Trường Đại học An Giang

We calculate collective excitations and damping rate in a double layer structure consisting of one monolayer gapped graphene sheet and a GaAs quantum well isolating two-dimensional electron gas within random-phase approximation at zero temperature. We observed that both in-phase optical and out-of-phase acoustic plasmon mode exist and can be un-damped in the system. The acoustic curve merges to single-particle excitation area boundary and disappear while the OP one crosses this border and continues in the region. Our analytical calculations present that the quantum well width has significant contribution only to acoustic mode in long wavelength limit. On the other hand, numerical results demonstrate that while both quantum well width and exchange–correlation effects decrease AC plasmon frequency, the OP one decreases with the increase in the band gap. Finally, taking into account local-field-correction in calculations leads to the decrease in only AC plasmon frequency, found mainly in large wave-vectors region.

Mathematical communication competence is one of the five core components of mathematical competence that should be developed for students. The development of verbal mathematical communication capacity for students in teaching Mathematics is crucial, because it is in line with the 2018 General Education Program in Mathematics and educational trends in the world. This study proposes a math teaching process with a scientific debate stage to develop students' verbal mathematical communication competence and illustrates this process through teaching problem solving on the topic “Limits of functions” in grade 11. Through the scientific debate stage, students have the opportunity to develop their ability to communicate mathematically orally and help them understand math concepts deeply. Teachers need to focus on developing verbal communication competence in the process of teaching Math to students to help them practice self-confidence, especially critical thinking.

Ralstonia solanacearum là vi khuẩn gây bệnh héo xanh trên 200 loài thực vật thuộc 50 họ khác nhau và được xếp thứ hai trong danh sách các tác nhân gây bệnh nguy hiểm nhất trên cây trồng. Để phòng trị bệnh héo xanh, nông dân thường sử dụng các biện pháp hóa học, tuy nhiên biện pháp này  đã cho thấy những tác động tiêu cực làm ảnh hưởng  đến  môi trường. Thực khuẩn thể ký sinh và ức chế vi khuẩn và sử dụng thực khuẩn thể được xem là biện pháp sinh học tiềm năng trong việc phòng trừ bệnh héo xanh. Nghiên cứu này được thực hiện nhằm phân lập các dòng thực khuẩn thể từ đất trồng cây dược liệu có khả năng ly giải vi khuẩn gây bệnh héo xanh trên cây trồng. Thực khuẩn thể được phân lập từ đất và khảo sát vết tan dựa vào phương pháp agar 2 lớp. Ba mươi lăm dòng thực khuẩn thể có khả năng ức chế vi khuẩn Ralstonia solanacearum đã được phân lập từ mẫu đất trồng cây dược liệu như cây gừng (Zingiber officinale), nghệ (Curcuma longa L.), húng chanh (Coleus aromaticus Benth) và đinh lăng (Polyscias fruticosa L.). Kết quả đánh giá phổ ký chủ của các dòng thực khuẩn thể phân lập cho thấy có 29 dòng thực khuẩn thể tạo vết tan rõ ràng đối với 9 dòng vi khuẩn gây bệnh Ralstonia solanacearum. Đặc biệt 7 dòng thực khuẩn thể ký hiệu ɸG7, ɸG8, ɸDL3, ɸDL6, ɸH6, ɸH23 và ɸH24 có khả năng ly giải vi khuẩn hơn 72 giờ trong điều kiện phòng thí nghiệm.

Phosphorous is one of the essential elements for living-forms on the Earth; however, the excessive presence of phosphate in the environment causes water pollution. Several methods have been developed and applied for phosphate removal in wastewater and adsorption is considered as a low-cost, simple, and stable technology for wastewater with low phosphate concentration. Although several mesoporous materials have been used as adsorbents, there has not been any report on the utilization of rice husk ash as support for iron oxide/hydroxide growth toward phosphate removal. In this study, flower-like iron(III) oxide/hydroxide on activated rice husk ash support (Fe-ARHA) was synthesized and applied as a novel material for phosphate removal in aqueous solution. ARHA was prepared by the chemical corrosion method with HF acid using bottom ash of a brick kiln using rice husk as fuel. Flower-like iron oxide/hydroxide was then grown on the surface of ARHA by precipitation of iron(III) sulfate using urea solution. The materials were then characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy to explore their properties. The mechanism for the formation and growth of flower-like iron oxide/hydroxide on the ARHA surface was proposed. In batch phosphate removal test, Fe-ARHA with Fe/ARHA ratio of 5 : 3 showed the highest adsorption capacity of 37.8 mg/g, which could be due to the interaction between iron oxide/hydroxide and ARHA support. This flower-like morphology and the interaction let more iron oxide/hydroxide surface be exposed to the water environment and effectively serve as adsorption sites for phosphate removal. These results prove the potential for the utilization of waste rice husk ash and iron oxide for water and advanced wastewater treatment applications.

