bluuebunny/crossref_metadata_2025 huggingface dataset:
Screening of several oxides used as efficient electrocatalysists for detection of 2,4‐dimethyl phenol in aqueous medium
Authors: Nhung Vu Thi Hong , Manh Nguyen Ba , Thu Vu Thi , Yen Pham Thi Hai , Giang Le Ha , Phong Pham Hong , Tuan Vu Anh , Ha Vu Thi Thu
Published: March 2024

A paste electrochemical sensor, based on a carbon paste electrode modified with different oxides, has been developed for investigation of 2,4‐dimethylphenol (2,4 DMP) oxidation in phosphate buffer solution (PBS) with pH of 7. In this study, Fe2O3, Al2O3, ZrO2 and SiO2 have been tested. Among these oxides, Al2O3 showed the best electrocatalysis on oxidation of 2,4 DMP at ratio of graphite powder/Al2O3/paraffin oil = 71/4/25. The high sensibility of Al2O3 for 2,4 DMP detection can be explained by the interaction between benzene rings of phenol and acid sites of Al2O3. From this result it opens a high potential application of sensors based on the electro acidic catalysts.
Sweet switching: Development of photoswitchable glycoconjugates ‐ Mini‐Review
Authors: Maisonneuve Stéphane , Lin Chaoqi , Xie Juan
Published: March 2024

Photochromism, a reversible photo‐induced transformation of a molecule between two isomers having distinguishably different absorption spectra, has found increasing applications in materials science, chemistry, biology and pharmacology. In this review, we summarize our recent efforts on the development of photoswitchable carbohydrates and their conjugates. Synthesis, photophysical properties and potential applications of azobenzene‐functionalized glycomacrolactones and glycolipids, as well as multichromophoric sugar bearing diarylethene photochrome and dicyanomethylene‐4H‐pyran fluorophore will be discussed and compared.
Norlignans from the aerial parts of Pouzolzia sanguinea
Authors: Nhung Le Thi Hong , Hoang Nguyen Huy , Tai Bui Huu , Nhiem Nguyen Xuan , Van Kiem Phan
Published: March 2024

Five norlignans, gnetifolin F (1), pouzolignan F (2), pouzolignan G (3), pouzolignan H (4), and pouzolignan L (5) were isolated from the aerial parts of Pouzolzia sanguinea leaves. Their chemical structures were determined using NMR spectra and in comparison with the reported literature. Compound 1 was reported from Pouzolzia genus for the first time.
Effect of epoxydized carbon nanotube master batch on polypropylene film properties
Authors: Van Khoi Nguyen , Thang Trang Vu , Phuong Hoang Thi
Published: March 2024

First, the surface of carbon nanotubes (CNTs) was modified by epoxidation reaction to create epoxidized CNTs (O<CNTs). Following step, master batches of O<CNTs (MB‐O<CNTs) with different O<CNTs contents (5‐12 wt%) were prepared by melt mixing in the presence of anhydride grafted polypropylene (PPgMAH). The CNTs content dispersed uniformly in master batch is 7 wt%. Finally, the effect of MB‐O<CNTs contents on some properties of polypropylene film (PP film) was studied. The PP film samples with different MB‐O<CNTs content (such that the O<CNTs content in the film varies from 0‐1.0 wt%) were prepared on film blowing extruder. The effects of O<CNTs contents on the mechanical, thermal and electrical properties of PP film samples were investigated. The study found that tensile strength of PP films increased significantly with increasing O<CNTs content while elongation at break decreased. In addition, the presence of O<CNTs slightly increased the degree of crystallization and crystallization temperature of PP films while the melting behavior did not change much. From FE‐SEM analysis, the good dispersion of O<CNTs in the PP films was obtained from PP films with O<CNTs content in the range of 0.2‐0.8 wt%. The presence of O<CNTs also changed the electrical properties of PP. The PP films were achieved the antistatic effect at O<CNTs content in the range of 0.2‐0.4 wt%. In addition, the results showed that the master batch processing helps O<CNTs to disperse more evenly in the PP film.
Investigation of acute toxicity of composite Cu2O NPs/Diatomite on white mice
Authors: Nga Dinh Thi , Nhung Dang Thi Thuy , Ngoc Tran Thi Thanh , Tuan Phan Dinh , Hien Nguyen Quoc
Published: March 2024

Cu2O NPs/diatomite is a composite material synthesized by chemical reduction method of Cu2+ ion adsorbed on diatomite. Cu2O NPs/diatomite is capable of adsorption of pollutants and microbial treatment, for aquaculture water treatment applications. The study focused on the acute toxicity determination of Cu2O NPs/diatomite material on Swiss white mice by oral tests. The results showed that Cu2O NPs/diatomite was almost non‐toxic with a test dose of 2,000 mg/kg of mice body weight, LD50 could not be determined. Monitoring the mice's activity after 14 days, the mice have normal activities, normal stool, urine, pink mucosa, smooth feather, good reflexes. Thus, with the very low acute toxicity on white mice, Cu2O NPs/diatomite was evaluated a good candidate for aquaculture treatment application.
Study on the interaction of K[PtCl3(L)] (L: safrole, methyleugenol, isopropyl eugenoxyacetate and piperidine)] with some heterocyclic bidentate amines
Authors: Chi Nguyen Thi Thanh
Published: March 2024

