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  • 1
    Online Resource
    Online Resource
    Comparison of the Basic Reproduction Numbers for COVID-19 through Four Waves of the Pandemic in Vietnam
    MDPI AG ; 2022
    In:  International Journal of Translational Medicine Vol. 3, No. 1 ( 2022-12-21), p. 1-11
    Details
    In: International Journal of Translational Medicine, MDPI AG, Vol. 3, No. 1 ( 2022-12-21), p. 1-11
    Abstract: Estimating the basic reproduction number (R0) of an infectious disease is a crucial step to describe the contagiousness and provides suggestions for interventions. To lift the effectiveness of preventive measures for the COVID-19 pandemic, we need to minimize the newly infected cases by reaching adequate herd immunity. This study thus aimed to compare the R0 through four waves of COVID-19 outbreaks in Vietnam and to calculate the minimal vaccination coverage in different populations. The data on the number of daily confirmed COVID-19 patients were collected from 21 January 2020 to 16 November 2021 from the daily reports through the four waves of the pandemic in Vietnam. The R0 values were estimated by exponential growth and the maximum likelihood methods to range from 1.04 to 3.31 from the first to the third wave. The fourth wave was the most severe, especially in the southern provinces, and the highest R0 was in Ho Chi Minh City. The herd immunity would range from 43.50% to 95.76% by various R0 values from different populations. Overall, the presence of new viral mutants increased the infectiousness and the vaccination coverage was higher to establish the required herd immunity in a high-density population. The results provide the basis for policy recommendations and resource allocation for vaccine management and distribution at a time when the COVID-19 pandemic is not yet over.
    Type of Medium: Online Resource
    ISSN: 2673-8937
    URL: Article
    DOI: 10.3390/ijtm3010001
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 3104818-3
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  • 2
    Online Resource
    Online Resource
    Ethnic Variations in Nutritional Status among Preschool Children in Northern Vietnam: A Cross-Sectional Study
    MDPI AG ; 2019
    In:  International Journal of Environmental Research and Public Health Vol. 16, No. 21 ( 2019-10-23), p. 4060-
    Details
    In: International Journal of Environmental Research and Public Health, MDPI AG, Vol. 16, No. 21 ( 2019-10-23), p. 4060-
    Abstract: (1) Background: Vietnam is a multiethnic country undergoing rapid economic development, the improvement in nutritional status in preschool children is not equally shared by all ethnic groups; (2) Methods: A cross-sectional study was performed from September–December 2018 on 16,177 children aged 24–60 months representing Kinh (n = 14421), Muong (n = 1307) and Tay (n = 449) ethnic groups. Prevalence of malnutrition, overweight, obesity and anthropometric indices were compared across ethnic groups, using WHO 2006 child growth standards; (3) Results: The prevalence of malnutrition among children of Kinh, Muong and Tay origins was 14.7%, 34.3% and 43.2%, respectively. The corresponding data for overweight was 5.5%, 2.7%, 2.2% and for obesity 2.8%, 0.8% and 0.4%, respectively. The prevalence of stunting remained the highest in three subtypes of malnutrition in all ethnic groups. Kinh children were heavier and taller than the other groups, while Muong children were taller than Tay children (p-value 〈 0.001); and (4) Conclusions: Malnutrition remains a major public health issue among children of minor ethnicities while overweight and obesity is an emerging challenge for the Kinh ethnic group. The results imply that a community-based intervention should be specific to ethnicity to reduce the gap in nutritional status between ethnic groups in Vietnam.
    Type of Medium: Online Resource
    ISSN: 1660-4601
    URL: Article
    DOI: 10.3390/ijerph16214060
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2175195-X
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  • 3
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    Online Resource
    Genetic Variation and Evolutionary History of the Threatened Dipterocarpus turbinatus C.F.Gaertn. Detected Using Microsatellites
    MDPI AG ; 2023
    In:  Diversity Vol. 15, No. 8 ( 2023-07-28), p. 894-
    Details
    In: Diversity, MDPI AG, Vol. 15, No. 8 ( 2023-07-28), p. 894-
    Abstract: Dipterocarpus turbinatus C.F.Gaertn. is a valuable timber tree indigenous to the lowland tropical forests of southern and central Vietnam. It is in danger of extinction due to fragmented habitats and overexploitation. Therefore, assessing the genetic diversity and demographic history of this species is essential to providing a platform for conservation activities. Herein, we analyzed 281 D. turbinatus trees from 10 populations representing their natural distribution range in Vietnam using nine polymorphic microsatellites to provide valuable information for conservation activities. We detected genetic diversity within these populations (0.285 and 0.328 for observed and expected heterozygosity, respectively), as well as population genetic differentiation (a Wei and Cockerham value of 0.202 and a Hedrick value of 0.32). Clustering analysis based on different approaches revealed three genetic clusters which were significantly correlated to gene flow across the geographic distribution range of D. turbinatus in tropical evergreen forests. Approximate Bayesian computation suggested that the D. turbinatus populations had an evolutionary history consistent with divergence during the last glacial maximum. Based on our results, we recommend the in situ conservation of several populations with high genetic diversity, high allelic richness, or private alleles, and the gathering of the seeds of the remaining populations for ex situ conservation.
