Tạp chí Khoa học Trường Đại học Sư phạm Hà Nội 2: Chuyên san Khoa học Tự nhiên và Công nghệ

On the second Hilbert coefficients and Cohen-Macaulay rings

2024-04-09T11:19:30+07:00

In this paper, we investigate the relationship between second Hilbert coeficients and the index of reducibility of parameter ideals. We give some characterazations of Cohen-Macaulay rings via the above invariants.

Criteria for finite-time stability of singular large-scale discrete-time delay systems

2024-04-10T11:59:29+07:00

This paper concerns a problem of finite-time stability for a class of linear singular large-scale systems with delays. Based on matrix transformations, Lyapunov function method combined with new estimation techniques, we derive sufficient conditions for solving the finite-time stability of the system. A numerical example is given to illustrate the validity and effectiveness of the theoretical results.

The photothermal effect of gold nanoparticles prepared by electrochemical method at different voltages

2024-04-10T12:04:21+07:00

This paper was performed to evaluate the photothermal effect of pure gold nanoparticles (Au NPs) prepared by electrochemical method at different voltages, under laser irradiation in the safe wavelength range. The formation, morphological, and structural properties of Au NPs were analyzed by UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The stability and dispersion of Au NPs were investigated by dynamic light scattering (DLS) and Zeta potential measurements. The photothermal effect was evaluated by the temperature change of the sample under the green laser irradiated at a wavelength of 532 nm. The results showed the formation of the Au NPs has a spherical shape and high purity; the particle size distribution is in the range of 10 - 40 nm depending on the synthesis voltage, and the absorption peak is in the range of 530 to 556 nm. The temperature of the Au NPs solution increased by 1.3 to 6 ^oC, compared to that of bi-distilled water under the same conditions of laser irradiation. This paper shows the photothermal effect of Au NPs prepared by the electrochemical method at different voltages, it changed markedly when irradiated with a green laser in the safe wavelength range.

Propagation of a U16 hybid Eucalyptus line by plant cell tissue culture

2024-04-10T12:07:47+07:00

Eucalyptus is one of the important plant species for paper pulp, fuel wood, and timber. In this study, a hybrid Eucalyptus, U16 line, was investigated for rapid in vitro propagation. The apical and adventitious shoots served as initial explants. These were free-disease symptoms that were collected for surface sterilization. Different disinfectants including mercuric and Javel solutions at different concentrations and treated times were performed. The results showed that explants were cleaned under taping water with soap, rinsed in 70^oEtOH for 1 minute, and then immersed in 10% Javen solution for 15 minutes and 0.1% HgCl₂ for 10 minutes gave the highest disinfection rate that was 46.5%. The modified MS medium included basal MS, 30 g/L sucrose, and 7 g/L agar supplemented with 20 ml/L of coconut water (MS medium*) was the most suitable for the rapid multiplication of Eucalyptus lines U16, the shoot multiplication coefficient reached 1.56. In vitro multiplication of eucalyptus U16 was carried out by culturing disinfected shoot segments on the MS* medium supplemented with BAP 1.5 mg/L and kinetin 1.0 mg/L which gave the highest shoot multiplication coefficient (3.24 shoot per explant). The in vitro rooting medium of the U16 line was basal MS supplemented with 1.0 mg NAA/L, the rooting rate was 90.49%, the number of roots was 8.3, and the roots expressed strong growth.

Chemical components and anti-acetylcholinesterase activity of Piper lolot leaves oil

2024-04-10T12:10:56+07:00

Essential oil of Piper lolot leaves in Quang Nam-Da Nang do obtain via the steam distillation method with oil collection efficiency reaching 0.68%. The chemical components of the essential oil from Piper lolot leaves in Quang Nam-Da Nang are determined via the GC-MS method that includes 20 compositions (99.97%), among which the main compositions are myristicin (72.70%), asarone (5.16%), β-bisabolene (3.59%), γ-asarone (3.52%), caryophyllene (2.63%), and α-copaene (1.93%). The essential oil of Piper lolot leaves in Quang Nam-Da Nang also showed potent anti-acetylcholinesterase activity with IC₅₀ (µg/mL) = 28.72±2.80 compared to galantamine (a positive control) and essential oils, extract from Piper species.

Decay of charged Higgs boson in the 3-3-1 model with neutral leptons

2024-04-10T12:14:11+07:00

In the model 3-3-1 with neutral leptons, we used the condition imposed on the Higgs potential to derive mass spectra and physics states of neutral and charged Higgs bosons related to . We also calculate all couplings and give Feynman diagrams. Most importantly, we give analytical results for the contributing components and the total amplitude of .

Green synthesis of UV absorber (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol by microwave method

2024-04-10T12:19:22+07:00

In this work, a UV absorber compound (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol was synthesized by microwave method using a two steps protocol. In the first step, α-(4-hydroxyphenylimino)-o-cresol (1) was synthesized from 4-aminophenol and salicylaldehyde by circulating under microwave heating at 60 ^oC for 8 minutes, the reaction yield reached 82.91 %. In the second step (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol (2) was synthesized from precursor (1) and benzyl bromide by circulating under microwave heating at 80 ^oC for 3 minutes, the reaction yield reached 25.08 %. The overall yield for the synthesis of UV absorber 2 was 20.79 %. The molecular structures of precursor (1) and product (2) were analysed by high performance liquid chromatography - mass spectrometry (LC/MS) and nuclear magnetic resonance (NMR) methods. The UV absorbance of precursor (1) and product (2) was investigated by UV absorption spectrometry. The obtained results show that product (2) has a higher UV absorption intensity than precursor (1), the UV absorption region extends from 240 nm to 390 nm, the maximum absorption peak is at the wavelength (λ_max) of 350 nm. The UV absorber (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol with cyclic structure, low molecular weight, and high UV absorbance has potential application as an UV absorber for greenhouse covering plastic, paint and ink systems.

The roles of intermediate fluorophores on the optical properties of bottom-up synthesized carbon nanodots

2024-04-10T12:24:25+07:00

Carbon nanodots (CNDs) are the latest nano-sized carbon materials having unique properties such as biocompatible, highly photoluminescent, and nontoxic which are suitable for diverse applications including lighting, sensing, bioimaging, and biochemical analyzing. CNDs could be synthesized by top-down methods in which graphite is fragmented into nano-sized graphene dots. Alternatively, CNDs could be formed by a bottom-up synthetic strategy where organic molecules are fused together via complex condensation and carbonization processes. Although a great number of organic molecules have been used successfully to prepare CNDs there are very few CNDs that exhibit the quantum size effects. The absorption and emission properties of bottom-up synthesized CNDs rely vastly on molecular-like fluorophores which are the intermediates formed during the fusion of molecular precursors and are incorporated into CNDs in the later states of carbonization processes. This review aims to demonstrate recent understandings on the formation of intermediate fluorophores and their contribution to the optical properties of CNDs.