The interactions between K[PtCl3(L)] (L: safrole/1a, methyleugenol/1b, isopropyl eugenoxyacetate/1c, piperidine/1d) and heterocyclic bidentate amines (1,10‐phenalthroline/Phen, 2,2’‐bipyridine/Bpy, 4,4’‐dimethyl‐2,2’‐bipyridine/MeBpy, and 8‐aminoquinoline/NH2Q) were investigated for the first time. The results show that the amines readily replace the L ligand, the arylolefin or piperidine, to form complexes of the formula cis‐[PtCl2(amine)] (amine: Phen/2, Bpy/3, MeBpy/4 and NH2Q/5) in very high yields (90‐95 %). The structures of 2‐5 were analyzed by Pt percentage, IR spectroscopy, and also by ESI‐MS, 1H NMR spectroscopy for 5. The result of testing in vitro cytotoxicity of complex 5 against Hep G2, RD, MCF‐7 and Fl human cancer cell lines indicates that complex 5 exhibits greater activity against RD cell line in comparison to cisplatin with IC50 value of 6.96 μg/ml.
The promotion effect of iron to Cu/ZSM‐5 catalyst for NOx removal by NH3‐SCR
Authors: Doan Tuan , Dang Anh , Nguyen Dat , Tran The , Vuong Thanh Huyen , Le Minh Thang , Pham Thanh Huyen
Published: March 2024

The Cu/ZSM‐5 and Cu‐Fe/ZSM‐5 catalysts (ZSM‐5 with Si:Al ratio of 25:1) were created utilizing the liquid ion‐exchange technique. The effects of Fe on the physical and chemical characteristics of Cu/ZSM‐5 catalysts were investigated using X‐ray diffraction, field‐emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, nitrogen adsorption/desorption, and temperature‐programmed ammonia desorption. The coordination and valence state of copper and iron elements at intersections or in channels of ZSM‐5 was determined by the electron paramagnetic resonance technique. The effects of metal doping on the structure and catalytic activity of all catalysts were comprehensively investigated for NOx removal utilizing selective catalytic reduction with ammonia (NH3‐SCR). The results indicated that the promotion of iron significantly increased the NOx conversion and N2 selectivity of the Cu/ZSM‐5 catalyst for NH3‐SCR in the temperature range from 200 to 600 °C, and catalysts were highly resistant to high space velocity. This article describes a simple and uncomplicated method for synthesizing the commercially viable catalyst used in NH3‐SCR technology to reduce NOx emissions.
Study on some characteristics of fish scale collagen modified by UV irradiation
Authors: Dan Pham The , Hoang Thai , Chinh Nguyen Thuy , My Do Thi , Thang Dam Xuan , Trung Vu Quoc
Published: March 2024

Collagen is a structural protein composed of three α‐chains wound together in a tight triple helix, occurring abundantly in the skin and connective tissues of mammals, as well as other clades of the animal kingdom. Many studies have demonstrated that collagen has good biocompatibility and contains essential amino acids of great value to the medical and pharmaceutical industry. In this study, collagen was extracted from common carp (Cyprinus carpio) scales and physically modified by UV irradiation. Methods of IR, HPLC and FESEM analysis were used for determination of functional group, chemical composition and morphological changes of modified collagen samples. The denaturation temperature of collagen samples was determined based on the change in relative viscosity of collagen solution as increasing temperature from 10 oC to 50 oC. Finally, hemostatic activity of the modified collagen samples was assessed in vitro. The obtained results showed that UV‐treatment of collagen led to significant changes in its properties. After UV treatment, the thermal stability and hemostatic ability of modified collagen samples was improved. Overall, total irradiation duration of 3.6s to 6s was adequate, and produced collagen samples with improved thermal stability and hemostatic activity.
Prediction of tensile strength of combine aged natural rubber/chloroprene rubber (NR/CR) blends using experimental statistical model
Authors: Hung Dang Viet , Quang Nguyen Trong , Tung Nguyen Huy , Linh Nguyen Pham Duy , Hai Pham Hong , Chuong Bui
Published: March 2024

For prediction of tensile strength of combine aged NR/CR blends, samples with NR/CR ratios of 100/0, 95/5 and 90/10 were subjected heat aging at various temperatures, namely 100, 110 and 120°C, each for 22 h, followed by dynamic tensile loadings to 140 % and frequency 300 cycles/min. Then the tensile strengths of aged samples were defined. Based on obtained experimentally values the experimental statistical model was built using FORTRAN language. The model result in prediction equation for tensile strength of NR and NR/CR blends with low CR (not higher 10 %) contents. This equation seems to have fine usability, having relative error between calculated and experimentally defined values of tensile strength less than 10 % in the considered range of experiments.
Theoretical study on inhibitability of some natural alkaloids against influenza virus hemagglutinin and SARS‐CoV‐2 main protease
Authors: Bui Thanh Q. , Hai Nguyen Thi Thanh , Van Chen Tran , Quy Phan Tu , Du Ly Nguyen Hai , Cuong To Dao , Triet Nguyen Thanh , Thuy Nguyen Thi Thu , Nhung Nguyen Thi Ai
Published: March 2024

Berberine (V1), lycorine (V2), hemanthamine (V3), aloperin (V4), dendrobine (V5) possess structural frameworks resembling known anti‐influenza and anti‐SARS‐CoV‐2 drugs, thus subjected for a computational screening. Their quantum properties were examined using density functional theory (DFT); the ligand‐protein inhibitability was evaluated using molecular docking simulation; physicochemical properties were obtained from QSARIS‐based analysis in reference to Lipinski's rule of five; pharmacokinetic parameters were assessed by ADMET‐based analysis. DFT calculations indicate that there are no abnormal bonding constraints observed; NBO analysis suggests all possessing favorable electric configurations for intermolecular inhibition. Regarding ligand‐2VIU, the order for static inhibitability is V3‐2VIU > V2‐2VIU > V1‐2VIU > V5‐2VIU > V4‐2VIU; Regarding ligand‐6LU7, the corresponding order follows: V2‐6LU7 > V3‐6LU7 > V1‐6LU7 > V5‐6LU7 > V4‐6LU7. An exceptional hydrophilic bonding (π‐cation) with the associated Gibbs free energy of ‐10.9 kcal.mol‐1 is detected in inhibitory complex V1‐2VIU. QSARIS‐based analysis reveals that all the candidates are highly bio‐compatible. ADMET‐based analysis specifies V2 and V3 as being safe and suitable for the use as orally administrated drugs. The results encourage further investigations for more in‐depth mechanisms and experimental validations, such as molecular dynamics simulation and in vitro enzyme assays.
Silver nanoparticles decorated a hybrid of PANI/MoS2 and PANI/WO3 as potential catalysts for direct photoelectrochemical oxidation of glucose
Authors: Thu Nguyen Minh , Van Tuan Dinh , Ngan Dang Thi Thuy , Nam Pham Hong , Van Quynh Nguyen
Published: March 2024