Analytic formulas for one-loop contributions to (g−2)e,µ anomalies and decays amplitudes  are explicitly derived for the 3-3-1 model with inverse seesaw neutrinos (3-3-1ISS). Using these formulas to investigate  defined as the discrepancies of (g−2)e,µ anomalies between the standard and the 3-3-1ISS models, our numerical investigations showed that  can reach the maximal values of around 2.5 10-14 and 1.4 10-14 for normal and inverted order schemes of neutrino oscillation data, respectively. The analytic formulas derived in this work are very useful for estimating dominant contributions to  in new extended versions of the 3-3-1-1ISS model explain successfully the experimental data of (g−2)e,µ.

We consider a double-layer structure consisting of a bilayer graphene sheet and a two-dimensional electron gas, isolated in a very thin GaAs quantum well. The collective excitations are determined from the zeroes of the dynamical dielectric function within the random-phase approximation, taking into account the temperature effects. Numerical calculations present that two plasmon modes exist in the system, similar to those in other double-layer structures. While the optical mode continues in the interband single-particle excitation area, the acoustic mode only crosses the intraband single-particle excitation boundary and disappears. Also, our investigations show that plasmon properties in the system are affected significantly by most of the chosen factors. Plasmon frequency increases as the separation increases while the increase in carrier density decreases noticeably these frequencies. Temperature affects plasmon characters similarly to but more weakly than that does in monolayer grapheme—two-dimensional electron gas double-layer structures. Finally, the temperature can increase the effects of some other parameters on plasmon properties of the system, so this factor should be taken into account in calculations to improve the model for better results.

Analytic formulas for one-loop contributions to (g−2)e,µ anomalies and decays amplitudes  are explicitly derived for the 3-3-1 model with inverse seesaw neutrinos (3-3-1ISS). Using these formulas to investigate  defined as the discrepancies of (g−2)e,µ anomalies between the standard and the 3-3-1ISS models, our numerical investigations showed that  can reach the maximal values of around 2.5 10-14 and 1.4 10-14 for normal and inverted order schemes of neutrino oscillation data, respectively. The analytic formulas derived in this work are very useful for estimating dominant contributions to  in new extended versions of the 3-3-1-1ISS model explain successfully the experimental data of (g−2)e,µ.

Mần ri hoa tím là một loài thực vật có hoa thuộc chi Cleome thuộc họ Cleomaceae. Mần ri cómùi thơm nhẹ, tính ấm, có khả năng giải độc gan. Hoa cúc được sử dụng phổ biến trên thế giớivới mùi thơm rất dễ chịu. Hoa cúc có công dụng bảo vệ tim, tăng cường hệ miễn dịch, làm dịu cácdây thần kinh và điều trị các vấn đề hô hấp. Mần ri rất dễ trồng và rẻ vì thế kết hợp cùng với hoacúc để tăng hương thơm và hài hòa màu sắc. Sự kết hợp giữa mần ri và hoa cúc tạo ra một sảnphẩm trà giải khát có chất lượng, cần thiết và phù hợp với mọi người. Nghiên cứu này được tiếnhành để khảo sát tỷ lệ mần ri và hoa cúc thích hợp để đạt giá trị cảm quan cao và ảnh hưởng củađộ brix và tỷ lệ nước ép chanh đến hàm lượng axit tổng, độ pH và giá trị cảm quan của sản phẩm.Kết quả nghiên cứu cho thấy tỷ lệ tối ưu của mần ri là 15%, hoa cúc là 1,5%, độ brix là 12 và 4%nước ép chanh là sự lựa chọn tối ưu cho sản phẩm.

Amine-SiO2 material (basically on silicon dioxide) was synthesized by the grafting method with triamine silane to form activated amine groups on the surface of SiO2 support and was applied as a novel adsorbent for nitrate removal from aqueous solution. The characterizations of Amine-SiO2 were determined by using TGA, FTIR, BET, SEM. Nitrate adsorption capacity and durability of Amine-SiO2 were compared with the anion exchange resin (Akualite A420 commercial). The results showed that Amine-SiO2 had high nitrate adsorption capacity, ~ 1.14 fold higher than the Akualite A420 ion exchange resin, based on the adsorption efficiency. This might be due to a strong affinity for nitrate ions of the activated amine groups on the surface of SiO2 support. In addition, the experimental results also proved that Amine-SiO2 material had good durability (stable performance after 10 regeneration times).