HNUE Journal of Science: Natural Sciences (HNUEJS.NS) has the international standard series number ISSN: 2354-1059, publish original research in natural sciences and engineering including mathematics, biology, chemistry, informatics, geographics and physics. This journal is indexed by the State Council for Professor of Vietnam for publications in Biology , Geography, Physics and Chemistry as 0.75/1.0 points, and 0.5/1.0 points for publications in Mathematics and Information Technology. HNUEJS.NS publishes quarterly in March, June, September and December.
MORPHOLOGICAL AND PHASE EVOLUTION OF COBALT SULFIDE ON CARBON CLOTH VIA CONTROLLED HYDROTHERMAL SYNTHESIS FOR HIGH-PERFORMANCE FLEXIBLE SUPERCAPACITORS
Cobalt sulfide nanoparticles were successfully synthesized on carbon cloth (CC) via a one-step hydrothermal method, with varying precursor ratios, hydrothermal temperatures, and hydrothermal times. The crystalline structure, morphology, and composition of the as-prepared CoS were analyzed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM, and energy-dispersive X-ray spectroscopy (EDS). Structural analyses confirmed the formation of the hexagonal phase of CoS. Electrochemical measurements revealed that the CoS electrode, prepared with a Co:S ratio of 1:2 at 1600C for 15 h exhibited the highest specific capacitance of 424 F g-1 at a current density of 1 A g-1 and 350 F g-1 at a current density of 5 A g-1. Moreover, the electrode also demonstrated excellent cycling stability, retaining pproximately 90 % of its initial specific capacitance after 1000 charge-discharge cycles at a current density of 2 A g-1. These results highlight a facile, cost-effective, easy-to-implement, and efficient method for utilizing cobalt sulfide-based electrodes for flexible supercapacitor applications.
cobalt sulfide, carbon cloth, flexible supercapacitor
Copyright (c) 2025 Journal of Science Natural Science
EFFECTS OF ALCOHOL-SOLUBLE COMPONENTS IN SOYMILK RESIDUE ON PLASMA LIPID LEVELS, LIPID DIGESTIONAND BODY WEIGHT GAIN IN SWISS MICE
The present study was conducted to examine the effects of alcohol-soluble components (alcohol extract, AE) in soymilk residue (SR) on body weight gain, plasma lipid levels, and lipid digestion in Swiss mice. Aqueous ethanol was used to extract the SR, afterwhich the residue and the supernatant were separated. The supernatant was then dried to produce the AE. Four experimental diets were formulated and designated as CD (control diet), CD+AE20 (CD supplemented with 20 g AE/kg), CD+AE40 (CD supplemented with 40 g AE/kg), and CD+AE60 (CD supplemented with 60 g AE/kg). Six mice (with an initial body weight of 24 g) were distributed into each of eight cages, with two replicate cages per dietary treatment. The experimental mice were fed with the test diets ad libitum for 4 weeks. The results showed that the final body weights of mice fed with AE-supplemented diets were lower than those fed with the control diet, while no differences in feed intake were found among the treatments. Moreover, the AE significantly reduced body weight gain with significant differences observed in mice receiving AE supplementation levels of 40 and 60 g/kg. The mice fed with AE-supplemented diets exhibited lower plasma concentrations of total cholesterol, low-density lipoprotein, and triglyceride as well as lower intestinal total bile acid level and lipase activity, but higher lipid content in feces, compared with those fed with the control diet. These findings indicated that the AE in SR negatively affected the lipid digestion process, therefore reducing plasma cholesterol levels and body weight gain in Swiss mice.