This paper presents an effective electrodeposition method for generating hybrid material based on polyaniline (PANI), n‐type semiconductor (MoS2/WO3), and silver nanoparticle (AgNPs) which can trigger direct oxidation glucose in solution without an enzyme catalyst. To do so, the working electrode surface is firstly electrochemically modified by the PANI layers decorated with MoS2 and/or WO3, then electrodeposition of AgNPs on the as‐prepared electrode is carried out subsequently. The addition of WO3 and/or MoS2 and AgNPs to PANI matrix improves interfacial charge transfer efficiency. Especially, under light irradiation, the synergistic effect of n‐type semiconductor and AgNPs into the PANI matrix prompted its higher electrocatalytic activity which is exploited for direct oxidation of glucose in solution without the presence of any enzyme. This strategical approach reveals a promising manner for generating non‐enzymatic glucose electrochemical sensors upon laser excitation.
UV‐curing of coatings based on black seed oil modified epoxy resin
Authors: Hien Le Xuan , Thanh Do Minh , Duc Nguyen Minh
Published: March 2024

UV‐curing of the coatings based on epoxy resin modified by black seed oil (EBSO); 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexane carboxylate ‐ a biscycloaliphatic diepoxide (BCDE) and photoinitiator triarylsulfonium hexafluoroantimonate salts (TAS) with various EBSO/BCDE weight ratios have been investigated. The variation of TAS and functional groups in the coatings like epoxy, hydroxyl, ether during the curing was followed by IR‐spectrometric analysis. The performance of the cured coatings has been determined. It was showed that increase of the EBSO/BCDE weight ratio from 20/80 to 80/20 led to changes both photocrosslinking and properties of investigated coatings: Consumption of total epoxy groups from 4.62 to 0.77 mole/kg, gel fraction from 76.9 % to 73.25 %, swelling degree from 235 % to 559 %, relative hardness from 0.84 to 0.16, flexibility from 10 to 1 mm, impact resistance from 5 to 60 kG.cm while gloss at 60o remained to be 100 % after 1.2s of UV‐ exposure.
DPPH radical scavenging of G&A‐MI Maillard intermediates (alpha‐D‐Glucopyranose/alpha‐L‐Alanine) improved by ZSM‐5
Authors: Long Huang , Jing Zhang , Man Xiong , Xuan Bie , Yawei Dong , Ben Wang , Yikun Chen , Ronghua Huang
Published: March 2024

This paper prepared alpha‐D‐glucopryanose/alpha‐L‐Alanine Maillard intermediates in acid or basic catalyst (labelled as G&A‐MIa and G&A‐MIb) with different molecular weights. ZSM‐5 greatly affected their pyrolysis behaviors. After ZSM‐5 added, the endothermal or mass loss peaks for both G&A‐MIa and G&A‐MIb decreased to lower temperature with different extents. For an instance, endothermal peaks of G&A‐MIb‐2000 at 647°C decreased to 614°C, and its mass loss peak at 167.3°C decreased to 147.0°C. Their pyrolysis under N2 atmosphere or 90%N2 + 10%O2 presented that additional of ZSM‐5 obviously enhanced the generation of volatiles, especially 4H‐Pyran‐4‐one, 2,3‐dihydr o‐3,5‐dihydroxy‐6‐methyl (PODDM). We assigned the ZSM‐5 influence to its sensitivity on C‐N and C‐O bonds among MIs. DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) radical scavenging by volatile absorption solution confirmed that ZSM‐5 obviously improved the antioxidant activity. This would be good news because application of ceramic cookers contains similar components to ZSM‐5.
Low‐lying states of FeSin−/0/+ (n = 1‐2) clusters from DMRG‐CASPT2 calculations
Authors: Van Tan Tran , Tri Tran Quoc , Cang Phan Trung , Hanh Nguyen Thi Hong , Linh Ho Sy , Tan Nguyen Phu , Hendrickx Marc F.A.
Published: March 2024

The electronic states of FeSin−/0/+ (n = 1‐2) clusters have been investigated with DFT, CASPT2, and DMRG‐CASPT2 methods. By using relatively large active spaces, the DMRG‐CASPT2 method is found to provide highly accurate relative energies for the various relevant electronic states. Leading configurations, bond distances, harmonic vibrational frequencies, and relative energies for the low‐lying states of the title clusters are reported. Electron detachment energies for the ground states of the anionic and neutral clusters were estimated at the DMRG‐CASPT2 level. Franck‐Condon factor simulations were performed for transitions from the anionic ground state to the neutral ground state and from the neutral ground state to the cationic ground state with the purpose to produce the vibrational progressions.
Predicting composition of combustion products of the pyrotechnic based on Magnesium‐Teflon‐Viton
Authors: Son Nguyen Nam , Sang Dam Quang , Van Tinh Nguyen
Published: March 2024

Determining the equilibrium composition of combustion products is important in studying high‐energetic materials such as explosives, propellants, and pyrotechnics. This paper presents a theoretical method and computer program named CAL to predict the composition of combustion products of pyrotechnic mixture based on Magnesium‐Teflon‐Viton by the Gibbs free energy minimization principle. Computer program CAL was developed using the fmincon tool in MATLAB. The reliability of CAL was confirmed when comparing its calculation results with ones obtained by other software and experimental data.
Evaluation of the effect of the chitosan/carrageenan ratio on lovastatin release from chitosan/carrageenan based biomaterials
Authors: Hung Ha Manh , Manh Vu Quoc , Thao Vu Thi Thu , Thuy Dao Thi Phuong , Dung Pham Tien , Viet Nguyen Thi Bich , Linh Duong Khanh , Linh Nguyen Ngoc , Oanh Doan Thi Yen , Chinh Nguyen Thuy , Hoang Thai , Trung Vu Quoc
Published: March 2024

