Search Results (94)

Red sage (Salvia miltiorrhiza Bunge) is a perennial herb containing various bioactive compounds that promote human health. In this study, single-factor experiments were first conducted, followed by the optimization of extraction conditions to maximize the saponin content from red sage root extracts. In the single-factor experiments, the highest saponin content (47.5 ± 0.88 mg/g) was obtained using 80% ethanol, a solvent-to-material ratio of 40:1 (mL/g), an extraction period of 3 h, and an extraction temperature of 60 °C. Response Surface Methodology (RSM) was performed to optimize the extraction parameters with a material-to-solvent ratio of 41.31:1 (mL/g), an extraction temperature of 58.08 °C, and an extraction time of 3.16 h. Under these optimized conditions, the experimental saponin content reached 47.71 ± 0.15 mg/g. Additionally, crude extract of red sage exhibited antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals with an IC₅₀ value of 16.24 µg/mL. This extract also demonstrated anticancer against 61.79 ± 3.57% HepG2 cancer cells at a concentration of 100 µg/mL. Full article

Resol phenol–formaldehyde (PF) resin was modified with 2.5 and 5.0 wt% polymethylhydrosiloxane (PMHS). This study characterizes the modified resin and its subsequently fabricated glass fiber (GF)-reinforced composites (30–60 wt% GF). Formation of an organic–inorganic hybrid network, via reaction between Si-H groups of PMHS and hydroxyl (-OH) groups of the resol resin, was confirmed by FTIR and ¹H NMR. DSC and TGA/DTG revealed enhanced thermal stability for PMHS-modified resin: the decomposition temperature of Resol–PMHS 5.0% increased to 483 °C (neat resin: 438 °C), and char yield at 800 °C rose to 57% (neat resin: 38%). The 60 wt% GF-reinforced Resol–PMHS 5.0% composite exhibited tensile, flexural, and impact strengths of 145 ± 7 MPa, 160 ± 7 MPa, and 71 ± 5 kJ/m², respectively, superior to the unmodified resin composite (136 ± 6 MPa, 112 ± 6 MPa, and 51 ± 5 kJ/m²). SEM observations indicated improved fiber–matrix interfacial adhesion and reduced delamination. These results demonstrate that PMHS modification effectively enhances the thermo-mechanical properties of the PF resin and its composites, highlighting potential for industrial applications. Full article

In this study, we present a novel surface-enhanced Raman scattering (SERS) substrate based on porous silicon microcavities (PSiMCs) decorated with silver nanoparticles (AgNPs) for ultra-sensitive molecule detection. This substrate utilizes a dual enhancement mechanism: the localized surface plasmon resonance (LSPR) of AgNPs and the optical resonance of the PSiMC structure, which together create intense electromagnetic hot spots and prolong photon–molecule interactions. The porous architecture provides a large surface area for uniform nanoparticle distribution and efficient analyte adsorption. The AgNP/PSiMC substrate demonstrates an impressive detection limit of 1.0 × 10⁻¹³ M for rhodamine101 and 1.0 × 10⁻¹⁰ M for methyl parathion, outperforming many previously reported SERS platforms. Furthermore, the substrate exhibits excellent signal uniformity (RSD ≈ 6.14%) and long-term stability, retaining over 50% signal intensity after 28 days. These results underscore the potential of AgNP/PSiMCs as highly efficient, reproducible, and scalable SERS platforms for trace-level chemical and environmental sensing applications. Full article

