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Hexamethylol melamine resins (HMM) with low crystallization water content and low viscosity were prepared by inhibiting the condensation polymerization of low hexamethylol melamine. The effects of catalyst, pH, formalde-hyde/melamine ratio, reaction temperature and time on the synthesis parameters of HMM were investigated. The results showed that the sample (HMM8) synthesized with Na2CO3-NaHCO3 as catalyst had the crystallization water content lower than 10%, being with a viscosity of about 0.26 Pa·s. The melting temperature of HMM8/polyvinyl alcohol (PVA) curing system was about 164.3 °C. It was found that the higher the amount of formaldehyde, the greater the hydroxyl methyl bounded to each triazine ring. Compared with the traditional melamine formaldehyde resin which had the crystallization water content of about 20–30%, the production of this resin was expected to reduce the energy consumption of industrial reaction, while the resin with 10% crystallization water content was more conducive to the development of alloying HMM/PVA composite membrane.

Traditional granary monitoring system adopts RS-485 and CAN bus or other cable transmission modes, in which there exist problems of wiring complexity, high cost, high failure rate and difficult to maintain, etc. Aiming at these problems, this paper designs a kind of granary temperature and humidity monitoring system based on Zigbee. Grain monitoring network is mainly composed of the Zigbee sensor nodes and the sink node, and the sensor node is composed of CC2430 combined with temperature and humidity sensor SHT11. The sink node is responsible for receiving data from the sensor nodes and then the data will be processed by the CC2430, and is delivered to monitoring center PC through the RS232 serial port, thus realizing the temperature and humidity data acquisition, display and storage. [ABSTRACT FROM AUTHOR]

Trichosanthin is a protein used medicinally in China for abortifacient purposes. It is also an RNA N-glycosidase which inactivates eukaryotic ribosomes by removing adenine 4324 from 28S rRNA. Site-directed mutagenesis was performed to probe the role of Gln156. Glul60 and Glu189 in the active site of trichosanthin. The purified altered proteins were assayed for their potency in inhibiting in vitro protein synthesis. The data indicate Glu160 is involved in the catalytic reaction. Kinetics studies suggest the carboxylate group of Glul60 serves to stabilize tile transition-state complex. Similar to ricin A, the variant [E160A]trichosanthin is more potent titan [E160D]trichosanthin. This is because Glu189 serves as a back-up of the carboxylate group in case Glul60 is mutated to alanine. However. removal of Glu189 in the presence of Glul60 does not effect the ID50, value drastically. An activity of 1800-fold less than that of the wild-type protein was found when both Glul60 and Glu189 were changed to alanine, indicating that some other residues in the active site are also taken part in the lowering of energy barrier for the catalytic reaction. Although Gln156 is highly conserved in related proteins, its mutation to alanine only slightly decreases the activity, showing thai this residue does not participate directly in catalysis. [ABSTRACT FROM AUTHOR]