The chitosan/carrageenan/lovastatin biomaterials were prepared using a solution technique with 5 % lovastatin and a variable chitosan/carrageenan mass ratio. Fourier transform infrared spectroscopy (FT‐IR) and field emission scanning electron microscopy (FESEM) images revealed that the complex's components were well dispersed into each other without changing the chemical structure, forming dipole interactions and hydrogen bonds among them. The abilities to release Lovastatin (Lov) in pH 2 and pH 7.4 solutions, corresponding to the environments in stomach and intestinal fluids, respectively, are both affected by the ratio of polymer components. The best results were obtained with the chitosan/carrageenan/lovastatin (w/w/%w = 10/90/5%) (CsCL195) biomaterial sample in which the particles are evenly dispersed. While the drug release process was poor in the pH 2 solution (gastric juice), a good release observed in the pH 7.4 solution (intestinal fluid) allows facilitating drug absorption through the intestinal mucosa cells into the blood, from which the effects of hypercholesterolemia treatment can be obtained.
Synthesis, structure and anticancer activities of Cd(II), Cu(II) and Pd(II) complexes with 5,7‐dichloro‐8‐hydroxylquinoline‐2‐carboxaldehyde‐4‐chloro‐2‐aminothiophenol
Authors: Duong Hoang Tuan , Giang Ninh Thi Minh , Ngoc Nguyen Thi Bich , Hai Le Thi Hong
Published: March 2024

Three new complexes of Cd(II), Cu(II) and Pd(II) with 5,7‐dichloro‐8‐hydroxyquinoline‐2‐carboxaldehyde‐4‐chloro‐2‐aminothiophenol (QNS), that are [Cd(QNS‐1H)Cl] (1), [Cu(QNS‐1H)2] (2) and [Pd(QNS‐1H)Cl] (3), were synthesized. Their structures were determined by ESI‐MS, EDX, IR and 1H NMR spectroscopies. The results showed that in (1) and (3) complexes the ratio of M(II):QNS ligand is 1:1, M(II) is bound to QNS through O, Nquinoline and Nbenzothiazole atoms. In complex (2), Cu(II) is bound to the QNS ligand in the 1:2 ratio through Oquinoline and Nquinoline atoms. The complexes were tested for cell in vitro cytotoxicity on human cancer cells. Complex (1) gives better antitumor activity than the remaining complexes on four cancer lines including KB, Hep‐G2, A549 and MCF‐7. The effect of complex (1) on KB and MCF‐7 is higher than cisplatin, a cancer treatment drug, with IC50 values of 15.01 and 17.94 μM, respectively.
Herrmananes A and B, two new sulfated hydrocarbons from the sea cumber Stichopus herrmanni
Authors: Vien Le Thi , Hanh Tran Thi Hong , Quang Tran Hong , Van Thanh Nguyen , Cuong Nguyen Xuan , Nam Nguyen Hoai
Published: March 2024

Using various chromatographic separations, two new sulfated hydrocarbons namely herrmananes A and B (1 and 2) were isolated from the aqueous fraction of the methanol residue of the sea cucumber Stichopus herrmanni. Their chemical structures were elucidated by extensive analysis of the 1D, 2D NMR and HR‐QTOF mass spectra. In addition, compound 1 showed significant cytotoxicity on SK‐Mel‐2 cell line with IC50 value of 23.12 ± 1.87 μM, whereas 2 exhibited moderate effect on this cell line with IC50 value of 55.28 ± 4.17 μM.
Cost‐effective fast prototyping using a dry film photoresist for micromixers towards point‐of‐care devices
Authors: Quynh Luc Nhu , Doanh Vu Viet , Thao Pham Ngoc
Published: March 2024

This paper deals with a novel structure of serpentine micromixer with its high mixing efficiency and its fabrication of soft photolithography molds using dry film photoresist as an alternative to the conventional liquid photoresist, such as SU‐8. This method provides simplification, significant time‐savings, low cost due to non‐cleanroom setting and less toxic developer solution. In this paper, the design, simulation, fabrication and experimental analysis of the passive micromixers have been presented. The mixing efficiency of the chip was implemented by using of micro‐barrier structure along its meander microchannel. The serpentine structures with and without embedded grooves on their micro sidewalls were designed and compared together in order to prove good mixing performance. Experimental measurements were introduced using white and green food dyes as the mixing fluids. The mixing efficiencies of micromixers were determined and compared in the analytical model and the mixing test. It was found that grooved structures significantly enhanced the performance of the serpentine micromixers due to induce perturbations in the flow field. By optimizing the design of the serpentine micromixers equipped with embedded grooves under its simple fabrication method making this study a promising solution for a wide variety of application.
Synthesis of hierarchical binary core‐branch nanocomposite of carbon microspheres@α‐Fe2O3 for enhancing electrochemical behavior
Authors: Hai Ho Van Minh , Anh Nguyen Thi Hong , Ky Vo The , Thang Nguyen Quoc , Van Cuong Nguyen
Published: March 2024