alcohol-soluble components, soymilk residue, plasma cholesterol, lipid digestion, weight gain, mice
BUILDING A VIETNAMESE MATH CHATBOT BASED ON RAG AND LLM: SYSTEM DESIGN, IMPLEMENTATION AND EXPERIMENTAL EVALUATION
In recent years, large language models (LLM) and Retrieval-Augmented Generation (RAG) techniques have opened up new opportunities for the development of intelligent learning assistant systems. Nevertheless, the direct application of LLMs to Vietnamese Mathematics still has several limitations, including the illusion effect, a lack of knowledge base, failures to adhere to the Vietnamese education curricula, and difficulty in proceessing complex-related image issues. This paper presents the design, implementation, and experimental evaluation of a Vietnamese Mathematics Chatbot system based on the RAG architecture combined with LLM. The system comprises: (i) a pineline for collecting and standardizing Mathematics data from textbooks, exam questions and reference materials; (ii) a Milvus vector database to store embeddings generated by the BGE-m3 model; (iii) a multi-task pipeline coordinated by LangGraph; (iv) the inference component uses the Qwen3-VL-8B model implemented via vLLM; and (v) the WebUI user interface supports multimodal queries (text + image). Experimental results show that the system competently delivers detailed solutions, maintains the conversation flow, and significantly mitigates hallucination compared to pure LLM. The system also demonstrates potential for application in teaching and learning Mathematics, especially in situations requiring accurate knowledge retrieval and step-by-step explanations. These results suggest directions towards developing specialized learning assistants within the context of Vietnamese education.
Math Chatbot, generative artificial intelligence, RAG, large language models, Milvus, vLLM, LangGraph, mathematics education
REMARKABLE RECORDS OF MAMMALS AND CONSERVATION STATUS OF Sundasciurus hippurus AND Macaca fascicularis FROM U MINH HA NATIONAL PARK, SOUTHERN VIETNAM
U Minh Ha is one of the most prominent national parks in southern Vietnam; however, its mammalian fauna remains poorly studied. To address this gap, we conducted a field survey using camera traps and direct transect observations between June and July 2024. The survey yielded photographic records of eight confirmed species (Tupaia belangeri, Macaca fascicularis, Rattus tanezumi, Sundasciurus hippurus, Prionailurus bengalensis, Lutra sumatrana, Paradoxurus hermaphroditus, and Sus scrofa) representing eight genera, eight families, and five orders. Among these, M. fascicularis and L. sumatrana are listed as Endangered, and S. hippurus as Near Threatened on the IUCN Red List. Notably, M. fascicularis and S. hippurus were frequently recorded throughout the park, while L. sumatrana was documented only twice. Other mammalian taxa, such as bats, were also observed but excluded from the present study pending further taxonomic and conservation assessment. This study provides valuable records supported by verified photographs for all eight documented mammal species, offering robust confirmation of their presence in U Minh Ha National Park. Overall, our findings underscore the park’s importance as a potential hotspot for future research on mammalian diversity and broader biodiversity, with particular relevance to ecological patterns, species distribution, and conservation efforts in Vietnam and the wider Southeast Asian region.
biodiversity, conservation, distribution, ecology, mammals
ON BALANCING NUMBERS BY THE MATRIX METHOD
In this study, we define a balancing B-matrix which is similar to the Fibonacci Q-matrix and the Lucas QL-matrix. Using this matrix representation, we obtain some well-known equalities and a Binet-like formula for balancing numbers. Moreover, some arithmetic properties of balancing numbers are established.
Balancing numbers, matrix methods, matrix representation
CHARACTERIZATION OF A CHITOSAN/POLYANILINE FILM LOADED WITH LOVASTATIN
This research aims to address these challenges by dispersing the drug within both a single biopolymer matrix (chitosan) and a dual biopolymer matrix (chitosan/polyaniline). The results indicated that, among the single-matrix chitosan/lovastatin (CsL) samples, the CsL10 CsL10 exhibits the most favorable drug-release behavior over 30 h, achieving a cumulative release of 96% in simulated intestinal fluid (pH 7.4) while providing effective drug protection of 10.5% in simulated gastric fluid (pH 2.0). These findings suggest a promising platform for further development. Building upon this direction, the study was extended to incorporate polyaniline to enable live-function monitoring and tissue stimulation. The results showed that the chitosan/polyaniline/lovastatin (CsPL) samples met the initial expectations, with the CsPL7 sample exhibiting drug release rates of 92.23% and 18.58% in the simulated intestinal and gastric environments, respectively. Analytical techniques, including FT-IR, FESEM, DSC, and UV-Vis, were employed to gain a deeper understanding of the interactions between the polymer components and the drug substance.