    Type of Medium: Online Resource
    ISSN: 1424-2818
    URL: Article
    DOI: 10.3390/d15080894
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2518137-3
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  • 4
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    Comparison of Machine Learning Methods for Estimating Mangrove Above-Ground Biomass Using Multiple Source Remote Sensing Data in the Red River Delta Biosphere Reserve, Vietnam
    MDPI AG ; 2020
    In:  Remote Sensing Vol. 12, No. 8 ( 2020-04-23), p. 1334-
    Details
    In: Remote Sensing, MDPI AG, Vol. 12, No. 8 ( 2020-04-23), p. 1334-
    Abstract: This study proposes a hybrid intelligence approach based on an extreme gradient boosting regression and genetic algorithm, namely, the XGBR-GA model, incorporating Sentinel-2, Sentinel-1, and ALOS-2 PALSAR-2 data to estimate the mangrove above-ground biomass (AGB), including small and shrub mangrove patches in the Red River Delta biosphere reserve across the northern coast of Vietnam. We used the novel extreme gradient boosting decision tree (XGBR) technique together with genetic algorithm (GA) optimization for feature selection to construct and verify a mangrove AGB model using data from a field survey of 105 sampling plots conducted in November and December of 2018 and incorporated the dual polarimetric (HH and HV) data of the ALOS-2 PALSAR-2 L-band and the Sentinel-2 multispectral data combined with Sentinel-1 (C-band VV and VH) data. We employed the root-mean-square error (RMSE) and coefficient of determination (R2) to evaluate the performance of the proposed model. The capability of the XGBR-GA model was assessed via a comparison with other machine-learning (ML) techniques, i.e., the CatBoost regression (CBR), gradient boosted regression tree (GBRT), support vector regression (SVR), and random forest regression (RFR) models. The XGBR-GA model yielded a promising result (R2 = 0.683, RMSE = 25.08 Mg·ha−1) and outperformed the four other ML models. The XGBR-GA model retrieved a mangrove AGB ranging from 17 Mg·ha−1 to 142 Mg·ha−1 (with an average of 72.47 Mg·ha−1). Therefore, multisource optical and synthetic aperture radar (SAR) combined with the XGBR-GA model can be used to estimate the mangrove AGB in North Vietnam. The effectiveness of the proposed method needs to be further tested and compared to other mangrove ecosystems in the tropics.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs12081334
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2513863-7
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  • 5
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    Online Resource
    A Simple Empirical Band-Ratio Algorithm to Assess Suspended Particulate Matter from Remote Sensing over Coastal and Inland Waters of Vietnam: Application to the VNREDSat-1/NAOMI Sensor
    MDPI AG ; 2020
    In:  Water Vol. 12, No. 9 ( 2020-09-21), p. 2636-
    Details
    In: Water, MDPI AG, Vol. 12, No. 9 ( 2020-09-21), p. 2636-
    Abstract: VNREDSat-1 is the first Vietnamese satellite enabling the survey of environmental parameters, such as vegetation and water coverages or surface water quality at medium spatial resolution (from 2.5 to 10 m depending on the considered channel). The New AstroSat Optical Modular Instrument (NAOMI) sensor on board VNREDSat-1 has the required spectral bands to assess the suspended particulate matter (SPM) concentration. Because recent studies have shown that the remote sensing reflectance, Rrs(λ), at the blue (450–520 nm), green (530–600 nm), and red (620–690 nm) spectral bands can be assessed using NAOMI with good accuracy, the present study is dedicated to the development and validation of an algorithm (hereafter referred to as V1SPM) to assess SPM from Rrs(λ) over inland and coastal waters of Vietnam. For that purpose, an in-situ data set of hyper-spectral Rrs(λ) and SPM (from 0.47 to 240.14 g·m−3) measurements collected at 205 coastal and inland stations has been gathered. Among the different approaches, including four historical algorithms, the polynomial algorithms involving the red-to-green