Spectrometric elucidation of intermediates in asymmetric transfer hydrogenation of ketones catalyzed by complex of ruthenium (II) and isosorbide-based ligand

The use of electrospray ionization mass spectrometry for the detection of the intermediate species involved in the ruthenium(II)/β-amino-alcohol derived from isosorbide reduction of ketones to alcohols is described. The formation of active complex of ruthenium (II) for catalyzing the asymmetric transfer hydrogenation of ketones was observed from 1H-NMR spectra. From high resolution mass spectra, peaks of group of isotopes allow to conform the existence of active species of ruthenium (II) in the presence of isosorbide-based ligand. The recorded high resolution mass spectra when following the typical protocol for the asymmetric transfer hydrogenation of acetophenone confirmed an involvement of the active complex mono-hydride ruthenium in the catalytic circle. As a result, high resolution mass spectra in research on catalytic mechanism can be therefore employed as an alternative tool for studying catalytic mechanism. Keywords. Asymmetric catalysis, isosorbide, asymmetric transfer hydrogenation

An analysis of winning streak's effects in language course of “Duolingo” *

This paper explores the effects of the winning streak on users' motivation and engagement in Duolingo's language course. The winning streak has been used in sport and video games to describe a consecutive number of successful actions and increase players' attention to complete their goal. Similarly, in gamified education system, the winning streak is employed as a game element to boost up motivation of learners. By applying game refinement theory as an assessment method, enjoyment of two user groups in Duolingo is measured to compare. The results indicate that the winning streak can boost up learners' motivation and attention to complete their goals. It also expressed that the winning streak is more significant for advanced learners who are in the high level of milestone than those who are in the low level of milestone

THE IMPACT OF MOVEMENT GAMES ON MALE PHYSICAL FITNESS IN PHYSICAL EDUCATION COURSES AT SAIGON UNIVERSITY, VIETNAM

Movement games not only help students improve their general fitness but also help increase excitement during exercise. However, the impact of movement games on physical development has not been determined, especially for non-sports majors. The purpose of this study was to find out the impact of movement games on male physical fitness in Physical Education courses. 51 healthy male student volunteers were randomly divided into 3 groups (15w, 7w, and control). Movement games were selected and applied to the experimental group (15w and 7w), while the control group did not apply movement games and practice according to the preset 15-week training program. The results in this study indicated that the application of MG for male students at Saigon University during PE courses had a positive way to enhance general physical fitness (i.e., the explosive power of the legs, agility, speed, and maximal aerobic speed). Future studies should focus on the impact in the time of movement games application, specific characteristics to different schools, as well as the evolution of physical development at each age when using the movement games.  Article visualizations

BARRIERS PREVENTING EFL TEACHERS FROM PARTICIPATING AND CONSTRUCTING COMMUNITIES OF PRACTICE

Communities of practice (CoPs) appeared to be one of the possible solutions for professionals, especially EFL teachers, who have to deal with an increasing number of complicated tasks and problems which cannot be individually solved effectively. However, CoPs were reported in several studies not to reach the popularity they deserve. Hence, this study is aimed at identifying the barriers that prevent EFL teachers from participating and constructing CoPs. The study was conducted in different cities and provinces in the Mekong Delta. A questionnaire was employed to examine participants’ agreement on the suggested barriers described in the theoretical framework, and interviews were used to confirm and improve the results of the quantitative data collected. Regarding the research participants, 116 EFL teachers in public schools and English centers in the Mekong Delta responded to the questionnaire, while seven of them were chosen to conduct the interviews. The findings were classified into teacher-related and organization-related barriers. While the former includes cultural and psychological factors, the latter consists of barriers from school leaders’ power and policies.  Article visualizations

Secrecy outage probability of a NOMA scheme and impact imperfect channel state information in underlay cooperative cognitive networks

Security performance and the impact of imperfect channel state information (CSI) in underlay cooperative cognitive networks (UCCN) is investigated in this paper. In the proposed scheme, relay R uses non-orthogonal multiple access (NOMA) technology to transfer messages e1, e2 from the source node S to User 1 (U-1) and User 2 (U-2), respectively. An eavesdropper (E) is also proposed to wiretap the messages of U-1 and U-2. The transmission's security performance in the proposed system was analyzed and performed over Rayleigh fading channels. Through numerical analysis, the results showed that the proposed system's secrecy performance became more efficient when the eavesdropper node E was farther away from the source node S and the intermediate cooperative relay R. The secrecy performance of U-1 was also compared to the secrecy performance of U-2. Finally, the simulation results matched the Monte Carlo simulations well.Web of Science203art. no. 89