The Mekong Delta, an important agricultural and economic hub in Vietnam, has suffered from severe water quality issues caused by both natural and anthropogenic forces. This paper aims to conduct a rational statistical approach to evaluate the current situation of surface water quality in the Mekong Delta, applying Factor Analysis (FA), Principal Component Analysis (PCA), and Agglomerative Hierarchical Clustering (AHC) to a database of 3117 samples collected by national and provincial monitoring stations. The results revealed significant contamination with organic pollutants (BOD5: 3.50–172.870 mg/L, COD: 6.493–472.984 mg/L), pesticides (e.g., DDTs: n.d to 1.227 mg/L), trace metals (As: 0.006–0.046 mg/L, Cr: n.d–1.960 mg/L), and microbial indicators (Coliforms: n.d–45,100 MPN/100 mL), often higher than the WHO drinking water threshold. PCA/AHC analysis identified the following five major pollution components: (1) organic pollution and sewage/industrial and deposited chemicals (PCA1—23.08% variance); (2) pesticide and agricultural runoff derived contamination with Hg (PCA2—15.44%); (3) microbial pollution of the water was found to correlate positively with Zn and Cu content (PCA3—8.90%); (4) salinity was found to mobilize As and Cr (PCA4—8.00%); (5) nutrient/microbial pollution presumably from agricultural and sewage inputs (PCA5—7.22%). AHC showed some spatial variability that grouped samples in urban/industrial (Cluster 1), rural/agricultural (Cluster 2), and a highly contaminated one, where water was toxic and presented with microbial and Cd contamination (Cluster 3). Levels of pesticides, Cr, and microbial pollution were higher than reported in previous Mekong Delta studies and exceeded regional trends. These results emphasize the importance of holistic water management strategies, including better wastewater treatment, pesticide control, sustainable farming, and climate-adaptive measures to reduce saltwater intrusion and safeguard drinking water quality for the Mekong Delta. Full article

The high-pressure die-casting (HPDC) process involves injecting molten light metal into a steel mold under high pressure, resulting in parts with excellent surface quality and precise dimensions. However, this process subjects the mold to thermal fatigue and mechanical stress, which can lead to damage over time. This study investigated the wear characteristics of two types of inserts made from different steel materials, SKD61 steel and FDAC steel, under HPDC conditions. A thorough approach that combined computer simulations, experiments, and 3D scanning was employed to analyze wear patterns and dimensional changes after up to 300 casting cycles. The results indicate that the SKD61 steel outperformed the FDAC steel in terms of wear resistance and dimensional stability. The maximum deposition values of the SKD61 mold were only 0.009 mm, which was only 25% compared to the FDAC mold, indicating a significantly higher wear resistance. These findings are crucial for selecting and enhancing insert materials in HPDC, ultimately leading to higher-quality and more efficient casting. Full article

Background/Objectives: Limited data exist on the nutritional status of Vietnamese children aged 5 years and older. This study aimed to (1) determine the nutritional status and (2) assess the associations between malnutrition and socio-demographic factors among children and adolescents aged 5–19 years old in selected provinces in Vietnam. Methods: A cross-sectional study was conducted on 3055 children aged 5–19 years old. Children’s weight and height were collected to calculate BMI for Age Z-score and Height for Age Z-score to determine the prevalence of overweight/obesity, stunting, thinness/underweight, stunted-overweight, stunted-underweight, at least one type of undernutrition, and at least one type of malnutrition. Results: The prevalence of stunting and thinness/underweight was around 10%, overweight and obesity was 14.5%, while the prevalence of malnutrition was 36.5%, with 19.7% of children experiencing at least one form of undernutrition. Significant associations were found between malnutrition and socio-demographic factors such as age, ethnicity, and the number of household possessions. Stunting was more prevalent among older children and those from lower-income households, whereas overweight and obesity were more common in wealthier families. Conclusions: These novel findings highlight the need for targeted interventions addressing both undernutrition and obesity in Vietnam’s diverse demographic groups. Full article

