An explicit Fourier-Klibanov method for an age-dependent tumor growth model of Gompertz type

This paper proposes an explicit Fourier-Klibanov method as a new approximation technique for an age-dependent population PDE of Gompertz type in modeling the evolution of tumor density in a brain tissue. Through suitable nonlinear and linear transformations, the Gompertz model of interest is transformed into an auxiliary third-order nonlinear PDE. Then, a coupled transport-like PDE system is obtained via an application of the Fourier-Klibanov method, and, thereby, is approximated by the explicit finite difference operators of characteristics. The stability of the resulting difference scheme is analyzed under the standard 2-norm topology. Finally, we present some computational results to demonstrate the effectiveness of the proposed method.Comment: 19 pages, 56 figures, 1 tabl

ONLINE LEARNING AND ITS POTENTIAL IN DEVELOPING EFL LEARNER AUTONOMY: ENGLISH-MAJORED STUDENTS' PERCEPTIONS

Learner autonomy is now regarded as a desirable goal in tertiary education as it is found to comply with learner-centered approaches and enable students to pursue life-long learning (Sinclair, 2000a; Ciekanski, 2007). In the time of COVID-19 pandemic, the essential to conduct in-depth investigations into leaner autotomy and online learning has become more urgent, especially in the context of a university in Vietnam. This quantitative research responded to such a pressing call by exploring two aspects: (1) the students’ perception of online learning, and (3) the potentiality of online learning for developing learner autonomy. Quantitative data were collected through questionnaires administered to 199 English-majored students in the context of a university in Mekong Delta. The results revealed that the students possessed positive perceptions toward online learning. Furthermore, the potentiality of online learning was explored including the ability of (1) planning learning experience, (2) evaluating learning performance, (3) determining learning goals, (4) self-controlling learning process, (5) taking responsibility for learning decision. Last but not least, this study expected that the proposed pedagogical implications will contribute to the innovation of promoting learner autonomy in online learning in the context of a university in the Mekong Delta of Vietnam.  Article visualizations

The Effects of Collaborative Learning on Young ESL Learners’ L2 Anxiety and Speaking Performance

Foreign Language Anxiety (FLA) is one of the issues of interest attracting researchers in recent decades. However, while collaborative learning introduced a prospective tool for FLA, it has not been much researched in the L2 classroom context, particularly in Vietnam. This paper focuses on using collaborative learning to reduce foreign language anxiety and enhance the L2 speaking performance of young learners at an English center in Ho Chi Minh City. A combination of tools, including Aydin et al.’s (2017) Children Foreign Language Anxiety Scale (CFLAS) for the pre-tests and post-tests, the teacher’s diary, and follow-up interviews, was used to measure the changes in learner’ FLA level and speaking performance. After five-week implementations, these learners’ FLA was slightly alleviated, and their speaking performance was improved using a collaborative learning approach. Moreover, learners were found to have positive attitudes and experience with learning in the new approach. These findings implied that collaborative learning could be a potential treatment to help L2 learners uncover their anxious selves and find more confidence in using the target languag

A Study of Asparagus Preservation Capacity of Chitosan-Alginate and Chitosan-Carrageenan Biofilms

Fresh postharvest green asparagus rapidly deteriorate due to its senescence process and high transpiration rate. This thesis aims to utilize the available sources of carrageenan and alginate for combining with pure chitosan coating solution, thus create a new multi-component coating that can overcome the limitations of pure chitosan coating, and show more effective in maintaining the quality of postharvest green asparagus. The gel solution ratio 2:1 (v/v) of chitosan 1% (w/v) and alginate 0.2% (w/v), had ability to prolong shelf-life of asparagus for 3 days (from weight loss point of view) and 7 days (from visual quality point of view) compared to control sample. The weight loss was less than about 12% and also ensured lower firmness change, maintained higher chlorophyll content, exhibiting better quality of asparagus compared to control and chitosan coated sample. The chitosan-alginate (2:1 v/v) coated asparagus achieved highest sensory score in day 7 and 14 of storage and lowest total aerobic growth in 14 days of storage at 4 ºC. The coating biofilm of chitosan-alginate could be considered as the new multi-component edible coating which showed high effectiveness in quality preservation and shelf-life extension of asparagus

THE DIFFICULTIES IN ORAL PRESENTATION OF ENGLISH-MAJORED JUNIORS AT TAY DO UNIVERSITY, VIETNAM

It could be broadly accepted that oral presentations are becoming important for students. It is required in almost every field and in the university environment. To succeed in the university environment and in their future jobs, these students need to improve their oral presentation skills. However, one of the drawbacks of using oral presentations in the language classroom is that students often find oral presentations extremely challenging. Therefore, the researcher conducted this research with the main goal of finding out common problems when giving an oral presentation to English-majored juniors at Tay Do University. Ninety juniors majoring in English at Tay Do University were selected to take part in the study. Data are gathered through questionnaires and interviews. The researcher used quantitative and qualitative methods to do the research. From the collected data, when they give a presentation, students usually make some mistakes such as problems in vocabulary, grammar, pronunciation, psychological and background knowledge. Through this study, they would recognize their own problems when giving a presentation. Besides, understanding students' learning difficulties may also enable teachers to help students develop effective learning strategies and ultimately improve their presentation skills. It is hoped that this research can be helpful for not only students but also teachers in learning and teaching English.  Article visualizations