A facial strategy for the synthesis of hierarchical binary core‐branch carbon microspheres (CMS)@α‐Fe2O3 is presented. X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), energy‐dispersive X‐ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution TEM (HR‐TEM), and Brunauer–Emmett–Teller (BET) were used to characterize the structural and morphological properties of the products. XRD diffraction analysis of CMS@α‐Fe2O3 reveals the highly crystalline nature of α‐Fe2O3 in the hierarchical binary core‐branch CMS@α‐Fe2O3 nanocomposite. Morphological analyses show that the α‐Fe2O3 shell layer grew onto the surface of CMS to form nanoscale heterointerfaces in the core‐branch structure, demonstrating the effectiveness of the synthesized route. More importantly, CMS@α‐Fe2O3 demonstrated superior electrochemical behavior to CMS. The enhanced CMS@α‐Fe2O3 electrochemical performance can be attributed to its large specific surface area, which allows for the rapid transfer of electrons into the electrode during the redox process.
An efficient synthesis of acridine‐aza‐anthraquinone hybrid compounds under microwave irradiation
Authors: Anh Dang Thi Tuyet , Giang Le Nhat Thuy , Van Tuyen Nguyen , Giang Nguyen Thi Quynh , Thanh Nguyen Ha
Published: March 2024

The efficient synthesis of 12‐substituted‐3,4,4a,5,12,12a‐hexahydrobenzo[b]acridine‐1,6,11(2H)‐triones starting from 2‐amino‐1,4‐naphthoquinone, 1,3‐cyclohexanedione, and different (hetero)aromatic aldehydes was developed. These reactions were carried out in acetic acid under microwave irradiation in the presence of p‐toluenesulfonic acid as catalyst. The structure of the newly synthesized compounds were confirmed employing spectroscopic data as well as elemental analysis. The plausible mechanism of these three‐component domino reactions was also described.
Secondary metabolites from leaves of Knema pachycarpa possessing cytotoxic and acetylcholinesterase inhibitory activities
Authors: Thanh Le Nguyen , Giap Tran Huu , Oanh Vu Thi Kim , Hue Vu Thi , Phuong Diep Thi Lan , Thuc Dinh Ngoc , Cong Nguyen Thanh , Vuong Nguyen Quoc
Published: March 2024

Phytochemical study of Knema pachycarpa leaves led to the isolation of ten compounds. Their chemical structures were determined as (7”R, 8”R)‐hydnocarpin D (1), (7”R, 8”R)‐hydnocarpin (2), sinaicitin (3), (‐)‐globulol (4), β‐caryolanol (5), phytol (6), biochanin A (7), chrysoeriol (8), tanoside II (9) and astragalin (10) using NMR and MS spectral data. Among the isolates, (7”R, 8”R)‐hydnocarpin (2) showed good cytotoxic activity against KB, HepG‐2, Lu and MCF‐7 cancer cell lines with IC50 values from 13.99±0.62 μg/mL to 30.65±1.44 μg/mL. Compound 4 showed selective cytotoxicity against LU cancer cell line and significant acetylcholinesterase (AChE) inhibition with IC50 values of 12.31±0.51 μg/mL and 5.12±0.22 μg/mL, respectively.
Synthesis of yellow and green phosphors based on zinc orthosilicate doped by manganese at low temperature by impregnation – coprecipitation method
Authors: Thanh Nguyen Thi , Thanh Le Xuan
Published: March 2024

This work studies the influence of magnesium concentration, sintering temperature, boric and acetic acid to synthesize yellow and green phosphors based on zinc orthosilicate doped by manganese at low temperature by a novel approach, the impregnation ‐ coprecipitation method. The samples were investigated by thermal analysis, luminescence spectroscopy, XRD, SEM and EDS. The results showed that the single‐phase zinc magnesium orthosilicate/borosilicate phosphors doped by manganese with rhombo. H. axes structure of α‐Zn2SiO4 were successfully synthesized when sintering corresponding precursors at 900°C for 45 minutes. Their luminescence efficiency is higher than that of the control samples prepared by coprecipitation method. The magnesium content for the maximum luminescence efficiency is 20 mol % per mol of metal ions. The highest luminescence product consists of spheroidal and relatively uniform particles with sizes around 0.6‐1.0 μm. The variation of the precipitated precursor with temperature, the influence of sintering temperature on structure and luminescence, the mineralization role of boric acid and the chemical reactions that occur with generation of precipitated precursors and upon heating to give luminescent solid solution products are mentioned.
HO● ‐ initiated oxidation of isoleucine amino acid in the aqueous phase
Authors: Lan Nguyen Thi Huong , Hieu Truong Dinh , Chinh Ngo Thi , Le Anh Nguyen Thi , Nhi Pham Thi Yen , Quang Dao Duy
Published: March 2024

Protein damage by the direct oxidative attack on amino acid side chains is considered the main cause of human aging and diseases. Therefore, a better understanding of the oxidation process is necessary for screening and designing new drugs. In this work, the oxidation of L‐isoleucine (Ile) by HO● radical was mechanistically and kinetically studied using M05‐2X/6‐311++G(3df,3pd)//M05‐2X/6‐311++G(d,p) level of theory. All possible hydrogen transfer (HT) and single electron transfer (SET) reactions are considered in the aqueous phase. The results showed that the overall diffusion‐controlled rate constant is equal to 4.82×109 M‐1s‐1 at 298.15K. The zwitterionic form is the main existing form that plays an essential role in the HO● ‐ initiated oxidation of Ile (99.98%). The most preponderant reactions are found at C6‐H (36.19%) and C8‐H (37.77%) positions. Finally, the influence of temperature on the overall rate is also evaluated.
Improving corrosion resistance of pure titanium by simple and controlled oxidation for biomedical applications
Authors: Linh Nguyen Thi Truc , Tung Mai Thanh , Tuan Phan Dinh
Published: March 2024

