VNUHCM Journal of Science and Technology Development 2022-08-31T03:11:27+00:00 Phuc Van Pham Open Journal Systems Combination of NAA and TXRF: an improved method to detect elements in the moss technique 2022-08-31T02:48:14+00:00 Son An Nguyen Khiem Hong Le Sang Thi Minh Nguyen <p><strong>Introduction</strong>: Due to industrial development, agriculture, and urbanization, environmental pollution is a serious problem worldwide. In particular, air pollution is becoming increasingly serious. To evaluate the impact of air pollution in major cities of the country, various methods of air collection and treatment and assessment through monitoring stations are being developed. However, the main disadvantage of the installation of monitoring stations is the cost of investment for operations, maintenance, and equipment. In this study, to reduce costs, Babular Indica moss was chosen as a biological indicator. Two techniques, NAA and TXRF, were combined to increase the number of trace elements detected in moss samples.</p> <p><strong>Methods</strong>: A combination of two multielement analysis techniques, NAA and TXRF, are used to detect trace elements from atmospheric deposition in Barbula indica moss collected in Bao Loc, Vietnam.</p> <p><strong>Results</strong>: The two methods are highly complementary, allowing us to determine 42 elemental concentrations in 11 moss samples. Twenty-nine elements were identified with NAA: Na, Mg, Cl, K, Sc, V, Cr, Mn, Fe, Co, Zn, As, Se, Br, Rb, Sb, I, Cs, La, Ce, Sm, Eu, Tb, Dy, Yb, Hf, Ta, Th and U. Twenty-four elements were identified with TXRF: Al, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Rb, Sr, Y, Ag, Sn, Sb, Ba and Pb. Eleven elements were identified by both techniques.</p> <p><strong>Conclusion</strong>: This study shows that NAA and TXRF combine efficiently and provide a more comprehensive detection of trace elements in moss samples than is possible with either technique alone.</p> 2022-08-31T00:00:00+00:00 ##submission.copyrightStatement## Decay of charged leptons l_i→l_j γ in the 3-3-1 model with neutral leptons 2022-08-31T02:58:31+00:00 Ha Thanh Hung Vuong Minh Nguyen Huan Phuc Hoang <p>The 3-3-1 model with neutral leptons exists a source of lepton -flavor-violating (LFV) due to oscillations of active neutrinos and the mixing of exotic leptons. The investigation of component contributions for l<sub>i</sub>&nbsp;-&gt;&nbsp;l<sub>j</sub>&nbsp;\gamma&nbsp; helps to select the parameter space regions which suitable with the current experimental data. We show that, in the parameter space regions where Br(\mu -&gt; e\gamma)&nbsp; &nbsp;satisfies the experimental limits,&nbsp;&nbsp;Br(\tau -&gt; e\gamma)&nbsp;and &nbsp;Br(\tau -&gt; \mu\gamma) are also smaller than the upper bound of the experimental data.&nbsp;</p> 2022-08-31T00:00:00+00:00 ##submission.copyrightStatement## Application of Antioxidant in BOPP book cover recycling 2022-08-31T03:11:27+00:00 Cuong Ngoc Hoang Nguyet Thi Hoa Xuan Le <p>BOPP (biaxial oriented polypropylene) thin films are commonly used as book covers at schools in Vietnam. At the end of every academic year, a large quantity of BOPP book covers become waste. Therefore, the selective collection and recycling of this material are necessary. The plastic material was separated from paper directly by students from the school, and then it was shredded into small pieces and extruded into pellets with and without antioxidants. The composition of the commercial antioxidant was confirmed by FTIR analysis as a blend of 1:2 by weight of Irganox1010/Irgafos 168. The melt index test showed that after thermal aging of recycled PP pellets at 200 ◦C, they were strongly degraded. However, the addition of antioxidants to the recycled PP samples effectively protected them from degradation. The melt viscosity of recycled PP followed by a mini twin screw extruder also confirmed the protective role of the antioxidant. The larger the quantity of antioxidant used, the more stable the torque or melt viscosity of PP became. The optimal usage of 1% Irganox B 215 can protect PP from further degradation.</p> 2022-08-31T00:00:00+00:00 ##submission.copyrightStatement##