Experimental Evaluation on Engineering Properties and Drying Shrinkage of No-Cement Mortar Produced by Alkaline Activation of Fly Ash-Slag Mixtures

Turning locally available industrial by-products such as fly ash (FA) and ground granulated blast-furnace slag (GGBFS) into cement-free materials has been recently received much attention from researchers. Following this trend, the present study produces alkali-activated mortars (AAFS) using a mixture of FA and GGBFS as a precursor activated by an alkaline solution of sodium hydroxide and sodium silicate. Five AAFS mixtures were prepared for the evaluation of engineering properties, drying shrinkage, and microstructural observation using various FA/GGBFS ratios of 30/70, 40/60, 50/50, 60/40, and 70/30. The experimental results show that the proportions of FA and GGBFS significantly affected the performance of the AAFS in both fresh and hardened stages. Higher GGBFS content resulted in a reduction in flowability and higher fresh unit weight. The GGBFS-rich AAFS developed its mechanical strength faster than the FA-rich AAFS and the strength gain of the GGBFS-rich AAFS was significantly higher than that of the cement-based mortar at only 1-day old, confirming the applicability of AAFS as a structural material and its potential to replace cement in the no-cement mortar production. The AAFS sample incorporating 60% of GGBFS and 40% of FA exhibited the highest strength, lowest water absorption, and less drying shrinkage with a relatively dense microstructure among the AAFS samples

Reproductive Biology of Moonlight Gourami (Trichopodus microlepis) in U Minh Thuong and U Minh Ha National Parks

This study aimed to provide information about the reproductive biology of moonlight gourami (Trichopodus microlepsis) distributed in U Minh National Parks. Fish samples were collected monthly from January to October 2019 at two locations: U Minh Ha (UMH, Ca Mau, n=462) and U Minh Thuong (UMT, Kien Giang, n=635). Results showed that the maturation-stage ratios of females were similar between the two fish populations. Mature females (with stage IV-ovaries) and the increase in their gonadal somatic index (GIS) were found from June to October, indicating that this period is their spawning season. GSI reached the highest values in August with 8.04% in UMH and 6.44% in UMT. Female fish of the UMH population showed higher average fecundity (7,483±3,008 eggs/female) and larger egg diameter (762±55 µm) than those of UMT (6,898±2,952 eggs/female and 754±43 µm, respectively), but these differences were not significant (p>0.05)

NUTRIENT RECOVERY AND POLLUTANT REMOVAL FROM PIGGERY WASTEWATER BY SPIRULINA CULTIVATION

Spirulina is noticed for great applications on food supplements, animal feeds, pharmaceutical, cosmetics, biofuel, fertilizer, etc. Spirulina cultures in wastewaters could enhance the feasibility of commodities due to its ability to reduce the cost of biomass production and remove pollutants in wastewaters. This study investigates the effects of wastewater pretreatment using various aeration periods (i.e. from 3 to 7 days), the supplement of bicarbonate and N:P ratios on the growth of Spirulina sp. HH to produce protein-rich biomass. The work showed that Spirulina sp. had the ability to effectively remove ammonium, with the highest efficiencies up to 99.9 %. However, the high concentration of ammonium in wastewater, from 125 mg N/L upward, caused a decline in the growth rate of Spirulina. The growth and remediation potential of Spirulina sp. were in the best condition with the N:P ratio of the medium in the range of 19:1-22:1. This study suggested a procedure to cultivate Spirulina sp. in piggery wastewater and remove pollutants efficiently

Genetic diversity of two successive generations of selection in bighead catfish (Clarias macrocephalus) populations

Selective programs associated with domestication can improve fish production but also can have an impact on broodstock’s genetic diversity. In this study, the genetic diversity of original sources (G0) from wild and cultured bighead catfish populations, as well as the two successive generations (G1 and G2) subjected to selection experiments, was assessed. G0 wild adults were collected in Ca Mau conservation area and G0 cultured fish were from a hatchery in Can Tho. The G1 fish included pure crosses and crossbreeds of G0, while G2 was the offspring of the selected G1. Fin clips from 27 to 29 individuals of each fish group were randomly sampled for genetic analysis. The amplification results using six ISSR primers showed that the genetic diversity was relatively higher in G0 (effective number of alleles Ne from 1.43 to 1.49; heterozygosity He from 0.265 to 0.290) than in G1 (Ne = 1.32±0.04; He = 0.201±0.023) and G2 (Ne = 1.34±0.04; He = 0.216±0.023). Genetic differences increased between the original populations and the descending generations. To reduce the detrimental impacts of low genetic diversity in domesticated bighead catfish in the Mekong Delta, it is recommended that broodstock in later generations should be produced in a larger..