Determination of low boron concentrations in nutrient solution
To study boron (B) deficiency and toxicity in plants in flowing solution culture, it is necessary to establish a wide range of solution B concentrations. The ability of inductively coupled plasma atomic emisson spectrophotometry (ICPAES) to determine solution B concentrations ranging from 0.15 μM to 925 μM was investigated. The reliablity of B concentration determination in nutrient solutions containing <10 μM B is poor. A technique, involving sorption by a B-specific resin (Amberlite-743), was established to concentrate the B present in low B nutrient solutions and to enable reliable measurement using ICPAES following elution from the resin. Acceptable, reproducible recoveries of B from low B solutions, containing known concentrations of B, were obtained using this technique. The technique enables the imposition, monitoring and maintenance of solution B concentrations well below the direct detection limits of ICPAES and colorimetric procedures. ei]L V Kochian
Boron content in daily meals for preschool children and school youth
Boron content in daily me als for preschool children and school youth was studied in this research. The boron content was measured in the meals taken from Wroclaw preschool and boarding school in December, March, June, and September. The whole meal was homogenized. Four grams of sample were mineralized and analyzed by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Statistical assessment of the results was made with the Statistica v.5.1 program. The recovery was determined by the use of the standard additions method to evaluate the accuracy of the procedure. The mean boron content in 1 kg dry weight of a preschool meal was 2.31 mg B/kg dry wt, and in boarding-school meals, it was 2.15 mg B/kg dry wt. Based on these results, the estimated daily boron intake was calculated. The daily boron intake from food by preschool children was found to be 1.01 mg B/d for children and 1.2 mg B/d for youth. The actual intake of boron from food was determined after having related the quantity of the element to 1 kg of body weight. In the case of children, the mean intake of boron was 0.05 mg B/kg body wt/d, whereas in teenagers, it was 0.016 mg B/kg body wt/d. The results of this research show no significant differences between daily boron intake for preschool children and boarding-school youth.
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.