Streptomyces diastatochromogenes Tü6028 is known to produce the polyketide antibiotic polyketomycin. The deletion of the pokOIV oxygenase gene led to a non-polyketomycin-producing mutant. Instead, novel compounds were produced by the mutant, which have not been detected before in the wild type strain. Four different compounds were identified and named foxicins A–D. Foxicin A was isolated and its structure was elucidated as an unusual nitrogen-containing quinone derivative using various spectroscopic methods. Through genome mining, the foxicin biosynthetic gene cluster was identified in the draft genome sequence of S. diastatochromogenes. The cluster spans 57 kb and encodes three PKS type I modules, one NRPS module and 41 additional enzymes. A foxBII gene-inactivated mutant of S. diastatochromogenes Tü6028 ΔpokOIV is unable to produce foxicins. Homologous fox biosynthetic gene clusters were found in more than 20 additional Streptomyces strains, overall in about 2.6% of all sequenced Streptomyces genomes. However, the production of foxicin-like compounds in these strains has never been described indicating that the clusters are expressed at a very low level or are silent under fermentation conditions. Foxicin A acts as a siderophore through interacting with ferric ions. Furthermore, it is a weak inhibitor of the Escherichia coli aerobic respiratory chain and shows moderate antibiotic activity. The wide distribution of the cluster and the various properties of the compound indicate a major role of foxicins in Streptomyces strains.
Using various chromatographic methods, a new hexacyclic triterpenoid, 2β,3β,24β-trihydroxy-12,13-cyclotaraxer-l4-en-28oic acid (1), together with ten known compounds, 2α,3α,23-trihydroxyurs-12,20(30)-dien-28oic acid (2), 6,7-dehydroroyleanone (3), horminone (4), 7-O-methylhorminone (5), sugiol (6), demethylcryptojaponol (7), 14-deoxycoleon U (8), 5,6-didehydro-7-hydroxy-taxodone (9), ferruginol (10), and dichroanone (11), were isolated from the roots of Salvia deserta. Their structures were identified on the basis of spectroscopic analysis and comparison with the reported data. The individual compounds (1, 3 - 8) were screened for cytotoxic activity, using the sulforhodamine B bioassay (SRB) method. As the results, Compounds 3, 5, and 8 showed cytotoxic potency against A549, MDA-MB-231, KB, KB-VIN, and MCF7 cell lines with IC values ranging from 6.5 to 10.2 μm.
Noise, bistable system and input signal are the three essential factors in stochastic resonance (SR). The noise-induced SR method, the parameter-tuning SR method, and the twice sampling SR method change the characteristics of the noise, the bistable system and the input signal, respectively. With the new cooperation, they can all produce the SR phenomena when the system exceeds the small-parameter area. If treating the strong noise and the input signal with large frequency, the actions of the system parameters can build the system behavior in an orderly way, associated with the twice sampling frequency. The united parameter-tuning SR method adjusts the system parameters to fit the normalized frequency after the twice sampling SR, in order to make the optimal noise intensity. The application to the flow meter vibration test has presented the practicability and effectiveness of the united parameter-tuning SR method.
As the premise, exploring aero-engine structure parts damage accurately can guarantee safety of the aero-engine structure parts, which are restricted by the working condition under the high temperature, high pressure and high speed. Analyzed the structure parts modal parameters by the modal theory, and researched the facts how to influence the modal parameters based on the different damage extent of the structure parts. Then construct the different damage extent structure models on the structure junctions with the finite element analysis method. At last, constructed and verified seven models with the example of aero-engine turbine structure damage in the constant temperature. The results were shown that the characteristic parameters with the inherent frequency and the inherent frequency deviation square can explore the structure damage accurately, but have no significant influence on the structural damages. So it will be important for us to ensure reliable operation and structure damage identification timely by the proposing the structure damage parameters.
The multiple simultaneous faults diagnosis is not deeply studied so far. The methods for multiple simultaneous faults diagnosis are put forward. According to the characteristics of hydropower unit, the hierarchical faults decoupling methods are discussed in detail. The simulation calculation of the cylinder controlled by valve is taken as an example for decoupling of hierarchical fault .
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