Synthese eines Pentapeptidderivates der Insulinsequenz A17-A21

Synthesis of a Pentapeptide Derivative of the Insulin Sequence A₁₇–A₂₁ The synthesis of the protected pentapeptide derivative N-2-(p-biphenylyl) isopropyloxycarbonyl-γ-t-butyl-L -glutamyl-L -asparaginyl-O-t-butyl-L-tyrosyl-S-diphenylmethyl-L -cysteinyl-L-asparagine t-butyl ester is described. Its amino acid sequence corresponds to the sequence 17–21 of the insulin A-chain.     

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Bandpass sigma-delta modulation

A bandpass version of sigma-delta modulation is presented, with simulation results for second- and fourth-order convertors. For the fourth-order convertor operating at 8 MHz, simulations demonstrate a resolution of 16 bits over an 8 kHz band centred at 1 MHz. Applications may include analogue/digital conversion for AM radio, and digital/analogue conversion for narrowband RF systems.<>     

Knowledge-Based SAR Processing and Geocoding: The Elementary Components of the German Processing and Archiving Facility for High Throughput and High-Precision Processing of ERS-1 SAR Data

Future microwave sensors such as the active microwave instrument (AMI) of the first European remote sensing satellite (ERS-1) to be launched in 1990 will be increasingly conducted in an operational mode. This fact implies an increased amount of synthetic aperture radar (SAR) data to be processed systematically, and, furthermore, combines with the growing needs of the user community in terms of various product levels, adequate production, and organization schemes. Among these needs are the requirements regarding much improved radiometric and absolute geometric accuracy of the generated SAR images. Therefore, an end-to-end SAR processing system has been designed that is significantly different from existing ones. The challenging requirements for high precision combined with high throughput of the generated products will be met by two systems: the knowledge-based intelligent SAR processor (ISAR) and the geocoding system. They represent the backbone of a distributed computer network engaged in SAR processing and image restitution within the German Processing and Archiving Facility (D-PAF) for ERS-1, which shall be built up and operated by the German Aerospace Research Establishment (DFVLR). This paper describes the requirements for the system as well as the specific hardware and software concepts.     

In situ FTIR studies on the conversion of methanol over acidic forms of various zeolites

In situ investigations of the interaction of methanol on zeolites of the faujasite, pentasil and mordenite types were performed. We suppose that CH₃)- or (CH₃)₂O… species exist on the surface of the H-ZSM-5 zeolite in the temperature range between 380 and 470 K which desorb above 470 K and form dimethyl ether (DME). The band at 1502 cm⁻¹ represents aromatics being intermediates in the aromatization of methanol. The band at 1595 cm⁻¹ is due to polymeric “coke” which cannot be removed from the zeolite up to 670 K. In the case of the H-Y zeolite no band at 1500 cm⁻¹ assigned to aromatics could be observed.     

Metabolism and pharmacokinetics of N1,N11-diethylnorspermine

The pharmacokinetics and metabolism of N1,N11-diethylnorspermine (DENSPM) is described. When administered to dogs as an intravenous bolus, DENSPM was shown to have a plasma half-life of 72.8 +/- 11.8 min, with an early distribution phase half-life of approximately 4 min and an apparent volume of distribution of 0.216 +/- 0.032 liter/kg. The renal clearance half-life was 59.7 +/- 7.6 min, with 48.8 +/- 12.5% of the drug recovered in the urine between 0-4 hr unchanged. In three other experiments, the drug was administered to dogs by constant rate intravenous infusion over periods ranging from 10 min to 2 hr. Analysis of plasma concentration-time data and urinary excretion data yielded pharmacokinetic parameters in general agreement with the intravenous bolus experiments. DENSPM metabolites were identified in both beagle dog and mouse tissues. Tissues were sampled from a single beagle 24 hr posttreatment, and rodent samples were examined at 12, 24, 48, and 96 hr posttreatment. Both the concentration of DENSPM and the metabolic profile were shown to vary in the lung, liver, spleen, and kidney. Although all the tissues examined contained DENSPM and its metabolites, the liver and kidney had the highest level of metabolites that included N1-ethylnorspermine, N1-ethylnorspermidine, N1-ethyl-1,3-diaminopropane, and norspermidine. These data suggest that DENSPM is metabolized by N-deethylation and step-wise removal of aminopropyl equivalents by spermine/spermidine N1-acetyltransferase/polyamine oxidase, a metabolic pathway unique to the polyamines.