Background/Objectives: Venous thromboembolism (VTE) is related to maternal mortality, especially after the coronavirus disease (COVID-19) pandemic. The Royal College of Obstetricians and Gynecologists (RCOG) guidelines’ risk assessment score has been established to reduce thrombotic complications during pregnancy. Recently, it was found that the soluble fibrin monomer complex (SFMC) could be an alternative to D-dimer (DD), which has been used to assess the risk of VTE. This study aims to reveal the difference between FM and DD concentrations in low- and high-VTE-risk groups according to the RCOG’s guidelines. Method: This observational study was conducted at the Department of High-Risk Pregnancy, Tu Du Hospital, Vietnam between August 2023 and April 2024. This study enrolled 100 pregnant women beyond 28 weeks of gestation at low risk (≤2 points) and high risk (≥3 points) of VTE assessment following the RCOG guidelines’ score. Blood samples were collected for the SFMC and DD tests before delivery. Statistical tests were used to compare the difference in SFMC and DD concentrations between the two groups. A p-value < 0.05 is considered statistically significant. Results: We found no significant difference in DD and SFMC tests between low and high VTE risk (1.61 [1.30–2.30] vs. 1.51 [0.91–2.13]; 5.00 [1.36–9.78] vs. 3.74 [1.28–14.63], respectively; p > 0.05). The length of hospital stay in the high-risk group is longer than that of the low-risk group and involves postpartum infection. In addition, we found no significant correlation between the gestational age and SFMC or DD concentration. However, a moderate positive correlation between the two tests was found. Similarly, no significant correlation between the VTE score and SFMC or DD concentration was found in the present study. Conclusions: The soluble fibrin monomer complex and D-dimer tests are not significantly different between low-risk and high-risk groups determined through VTE evaluation before delivery according to the RCOG guidelines. The fibrin-linked tests need to be individualized and applied among pregnant women with higher scores of VTE risk based on maternal and pregnancy characteristics during antenatal care. Further studies with a larger number of participants are required to strengthen the findings. Full article

In the field of biomedical engineering, the issue of drug delivery constitutes a multifaceted and demanding endeavor for healthcare professionals. The intravenous administration of pharmacological agents to patients and the normalization of average arterial blood pressure (AABP) to desired thresholds represents a prevalent approach employed within clinical settings. The automated closed-loop infusion of vasoactive drugs for the purpose of modulating blood pressure (BP) in patients suffering from acute hypertension has been the focus of rigorous investigation in recent years. In previous works where model-based and fuzzy controllers are used to control AABP, model-based controllers rely on the precise mathematical model, while fuzzy controllers entail complexity due to rule sets. To overcome these challenges, this paper presents an adaptive closed-loop drug delivery system to control AABP by adjusting the infusion rate, as well as a communication time delay (CTD) for analyzing the wireless connectivity and interruption in transferring feedback data as a new insight. Firstly, a nonlinear backstepping controller (NBC) is developed to control AABP by continuously adjusting vasoactive drugs using real-time feedback. Secondly, a model-free deep reinforcement learning (MF-DRL) algorithm is integrated into the NBC to adjust dynamically the coefficients of the controller. Besides the various analyses such as normal condition (without CTD strategy), stability, and hybrid noise, a CTD analysis is implemented to illustrate the functionality of the system in a wireless manner and interruption in real-time feedback data. Full article

Enhancing the efficiency is an essential target of the wireless power transfer (WPT) technology. Enabling the WPT systems requires careful control to prevent power from being transferred to unintended areas. This is essential in improving the efficiency and minimizing the flux leakage that might otherwise occur. Selective field localization can effectively reduce the flux leakage from the WPT systems. In this work, we propose a method using a digital honeycomb metamaterial structure that has a property operation as a function of switching between 0 and 1 states. These cavities were created by strongly confining the field by using a hybridization bandgap that arose from wave interaction with a two-dimensional array of local resonators on the metasurface. A WPT efficiency of 64% at 13.56 MHz was achieved by using the metamaterial and improved to 60% compared to the system without the metamaterial with an area ratio of Rx:Tx~1:28. Rx is the receiver coil, and Tx is the transmitter one. Full article

The design and control of lower-limb rehabilitation robots for patients after a stroke has gained significant attention. This paper presents the dynamic analysis and control of a 3-degrees-of-freedom lower-limb rehabilitation robot using combined position–force control based on the force feed-forward and compensative gravity proportional derivative methods. In the lower-limb rehabilitation robot, the interaction force between the patient with the joints and links of the robot is uncertain and nonlinear due to the disturbance effect of Coriolis force, centrifugal force, gravitational force, and friction force. During recovery stages, the forces exerted by the patient’s lower limbs are also considered disturbances. Therefore, to meet the quality requirements in using the rehabilitation robot with different recovery stages of patient training, combining position control and force control is essential. In this paper, we proposed a combination of proportional–derivative gravity compensation motion control and force feed-forward control to form an advanced combined controller (position–force feed-forward control—PFFC) for a 3 DOF lower-limb functional rehabilitation robot. The forces can be sensed using a 3-axis force sensor. In addition, the robot’s position parameters are also measured by encoders. The control algorithm is implemented on the STM32F4 Discovery board. A verified test of the proposed control method is shown in the experiments, showing the good performance of the system. Full article