chitosan/PANi/lovastatin biocomposites, chitosan/lovastatin biocomposites, lovastatin release, polyaniline
MICROSATELLITE HYBRID STRUCTURE USING ALUMINUM 7075-T6 AND CFRP FOR IMPROVED LAUNCH PERFORMANCE SURVIVABILITY
This study presents the structural design and simulation of a 50 kg-class microsatellite developed for compatibility with the JAXA Epsilon launch vehicle. A hybrid architecture combining Aluminum 7075-T6 and Carbon Fiber Reinforced Polymer (CFRP) was employed to meet stringent mass, stiffness, and vibration requirements. The final structure, measuring 480 × 488 × 550 mm, achieved a total mass of 45 kg, falling within the required launch envelope. Finite element simulations were conducted using ANSYS 2024R2 to evaluate modal, sine-sweep, random vibration, and shock responses under launch-induced conditions. The first three natural frequencies, 118.99 Hz (X-axis), 123.77 Hz (Y-axis), and 240.42 Hz (Z-axis), surpassed the required thresholds, avoiding resonance with vehicle-induced excitations. Vibration analyses confirmed that peak acceleration responses remained within safe operational margins, with sine-sweep, random vibration, and shock responses showing no modal amplification. Component-level stress simulations revealed von Mises stress values well below material limits across all critical subsystems. These results validate the structural integrity and dynamic survivability of the hybrid microsatellite, demonstrating its readiness for spaceflight.
microsatellite, hybrid structure, aluminum 7075-T6, CFRP, vibration analysis, finite element simulation
OPTIMAL ATTENUATION CONTROL OF 2-D POSITIVE ROESSER SYSTEMS WITH BOUNDED DISTURBANCES
In this paper, performance analysis and controller design problems subject to an optimal attenuation level are studied for 2-D positive systems with bounded input disturbances. First, some novel comparison techniques for state estimations subject to peak values of external disturbances are presented to derive a characterization for l∞-induced norm of the input-output operator. Then, we derive the necessary and sufficient linear programming (LP) conditions for obtaining a controller gain of an l∞-induced performance with a prescribed attenuation level. Numerical examples are given to illustrate the effectiveness of the proposed method.
2-D systems, Roesser model, positive systems, l∞-induced, linear programming
SELF-DIFFUSION OF BCC INTERSTITIAL ALLOY FeSi
In this work, we present analytical formulations for self-diffusion parameters, namely the activation energy, pre-exponential factor, and self-diffusion coefficient as functions of temperature, pressure, interstitial atom concentration, and strain in a BCC interstitial binary alloy, derived using the statistical moment method (SMM). These theoretical models are utilized to perform numerical simulations for the FeSi alloy. The computed SMM values for FeSi are compared with those obtained for pure Fe. The SMM results for Fe show strong consistency with existing experimental measurements and alternative computational data. The additional SMM findings are novel and offer predictions that can guide future experimental investigations.
FeSi, self-diffusion, activation energy, pre-exponential factor, self-diffusion coefficient
OPTIMAL PARTICLE SIZE OF Ag3PO4 PHOTOCATALYSTS ACHIEVED BY pH-CONTROLLED SYNTHESIS
Silver orthophosphate (Ag3PO4, APO) was synthesized by a simple co-precipitation method using AgNO3 and K2HPO4.3H2O as precursors. The pH of the precursor solution was adjusted by adding a HNO3 solution (0.5 M), which effectively controlled the particle size without altering the crystal structure. The samples in this work were prepared as APO–xH, where x represents the volume (mL) of HNO₃ added (0, 0.5, 1.0, 1.5, 2.0, and 2.5 mL). The particle size decreased systematically from ~450 nm (APO–0H) to ~150 nm (APO–2.5H). APO–1.5H, with an average size of ~250 nm, represented the “optimal size,” achieving complete degradation of 10 ppm Rhodamine B within 14 minutes under visible light irradiation from a 50 W compact fluorescent lamp, twice as fast as pristine APO. In preliminary cycling performed only on the reference APO–0H sample, the RhB degradation efficiency decreased to ~30% by the fifth cycle under visible-light irradiation. These findings confirm that the optimal photocatalytic activity of Ag3PO4 does not originate solely from increased surface area but from a balance between particle size, morphology, and structural stability. This work provides a simple approach to tailor Ag3PO4 for efficient visible-light-driven water treatment.