reflectance ratio presents the best performance on the validation data set (mean absolute percent difference (MAPD) of 18.7%). Compared to the use of a single spectral band, the band ratio reduces the scatter around the polynomial fit, as well as the impact of imperfect atmospheric corrections. Due to the lack of matchup data points with VNREDSat-1, the full VNREDSat-1 processing chain (atmospheric correction (RED-NIR) and V1SPM), aiming at estimating SPM from the top-of-atmosphere signal, was applied to the Landsat-8/OLI match-up data points with relatively low to moderate SPM concentration (3.33–15.25 g·m−3), yielding a MAPD of 15.8%. An illustration of the use of this VNREDSat-1 processing chain during a flooding event occurring in Vietnam is provided.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w12092636
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2521238-2
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  • 6
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    Online Resource
    Subcritical Water Extraction of Epigallocatechin Gallate from Camellia sinensis and Optimization Study Using Response Surface Methodology
    MDPI AG ; 2020
    In:  Processes Vol. 8, No. 9 ( 2020-08-22), p. 1028-
    Details
    In: Processes, MDPI AG, Vol. 8, No. 9 ( 2020-08-22), p. 1028-
    Abstract: Background: Camellia sinensis is a plant whose leaves and buds are used to produce tea. With many medicinal activities already found, green tea has been consumed widely in the world. Methods: The subcritical water extraction (SWE) of epigallocatechin gallate (EGCG) from green tea leaves and the effect of the different extraction conditions are investigated by response surface methodology (RSM). Furthermore, the model of the extraction processes is reviewed for application at the industrial scale. Results: Based on the RSM data, the maximum yield of extraction is determined via optimizing different parameters of the extraction processes. Optimal conditions are as follows: extraction time of 6 min, extraction temperature at 120 °C, and a sample/solvent ratio of 1:40 g/mL. Under such conditions, the best yield of EGCG is 4.665%. Moreover, the model of the extraction processes, which can be utilized for industry scale purpose, indicates a good correlation with the experimental data. Conclusions: Overall, SWE is competent and environmental-friendly, and it is also a highly selective and fast method. SWE is a promising method to take the place of organic solvents used in the extraction of weak polar and even non-polar natural compounds. Further studies on the scale-up of the extraction processes are ongoing.
    Type of Medium: Online Resource
    ISSN: 2227-9717
    URL: Article
    DOI: 10.3390/pr8091028
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2720994-5
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  • 7
    Online Resource
    Online Resource
    Water-Borne ZnO/Acrylic Nanocoating: Fabrication, Characterization, and Properties
    MDPI AG ; 2021
    In:  Polymers Vol. 13, No. 5 ( 2021-02-26), p. 717-
    Details
    In: Polymers, MDPI AG, Vol. 13, No. 5 ( 2021-02-26), p. 717-
    Abstract: This work aims to explore how ZnO nanoparticles enhance the mechanical, photoaging, and self cleaning properties of water borne acrylic coating. Micro/nano ZnO particles (at 2 wt.% of total solid resin) were dispersed into the acrylic polymer matrices using ultrasonication to understand the effect of the size of the coating properties. The effect of ZnO particles on the properties of composite coatings (25 µm of thick) have been evaluated through various tests, such as abrasion measurement, ultraviolet/condensation (UV/CON) weathering aging, and methylene blue self cleaning. Experimental data indicated that the incorporation of ZnO particles enhanced both abrasion resistance and methylene blue removal efficiency of the water borne acrylic coatings, with nano ZnO particles being the best. However, the weathering degradation of nanocomposite coatings was more severe as compared to the coating with micro ZnO (at the same ZnO content).