Environmental changes and human impact can alter biodiversity in negative manners that affect mankind’s sustainable development. Particularly, such effects on inland waters are even more concerning, as those ecosystems play essential roles in sustaining human life as well as relevant wildlife. Thus, in this study, we investigated such effects on microbial diversity in inland waters in Vietnam using bacterial communities in sediment as indicators. To do this, we collected sediment samples from various locations in three respective regions (Red river in the north, Ba river in the central area, and Mekong delta flood zone in the south) using standard methods, extracted their total DNA, sequenced their V3-V4 16S rRNA gene fragments using an Illumina Miseq platform and analyzed the sequences to infer the diversity of the bacterial communities in the samples. These communities were compared in terms of richness (alpha diversity) and composition (beta diversity), and the correlations between their diversity levels and environmental factors, as well as human activities, were analyzed by using standard statistical tools. Our results showed that the communities were different from each other solely by region, in richness and critically in composition, although there were some communities distinctively different from all the others. Among environmental factors, only water salinity (and conductivity) had negative correlations with alpha-diversity indices of the bacterial communities, and phosphate concentration and turbidity had positive correlations, while the other factors had almost no correlations, which partially explains the region-specific diversity. These results also suggest that climate change incidences, especially sea intrusion, can have significant effects on microbial diversity in inland waters. The impact of human activities did not appear severe, solely affecting bacterial community richness, but not significantly affecting bacterial community composition. However, apparently reduced bacterial diversity in several sites with intense human impacts and distinct environmental conditions should be noted and deserve further investigation. Full article

Groundwater sources have been exploited excessively for numerous purposes worldwide, leading to increasingly severe depletion. However, the replenishment of groundwater sources has not usually been a focus in economically and socially underdeveloped countries and regions. In coastal provinces of the Vietnamese Mekong Delta (VMD), rural areas are facing difficulties in accessing fresh water due to shortages from the water supply plant and excessive use of groundwater, highlighting an urgent need for sustainable development solutions. Our study first conducted interviews with 200 households in Ca Mau Province of the VMD to identify the current situation and the challenges and obstacles of rainwater harvesting and to find sustainable and proactive solutions. We then analyzed daily rainfall data from 10 meteorological stations to construct four scenarios of the water balance method: (i) potential rainwater harvesting based on existing roof area; (ii) optimal scale of storage tank and catchments for different levels of water usage; (iii) tank scale utilizing rainwater entirely during the rainy season and basic needs during the dry season; and (iv) integrated water supply between rain and groundwater. The results showed that using rainwater entirely for domestic water supply requires large storage tank capacities, making these scenarios difficult to achieve in the near future. Our research introduces a novel integrated water supply approach to storing rain and groundwater that has demonstrated high effectiveness and sustainability. With existing tank capacities (0.8 m³ per person), rainwater could only meet over 48% (14 m³ per year) of the water demand while requiring 14.8 m³ of additional groundwater extraction. With a tank capacity of 2.4 m³ per person, ensuring rainwater harvesting meets basic demand, harvested rainwater could satisfy 64% of the demand, with artificial groundwater supplementation exceeding 1.79 times the required extraction, while excess rainwater discharge into the environment would be minimal. Our research results not only provide potential solutions for rainwater and groundwater collection to supplement sustainable domestic water sources for Ca Mau but also serve as an example for similar regions globally. Full article

