HPU2 Journal of Science: Natural Sciences and Technology

Hydrothermal synthesis of CdTe quantum dots using ammonia as a reducing agent

Jung Hoon Song — 2024-08-30

Water-soluble CdTe quantum dots (QDs) have been applied in various fields, such as photoluminescent imaging, labeling agents in immune analysis, heavy metal ion sensing, and solar cells. The synthesis of CdTe QDs has relied vastly on reactions between Cd²⁺and Te^2- ions in the presence of mercapto ligands. Te^2- ions are usually formed in situ in the synthetic solution by reducing tellurite ions with hydride salts, such as NaBH₄ which gives rise to the emission of highly explosive hydrogen gas. Herein, we report a novel method to synthesize CdTe QDs by using ammonia as a reducing agent. We demonstrate that under hydrothermal conditions, ammonia can reduce tellurite forming telluride ions which react with cadmium ions in the presence of glutathione forming CdTe QDs. The resultant QDs exhibited high photoluminescence and resolvable absorption. The synthetic method demonstrated herein could reduce the cost of CdTe-based quantum dots for rapid deployment.

Structure, magnetic properties and magnetocaloric effect of \(Fe_{81-x}Cr_{x+4}B_2Zr_{10}Nd_3\) rapidly quenched alloys

Hai-Yen Nguyen — 2024-08-30

This paper presents, we present the structure, magnetic properties, and magnetocaloric effect of the Fe_81-xCr_x₊₄B₂Zr₁₀Nd₃ (x = 0, 1, 2, and 3) alloy ribbons. The alloy ribbons were prepared by using the melt-spinning method. Structural analysis by X-ray diffraction shows that the obtained alloy ribbons are almost amorphous. Curie temperature of the alloy ribbons decreases from 310 to 275 K when x increases from 0 to 3. Under a magnetic field change of 12 kOe, the maximum magnetic entropy change \(|\Delta S_m|_{\text{max}}\) of the Fe₈₀Cr₅B₂Zr₁₀Nd₃alloy ribbon is found to be 1.05 J.kg^-1.K^-1 at 302 K. In addition, the large refrigerant capacity (RC > 80 J∙kg^-1 with \(\Delta H=12\) kOe) at room temperature is obtained in the alloy ribbon. Thus, the alloy ribbons can be considered a potential magnetic refrigerant in the room temperature range.

The decay of SM-like Higgs boson \(h_0^1 \to Z \gamma\) in a G221 model

Thi-Hong Trinh — 2024-08-30

The decay of SM-like Higgs boson \(h_0^1 \to Z \gamma\) in the G221 model which is one of all models beyond the SM (BSM) has been investigated. This decay channel has not been observed experimentally. In the framework, we indicate that new particles predicted by this model may significantly affect the previously mentioned decay channel of the SM-like Higgs boson. We will study the effects of the new heavy-charged boson, the charged Higgs boson was not included previously. We are namely, contributing from the diagram both Higgs boson and charged boson. The calculated results are expressed in terms of Passarino-Veltman functions, the numerical evaluation of which can be obtained using LoopTools. Our numerical investigation presents some details and properties of this decay. These may prove useful for comparison with future experimental results that could be detected.

A note on the existence of solutions to the semi-affine variational inequalities problems

Van-Dong Vu — 2024-08-30

The semi-affine variational inequality problem offers a general and versatile framework applicable to many problems in economics, mathematical physics, operations research, and mathematical programming. One of the important applications of the semi-affine variational inequality problem is quadratic programming. It is well-known that the first-order necessary optimality condition for a constrained optimization problem can be rewritten as a variational inequality. This paper investigates the existence of solutions for the semi-affine variational inequality problem in the finite-dimensional Hilbert spaces. Under suitable conditions, we show that the solution set of the semi-affine variational inequality problem is nonempty. The obtained results contribute to and complement the existing literature.

Right-angled Artin groups and representation liftings

Thi-Tra Nguyen — 2024-08-30

The lifting problems are interesting problems of number theory. There are many mathematicians who study lifting problems with different classes of groups. They prove the lifting problems with different classes of groups using various methods. Recently, right-angled Artin groups have attracted much attention in number theory. They have nice structure and properties. Currently, we study right-angled Artin groups with different problems related to them. One of those problems is that we want to prove the lifting problem is associated with this class of groups. We have obtained a result for this problem. In this paper, we will show that a mod Heisenberg representations of a right-angled Artin group can be lifted to a mod representation.

