Journal of Tropical Science and Engineering

The effectiveness of portable heat patch in protecting the health of military personnel operating in cold conditions in Northern Vietnam

This study provides a scientific basis for applying portable heat patches as auxiliary equipment to support military personnel during extreme cold weather in Northern Vietnam. An experimental survey was conducted with 50 volunteer soldiers, divided into a control group (NC) and an experimental group (TN), with no significant baseline differences in physiological indices (p > 0.05). Survival indicators (core temperature (Tcore), finger temperature (Tfinger), heart rate, blood pressure), subjective cold perception, and the heat retention capacity of the patch were monitored. Statistical methods were used to compare group differences and Pearson correlation analysis was conducted to examine the relationships between variables. The heat patch effectively supported thermoregulation, with Tcore in the TN group maintained 0.2–0.5°C higher than in the NC group, and Tfinger increased by up to 2°C, indicating improved peripheral circulation. The patch also reduced cold-induced increases in heart rate and enhanced overall thermal comfort (p < 0.05). Its temperature remained stable within the safe range of 38–43°C for up to 12 hours. Strong correlations were observed between patch temperature and cold sensation scores (r = –0.620, p < 0.01), along with moderate correlations with Tcore (r = 0.350, p < 0.01) and Tfinger (r = 0.318, p < 0.01), confirming its warming effectiveness in cold environments. Overall, the portable heat patch represents a practical, rapid-response warming solution suitable for military personnel facing sudden severe cold during winter operations in Northern Vietnam

Biological characteristics and environmental application potential of Bacillus velezensis TSD5 isolated from a coral island soil in Khanh Hoa Province, Vietnam

Halotolerant bacteria play vital roles in saline ecosystems, particularly in extreme habitats such as offshore coral island soils in Khanh Hoa Province, Vietnam. In this study, an indigenous strain, Bacillus velezensis TSD5, was characterized for its extracellular enzymatic, plant growth-promoting, and stress-tolerance traits. The strain produced a substantial amount of indole-3-acetic acid (IAA, 12.76 mg/L), exceeding levels reported for reference strains and thereby highlighting its potential role in stimulating plant root development under saline conditions. Extracellular enzyme analysis revealed strong cellulolytic (17.49 mm) and lipolytic (17.76 mm on olive oil) activities, along with amylase (8.15 mm) and protease (10.27 mm) activities, suggesting broad substrate-degradation capabilities relevant to soil nutrient cycling. In addition, TSD5 demonstrated the ability to degrade hydrocarbons, with halo diameters of 16.65 mm and 27.05 mm on diesel and crude oil, respectively, indicating its capacity to contribute to bioremediation in oil-contaminated environments. Stress-tolerance assays showed that TSD5 was able to survive up to 12.5% NaCl and 10% MgSO₄, confirming its marked halotolerance. The strain also displayed high tolerance to Pb(CH₃COO)₂ (900 µg/mL), ZnCl₂ (750 µg/mL), and FeSO₄ (750 µg/mL) but was more sensitive to Hg(NO₃)₂, Cd(NO₃)₂, NaAsO₂, and Cr(NO₃)₃, with thresholds ranging from 8–16 µg/mL. Together, these findings provide new insights into the ecological roles of EPS-producing halotolerant bacteria from offshore coral islands and underscore their potential applications in agriculture, bioremediation, and biotechnology under saline- and metal-stressed conditions. The ability of B. velezensis TSD5 to simultaneously withstand salt stress, promote plant growth, and degrade hydrocarbons highlights its promise as a multifunctional microbial resource for sustainable soil management and ecological restoration in polluted environments.

Assessment of the current status of floristic diversity in Song Hinh - Tay Hoa protection forests

