HPU2 Journal of Science: Natural Sciences and Technology

Polyethylene degradation ability of superworms (Zophobas morio) and isolation of polyethylene-degrading microorganisms from superworm gut and landfill soil

Minh-Nguyet Nguyen Thi, Mai-Ngoc Tran, Phuong-Nhi Tran — Fri, 28 Aug 2026 00:00:00 +0700

Plastic pollution, particularly polyethylene (PE), represents a major global environmental challenge. This study aimed to evaluate the ability of superworms (Zophobas morio) to consume polyethylene and to isolate bacterial strains with potential PE-degrading capacity from landfill soil and the superworm gut. After 28 days of feeding on PE as the sole carbon source, an average PE mass reduction of 11 ± 2.25 mg/week (n = 3) was observed. Microbial isolation resulted in 11 bacterial strains, of which three strains (D2, D4, and RS1) grew on selective media containing PE as the sole carbon source. These findings provide preliminary evidence of the role of superworms and associated microorganisms in polyethylene consumption. However, further studies using physicochemical, enzymatic, and molecular approaches are required to confirm actual biodegradation mechanisms.

Production of virgin coconut oil from desiccated coconut

Fri, 28 Aug 2026 00:00:00 +0700

Virgin Coconut Oil (VCO) is a high-value product with diverse food, cosmetic, and nutraceutical applications. Its production presents a significant economic opportunity for coconut cultivators. However, prevailing local production methods often yield a product that fails to comply with national and international quality standards, diminishing its commercial value and restricting market access. This report details a standardized process for producing VCO on a household scale using the dry-pressing method. The investigation demonstrates that oil produced via this methodology consistently meets the quality parameters stipulated by the Asian and Pacific Coconut Community (APCC) standards. The adoption of this process has the potential to enhance the economic value and marketability of locally produced Virgin Coconut Oil.

Taxonomic characteristics of the genus Combretum Loefl. in Vietnam

Hong-Anh Le, Quynh-Chi Pham, Thi-Thuy Nguyen, Thanh-Hoa Mai, Minh-Tam Ha — Fri, 28 Aug 2026 00:00:00 +0700

The genus Combretum Loefl. encompasses around 250 species, predominantly inhabiting tropical and subtropical zones. However, updated taxonomic clarification for the genus in Vietnam remains limited. In Vietnam, the genus comprises 11 species and 1 variety, which are found along forest edges, stream banks, and ravines of secondary forests scattered all over the country, rarely cultivated. Characterized as woody climbers, or straggling, rarely small trees; leaves simple, opposite, whorled, lower surface often scaly and often with domatia (shapes tufted hairs in axils of lateral veins); flowers bisexual; stamens usually exserted from calyx tube; disk usually present; ovaries inferior, 1-loculed; fruits dry, indehiscent; 4-5-winged, or 4-5-ridged; seed with cotyledons convolute and without endosperm. Combretum species contribute significantly to forest ecosystem dynamics and offer diverse applications. Among them, Combretum micranthum and Combretum quadrangulare were assessed on the IUCN Red List of Threatened Species in 2025, but are listed as Least Concern (LC). Nine species are utilized in traditional medicine, and one species (Combretum micranthum) is used for ornamental purposes.

This study presents a comprehensive account of the genus Combretum in Vietnam, detailing its key morphological features, patterns of distribution, habitat preferences, ecological functions, and practical uses. Additionally, a dichotomous identification key is proposed to aid in distinguishing all taxa found in the flora of Vietnam.

The state of axion in a DFSZ model

Minh-Vuong Nguyen, Thi-Mai Dinh, Phuc-Tung Dinh, Thanh-Hung Ha — Fri, 28 Aug 2026 00:00:00 +0700

We investigate Peccei–Quinn (PQ) symmetry in the Dine–Fischler–Srednicki–Zhitnitsky (DFSZ) model, which is widely regarded as an elegant solution to the strong CP problem. In this work, the axion state is described in terms of the original pseudo-scalar fields, while the mass spectra of the CP-odd and CP-even Higgs bosons are also derived. Based on the Yukawa Lagrangian and the Higgs potential of the model, we determine the PQ charges of the fields and show that they depend on the PQ charge of the singlet scalar of \(SU(2)_L\otimes U(1)_Y\) . Using the relations among these PQ charges, we further express the axion state in terms of the original complex scalar components. Our results clarify the structure of PQ symmetry and the scalar sector in the DFSZ model, providing a basis for further studies on axion interaction with matter, the origin of axion properties, and possible phenomenological or experimental signatures.