Study on the adsorption L- and D- proline on MKN-MWCNT-P5000 carbon nanotubes from aqueous solutions

Dinh-Tuan Le — 2024-08-30

Carbon nanotubes (CNTs) are a new type of nano-adsorbent material with unique properties, which are promising adsorbents for the separation of enantiomers. Information regarding the interaction mechanism of enantiomers with carbon nanotubes has not yet been fully explored yet. In this work, we studied the adsorption of L and D-proline on carbon nanotubes in aqueous solution. Adsorption isotherms of enantiomers proline on multi-walled carbon nanotube MKN-MWCNT-P5000 from aqueous solution at 25℃ were constructed. The results of the experiments show that the adsorption capacity of the D-isomer is higher than that of the L-isomer. The separation coefficient of enantiomers on carbon nanotubes is in the range of 1.88–7.92. L-proline was adsorbed on CNTs as zwitterions and clusters of 62 molecules; and D-proline - in the form of zwitterions and clusters of 33 molecules. The results of quantum chemistry show that the adsorption energy of the D-proline monomer on carbon nanotubes is greater than that of the L-isomer. The nature of the bond between enantiomers and nanotubes was Van der Waals force.

A convergence enhancement approach for tomographic reconstruction in ultrasonic tomography

Quang-Huy Tran — 2024-08-30

Ultrasound tomography is a non-invasive imaging technique that seeks to determine the internal distribution of acoustic properties within the body by analyzing measured ultrasound data. Based on the distorted Born iterative method (DBIM), this work suggests employing resolution-jumping and beamforming techniques for tomographic ultrasound imaging. The beamforming technique leverages multiple transmitting elements from the ultrasound probe, operating concurrently, to generate a focused and narrow beam. This targeted approach helps in reducing noise, thus enhancing the quality of the collected data. Meanwhile, resolution-jumping optimizes the imaging process by adjusting the resolution dynamically, thereby improving both the quality and speed of the reconstruction. The benefits of the proposed method are evident in the results of numerical simulations, which demonstrate a substantial improvement in the quality of image recovery. These simulations also highlight a significant reduction in the total runtime required for imaging, showcasing the efficiency of the approach. By combining these advanced methods, the work offers a promising pathway toward more accurate and faster tomographic ultrasound imaging, which could lead to better diagnostic capabilities in medical applications.

Viscosity solutions of the augmented K -Hessian equations in exterior domains

Trong-Tien Phan — 2024-08-30

This paper examines the Dirichlet problem for augmented k -Hessian equations in exterior domains. Building upon our previous results on the viscosity solutions to the Dirichlet problems for augmented k -Hessian equations in the bounded domain, and L. Dai, J. Bao's method to the k -Hessian equations in exterior domains, a sufficient condition for the existence and uniqueness of viscosity solutions to the Dirichlet problem for the augmented k -Hessian equations in exterior domains have been proven. During the process, a slight adjustment to the result on the existence and uniqueness of viscosity solutions to the problem in the bounded domains has been made for use in the present situation.

Essential oil of the leaves of Cinnamomum subpenninervium Kosterm. ex H. H. Pham and its antimicrobial activity

Quang-Huan Duong — 2024-08-30

The current study first describes the chemical composition of the leaf essential oil of Cinnamomum subpenninervium Kosterm. ex H.H. Pham collected from Nghe An province, Central Vietnam. By the GC-FID/MS (gas chromatography-flame ionization detection/mass spectrophotometry) analysis, more than thirty compounds were identified, representing 99.92%. The obtained essential oil from the fresh leaves was dominated by non-terpenic compounds (57.07%), monoterpene hydrocarbons (23.03%) and oxygenated monoterpenes (13.34%), as well as E-cinnamaldehyde (38.56%), linalool (12.20%), benzyl benzoate (11.33%), and α-pinene (8.12%). C. subpenninervium showed strong antimicrobial activity against the fungus Fusarium oxysporum ATCC 46591 with the MIC (minimum inhibitory concentration) value of 64 µg/mL.

A non-existence result for higher-order Hardy-Hénon inequality on punctured balls

Thi-Ngoan Tran — 2024-08-30

Let n and m be two positive integers such that \(n>2m\ge 4\). Let and be real such that \(\sigma<-2m\) and p > 1 . In this note, we are mainly concerned with non-negative and classical solutions of the high-order harmonic inequality \[(-\Delta)^{m} u \geq |x|^{\sigma} u^{p} ,\]

on the punctured ball \(B_R\setminus\{0\}\subset R^n\). Using the method of test functions, the Hölder's inequality, and integral estimates, we will prove that this inequality has no \(C^{2m}\) positive solution satisfying some sufficient conditions. It should be mentioned that our result, see Theorem 1.1 in the next section, in the high-order setting is analogous to that of Laptev for the case \(m=2\).