photocatalytic, silver phosphate, particle size
DENSITY FUNCTIONAL THEORY APPROACH IN INVESTIGATING STRUCTURAL AND ELECTRONIC PROPERTIES OF BISMUTH-BASED PHOTOCATALYSTS
Utilizing Density Functional Theory (DFT) as the computational method, we aimed to gain insights into the structural and electronic characteristics of Bi-based photocatalysts, particularly bismuth tungstate and bismuth molybdate. Both materials exhibit an orthorhombic structure and belong to the space group Pca21 under certain conditions. The exchange-correlation functional used throughout the study was the Perdew-Burke-Ernzerhof (PBE) functional within the generalized gradient approximation (GGA), enabling detailed analyses of their crystal structure, electronic band structure, density of states, and charge density. The electronic properties of both photocatalysts exhibit similar features as expected from the similarities in crystal structure. Notably, bismuth molybdate has a narrower band gap than bismuth tungstate, attributed to the atomic size difference between molybdenum and tungsten. The results confirm their semiconductor nature, highlighting their potential for sustainable-energy photocatalytic applications.
DFT, Bismuth tungstate, Bismuth molybdate, photocatalyst, band gap
EFFECT OF ULTRASOUND TREATMENT COMBINED WITH SODIUM HYDROGEN SULFITE ON THE QUALITY OF POSTHARVEST LONGAN FRUIT
Longan is one of the fruits with a high economic value in Vietnam and is grown in both Northern and Southern provinces. However, the quality of longan fruits deteriorates quickly after harvest. The study aimed to combine ultrasound (US) treatment with a sodium hydrogen sulfite (SHS) solution as the wave transmission medium to reduce color changes and maintain the quality of longan fruit during storage at 25℃. Longan fruit was treated with US at a frequency of 192 kHz combined with SHS solutions at concentrations of 0.25% and 0.5% (w/v) for 1.5, 2.5, and 5.0 minutes. The results showed that the 0.5% SHS + US 1.5 min treatment effectively delayed color change of longan peel and reduced weight loss of the fruit, but did not affect the edible quality, including total titratable acidity and soluble solid content (oBrix), while maintaining vitamin C, total phenolic content, and antioxidant activity of longan fruit, compared to the control during 8 days of storage at 25℃. These results suggest that ultrasound treatment combined with sodium hydrogen sulfite can be potentially used for the preservation of longan fruit.
antioxidant capacity, Dimocarpus longan L., longan fruit, sodium hydrogen sulfite, ultrasound
as the science and techniques applied after the harvesting of crops to preserve quality, minimize spoilage, ensure food safety, and improve marketability.
DIFFERENTIAL VARIATIONAL INEQUALITIES VIA THE EXTENDED LASALLE’S INVARIANCE PRINCIPLE APPROACH
In this work, we establish an extended LaSalle’s invariance for a class of nonautonomous differential inclusions in Euclidean spaces. We also give sufficient conditions for the stability of an equilibrium of differential variational inequalities. Special cases as linear complementarity problems, based on LaSalle’s invariance in both autonomous and non-autonomous cases, are also studied in this paper.
differential variational inequality; LaSalle’s invariance principle; Lyapunov functions
PRELIMINARY STUDY OF SPECIES COMPOSITION AND DISTRIBUTION OF BEETLES (INSECTA: COLEOPTERA) IN DU GIA COMMUNE, DU GIA NATIONAL PARK - DONG VAN KARST PLATEAU, TUYEN QUANG PROVINCE
This study investigated the species composition and distribution of beetles across three habitats in Du Gia commune, located within Du Gia National Park - Dong Van Karst Plateau, Tuyen Quang Province. The study employed a direct survey of beetles across three habitats, conducted over three sampling periods. A total of 39 beetle species, belonging to 10 families and 33 genera, were recorded. The family Coccinellidae contained the highest number of taxa, with 13 species (33.33%) and 10 genera (30.30%). Three families, Phalacridae, Ptinidae, and Scarabaeidae, had the lowest number, each with one species (2.56%) and one genus (3.03%). The distribution of beetle species varied among habitats. The natural forest habitat supported the highest diversity, with 38 species (97.45%) recorded; followed by the grassland and shrub habitat on the mountainside with 34 species (87.18%); and the agricultural land and fruit tree habitat with 24 species (61.52%). The composition of beetle species also varied across survey phases. Phase 1 (October 2024) yielded the highest species richness, with 39 species recorded (100%); Phase 2 (January 2025) with 21 species (53.85%); and Phase 3 (March 2025) with 35 species (89.74%).
