https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse <p>Journal of Tropical Science and Engineering is a multidisciplinary journal (chemistry and materials, biology and biomedicine) published since 2012 under the Press Operation License No.02/GP-BVHTTDL, dated January 16, 2026 issued by the Ministry of Culture, Sports and Tourism, and p-ISSN:3093-3633, e-ISSN: 3093-3803, assigned by the National Agency for Science and Technology Information and Statistics under the Ministry of Science and Technology.</p> en-US Fri, 04 Sep 2026 09:33:38 +0700 OJS 3.2.1.1 http://blogs.law.harvard.edu/tech/rss 60 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/799 In this work, a series of urea-modified GO-ZnO (U-GO-ZnO) hybrid materials were synthesized by modifying GO-ZnO nanocomposites with urea to enhance their anti-corrosive performance in saline environments. The incorporation of urea improves surface functionalization, interfacial interaction, and dispersion stability of GO-ZnO, thereby enhancing its protective performance on metallic substrates. The prepared GO-ZnO material was successfully modified with 3 wt.% urea, and the resulting U-GO-ZnO composites were systematically characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. FTIR and Raman analyses confirmed the chemical interaction between urea and oxygen-containing functional groups on the GO surface, while XRD patterns revealed the preserved crystalline structure of ZnO after modification. SEM micrographs showed a more uniform surface morphology and improved particle dispersion, supporting the positive role of urea functionalization. The anti-corrosion performance of U-GO-ZnO was evaluated using both the weight-loss method and potentiostatic polarization measurements under varying inhibitor concentrations and immersion durations. The results demonstrated that exposure time has a significant influence on corrosion inhibition efficiency. In a 3.5 wt.% NaCl solution, the concentration of 0.05 g/L exhibited the most promising inhibition efficiency, reaching 77.73%, 69.01%, and 87.21% after 30, 60, and 120 min, respectively. Furthermore, Nyquist impedance plots obtained by electrochemical impedance spectroscopy (EIS) revealed that electrodes immersed in 0.2 g/L U-GO-ZnO solution possessed the largest charge-transfer resistance, indicating the formation of a highly stable passive layer that effectively mitigates corrosion processes. These findings support the conclusion that urea-modified GO–ZnO is a promising anti-corrosive additive for metal protection applications. Tan Tai Do, S. V. Antonov, N. P. Bezrukov , V. V. Makarova, Thi Thu Hien Nguyen, Kim Thanh Nguyen, Thi Truc Suong Tran, Huynh Thanh Linh Duong, Boi An Tran Copyright (c) 2026 Journal of Tropical Science and Engineering https://creativecommons.org/licenses/by/4.0 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/799 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/822 Fine particulate matter (PM2.5) pollution is a major air quality concern in Hanoi, while information on PM2.5 - bound dioxin - like polychlorinated biphenyls (dl-PCBs) remains limited. This study investigated the concentrations, congener profiles, and potential sources of dl-PCBs associated with PM2.5 in central Hanoi during the dry season of 2025. Fourteen consecutive 24-h PM2.5 samples were collected from 4 to 19 April 2025 at an urban site influenced by traffic and other anthropogenic activities. Twelve dl-PCB congeners were analyzed according to U.S. EPA Method 1668B using high resolution gas chromatography high resolution mass spectrometry (HRGC - HRMS) with isotope-dilution quantification. The 24-h PM2.5 concentrations ranged from 32.4 to 83.1 µg/m3, averaging 60.3 µg/m3; 64.3% of samples exceeded the Vietnamese 24-h standard of 50 µg/m3, while the mean concentration was approximately four times the WHO guideline value of 15 µg/m3. Toxic equivalent concentrations of dl-PCBs ranged from 1 × 10-3 to 11 × 10-3 pgTEQ/m3, with an average of 4 × 10-3 pgTEQ/m3. Congener profiles were dominated by PCB-118 (36.3 - 52.9%) and PCB-105 (17.1 - 24.4%), together accounting for approximately 70% of total dl-PCBs, followed by PCB-77 (7.2 - 10.6%). This profile suggests that volatilization from PCB - containing products and materials may represent an important source of atmospheric dl-PCBs in central Hanoi, although contributions from thermal processes cannot be excluded. These findings provide baseline data on PM2.5 - bound dl-PCBs in central Hanoi, supporting future source apportionment studies, air - quality management, and environmental health assessments. Duy Linh Bui, Thanh Tuan Nguyen, Anh Le Hoang, Chau Thuy Pham, Duc Thang Nguyen, Dinh Phien Tran, Thi Thu Nguyen, Viet Thanh Nguyen, Thi Nang Nguyen Copyright (c) 2026 Journal of Tropical Science and Engineering https://creativecommons.org/licenses/by/4.0 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/822 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/863 Vietnam is one of the Southeast Asian countries most heavily affected by dengue, where Aedes aegypti (L.) and Aedes albopictus (Skuse) serve as the primary vectors. The increasing prevalence of pyrethroid resistance in these two mosquito species, particularly in Ho Chi Minh City, poses a significant challenge to vector control efforts. This study aimed to evaluate resistance to 0.75% permethrin and to investigate