In this study, the TiO2 passive layer was formed on a pure titanium substrate by simple oxidation in an aqueous solution of H2O2 35 wt.%. In order to determine the appropriate time for the oxidation of the pure titanium substrate, the corrosion rate of the metal in the solution of H2O2 was investigated. The electrochemical behaviour of the TiO2 passive layer on the Ti substrate was investigated in Hank's solution at 37.5°C. The results show that Tafel‐plot extrapolations from the potentiodynamic curves revealed a substantial improvement in the corrosion potentials for the TiO2 coatings. According to the theory calculation, to obtain the optimal surface roughness values, around 100 nm to 300 nm, the oxidation time in H2O2 35 wt.% solution is controlled in the range of 2‐5 hours. The results were explained by considering the effects of crystal morphology and roughness. The results indicated that the controlled oxidation‐prepared TiO2 coatings have attractive prospects for use in biomedical applications since better corrosion protection of pure Ti can be expected.
Effect of silane‐modified SiO2@Ce3+ nanoparticles on the mechanical property and anti‐corrosion for steel of the epoxy coating
Authors: Huu Nguyen The , Tam Dam Thi , Vy Do Truc , Anh Nguyen Tuan , Lu Le Trong , Lam Tran Dai , Vuong Nguyen Thien
Published: March 2024

In this work, nano‐SiO2 have been used as nanocarriers for loading Ce(III) ions (SiO2@Ce3+). After loading, silane coupling agent has been used to modify these nanocarriers (m‐SiO2@Ce3+). Then, these modified nanocarriers were added as green inhibitors into the inner epoxy coating matrix, which was based on the epoxy resin (DER 671X75) and hardener (polyamide Epicure 3125). Morphological study by FE‐SEM showed that the spherical nanoparticles (m‐SiO2@Ce3+) were in size < 100 nm and dispersed rather homogeneously into the polyme matrix. In addition, the addition of nanocarriers at a concentration of 2.5 wt.% into the epoxy polymer matrix enhanced significantly its mechanical property. Besides, the anticorrosion performance of the epoxy polymer matrix due to the presence of m‐SiO2@Ce3+ (at 2.5 wt. %) was proved by EIS analysis and salt spray tests.
Matrix removal and enrichment of cadmium atnd lead in mineral‐rich samples using liquid‐liquid extraction and analysis by flame atomic absorption spectrometry
Authors: Thien Vo Hoang , Van Dong Nguyen
Published: March 2024

The present work aimed to study matrix removal and enrichment of cadmium and lead in samples containing highly mineral‐rich using liquid‐liquid extraction. Cadmium and lead were extracted by sodium diethyldithiocarbamate (DDTC) and ammonium pyrrolidine dithiocarbamate (APDC) in pH 5.0 buffer solution (acetic acid/acetate) to chloroform. Cd and Pb in chloroform were re‐extracted to the aqueous phase by 1.5 M HNO3 and subsequently determined by flame atomic absorption spectrometry (F–AAS). Mineral‐rich samples (soil, sediment, sea salt, etc.) containing various concentrations of interferent elements (Fe (8‐25%), Al (5‐20%), Cu (400‐500 ppm), Zn (300‐400 ppm), NaCl (up to ⁓100%)) were used to determine the effectiveness of matrix removal. Fe was found to form an undissolved complex with APDC and co‐extracted with Cd and Pb, deteriorating the extraction and following analysis manipulation. 8‐hydroxyquinoline was successfully used as a masking reagent to reduce the co‐extraction of Fe, Al, and other elements with Cd and Pb in the form of dithiocarbamate complexes. In this study, enrichment factors of 5 – 10 could be achieved (from 50 to 5 mL). The recoveries of Cd2+ and Pb2+ ions from spiked agricultural soil, tea–planted soil, basalt soil, forestry soil, livestock feed, and sea salt were 97‐101 % and 87‐92% for DDTC and APDC reagents, respectively. The detection limits of cadmium and lead in soil are 0.0069 and 0.072 μgg−1; in livestock feed, 0.0085 and 0.082 μgg−1; in sea salt, 0.0075 and 0.076 μgg−1, respectively The quantification limit of cadmium and lead in a soil sample is 0.023 and 0.24 μgg−1; in livestock feed of 0.028 and 0.27 μgg−1; and in sea salt of 0.025 and 0.25 mgKg−1, respectively. The proposed approach for matrix removal and pre‐concentration of cadmium and lead can also be applied for mineral‐rich samples with better analytical performances when higher sensitivity and multi‐element detection techniques such as inductively coupled plasma optical emission spectrometry or inductively coupled plasma mass spectrometry are used.
Studying the influence of current density and solution pH on corrosion properties of obtained Zn‐nano SiO2 electroplating layers
Authors: Huong Nguyen Thi Thanh , Thang Le Ba , Bao Le Duc , Hieu Truong Minh , Nam Truong Thi , Giang Pham Thi Thu , Van Vy Uong
Published: March 2024

The influence of fabrication conditions on the corrosion properties of obtaining Zn‐SiO2 plating was studied by electrochemical measurement methods and salt spray acceleration test. In which the current density is changed from 1.5 to 3.5 A/dm2 and the solution pH is adjusted from 4.5 to 6.2. The obtained results show that the coating with the best corrosion resistance is obtained when applying the following manufacturing conditions: current density of 2 A/dm2, solution pH of 5.2‐5.4 at room temperature, stirring speed of 14 cycles/min.
Synthesis and antimicrobial activity of new glucosamine derivatives
Authors: Anh Le Duc , Bao Ninh Duc , Duc Le Viet , Van Chinh Luu , Cuong Nguyen Manh , Thuy Dinh Thi Thu , Hung Truong Ngoc
Published: March 2024

In this study, a series of reactions were used to protect and deprotect hydroxyl and amine groups of D‐glucosamine which was obtained by the hydrolysis of chitin in concentrated HCl. Amidation of this protected monomer with aromatic and heteroaromatic acids was carried out in dichloromethane in the presence of DCC as a coupling reagent to produce new amides in good yields. Their structures were determined by NMR and MS spectra while their antifungal and antibacterial activities were screened.
Determination of saturated fat, unsaturated fat, and trans fat in commercial instant noodles based on the analysis of fatty acid composition by gas chromatography
Authors: Hung Nguyen Khanh , Trang Nguyen Phuong , Du Nguyen Huy
Published: March 2024