species composition, distribution, beetles, Du Gia commune, Du Gia National Park - Dong Van Karst Plateau, Tuyen Quang
ASSESSMENT OF METEOROLOGICAL DROUGHT SEVERITY IN THE FORMER HA GIANG PROVINCE, NORTHERN VIETNAM
The former Ha Giang Province in Northeastern Vietnam, characterized by complex mountainous terrain and climatic variability, is prone to drought. This study assesses meteorological drought severity using the aridity index (K) and monthly drought frequency (P), derived from meteorological data (1960–2024) collected at 18 meteorological, hydrological, and rainfall stations across the study area. Results show that monthly K values ranged from 0.1 to 3.1, peaking in February, while annual averages ranged from 0.1 to 0.5. Based on P, drought severity was classified into three levels: mild, moderate, and severe, with the highest frequencies in December and April. These findings provide a scientific basis to support disaster prevention and drought mitigation efforts in the region.
meteorological drought, Ha Giang, aridity index (K), monthly drought frequency (P)
THE THERMODYNAMIC CONTACT ANGLE IN THE PREWETTING PHASE OF A BINARY BOSE-EINSTEIN CONDENSATE MIXTURE
To investigate the prewetting state of a Bose-Einstein condensate (BEC) mixture adsorbed on an optical hard wall at zero temperature, we consider a system in which condensate 1 coexists with condensate 2 with the chemical potential held fixed. Using the double parabola approximation (DPA) and solving the coupled Gross-Pitaevskii equations, we derive an analytical expression for the thermodynamic contact angle based on Youngs equation. Although the resulting formula is not algebraically simple, it reveals that complete wetting can occur before the bulk coexistence point is reached, indicating the presence of a continuous (second-order) prewetting transition. Our findings are in agreement with theoretical predictions in the literature and emphasize that the wetting film thickness grows smoothly without a discontinuous jump. This work provides useful guidance for the design of experiments aimed at observing wetting phenomena in Bose-Einstein condensates.
Bose-Einstein condensate, Gross-Pitaevskii theory, Prewetting phase transition, Thermodynamic contact angle
ROOTS OF COMPLEX HARMONIC POLYNOMIALS IN ONE VARIABLE
In this paper, we establish some bounds on the moduli of the zeros of complex harmonic polynomials in one variable. We also present explicit examples that illustrate these results. Our findings contribute to a deeper understanding of zeros of complex harmonic polynomials in one variable.
harmonic functions, harmonic polynomials, complex polynomials
ULTIMATE BOUNDS OF RAPIDLY TIME-VARYING SYSTEMS: AN AVERAGING APPROACH
This paper addresses the problem of state bounding for rapidly time-varying linear systems with bounded disturbances. Based on an averaging method and Lyapunov scheme, we derive an explicit bound on the time-scale parameter for which an explicit form of asymptotic bound of solutions is obtained. An application in fast switching systems is presented to illustrate the effectiveness of the analysis results.
ultimate bounds, rapidly time-varying systems, averaging method
NEW DISTRIBUTIONAL RECORDS AND ACOUSTIC IDENTIFICATION OF HIPPOSIDERID BATS (CHIROPTERA: HIPPOSIDERIDAE) FROM SON LA AND LANG SON PROVINCES, NORTHERN VIETNAM
Son La and Lang Son provinces exemplify the characteristic natural conditions of Vietnam’s northwestern and northeastern regions, respectively. Defined by heterogeneous topography, diverse forest ecosystems, and extensive karst cave systems, these provinces constitute critical habitats supporting rich bat faunas, including species of conservation concern. However, local bat populations are increasingly threatened by illegal hunting, rapid urbanization, wind farm development, and other human activities. To assess the current diversity and conservation status of bats, which have been affected by these factors, we conducted intensive field surveys across representative habitats in Son La and Lang Son provinces with a focus on the family Hipposideridae. Six hipposiderid species were recorded during the surveys: Aselliscus stoliczkanus, Hipposideros armiger, H. cineraceus, H. gentilis, H. khaokhouayensis, and H. poutensis. They are distinct in morphological and acoustic characteristics. Among these, H. khaokhouayensis is globally rare and threatened, being listed as Endangered in Vietnam’s Red Data Book and as Vulnerable on the IUCN Red List of Threatened Species. It was recorded exclusively in Son La province, whereas the remaining five species were captured in both provinces. This study presents the first comprehensive comparative dataset on the echolocation calls of all six hipposiderid species recorded in the study areas, along with new distribution records of H. khaokhouayensis in northwestern Vietnam. These findings provide valuable insights into the regional diversity of Hipposideridae and establish a critical baseline for future taxonomic, ecological, conservation, and long-term monitoring research.
