The influence of physical-chemical characteristics of surface modified copper nanoparticles on E. coli cell population growth suppression and on electrostatic properties of their membranes
The biological activity of copper nanoparticles, able to suppress growth of E. coli cells population under contact interactions, was explored. Three types of samples with oxide layers of various sizes, thickness and composition were used in experiments. It was found out, that an increase in electron density on the external membrane of E. coli correlated with copper nanoparticles suppression capability and with lower activation energy of electron transfer on bacteria. The analysis of experimental data helps to correct conditions for obtaining nanoparticles with certain properties of their surface oxide layers. The character of temperature dependence of electron density reveals the electron type of conductivity in contact area of E. coli and nano-particles. These results help to find approach to understanding the nature of toxic influence of copper nano-particles on E. coli cells under contact interaction.
Changes in the electric characteristics of the inner surface of Escherichia coli cytoplasmic membrane after the binding of microdoses of copper to its outer surface
The electric characteristics of the surface structures of intact Escherichia coli spheroplasts and the spheroplasts with the outer membrane modified by microdoses of copper were studied by electron spin resonance using the positively charged spin probes of KATn type and the newly synthesized KAT15. The experimental results were analyzed using the Gouy-Chapman formalism. It was found that microdoses of copper ions bound to the outer surface of the cytoplasmic membrane influenced the charge density on the inner surface of the membrane.
Study on urea-modified phenol formaldehyde resin adhesive
A reasonable technology to synthesize Urea-Modified Phenol Formaldehyde resins is realized by reacting phenol,urea and formaldehyde.The resin's feasibility is explored.The experiment result of shows that storable stability of the modified resin is good.The curing temperature of PUF resins was 25 ℃,lower than that of PF resins.The curing speed of PUF resins is faster than that of PF resins at the same curing temperature.The physical properties of the birch plywood bonded with PUF resins is similar to that of the birch plywood bonded with normal PF resins.The mechanical properties of the birch plywood bonded with PUF resins can achieve the demands of GB/T9846-1988.Free formaldehyde content of plywood is lower than the E1 level set by GB18580-2001.The cost of the adhesive is lowered for the use of urea,and its comprehensive properties is better than that of PF resins.