Multi-station smart charging in Vietnam: a quadratic-programming approach under the 2025 retail-tariff revision

Kim-Thuy Dinh Thi — Fri, 28 Aug 2026 00:00:00 +0700

We formulate day-ahead smart charging of an electric-vehicle fleet across multiple public charging stations in Vietnam as a convex quadratic program. The objective combines time-of-use tariff cost, quadratic peak-shaving, and ramp-smoothing; the constraints enforce per-EV connection-window bounds, per-EV energy delivery, per-station transformer caps, and feeder-level caps where stations share a primary distribution feeder. Station connector-mix and rate caps are drawn from OpenChargeMap and co-located PV from NASA POWER; arrival traces are transplanted from the real Shenzhen UrbanEV benchmark and recalibrated to the 2024–2025 VinFast fleet. The tariff reflects the 2025 retail-tariff restructuring (Decision 14/2025/QD-TTg). Across five seeds: F1, single-station Smart charging at α=0 cuts tariff cost 21.6% over uncontrolled charging, trading down to about 10% for a two-thirds peak-power reduction at higher peak-shaving weights; F2, on a 500-EV five-station feeder at the binding 1 MW cap the decentralised baselines are feasible in only 3 of 5 seeds while the coordinated solver stays feasible in all 5, at a 0.3–0.9% cost edge; F3, the 2025 flat-midday bracket cuts cost 14.7%; F4, OSQP solves the 500-EV instance in about 2 s. The study is a reproducible proof of concept for Vietnamese multi-station smart charging.

Photocatalytic properties of \(\textbf{ZnO-TiO}_2\textbf{/g-C}_3\textbf{N}_4\) nanocomposites synthesized by a simple hydrothermal method

Fri, 28 Aug 2026 00:00:00 +0700

In the present study, a ZnO-TiO₂/g-C₃N₄ composite was successfully prepared by hydrothermal synthesis. XRD results confirmed the successful formation of the composite structure. The surface morphology, as observed by field-emission scanning electron microscopy, revealed that the material predominantly consisted of particles approximately 200 to 300 nm in size, together with a small number of rod-like structures. The UV–Vis spectra indicated that the composite exhibited absorption in the visible-light region. Photocatalytic degradation experiments using DB71 showed that the ZnO-TiO₂/g-C₃N₄ composite synthesized at 120 °C achieved a DB71 degradation efficiency of 27% in aqueous solution under visible-light irradiation. These results suggest that the ZnO-TiO₂/g-C₃N₄ composite has potential for application in the visible-light-driven treatment of DB71-contaminated water.

Structural cryptanalysis and storage efficiency of Kronecker-product diffusion layers for lightweight block ciphers

Thi-Tuyet Phan — Fri, 28 Aug 2026 00:00:00 +0700

Matrix-based linear transformations are fundamental to the diffusion properties of modern block ciphers. This paper investigates the algebraic structure and security of the Dual-Matrix Affine Modular construction \(C\equiv K_LMK_R+K_S\pmod p.\) Although it is structurally isomorphic to a constrained affine map on \(\mathbb{Z}_p^{n^2}\) via the Kronecker product \(K_R^T\otimes K_L\), this construction offers a significant efficiency advantage: it reduces the storage complexity from \(\mathcal{O}(n^4)\) (for a generic linear layer) to \(\mathcal{O}(n^2)\). We formally derive the effective key space and present a rigorous structural chosen-plaintext attack. We prove that by exploiting the tensor decomposition property, an equivalent key tuple can be recovered in \(\mathcal{O}(n^4)\) field operations, significantly bypassing the \(\mathcal{O}(n^6)\) complexity of generic affine cryptanalysis. Our results demonstrate that while insecure as a standalone primitive, this structure offers a favorable trade-off between large-state diffusion and implementation cost, making it a compelling candidate for the mixing layer in lightweight Substitution-Permutation Networks (SPNs).