biodiversity, conservation, distribution, echolocation, Hipposideridae
BIVARIATE POLYNOMIAL INTERPOLATION BASED ON LINE INTEGRALS
We study bivariate polynomial interpolation based on line integrals over line segments connecting two points on two fixed straight lines in the plane. We provide a characterization of the sets of segments that uniquely determine the interpolation polynomial. We also construct illustrative examples for specific cases.
Polynomial interpolation, Mean-value interpolation, Line integral
SYNTHESIS, STRUCTURAL STUDIES AND ACETYLCHOLINESTERASE INHIBITION ACTIVITY OF SOME (E)-2-METHOXY-3-NITRO-4-(3-OXO-3-ARYLPROP-1-EN-1-YL)PHENYL ACETATES
A semi-synthetic process from vanillin (isolated from vanilla) was developed to obtain new esters with potential inhibitory activity against the acetylcholinesterase (AchE.). 2-Nitrovanillin was synthesized from vanillin by esterification, nitration, and hydrolysis reactions. Four chalcones were synthesized by acid-catalyzed condensation reaction of 2-nitrovanillin and methyl aryl ketone. The identity of 2-nitrovanillin and four chalcones was confirmed by thin-layer chromatography compared with the known compounds. Subsequent esterification of the chalcones with acetic anhydride yielded four new derivatives of (E)-2-methoxy-3-nitro-4-(3-oxo-3-(aryl)prop-1-en-1-yl)phenyl acetate. The structures of the four new compounds were elucidated by 1H NMR and 13C NMR spectra. The four compounds were evaluated for their inhibitory activity against AChE. and three of them exhibited significant activity.
vanillin, chalcone, acetate, acetylcholinesterase
ASSESSING SOIL EROSION SEVERITY IN TEMPORAL AND SPATIAL PATTERN: A CASE STUDY IN THE PLEIKU PLATEAU, GIA LAI PROVINCE
Soil erosion is one of the major causes of land degradation and negatively impacts the soil environment in the world. There are two approaches to assessing soil erosion severity (SES) in terms of the decline of soil productivity in a given area: (1) classifying actual soil loss according to erosion risk classes, and (2) comparing actual soil loss to soil loss tolerance to classify erosion severity. This paper aims to explore changes in SES during 2005–2015 in the Pleiku Plateau, Gia Lai province, Vietnam, as a case study for comparing the two approaches. Regarding actual soil erosion, the average soil erosion rate declined by 0.16 ton/ha/year in the plateau terrain and increased by 0.02 ton/ha/year in the mountain relief. During 2005-2015, the low erosion risk area decreased by 6,302 ha, while the remaining erosion risk classes increased. With respect to soil erosion severity, the tolerable and moderate soil erosion acreages reduced by about 671.8 ha and 2,266.7 ha, respectively, and the high and severe ones increased; however, the severe soil erosion areas grew drastically. The differences between the two approaches come from consideration of the soil loss tolerance in assessing soil erosion severity. Thus, in order to assess SES for a region, comparing actual soil loss to soil loss tolerance provides SES indices that reflect the soil erosion problem, rather than only classifying actual soil loss. The findings are of enormous significance for environmental management, especially in addressing soil degradation.
soil erosion, severity, tolerance, changes, land cover, Pleiku
RESEARCH ON THE TECHNOLOGICAL PARAMETERS OF ORANGE RAKIA PRODUCTION
This research aims to identify the technological parameters involved in the production of rakia from Ha Giang oranges. The fermentation must was prepared by adding the disinfectant and antioxidant K2S2O5 at a concentration of 150 mg/L to ensure the sterility and stability of the orange juice for the subsequent fermentation stage. Using the native yeast strain Saccharomyces cerevisiae HB2 isolated from oranges, the factors influencing the fermentation process were determined, including fermentation temperature of 30oC, initial total soluble solids after adding sugar of 20°Bx, initial yeast cell density of 8.5 x 106 CFU/mL, and pH of 4.1. At the pilot scale of 5 liters, after fractional distillation and the removal of 3% ethanol from the head and 3% from the tail fractions, the resulting heart fraction had an alcohol concentration of 53% vol. After dilution to a final alcohol concentration of 35% vol by distilled water, the finished rakia had a characteristic orange aroma. The sensory score achieved was 18.16, which is in the ‘good’ category.