knockdown resistance (kdr) mutations in IIS6 and IIIS6 domains of the voltage-gated sodium channel (VGSC) gene among resistant Ae. aegypti and Ae. albopictus individuals that survived bioassay exposure. The results showed that moderate levels of permethrin resistance were detected in both mosquito populations, Ae. aegypti and Ae. albopictus, with mortality rates ranging from 80.43% to 86.96% in Ae. aegypti and from 84.45% to 88.89% in Ae. albopictus. The Ser989Pro, Ile1011Met, and Val1016Gly mutations were not detected. In contrast, the Phe1534Cys mutation was observed at high frequencies, occurring in 80% (20/25) of Ae. aegypti and 92% (23/25) of Ae. albopictus specimens analyzed. The 1534C allele frequency was 0.62 in Ae. aegypti and 0.68 in Ae. albopictus, indicating comparable levels of the mutant allele in both species. Allele frequencies were calculated within the resistant group, and no statistically significant differences were detected between the two species. This study focused on resistant phenotypes without assessing haplotype structure or comprehensive genotype-phenotype associations. Nevertheless, its findings provide updated data on VGSC mutations linked to permethrin resistance in Ho Chi Minh City, thereby contributing to ongoing insecticide resistance surveillance and management within vector control programs. Van Hiep Nguyen, Van Truong Tran, Thi Dung Nguyen, Viet Hang Huynh, Duc Chung Nguyen, Tuan Long Nguyen, Thi Ngoc Han Dang, Thanh Tan Le Copyright (c) 2026 Journal of Tropical Science and Engineering https://creativecommons.org/licenses/by/4.0 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/863 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/891 The Picobirnaviridae family comprises small, non-enveloped viruses with a bi-segmented, double-stranded RNA genome, exhibiting broad host range and high genetic diversity. Despite over 7,000 entries in public databases, only 53 originate from bats, and merely one contains a near-complete capsid protein sequence, highlighting a significant knowledge gap. This study reports the detection and genomic characterization of a novel picobirnavirus derived from Pipistrellus ceylonicus bat from the Kon Chu Rang Nature Reserve, Gia Lai province, Vietnam. Using metagenomic sequencing, we obtained genomic sequences for both segments (dsRNA1: 1,902 bp; dsRNA2: 1,626 bp), encoding the capsid protein and RNA-dependent RNA polymerase (RdRp), respectively. Phylogenetic analysis of RdRp amino acid sequences robustly placed the virus within the International Committee on Taxonomy of Viruses (ICTV)-recognized genogroup 2 and the proposed genus Alphapicobirnavirus. The obtained capsid protein showed the highest sequence similarity to picobirnaviruses isolated from a human and a macaque (genetic distances of 0.59 and 0.62), while exhibiting a distant relationship (divergence of 0.79) to the only known near-complete bat picobirnavirus capsid sequence. This significant genetic distance, particularly from the sole chiropteran reference, supports the identification of a novel viral species within the Picobirnaviridae family. The characterized virus expands the known diversity of bat-related picobirnaviruses and provides crucial genomic data, contributing to a more accurate understanding of the family's evolution and host range. Ivan Fedorovich Stetsenko, Polina Andreevna Nikolaeva, Vasilina Konstantinovna Lapshina, Diana Agaronovna Grigoryan, Thi Mo Luong, Van Truong Tran, Ilya Olegovich Prikhodko, Alexander Pavlovich Yuzefovich, Alina Dmitrievna Matsvay Copyright (c) 2026 Journal of Tropical Science and Engineering https://creativecommons.org/licenses/by/4.0 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/891 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/872 Rhizocephalans are highly specialized parasitic crustaceans commonly infesting decapod hosts, including swimming crabs, and often exert profound effects on host growth and development. Their extremely reduced morphology, however, makes taxonomic identification difficult. In this context, molecular genetic tools have become increasingly valuable for resolving taxonomic relationships within the group. Nevertheless, genetic information in this group remains limited, and only a few representative species have been investigated in detail regarding their biological effects on hosts. For many other rhizocephalans, the extent of host impact remains largely unexplored. The rhizocephalan Sacculina lata has been recorded parasitizing the portunid crabs Charybdis miles and Podophthalmus vigil in the western Pacific region, including Vietnam. Despite these records, the parasite’s morphology has been documented only through schematic illustrations, while detailed photographic documentation, molecular data, and information on host impacts have not been reported. Accordingly, this study employed an integrative morphological and molecular approach to investigate S. lata infesting swimming crabs (Podophthalmus vigil) collected from Nha Trang Bay, Khanh Hoa, Vietnam. Direct observation of fresh specimens, scanning electron microscopy, and histological sections provided a more comprehensive characterization of the parasite’s morphological features. Among 542 examined crabs, infestation prevalence was low (3.51%), showed a clear relationship with host size, and was not associated with host sex. Analyses of nuclear (18S rRNA) and mitochondrial (COI) markers clarified the phylogenetic position of S. lata, revealing a close relationship with Sacculina angulata and several congeners. Parasitism induced pronounced feminization of the abdomen and secondary sexual traits in male hosts, whereas infested females exhibited no significant abdominal modification. Overall, these findings provide new taxonomic, molecular, and ecological insights into rhizocephalan parasitism in an economically important swimming crab species. Le Thi Kieu Oanh, Nguyen Phuong Lien, Hoang Thi Ngoc Anh, Nguyen Thi Hai Thanh, Nguyen Trinh Duc Hieu, Vo Thi Ha Copyright (c) 2026 Journal of Tropical Science and Engineering https://creativecommons.org/licenses/by/4.0 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/872 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/844 Understanding spatial variation in avian diversity across habitat types is essential for effective conservation planning in tropical protected areas. This study provides the first habitat-explicit, landscape-scale assessment of bird diversity in Bai Tu Long National Park, northeastern Vietnam, based on systematic surveys conducted across eight major habitat types. Using presence-absence data combined with species accumulation analysis (Chao2), Jaccard similarity, and habitat-specific species occurrence, we documented 161 bird species belonging to 52 families and 16 orders, with high sampling completeness (S_obs/Chao2 = 0.97). Species richness varied markedly among habitats, with evergreen broadleaf forest on soil mountains (E1) supporting the highest richness and the greatest number of habitat-restricted species, followed by evergreen broadleaf forest on limestone mountains (E2) and agricultural land (E8). In contrast, coastal and marine-associated habitats, including mangrove forests (E3), karst lagoons within limestone mountains (E6), coral reefs (E4), and seagrass beds (E5), supported fewer species but contributed distinct assemblages characteristic of open or aquatic environments. Jaccard similarity analysis revealed strong compositional differentiation between forest and non-forest habitats, indicating high beta diversity driven by habitat heterogeneity. Notably, 17 recorded species are of conservation concern according to the Vietnam Red Data Book, the IUCN Red List, and Circular No. 27/2025/TT-BNNMT of the Ministry of Agriculture and Environment. These findings demonstrate that structurally complex forest habitats function as primary reservoirs of avian diversity, while coastal habitats provide complementary ecological contributions that enhance landscape-level biodiversity. The study provides an important baseline for long-term biodiversity monitoring. It highlights the importance of habitat-based, multihabitat conservation strategies for tropical coastal protected areas located along the East Asian-Australasian Flyway. Hong Phuong Pham, The Dung Dinh, Trung Dung Ngo, Ngoc Huyen Dang, Huu Hiep Nguyen, Huu Coi Tran, Xuan Tuong Ngo Copyright (c) 2026 Journal of Tropical Science and Engineering https://creativecommons.org/licenses/by/4.0 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/844 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/845 The effective implementation of bioremediation is often constrained by the stability and delivery of microbial inocula. This study investigated the development and optimization of a hydrocarbon-degrading consortium comprising three indigenous bacterial strains: Rhodococcus ruber JN5.2, Stenotrophomonas acidaminiphila ZB2.1, and Bacillus amyloliquefaciens MD3.3. Phylogenetic analysis confirmed the taxonomic diversity of the members, while cross-streak assays established total biological compatibility, enabling stable coexistence. In synthetic wastewater containing 5% (v/v) oil, the bacterial consortium achieved a total petroleum hydrocarbon (TPH) removal efficiency of 78 ± 6% within 14 days. This performance significantly exceeded that of individual strains (51-54%), supported by a Synergy Index (SI) of 1.48 and a peak biomass density of 8.6 ± 0.9 × 10⁸ CFU/mL. To enhance practical applicability, freeze-drying conditions were optimized. Harvesting biomass at the 24-hour growth phase and utilizing a protective formulation of 10% skim milk, 5% sodium glutamate, and 20% bentonite preserved bacterial viability at ≥ 9.3 log₁₀ CFU/mL after one month of storage. The consortium was evaluated in three formulations: liquid culture, freeze-dried powder (FDO-VN25), and alginate-immobilized beads. Validation using real car-washing wastewater (TPH ≤ 100 mg/L) revealed that while all the formulations improved degradation, the alginate-immobilized system consistently exhibited the highest stability and efficacy, achieving over 60% TPH removal after 14 days. These results demonstrate that integrating a native multi-species consortium with optimized lyophilization and alginate encapsulation provides a robust microbial solution for treating low-strength petroleum-contaminated effluents in complex environments. Thi Kim Thanh Nguyen, Thi Huong Vu, Dinh Kha Trinh, Thi Hieu Thu Nguyen, Viet Cuong Nguyen, Khac Trinh Nguyen, Van Long Nguyen, Van Manh Nguyen, Cao Cuong Ngo, Thi Tuyen Do Copyright (c) 2026 Journal of Tropical Science and Engineering https://creativecommons.org/licenses/by/4.0 https://jtse.tapchikhcnnd.mod.gov.vn/index.php/jtse/article/view/845