RESUMO
Bubbling carbonation is the most widely used method for production of CaCO3. A structure-controllable preparation of calcium carbonate with homogeneous crystallinity and narrow particle size distribution is generally required. In this work, a gas distributor is designed and fabricated by light-curing three-dimensional (3D) printing technology to optimize the pore size and distribution of the distributor. The printed gas distributor is combined with a home-made glass vessel to form a simple carbonation reactor without the need for stirring. With the optimized gas flow rate and concentration of Ca(OH)2, this reactor produces small-sized bubbles continuously and uniformly. A homogeneous bubble flow regime can be thus easily formed with the printed distributor, which leads to an enhanced production of calcium carbonate at room temperature with a uniform morphology and narrow particle size distribution. The time required for carbonization is significantly reduced as well. The present study extends the 3D printing to the construction of bubbling reactors with broad applications beyond production of CaCO3.
RESUMO
OBJECTIVE: To survey nonsymptomatic HBsAg carriers in the Uighur and Han populations in Khotan Area of Xinjiang Autonomous region. METHOD: HBsAg was detected using colloidal gold-labeled double antibody sandwich method. RESULTS: These investigations included 2 597 subjects consisting of 2 022 Uighur and 575 Han subjects. The total HBsAg carrier rate in the Uighur population was 1.48% (30/2 022), specifically 1.078% in male and 1.59% in female subjects. No significant differences were observed in the age between male and female HBsAg carriers, who had an average age of 35 years. In the Han population, the total HBsAg carrier rate was 6.09% (30/575), and was 5.6% in male and 4.4% in female subjects. The average age of the male carriers was 36.3 years and 27.6 years in the female carriers, which showed significant difference in respect to HBsAg carrier rate. The HBsAg carrier rate showed significant difference between Uighur and Han populations in Khotan Area (P<0.01). CONCLUSIONS: The HBsAg carrier rate in Uighur population in Khotan Area is consistent with that in areas with low HBV infection, whereas the Han population exhibit features similar to those in areas with moderately HBV prevalence in the inland regions. The low HBsAg carrier rate in Uighurs might be attributed to the their customs in diet, eating habit, local living environment and the difference in HLA gene distribution. The authors suppose that such antigens as HLA-Bw41 might be protective against HBV infection.