In the food processing sector, it is crucial to identify the composition and fat content of items that have undergone heat‐processing. The total fat content is the primary factor used to determine the fat content of instant noodle products. As a result, a technique must be developed to identify fat content by determination of fatty acid composition, particularly trans fatty acids. In this study, we used the reliable GC‐FID/MS technique to analyze the methyl ester derivatives of 37 different kinds of fatty acids. The results showed that high saturated fat concentration in all samples was mostly palmitic acid, whereas the low unsaturated fatty acid content in the cis form was primarily oleic acid and linoleic acid. The amount of monounsaturated and polyunsaturated fats is quite low. Trans fat level was almost non‐existent in all samples. The amounts of palmitic acid and oleic acid in the samples ranged from 4.10% to 12.84% and 2.62% to 7.65%, respectively, as did linoleic acid and stearic acid. Monounsaturated and polyunsaturated fatty acid concentration ranged from 2.62% to 7.82% and 0.52 to 1.81%, respectively. The proportion of polyunsaturated fat to saturated fat was quite low. Therefore, it is essential to have procedures in place to keep an eye on the saturated fatty acid level, which has a negative impact on consumers' health. The findings of experimental research demonstrated that trans fatty acids were not present in instant noodle products. It revealed that the food processing sector has advanced favorably and catered to the demands of both the domestic and international markets.
Nanostructured lubricant additives for titanium alloy: Lubrication by the solid-liquid interface with Coulomb repulsion
Authors: Duan Linlin , Jia Dan , Li Jian , Liu Jianfang , Duan Haitao
Published: March 2024

In this work, the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid-liquid nanosized contact interface is taken, and the superior friction-reducing property of Cu3(PO4)2·3H2O (CuP) oil-based additives has been confirmed for titanium alloy. Three-dimensional (3D) CuP nanoflowers (CuP-Fs) with a strong capillary absorption effect are prepared to achieve the homogeneous mixing of solid CuP and lubricating oil. Lubrication by CuP-Fs additives for titanium alloy, friction coefficient (COF) can be reduced by 73.68%, and wear rate (WR) reduced by 99.69%. It is demonstrated that the extraordinary friction-reducing property is due to the repulsive solid-liquid interface with low viscous shear force originating from Coulomb repulsion between polar water molecules in CuP and non-polar oil molecules. However, any steric hindrance or connection between this repulsive solid-liquid interface will trigger the adhesion and increase the viscous shear force, for example, dispersant, hydrogen bondings, and shaky adsorbed water molecules. Besides, the lamellar thickness of CuP and the molecular size of lubricant both have a great influence on tribological properties. Here the lubrication mechanism based on interface Coulomb repulsion is proposed that may help broaden the scope of the exploration in low-friction nanomaterial design and new lubricant systems.
Are regime changes always bad economics? Evidence from daily financial data
Authors: Incerti Devin , Incerti Trevor
Published: March 2024

Political instability is commonly thought to discourage investment and reduce economic growth. We challenge this consensus by showing that instability does not systematically depress investment. Using an event study approach, we examine daily returns of national financial indices in every country that experienced an irregular regime change subject to data availability. Returns following resignations are large and positive (+4 percent), while those following assassinations are negative and smaller in magnitude (−2 percent). The impact of coups tends to be negative (−2 percent), but we show that a pro-business coup results in large positive returns (+10 percent). We also find evidence that authoritarian or anti-business regime changes are more likely to lead to capital flight than democratic or pro-business changes. The immediate impact of political instability on investment is therefore dependent on the type of regime change and its expected impact on future growth.
Constitutionalizing Mass Surveillance in the EU: Civil Society Demands, Judicial Activism, and Legislative Inertia
Authors: Celeste Edoardo , Formici Giulia
Published: March 2024

Despite the shock provoked by the Snowden revelations, mass surveillance is still a reality in the EU. However, over the past few years, it has been possible to observe a gradual constitutionalization of these practices. This Article maps the ongoing process of progressively defining the constitutional limits and societal affordances of mass surveillance in the EU by focusing on the three main actors who contribute to it. First, this Article presents civil society as the propeller of this trend. Civil society not only advocated for a ban on general surveillance systems in the aftermath of the Snowden revelations, but also promoted a series of strategic litigations to challenge state surveillance practices at national and EU levels. Second, it analyses CJEU case law as the main constitutionalizing engine of this process. The Court pragmatically ascertained that an absolute prohibition of mass surveillance did not appear to be a realistic solution and put significant effort into actively defining the legal boundaries of these practices by striving to find an equilibrium between Member State interests and citizens’ fundamental rights. Third, it considers the approaches taken by national legislators to be a slowing factor. States are still reluctant to incorporate the constitutional standards progressively developed by courts despite the now significant body of judicially created parameters in the field.
Wave scattering and radiation by a surface-piercing vertical truncated metamaterial cylinder
Authors: Zheng S. , Liang H. , Greaves D.
Published: March 2024

In this paper, we study wave scattering and radiation by a surface-piercing vertical truncated metamaterial cylinder composed of a closely spaced array of thin vertical barriers, between which fluid can flow. A theoretical model is developed under full depth-dependent linearised water wave theory, where an effective medium equation and effective boundary conditions are employed, respectively, to describe the fluid motion inside the cylinder and match the flow between the fluid regions in and outside the metamaterial cylinder. A damping mechanism is introduced at the surface of the fluid occupied by the metamaterial cylinder to consider the wave power dissipation in narrow gaps between the thin vertical plates. The wave excitation forces acting on the cylinder and the hydrodynamic coefficients can be calculated straightforwardly in terms of the velocity potential inside the cylinder. An alternative way is by using the velocity potential outside the cylinder, the expression of which has the reduction of the integral and an infinite accumulation that are included in the straightforward expression. The results highlight the patterns of the radiated waves induced by the oscillation of the cylinder and the characteristics of the hydrodynamic coefficients. The metamaterial cylinder when fixed in place and with a damping mechanism included is found to capture more wave power than that of a traditional axisymmetric heaving wave energy converter over a wide range of wave frequencies.
Modelling the unsteady lift of a pitching NACA 0018 aerofoil using state-space neural networks
Authors: Damiola Luca , Decuyper Jan , Runacres Mark C. , De Troyer Tim
Published: March 2024

