Absolutberechnung heterogener Reaktionsgeschwindigkeiten

Summary Experimental results are reported concerning the decomposition of C₂H₅Cl with some chlorides as catalysts. Activation energies were found between 12 and 42 kcal/M, and an exponential relation between activity and activation energy within 8 powers of ten could be verified. A measurement of the surface conditions by adsorption gives some indications of the number of the centres of minimum and maximum activity. On the assumption of a quantum-mechanical leakage of an electron as the rate-determining step the experiments can be evaluated quantitatively in a satisfactory way.     

In situ experimental evidence of the fate of a phytodetritus pulse at the abyssal sea floor

More than 50% of the Earth' s surface is sea floor below 3,000 m of water. Most of this major reservoir in the global carbon cycle and final repository for anthropogenic wastes is characterized by severe food limitation. Phytodetritus is the major food source for abyssal benthic communities, and a large fraction of the annual food load can arrive in pulses within a few days. Owing to logistical constraints, the available data concerning the fate of such a pulse are scattered and often contradictory, hampering global carbon modelling and anthropogenic impact assessments. We quantified (over a period of 2.5 to 23 days) the response of an abyssal benthic community to a phytodetritus pulse, on the basis of 11 in situ experiments. Here we report that, in contrast to previous hypotheses, the sediment community oxygen consumption doubled immediately, and that macrofauna were very important for initial carbon degradation. The retarded response of bacteria and Foraminifera, the restriction of microbial carbon degradation to the sediment surface, and the low total carbon turnover distinguish abyssal from continental-slope 'deep-sea' sediments.     

Stochastic sensors inspired by biology

Sensory systems use a variety of membrane-bound receptors, including responsive ion channels, to discriminate between a multitude of stimuli. Here we describe how engineered membrane pores can be used to make rapid and sensitive biosensors with potential applications that range from the detection of biological warfare agents to pharmaceutical screening. Notably, use of the engineered pores in stochastic sensing, a single-molecule detection technology, reveals the identity of an analyte as well as its concentration.     

Decreased virulence of recombinant vaccinia virus expression vectors is associated with a thymidine kinase-negative phenotype

Recent advances in molecular genetics have led to the possibility of using large DNA viruses, such as vaccinia virus, as a biological delivery system for immunizing man against unrelated disease-causing agents. When live vaccinia virus recombinants expressing the hepatitis B virus surface antigen (HBsAg), the influenza A virus haemagglutinin, the herpes simplex virus (HSV) type 1 D glycoprotein, the rabies virus G glycoprotein and the vesicular stomatitis virus G glycoprotein were used for immunization, animals were protected upon challenge with the appropriate pathogenic agent. A major concern with using such vaccines, however, stems from the previously documented vaccinia virus-associated post-immunizing complications. We present here experimental evidence that thymidine kinase-negative (TK-) vaccinia virus recombinants, constructed by inserting a variety of DNA coding sequences into the vaccinia virus tk gene, are less pathogenic for mice than wild-type virus.