The Relationship between Online Learning and Student Satisfaction with Training Quality in Private Universities during the COVID-19 Pandemic

This study aims to explore the relationship between the influential factors of online learning and the satisfaction of economics and business majors with the quality of their training in the context of the Covid-19 pandemic. A total of 900 students in private universities completed a questionnaire. The principal findings of this research are that the students are satisfied with their online learning and that learning conferencing software is the most important driving factor leading to the students’ satisfaction when compared with learning conditions and learning devices. Another interesting finding is that the experience of using learning conferencing software results in a slight difference in the students’ perceived level of satisfaction, adding that users with more than two years’ experience are more satisfied with their training quality than users with less than one year’s experience. However, the results also show that students want to switch to offline learning when the pandemic is over. This study should, therefore, be of value to higher education authorities wishing to understand their students’ perceptions of online learning. In addition, results from the study suggest more managerial approaches as well as improve the online teaching quality during the pandemic

Chemical composition and antibacterial activities of essential oils from Homalomena pierreana (Araceae)

30-37Homalomena is a genus of the Araceae family which contains several remedies used extensively in traditional Vietnamese medicine. H. pierreana is a rare plant species of Homalomena genus and found only in Phu Quoc National Park, Phu Quoc Island, Kien Giang Province, Vietnam. Therefore, the number of studies about this species is limited and the bioactivity of this species is still unknown. In this study, the chemical composition of essential oils was investigated which was isolated from leaves and rhizomes of H. pierreana at the first time by GC-MS. Eight and twelve compounds were identified from the essential oils of rhizomes and leaves, respectively. The major component from both the rhizomes and the leaves was aromadendrene (44 and 48%, respectively). Furthermore, the antibacterial activity of essential oils collected from leaves and rhizomes of H. pierreana was investigated and it was observed that the essential oil of rhizomes could inhibit the growth of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, while the essential oil of leaves exhibited an inhibitory effect against Staphylococcus aureus and Escherichia coli.</em

Nghiên cứu so sánh cấu trúc, độ bền của cluster silic pha tạp sắt dạng trung hòa và cation, SinFe0/+ (n = 8-12), bằng phương pháp phiếm hàm mật độ

The geometries and stabilities of neutral and cationic Fe-doped silicon clusters SinFe0/+ (n = 8-12) have been investigated by using density functional theory at the B3P86/6-311+G(d) level of theory. The most stable isomers of the neutral SinFe clusters adopt high-symmetrical structure where the Fe atom binds with all of the Si atoms of the cluster. The lowest-lying isomers of the cationic clusters have different structures from the neutral, and adopt lower coordination numbers. For exohedral structures, the neutrals favor low spin states, while the cation clusters favor higher spin states. However, the endohedral structures of both neutral and cation become more stable in the lowest spin state. The endohedral cage structure appeared at n = 10 for neutral and at n = 11 for cationic clusters. The analysis of average binding energy, second order difference of energy and HOMO-LUMO gap for both series of clusters found that the cationic clusters are more stable than the corresponding neutral. The Si12Fe0/+ cluster is found to be the most stable cluster in both series. Keywords. Density functional theory, B3P86, Fe-doped silicon cluster, structure, stability

Influence of Spray Rate on Structural and Optical Properties of Sprayed ZnO Films

In this report, the ZnO nanostructure films have been deposited by ultrasonic spray pyrolysis technique (USP) on fluorine doped tinoxide~(FTO) substrate using zinc acetate and aqueous 2-propanol as reactants. The effects of solution spray rate on structural, morphological and optical properties of ZnO nanostructure films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and UV-Vis measurements. ZnO films were crystallized in the hexagonal wurtzite phase and preferential orientation changed with changing of spray rate. Grain size and roughness of films depended on spray rate. Increasing spray rate made the films grown with bigger grain size and higher roughness. Band gap energy was determined from the UV-Vis. Its value was found to be of 3.25 eV and was almost independent on the spray rate

Elevated Levels of Cell-Free Circulating DNA in Patients with Acute Dengue Virus Infection

BACKGROUND: Apoptosis is thought to play a role in the pathogenesis of severe dengue and the release of cell-free DNA into the circulatory system in several medical conditions. Therefore, we investigated circulating DNA as a potential biomarker for severe dengue. METHODS AND FINDINGS: A direct fluorometric degradation assay using PicoGreen was performed to quantify cell-free DNA from patient plasma. Circulating DNA levels were significantly higher in patients with dengue virus infection than with other febrile illnesses and healthy controls. Remarkably, the increase of DNA levels correlated with the severity of dengue. Additionally, multivariate logistic regression analysis showed that circulating DNA levels independently correlated with dengue shock syndrome. CONCLUSIONS: Circulating DNA levels were increased in dengue patients and correlated with dengue severity. Additional studies are required to show the benefits of this biomarker in early dengue diagnosis and for the prognosis of shock complication

Chemical composition and antibacterial activities of essential oils from Homalomena pierreana (Araceae)

Homalomena is a genus of the Araceae family which contains several remedies used extensively in traditional Vietnamese medicine. H. pierreana is a rare plant species of Homalomena genus and found only in Phu Quoc National Park, Phu Quoc Island, Kien Giang Province, Vietnam. Therefore, the number of studies about this species is limited and the bioactivity of this species is still unknown. In this study, the chemical composition of essential oils was investigated which was isolated from leaves and rhizomes of H. pierreana at the first time by GC-MS. Eight and twelve compounds were identified from the essential oils of rhizomes and leaves, respectively. The major component from both the rhizomes and the leaves was aromadendrene (44 and 48%, respectively). Furthermore, the antibacterial activity of essential oils collected from leaves and rhizomes of H. pierreana was investigated and it was observed that the essential oil of rhizomes could inhibit the growth of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, while the essential oil of leaves exhibited an inhibitory effect against Staphylococcus aureus and Escherichia coli