The development of simple, low-order and accurate unsteady aerodynamic models represents a crucial challenge for the design optimisation and control of fluid dynamical systems. In this work, wind tunnel experiments of a pitching NACA 0018 aerofoil conducted at a Reynolds number

$Re = 2.8 \times 10^5$

and at different free-stream turbulence intensities are used to identify data-driven nonlinear state-space models relating the time-varying angle of attack of the aerofoil to the lift coefficient. The proposed state-space neural network (SS-NN) modelling technique explores an innovative methodology, which brings the flexibility of artificial neural networks into a classical state-space representation and offers new insights into the construction of reduced-order unsteady aerodynamic models. The work demonstrates that this technique provides accurate predictions of the nonlinear unsteady aerodynamic loads of a pitching aerofoil for a wide variety of angle-of-attack ranges and frequencies of oscillation. Results are compared with a modified version of the Goman–Khrabrov dynamic stall model. It is shown that the SS-NN methodology outperforms the classical semi-empirical dynamic stall models in terms of accuracy, while retaining a fast evaluation time. Additionally, the proposed models are robust to noisy measurements and do not require any pre-processing of the data, thus involving only a limited user interaction. Overall, these features make the SS-NN technique an excellent candidate for the construction of accurate data-driven models from experimental fluid dynamics data, and pave the way for their adoption in applications entailing design optimisation and real-time control of systems involving lift.
Life on the edge: subcritical pipe flow transition as a spectral submanifold
Authors: Schmid Peter J.
Published: March 2024

Subcritical pipe flow transition has received a great deal of attention over the past decades, as it constitutes a quintessential bifurcation process between two metastable fluid states: the laminar and turbulent solutions. Coherent lower-branch structures, forming flow states that facilitate between these two attracting equilibria, have been proposed that together form an edge manifold in phase space separating relaminarizing from transitioning perturbations. Typically, direct numerical simulations or low-dimensional model equations have been used to study this edge manifold with bisection methods. In the article by Kaszás & Haller (J. Fluid Mech., vol. 979, 2024, A48), an effective nonlinear invariant-manifold technique has been applied to extract a low-dimensional, global representation of the phase-space dynamics directly from simulation data. It allows the computation of the intersection of the edge manifold with a low-dimensional surface that is strikingly accurate in predicting the long-term dynamics of perturbations about the lower-branch solution and thus provides an accessible parameterization of the edge manifold for subcritical pipe flow transition.
Development of a new magnetic mirror device at the Korea Advanced Institute of Science and Technology
Authors: Oh D. , Choe M. , Baek G. , Kim D. , Jung B. K. , Chung K. J. , Kourakis I. , Sung C.
Published: March 2024

A new magnetic mirror machine named KAIMIR (KAIST mirror) has been designed and constructed at the Korea Advanced Institute of Science and Technology (KAIST) to study mirror plasma physics and simulate the boundary regions of magnetic fusion plasmas such as in a tokamak. The purpose of this paper is to introduce the characteristics and initial experimental results of KAIMIR. The cylindrical vacuum chamber has a length of 2.48 m and a diameter of 0.5 m and consists of three sub-chambers, namely the source, centre and expander chambers. A magnetic mirror configuration is achieved by electromagnetic coils with a maximum magnetic field strength of 0.4 T at the mirror nozzles and 0.1 T at the centre. The source plasma is generated by a plasma washer gun installed in the source chamber with a pulse forming network system. The typical discharge time is ~12 ms with a ~6 ms (1–7 ms) steady period. Initial results show that the on-axis electron density at the centre is 1019–20 m−3 and the electron temperature is 4–7 eV. Two parameters were varied in this initial phase, the source power and the mirror ratio, which is the ratio of highest to lowest magnetic field strength in the mirror-confined region. We observed that the increase of the electron density was mitigated for a source power above 0.2 MW. It was also found that the electron density increases almost linearly with the mirror ratio. Accordingly, the stored electron energy was also linearly proportional to the mirror ratio, similar to the scaling of the gas dynamic trap.
Temporal trend analysis of acute hepatitis B virus infection in China, 1990–2019
Authors: Han Ying , Li Yuansheng , Wang Shuyuan , Chen Jialu , Zhang Junhui
Published: March 2024

China faces challenges in meeting the World Health Organization (WHO)’s target of reducing hepatitis B virus (HBV) infections by 95% using 2015 as the baseline. Using Global Burden of Disease (GBD) 2019 data, joinpoint regression models were used to analyse the temporal trends in the crude incidence rates (CIRs) and age-standardized incidence rates (ASIRs) of acute HBV (AHBV) infections in China from 1990 to 2019. The age–period–cohort model was used to estimate the effects of age, period, and birth cohort on AHBV infection risk, while the Bayesian age–period–cohort (BAPC) model was applied to predict the annual number and ASIRs of AHBV infections in China through 2030. The joinpoint regression model revealed that CIRs and ASIRs decreased from 1990 to 2019, with a faster decline occurring among males and females younger than 20 years. According to the age–period–cohort model, age effects showed a steep increase followed by a gradual decline, whereas period effects showed a linear decline, and cohort effects showed a gradual rise followed by a rapid decline. The number of cases of AHBV infections in China was predicted to decline until 2030, but it is unlikely to meet the WHO’s target. These findings provide scientific support and guidance for hepatitis B prevention and control.