A first-principles study on the structural and electronic properties of ZnO clusters

Minh-Thu Le, Quoc-Van Duong — Fri, 28 Aug 2026 00:00:00 +0700

This work presents a first-principles study of the structural, energetic, and electronic properties of (ZnO)_n clusters with n =1 ÷ 10. Various low-energy isomers were constructed and fully optimized using density functional theory within the DMol3 framework with the GGA–PBE functional. The most stable geometries were identified based on total energy calculations. The results reveal a clear size-dependent structural evolution: small clusters (n ≤ 7) favor planar or ring-like geometries, while larger clusters (n ≥ 8) adopt compact three-dimensional configurations with higher symmetry. The calculated average binding energy increases with cluster size, indicating enhanced stability and a tendency for cluster growth. Electronic structure analysis shows that the valence band is mainly contributed by O-2p states, whereas the conduction band is primarily derived from Zn orbitals, confirming the semiconducting nature of the clusters. Charge density difference analysis indicates electron transfer from Zn to O atoms, suggesting strong Zn–O bonding with significant covalent character in these clusters.

Morphology and anatomy characterization of Ehretia acuminata R.Br in Viet Nam

Kim-Oanh Nguyen, Lan-Huong Do Thi, Thi-Tam Bui — Fri, 28 Aug 2026 00:00:00 +0700

Ehretia acuminata R.Br. (Boraginaceae) is a medicinal plant species widely distributed across tropical and subtropical regions, including Vietnam. However, detailed anatomical data for taxonomic identification and pharmacognostical applications remain limited. This study aims to investigate the morphological and anatomical characteristics of the vegetative organs of E. acuminata collected in Northern Vietnam. Our findings reveal that the leaves exhibit a bifacial structure with well-developed palisade mesophyll and loosely arranged spongy mesophyll. The epidermis consists of a single cell layer covered by a distinct cuticle, with stomata predominantly distributed on the abaxial surface. Stem anatomy demonstrates typical secondary growth with clearly differentiated vascular tissues arranged in a continuous ring, while the root structure shows characteristic development of secondary xylem. Key anatomical features, including the organization of the mesophyll, the structure of vascular bundles, and epidermal characteristics, are identified as valuable diagnostic markers for species identification. This study contributes to the anatomical database of the species in Vietnam and provides a foundation for subsequent taxonomic research and medicinal material standardization.

Evaluation of biochemical composition and sensory quality of ancient Shan tea trees (Camellia sinensis var. assamica) from Northern Vietnam

Fri, 28 Aug 2026 00:00:00 +0700

The study evaluated the biochemical characteristics and sensory quality of ancient Shan tea (Camellia sinensis var. assamica) products in Northern Vietnam, specifically in Cao Bo-Tuyen Quang, Van Chan, and Cao Son-Lao Cai. The sensory quality was assessed based on appearance, water color, aroma, and taste. Meanwhile, the main biochemical compounds, including tannin, polyphenols, caffeine, amino acids, reducing sugars, and total soluble solids, were analyzed in 10 Shan tea tree individuals with the highest sensory scores. The results showed that the Shan tea samples achieved high sensory quality with an average total score of 16.22/20. There was also a very strong correlation among the sensory indicators (r > 0.97). PCA analysis indicated that the first principal component explained up to 98.36% of the total sensory variation, showing how well the overall tea quality structure is intergrated. The biochemical components among samples showed clear differentiation, especially for polyphenols and tannins. These findings suggest that secondary metabolites play a key role in shaping the unique quality of ancient Shan tea trees in Northern Vietnam. Overall, this study provides a scientific foundation for conservation, germplasm selection, and the development of high-quality Shan tea products linked to ecological and indigenous values.