fermentation process, fermentation factor, orange juice, native yeast, rakia
EZMATH: DEVELOPING DIGITAL METHODS, A WEBSITE-BASED APPROACH TO SUPPORT TEACHING MATH WITH FIRST-GRADE VIETNAMESE CHILDREN WITH DYSCALCULIA
Dyscalculia is a term used to describe specific learning disabilities related to understanding numbers that affect the ability of children of all ages to understand, learn, and perform mathematics and number-based calculations. Estimates of the prevalence of dyscalculia range from 3% to 6% of the population, indicating the need for timely support solutions for teaching mathematics to students with mathematical difficulties. Therefore, the general objective of this study is to develop a digital tool in the form of an interactive learning website that provides many features and flexibility for children with dyscalculia. The solution was surveyed with 73 people working in and researching education for children with dyscalculia. The results show that the proposed solution is initially assessed to be appropriate and to offer an opportunity for developing a potential learning method to support children with dyscalculia.
dyscalculia, learning disabilities, support, inclusive education
THE PHYSICAL ORIGIN OF FIDELITY ENHANCEMENT IN THE TELEPORTATION PROTOCOL OF AN ARBITRARY TWO-QUBIT STATE UNDER AMPLITUDE-DAMPING NOISE ENVIRONMENT
A new analytical expression for the average quantum fidelity of a teleportation protocol for an arbitrary two-qubit state transmitted through an amplitude-damping noise environment has been established. This expression shows that the average fidelity depends not only on the purity measure and the bipartite entanglement measure of each parallel state forming the quantum channel, but also on the multipartite entanglement measure. This entanglement is generated between the qubits of each parallel state when they interact independently with the amplitude-damping environment. Based on this analytical relation, the physical mechanism for enhancing the teleportation protocol’s average quantum fidelity under two distinct amplitude-damping noise scenarios has been elucidated.
amplitude-damping noise, optimal averaged fidelity, entanglement measure, purity measure, multipartite entanglement
ASSESSMENT OF DROUGHT IN THE SOUTHERN SUB-REGION OF THE RED RIVER DELTA FOR AGRICULTURAL DEVELOPMENT
The southern sub-region of the Red River Delta possesses favorable natural conditions for agricultural development and plays an important role in the country’s agricultural output. Nevertheless, this region is highly vulnerable to natural disasters, particularly droughts, which pose significant challenges to agricultural productivity. This study applies a combination of statistical and spatial analysis methods to examine drought characteristics in the Southern Subregion of the Red River Delta. The research methodology included: (i) calculation of the K drought index, (ii) estimation of drought and extreme drought frequency, (iii) application of simple linear regression analysis, and (iv) interpolation using the Inverse Distance Weighting (IDW) method. Monthly precipitation and evapotranspiration data from 1991 to 2020 were utilized. The results show that droughts occurred in almost all months, except August and September, with the most severe events concentrated in December, January, and February. Although the region is relatively homogeneous, spatial variations are apparent. Ha Nam Province consistently recorded the lowest drought severity across all indicators, including drought frequency, extreme drought frequency, and the annual drought index. In contrast, a prominent elongated zone (or “trough”) with a high frequency of severe drought months is evident in the spatial distribution maps. Additionally, a drought tongue with increasing severity extends from Ha Nam in a northeast–southwest direction toward Van Ly (Nam Dinh). These findings provide critical insights for disaster risk reduction and serve as a scientific basis for agricultural planning and sustainable development in the region.
