese cabbage, chard, leek, spinach and Jerusalem artichoke, zinc was mainly found as low molecular weight species. In the present study, these important zinc compounds are further investigated. The determinations of the metal are performed by ET-AAS. The zinc complexes of all vegetables are anionic at pH 8.0 and show similar elution behaviour in gel permeation and anion exchange chromatography. Consequently, a great resemblance in structure between the low molecular weight zinc species from the different vegetables can be supposed. Exemplary, the zinc complexes of kohlrabi and Chinese cabbage are further examined. In more purified samples of these vegetables compared to zinc neither stoichiometric amounts of free protein amino acids nor nicotianamine, free malic acid, citric acid or phytic acid have been detected. Mainly glutamic acid is found in molar excess to zinc after acid hydrolysis in both cases. The cysteine contents of both zinc-binding fractions are very low. Conclusively, the wellknown γ-glutamylcysteinyl-glycines (phytochelatines) can not be responsible for the bonding of zinc in both ordinary vegetables. We suppose that zinc in kohlrabi and Chinese cabbage is bound to a glutamic acid derivative unknown as yet, possibly a malic acid ester.     

Low‐Cost Post‐Growth Treatments of Crystalline Silicon Nanoparticles Improving Surface and Electronic Properties

Freestanding silicon nanocrystals (Si‐ncs) offer unique optical and electronic properties for new photovoltaic, thermoelectric, and other electronic devices. A method to fabricate Si‐ncs which is scalable to industrial usage has been developed in recent years. However, barriers to the widespread utilization of these nanocrystals are the presence of charge‐trapping defects and an oxide shell formed upon ambient atmosphere exposure hindering the charge transport. Here, we exploit low‐cost post‐growth treatment routes based on wet‐etching in hydrofluoric acid plus surface hydrosilylation or annealing enabling a complete native oxide removal and a reduction of the defect density by up to two orders of magnitude. Moreover, when compared with only H‐terminated Si‐ncs we report an enhancement of the conductivity by up to a factor of 400 for films of HF etched and annealed Si‐ncs, which retain a defect density below that of untreated Si‐ncs even after several months of air exposure. Further, we demonstrate that HF etched and hydrosilylated Si‐ncs are extremely stable against oxidation and maintain a very low defect density after a long‐term storage in air, opening the possibility of device processing in ambient atmosphere.