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym13050717
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2527146-5
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  • 8
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    Online Resource
    Application of Plasma Activation in Flame-Retardant Treatment for Cotton Fabric
    MDPI AG ; 2020
    In:  Polymers Vol. 12, No. 7 ( 2020-07-16), p. 1575-
    Details
    In: Polymers, MDPI AG, Vol. 12, No. 7 ( 2020-07-16), p. 1575-
    Abstract: Cotton fabric treated by Pyrovatex CP New (PCN) and Knittex FFRC (K-FFRC) using the Pad-dry-cure method showed an excellent fire-retardant effect. However, it needed to be cured at high temperatures for a long time leading to a high loss of mechanical strength. In this study, atmospheric-pressure dielectric barrier discharge (APDBD) plasma was applied to the cotton fabric, which then was treated by flame retardants (FRs) using the pad–dry-cure method. The purpose was to have a flame-retardant cotton fabric (limiting oxygen index (LOI) ≥ 25) and a mechanical loss of the treated fabric due to the curing step as low as possible. To achieve this goal, 10 experiments were performed. The vertical flammability characteristics, LOI value and tensile strength of the treated fabrics were measured. A response model between the LOI values of the treated fabric and two studied variables (temperature and time of the curing step) was found. It was predicted that the optimal temperature and time-to-cure to achieve LOI of 25 was at 160 °C for 90 s, while the flame-retardant treatment process without plasma pretreatment, was at 180 °C and 114 s. Although the curing temperature and the time have decreased significantly, the loss of mechanical strength of the treated fabric is still high. The tensile strength and scanning electron microscopy (SEM) images of the fabric after plasma activation show that the plasma treatment itself also damages the mechanical strength of the fabric. X-ray photoelectron spectroscopy (XPS) spectra of the fabric after plasma activation and energy-dispersive spectroscopy (EDS) analysis of the flame retardant-treated (FRT) fabric clarified the role of plasma activation in this study.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym12071575
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2527146-5
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  • 9
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    Online Resource
    Effect of Calcium Hydroxide on Compressive Strength and Microstructure of Geopolymer Containing Admixture of Kaolin, Fly Ash, and Red Mud
    MDPI AG ; 2023
    In:  Applied Sciences Vol. 13, No. 8 ( 2023-04-17), p. 5034-
    Details
    In: Applied Sciences, MDPI AG, Vol. 13, No. 8 ( 2023-04-17), p. 5034-
    Abstract: The current study aims to investigate the effect of calcium hydroxide on the geopolymer derived from an admixture of the natural mineral (kaolin) and industrial by-products (fly ash, red mud). The compressive strength and microstructure were studied using compressive strength tests, X-ray diffraction, infrared spectroscopy, BET method, and scanning electron microscopy. For the investigated NaOH activator concentrations ranging from 4 M to 10 M, the compressive strength of the geopolymer first increases, then decreases with the increase of calcium hydroxide content. The optimal content of calcium hydroxide, which can give the highest compressive strength of the geopolymer prepared, is about 13% wt. of solid raw materials. The geopolymer materials produced at the 8 M NaOH activator have higher compressive strength than those prepared at 4 M, 6 M, and 10 M NaOH. There is a coexistence of geopolymerization gel and C-S-H/C-A-S-H gel in the materials prepared. Both porosity and the formation of N-A-S-H/C-S-H/C-A-S-H during the polymerization process are important for the mechanical properties of materials.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app13085034
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704225-X
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  • 10
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    Awareness Related to Cardiometabolic Diseases: A Cross-Sectional Study in Southern Vietnam
    MDPI AG ; 2021
    In:  International Journal of Environmental Research and Public Health Vol. 18, No. 19 ( 2021-09-28), p. 10209-
    Details
    In: International Journal of Environmental Research and Public Health, MDPI AG, Vol. 18, No. 19 ( 2021-09-28), p. 10209-
    Abstract: Background: the prevalence of cardiometabolic diseases (CMDs), such as type 2 diabetes mellitus (T2DM) and hypertension, is increasing rapidly in developing countries. This study aims to assess the awareness of CMD among a selected population in Vietnam. Method: a cross-sectional random sample of 402 Vietnamese citizens in two districts (Thu Duc and 12th district) in Ho Chi Minh City were interviewed. Data on knowledge, attitude, and preventive behavior (KAB) of the two conditions were collected through an interview-based questionnaire. Results: the mean (± SD) age was 47.75 (± 15.61) years, and around 60.2% were female. Multiple logistic regression was performed to explore the association of sociodemographic factors, disease status, and awareness of the CMD. Females showed better awareness than males (OR = 3.89 (1.28–11.78)), and those with T2DM and hypertension had a significantly better awareness (OR = 8.33 (2.44–28.37)) than those without CMD. Conclusion: the awareness of CMD in our sample was poor. An extensive effort to increase awareness of CMD prevention is needed. Future studies and interventions can be developed more efficiently by targeting the right population.
    Type of Medium: Online Resource
    ISSN: 1660-4601
    URL: Article
    DOI: 10.3390/ijerph181910209
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2175195-X
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