The Association of Cytokines with Severe Dengue in Children

Background: Dengue virus infection is a major public health problem. A hypothesis put forward for severe dengue is the cytokine storm, a sudden increase in cytokines that induces vascular permeability. Previous studies and our recent meta-analysis showed that IL-6, IL-8, IFNγ, TNFα, VEGF-A and VCAM-1 are associated with dengue shock syndrome. Therefore, in this study we aim to validate the association of these cytokines with severe dengue. Methods & Findings: In a hospital based-case control study in Vietnam, children with dengue fever, other febrile illness and healthy controls were recruited. Dengue virus infection was confirmed by several diagnostic tests. Multiplex immunoassay using Luminex technology was used to measure cytokines simultaneously. A positive association with dengue shock syndrome was found for VCAM-1, whereas a negative association was found for IFNγ. Furthermore, multivariate logistic analysis also showed that VCAM-1 and IFNγ were independently correlated with dengue shock syndrome. Conclusion: IFNγ and VCAM-1 were associated with dengue shock syndrome, although their role in the severe dengue pathogenesis remains unclear. Additional studies are required to shed further light on the function of these cytokines in severe dengue

Volatile Compounds in Citrus Essential Oils: A Comprehensive Review

[EN] The essential oil fraction obtained from the rind of Citrus spp. is rich in chemical compounds of interest for the food and perfume industries, and therefore has been extensively studied during the last decades. In this manuscript, we provide a comprehensive review of the volatile composition of this oil fraction and rind extracts for the 10 most studied Citrus species: C. sinensis (sweet orange), C. reticulata (mandarin), C. paradisi (grapefruit), C. grandis (pummelo), C. limon (lemon), C. medica (citron), C. aurantifolia (lime), C. aurantium (bitter orange), C. bergamia (bergamot orange), and C. junos (yuzu). Forty-nine volatile organic compounds have been reported in all 10 species, most of them terpenoid (90%), although about half of the volatile compounds identified in Citrus peel are non-terpenoid. Over 400 volatiles of different chemical nature have been exclusively described in only one of these species and some of them could be useful as species biomarkers. A hierarchical cluster analysis based on volatile composition arranges these Citrus species in three clusters which essentially mirrors those obtained with genetic information. The first cluster is comprised by C. reticulata, C. grandis, C. sinensis, C. paradisi and C. aurantium, and is mainly characterized by the presence of a larger abundance of non-terpenoid ester and aldehyde compounds than in the other species reviewed. The second cluster is comprised by C. junos, C. medica, C. aurantifolia, and C. bergamia, and is characterized by the prevalence of mono- and sesquiterpene hydrocarbons. Finally, C. limon shows a particular volatile profile with some sulfur monoterpenoids and non-terpenoid esters and aldehydes as part of its main differential peculiarities. A systematic description of the rind volatile composition in each of the species is provided together with a general comparison with those in leaves and blossoms. Additionally, the most widely used techniques for the extraction and analysis of volatile Citrus compounds are also described.This work was supported in part by the European Commission Horizon 2020 program TRADITOM grant 634561 and TomGEM grant 679796 to JR and AG.González-Mas, M.; Rambla Nebot, JL.; López-Gresa, MP.; Blazquez, M.; Granell Richart, A. (2019). Volatile Compounds in Citrus Essential Oils: A Comprehensive Review. Frontiers in Plant Science. 10:1-18. https://doi.org/10.3389/fpls.2019.00012S11810Abreu, I., Da Costa, N. C., van Es, A., Kim, J.-A., Parasar, U., & Poulsen, M. L. (2017). Natural Occurrence of Aldol Condensation Products in Valencia Orange Oil. Journal of Food Science, 82(12), 2805-2815. doi:10.1111/1750-3841.13948Ahmed, M., Arpaia, M. L., & Scora, R. W. (2001). Seasonal Variation in Lemon (Citrus limonL. Burm. f) Leaf and Rind Oil Composition. 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Protective and Enhancing HLA Alleles, HLA-DRB1*0901 and HLA-A*24, for Severe Forms of Dengue Virus Infection, Dengue Hemorrhagic Fever and Dengue Shock Syndrome

Dengue has become one of the most common viral diseases transmitted by infected mosquitoes (with any of the four dengue virus serotypes: DEN-1, -2, -3, or -4). It may present as asymptomatic or illness, ranging from mild to severe disease. Recently, the severe forms, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), have become the leading cause of death among children in Southern Vietnam. The pathogenesis of DHF/DSS, however, is not yet completely understood. The immune response, virus virulence, and host genetic background are considered to be risk factors contributing to disease severity. Human leucocyte antigens (HLA) expressed on the cell surface function as antigen presenting molecules and those polymorphism can change individuals' immune response. We investigated the HLA-A, -B (class I), and -DRB1 (class II) polymorphism in Vietnamese children with different severity (DHF/DSS) by a hospital-based case-control study. The study showed persons carrying HLA-A*2402/03/10 are about 2 times more likely to have severe dengue infection than others. On the other hand, HLA-DRB1*0901 persons are less likely to develop DSS with DEN-2 virus infection. These results clearly demonstrated that HLA controlled the susceptibility to severe forms of DV infection