This study surveys the impacts of injection parameters on the deformation rate of the injected flexure hinge made from ABS, PP, and HDPE. The flexure hinges are generated with different filling time, filling pressure, filling speed, packing time, packing pressure, cooling time, and melt temperature. The amplification ratio of the samples between different injection parameters and different plastic types is measured and compared to figure out the optimal one with a high amplification ratio. The results show that the relationship between the input and output data of the ABS, PP, and HDPE flexure hinges at different injection molding parameters is a linear relation. Changing the material or many injection molding parameters of the hinge could lead to a great impact on the hinge’s performance. However, changing each parameter does not lead to a sudden change in the input and output values. Each plastic material has different optimal injection parameters and displacement behaviors. With the ABS flexure hinge, the filling pressure case has the greatest amplification ratio of 8.81, while the filling speed case has the lowest value of 4.81. With the optimal injection parameter and the input value of 105 µm, the ABS flexure hinge could create a maximum average output value of 736.6 µm. With the PP flexure hinge, the melt temperature case achieves the greatest amplification ratio of 6.73, while the filling speed case has the lowest value of 4.1. With the optimal injection parameter and the input value of 128 µm, the PP flexure hinge could create a maximum average output value of 964.8 µm. The average amplification ratio values of all injection molding parameters are 6.85, 5.41, and 4.01, corresponding to ABS, PP, and HDPE flexure hinges. Generally, the ABS flexure hinge has the highest amplification ratios, followed by the PP flexure hinge. The HDPE flexure hinge has the lowest amplification ratios among these plastic types. With the optimal injection parameter and the input value of 218 µm, the HDPE flexure hinge could create a maximum average output value of 699.8 µm. The results provide more insight into plastic flexure hinges and broaden their applications by finding the optimal injection parameters and plastic types. Full article

This research focuses on the fabrication of plastic flexure hinges from diverse plastics such as ABS, PP, HDPE, and LDPE. To enhance hinge efficiency, the recycling ratios are also investigated. The amplification ratio of different recycle ratios and plastic types are measured. The results show that the input and output displacements of all PP, ABS, and HDPE hinges are linear. The presence of recycled plastics has no impact on this basis. The pure PP, ABS, and HDPE flexure hinges achieve the highest amplification ratios of 5.728, 8.249, and 5.668. The addition of recycled plastics reduces the amplification ratio. This decrease in the amplification ratio, however, is small. At a 25% recycle ratio, the PP, ABS, and HDPE flexure hinges have 12%, 13.3%, and 21.7% lower amplification ratios than the pure plastic hinges. Furthermore, the utilization of recycled plastics may lessen the need for new plastic made from raw materials. With the PP flexure hinge, a maximum input value of 157 µm could result in an output value of 886 µm. At a maximum input value of 115 µm, the ABS flexure hinge could achieve an output value of 833 µm. Finally, a maximum input value of 175 µm might result in an output value of 857 µm when using the HDPE flexure hinge. The average amplification ratio values for all recycling ratios for PP, ABS, and HDPE flexure hinges are, respectively, 5.35, 7.60, and 5.02. The ABS flexure hinge frequently outperforms the PP and HDPE flexure hinge in terms of amplification ratios. Among these plastics, HDPE flexure hinges have the lowest amplification ratio. In general, increasing the thermoplastic polyurethane (TPU) content of the LDPE/TPU blend increases the amplification ratio. The cause could be the TPU’s high compatibility with the LDPE polymer. The LDPE/TPU blend hinge offers a broader range of the amplification ratio of 2.85–10.504 than the PP, ABS, and HDPE flexure hinges. It is interesting that changing the blend percentage has a much greater impact on the amplification ratio than changing the recycling ratio. The findings broaden the range of applications for plastic flexure hinges by identifying optimal plastic types. The impact of the hinge shape on the performance of the injected plastic flexure hinge might be studied in further research. Full article

The desired performance of nucleic acid testing (NAT) may vary if used for disease diagnosis or for the evaluation of the therapeutic efficacy of a treatment, although in most cases, the same assay is used. However, these tests may not be affordable in many situations including in low/middle income countries that in response have developed domestic assays. Given the example of HCV NAT among people who inject drugs in Vietnam, we aimed at evaluating a domestic assay versus an FDA- and CE-approved assay. This cross-evaluation revealed that (i) the domestic assay had a poorer sensitivity with a threshold of detection above 10⁴ IU/mL, and (ii) the FDA-approved assay had a percentage of false negative results close to 1%. Together, in the present study, the domestic assay had a performance compatible with diagnosis purposes (given that this population was 70% HCV seropositive) but not compatible with HCV treatment monitoring (given that treatment failures are rare and the observed viremia frequently below the threshold of detection). This study highlights the need for a proper evaluation of HCV RNA domestic assays in order to efficiently contribute to the WHO HCV elimination target by 2030. Full article