natural disasters, drought, K drought index, drought frequency, dry seasons, Red River Delta
THE FIRST EVALUATION OF TYROSINASE AND ELASTASE INHIBITORY ACTIVITIES OF GRAYANANE-TYPE DITERPENOIDS ISOLATED
From the methanol extract of the aerial parts of Rhododendron brachycarpum, five grayanane-type diterpenoids were isolated. These grayanane-type diterpenoids were elucidated by detailed analyses of NMR and MS data and identified as grayanoside B (1), rhodomoside A (2), piersformoside B (3), grayanotoxin III (4), and grayanotoxin I (5), based on comparison with previously reported spectral data. All compounds were evaluated for inhibitory activity against tyrosinase and elastase. The results revealed that the compounds 1-5 exhibited weak tyrosinase inhibitory activity, whereas compounds 1, 3, and 4 showed strong elastase inhibition, with inhibition rates of 71.78%, 71.11%, and 85.19%, respectively, at a concentration of 1mM. This study represents the first report of the anti-tyrosinase and anti-elastase activities of grayane-type diterpenoids isolated from R. brachycarpum.
Rhododendron brachycarpum, grayanane-type diterpenoids, tyrosinase, elastase enzymes
INVESTIGATION OF THE PROPERTIES AND ENHANCED PHOTOCATALYTIC ACTIVITY OF Bi₂WO₆/g-C₃N₄ COMPOSITE MATERIALS
Bi₂WO₆/g-C₃N₄ composite materials with varying g-C3N4 weight fractions (5%, 10%, 15% and 20%) were successfully synthesized using a combined microwave-hydrothermal method. The structural, morphological, and optical properties of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis absorption spectroscopy, and photoluminescence (PL) spectroscopy. Photocatalytic performance was evaluated by the degradation of Rhodamine B (RhB) under simulated sunlight, employing a cutoff filter to eliminate wavelengths below 400 nm. The incorporation of g-C3N4 into Bi₂WO₆ was found to significantly modify its morphology and enhance its optical absorption. All composite samples exhibited superior photocatalytic activity compared to pure Bi₂WO₆, with the 10 wt% g-C3N4 composite achieving the highest degradation rate, approximately seven times that of pristine Bi₂WO₆. This enhancement is primarily attributed to the formation of a Z-scheme heterojunction between Bi₂WO₆ and g-C3N4, which promotes efficient charge separation and suppresses electron-hole recombination via electron trap centers.
composite materials, photocatalytic activity, hydrothermal method, semiconductor, heterojunction
STUDY ON THE SYNTHESIS OF g-C₃N₄/LaFeCuO₃ HYBRID MATERIALS FOR THE DEGRADATION OF CIPROFLOXACIN
In this study, the photocatalysts g-C₃N₄, LaFeCuO₃, and the composite 10%g-C₃N₄/LaFeCuO₃ were prepared using a combination of sol-gel, pyrolysis, and ultrasonic-assisted synthesis methods.Their surface characteristics, including the crystal structure, elemental composition, morphology, optical absorption, and electron-hole recombination, were investigated through XRD, EDX, FE-SEM, UV-vis DRS, and photoluminescence (PL) spectroscopy. The role of ammonium persulfate agent (APS) in the degradation of ciprofloxacin (CIP) under light irradiation in the absence of photocatalysts was also examined. Results indicated that APS generated highly oxidative radicals (SO₄•⁻ and •OH), contributing significantly to the degradation of CIP. The optimal APS volume was 0.8 mL of 0.25M APS, achieving 82.35% CIP degradation after 180 minutes. In the presence of both APS and photocatalysts, LaFeCuO₃, g-C₃N₄, and 10%g-C₃N₄/LaFeCuO₃ materials achieved degradation efficiencies of 81.78%, 78.61%, and 96.3%, respectively, under the same experimental conditions, specifically, a CIP concentration of 20 ppm, photocatalyst loading of 1.5 g/L, and solution pH of 4.6. This improvement is attributed to the enhanced formation of free radicals facilitated by the presence of the photocatalysts.
g-C₃N₄/LaFeCuO₃ composite, persulfate activation, ciprofloxacin degradation
ON STABILIZATION OF DISCRETE-TIME 2-D SYSTEMS IN ROESSER MODEL
This paper focuses on the stabilization problem of discrete 2-D linear systems described by the Roesser model. A tractable stability condition in terms of linear matrix inequalities is first reformulated. Then, two controller design schemes are developed to formulate stabilization conditions via state-feedback controllers (SFCs) and event-triggered controllers (ETCs). Numerical examples with simulations are given to illustrate the effectiveness of the design conditions.
2-D systems, Roesser model, event-triggered control