Understanding the current status of plant diversity in tropical forests is fundamental for developing effective strategies for conservation and sustainable management. This study assessed the floristic composition and diversity of the Song Hinh - Tay Hoa protection forests, a representative tropical ecosystem in south-central Vietnam. Field surveys followed by taxonomic identification recorded 1,163 species of vascular plants, belonging to four divisions, 175 families, and 679 genera. Angiosperms were overwhelmingly dominant (93.7%), with Euphorbiaceae, Fabaceae, and Moraceae identified as the most diverse families, reflecting a typical tropical forest structure. Analysis of life-form spectra revealed that phanerophytes constituted 79.45% of the flora, mainly mesophanerophytes and nanophanerophytes, a characteristic feature of humid tropical forests. The dominance of phanerophytes indicates a stable ecosystem with limited degradation. Floristic elements were mainly represented by the Indo-Malesian group (58.38%), confirming both the humid tropical nature of the vegetation and the transitional biogeographical position of the area - i.e., a junction where Indochinese (continental SE Asian) lineages overlap with Southern Chinese/East Asian and Malesian (insular SE Asian) floras. Importantly, 41 species of high conservation concern were documented, with many categorized from Critically Endangered to Vulnerable under the IUCN Red List (2025), the Vietnam Red Data Book 2024, and Circular 27/2025/TT-BNNMT. The presence of a relatively high proportion of Vietnamese endemic species (8.60%) further emphasizes the conservation significance of this forest as a biodiversity hotspot within tropical Asia. These findings underscore the urgent need to maintain forest cover, restrict overexploitation, and monitor life-form spectra as indicators of ecosystem health. By providing a comprehensive baseline of floristic diversity, this study offers essential evidence to guide biodiversity conservation, support sustainable forest management, and enhance resilience to climate change in the region.

Synthesis and in vitro cytotoxicity evaluation of murrayafoline a derived β-thioether alcohols

Three new β-thioether alcohol derivatives 7a-c of murrayafoline A with 1,3,4-oxadiazole-2-thiol derivatives 6a-c were successfully synthesized from murrayafoline A 1 and The corresponding thiols 6a-c by a simple three-step procedure involving N-alkylation of murrayafoline A with epichlorohydrin using NaH in THF yielding the intermediate 2, followed by N-glycydyl ring opening of 2 with 6a-c, which were prepared from the corresponding acids though steps including esterification with ethanol catalyzed by concentrated sulfuric acid, followed by nucleophilic substitution reaction in the refluxing point of methanol with hydrazine, and their cyclization of the obtained hydrazides with CS2 in potassium-ethanol to give 6a-c as the nucleophilic agents for the opening reaction of intermediate 2 yielding the designed targets 7a-c. The obtained target compounds were confirmed by spectroscopic data, including NMR and HRMS. Spectral data were in excellent agreement with their structures. Cytotoxic activity against A549 and Hep-2C cell lines was selected to explore the anticancer potencies of β-thioether alcohols 7a-c in comparison with the starting compound, murrayafoline A, and the positive control, ellipticine. The obtained results of chemistry and anticancer effects provided a useful profile for new structures of β-thioether alcohol derivatives 7a-c, as well as their biological activity toward A549 and Hep-2C cells. In addition, the safety evaluation of three β-thioether alcohols was conducted using normal cells VERO from the kidney of African monkeys. The results showed that they were non-toxic toward VERO cells. Among three β-thioether alcohols, only derivative 7a, containing a 4-methoxybenzyl group in the thiol moiety, exhibited weak cytotoxic activity against A549 and Hep-2C cell lines at the 50% inhibitory concentrations of 35.84 and 33.20 µM, respectively.

High adsorption capacity of Rhodamine B dye on bio-activated carbon derived from sugarcane bagasse

This paper details the synthesis, characterisation, and adsorption efficacy of bio-activated carbon (BAC) generated from sugarcane bagasse for the effective elimination of Rhodamine B (RhB) dye from aqueous solutions. Sugarcane bagasse, an accessible agro-industrial byproduct, was chemically activated with HCl and subsequently carbonized to yield a porous carbon material rich in surface functionalities. Structural and surface analyses validated the formation of a hierarchical mesoporous framework, as demonstrated by SEM, FTIR, XRD, EDX, and nitrogen adsorption–desorption tests, including predominant pore sizes within the 2–5 nm range and intact oxygenated groups conducive to dye adsorption. Batch adsorption tests exhibited fast elimination of RhB, reaching equilibrium in 20 minutes and sustaining removal efficiencies over 95% across a broad concentration spectrum. Kinetic modeling indicated that the pseudo-second-order model most accurately represented the adsorption process, emphasizing chemisorption as the primary mechanism, with heterogeneous surface interactions and pore diffusion effects. Isotherm analysis revealed that the Freundlich model exhibited the optimal fit (R² = 0.9950), indicating multilayer adsorption on energetically heterogeneous sites, with a maximum adsorption capacity (qmax) of 30.36 mg g⁻¹ as determined by the Langmuir model. Further fittings to the Temkin, Elovich, Henry, and Dubinin–Radushkevich models corroborated a synthesis of physical and chemical adsorption mechanisms. The findings validate that sugarcane-bagasse-derived BAC is an economical, sustainable, and efficient adsorbent, presenting considerable promise for practical wastewater treatment applications while facilitating the valorization of agricultural residues into valuable environmental remediation materials.