Equivariant Crossed Modules and Cohomology of Groups with Operators

In this paper we study equivariant crossed modules in its link with strict graded categorical groups. The resulting Schreier theory for equivariant group extensions of the type of an equivariant crossed module generalizes both the theory of group extensions of the type of a crossed module and the one of equivariant group extensions.Comment: 20 pag

Agri-Food Value Chain Performance during the COVID-19 Pandemic: An Empirical Study of Chu-mango Business Linkages in Dong Thap, Vietnam

This study aims to identify important factors that directly influence value chain performance (quality, responsiveness, flexibility and efficiency), which are explained by value chain integration (collaboration, commitment, coordination and joint decision-making) in the case of unexpected risk (the COVID-19 pandemic). This study contributes to maintaining the business linkage model among farmers – cooperatives – enterprises in the caseof the COVID-19 pandemic and quickly recovering after the COVID-19 pandemic. Structural equation modelling (SEM) was used for data analysis following an iterative process based on theoretical and empirical analyses toobtain a structural model fit and test the research hypothesis. The findings indicate that the VCI positively influenced the VCP of Chu-mango business linkages at the 1% significance level through coordination (Beta = 0.345;construct reliability (CR) = 3.272), collaboration (Beta = 0.289; CR = 3.128), and joint decision-making (Beta = 0.324; CR = 3.245). This study provides empirical data on the relationship between VCI and VCP through the Chu -mango value chain in Dong Thap Province during the COVID-19 pandemic to raise awareness from stakeholders and encourage value chain thinking to improve performance. This result may pave the way for relevant policymakers to look for policies and strategies for better inclusiveness of stakeholders to show the importance of the VCI in improving the performance. Moreover, the study is an empirical case contributing to the agribusiness value chain in a developing country; it applies the agribusiness value chain of the tropical fruit domain and can be used for otheragricultural products in other cases of unexpected risks

Changes of benthic macroinvertebrates in Thi Vai River and Cai Mep Estuaries under polluted conditions with industrial wastewater

The pollution on the Thi Vai River has been spreading out rapidly over the two lasted decades caused by the wastewater from the industrial parks in the left bank of Thi Vai River and Cai Mep Estuaries. The evaluation of the benthic macroinvertebrate changes was very necessary to identify the consequences of the industrial wastewater on water quality and aquatic ecosystem of Thi Vai River and Cai Mep Estuaries. In this study, the variables of benthic macroinvertebrates and water quality were investigated in Thi Vai River and Cai Mep Estuaries, Southern Vietnam. The monitoring data of benthic macroinvertebrates and water quality parameters covered the period from 1989 to 2015 at 6 sampling sites in Thi Vai River and Cai Mep Estuaries. The basic water quality parameters were also tested including pH, dissolved oxygen (DO), total nitrogen, and total phosphorus. The biodiversity indices of benthic macroinvertebrates were applied for water quality assessment. The results showed that pH ranged from 6.4 – 7.6 during the monitoring. The DO concentrations were in between 0.20 – 6.70 mg/L. The concentrations of total nitrogen and total phosphorous ranged from 0.03 – 5.70 mg/L 0.024 – 1.380 mg/L respectively. Macroinvertebrate community in the study area consisted of 36 species of polychaeta, gastropoda, bivalvia, and crustacea, of which, species of polychaeta were dominant in species number. The benthic macroinvertebartes density ranged from 0 – 2.746 individuals/m2 with the main dominant species of Neanthes caudata, Prionospio malmgreni, Paraprionospio pinnata, Trichochaeta carica, Maldane sarsi, Capitella capitata, Terebellides stroemi, Euditylia polymorpha, Grandidierella lignorum, Apseudes vietnamensis. The biodiversity index values during the monitoring characterized for aquatic environmental conditions of mesotrophic to polytrophic. Besides, species richness positively correlated with DO, total nitrogen, and total phosphorus. The results confirmed the advantage of using benthic macroinvertebrates and their indices for water quality assessment

Factors Affecting the Perception of Happiness among Teachers in Vietnam

Vietnam is in the process of implementing education reforms in which teachers play a crucial role in determining success. This study aims to identify the main factors influencing the perception of happiness at work of Vietnamese teachers during the period of educational reform. In any period, teachers are always considered as being the force behind the success of education. Therefore, teachers' happiness is the most vital factor to be taken into consideration when educating students. Identifying the factors that affect teachers' happiness at work is the key to improving their teaching quality and quality of life. This study was conducted to investigate the factors affecting the perceived happiness of secondary school teachers in Vietnam today, thereby objectively assessing the emotional status of teachers in Vietnam in relation to the work they are doing. The results are as follows: 1) Teachers face a lot of pressure from many sides; 2) There is still a large percentage of teachers who do not really attach importance to the teaching profession; 3) State policies have not helped teachers feel secure in their professional activities; 4) Teacher capacity still needs to be greatly improved; 5) It is necessary to strengthen the connection between teachers, educational leaders, policy makers, school administrators and colleagues. This study uses descriptive statistics to present the research results. The survey was carried out in September 2021

Antibacterial activity of Piper betle extracts on Helicobacter pylori and identification of potential compounds

Helicobacter pylori is one of the most common infectious bacteria in the world that causes gastric diseases leading to cancer. The increase of multiple antibiotic resistance rates of H. pylori have been reported worldwide. Thus, development of novel drugs is urgently required. Piper betle has many therapeutic values in traditional medicine. In this study, therefore, we investigated antibacterial activity of P. betle extracts and their fractions against a H. pylori strain isolated in Vietnam. The agar disk diffusion assay showed inhibition zone of ethyl acetate extract and methanol extract from P. betle leaf that of were 46 mm and 32 mm in diameter, respectively. After fractionation of the ethyl acetate extract through silica gel column chromatography, two peaks, PD2 and PD3, out of 12 fractions showed the strongest antibacterial activity. PD2 was sub-fractionated further by re-chromatography on the silica gel column, and subfraction TK12 gave best resolution on LC-MS analysis. Finally, 4 potential compounds, quercetrin, calodenin B, vitexin and plicatipyrone, were identified in TK12 fraction.