ẢNH HƯỞNG CỦA MẬT ĐỘ NUÔI LÊN TỐC ĐỘ TĂNG TRƯỞNG VÀ TỶ LỆ SỐNG CỦA CÁ ÔNG TIÊN (PTEROPHYLLUM ALTUM PELLEGRIN, 1930)

Three-day-old Angel fishes (Pterophyllum altum) were utilized to investigate the effect of stocking density on their growth performance and survival rate. The fish were cultured in 25 liter, glass tanks at different treatments of density, including 5 individuals/L, 10 inds/L,              15 inds/L and 20 inds/L (triplicated). The results after 84 days showed that growth and survival rate of angel fish were significantly influenced by stocking density. The length and weight of fish reared at 5 inds/L (9.597±0.002 mm; 11.700± 0.1 g) were the best and significantly higher than fish in the treatment  of 10 inds/L (9.167±0.058 mm; 11.067± 0.208g); 15 inds/L (7,699±0,03 mm; 10.933± 0,057 g) and 20 inds/L (4.928±0.004 mm; 7.900± 0.1g) (P0.05). The survival rate of 5 inds/L treatment 85% was significantly higher than that of other treatments (10 inds/L: 80.0±0,5%; 15 inds/L: 77.0±0,57% and 20 inds/L: 74.6±0.38%). In combination of these two factors, the density of 5 inds/L is recommended in culture of three day old to three month old angel fishes.Cá ông tiên (Pterophyllum altum) sau 3 ngày nở được nuôi trong các bể kính có thể tích 25 lít với các mật độ 5 con/lít, 10 con/lít, 15 con/lít và 20 con/lít (3 lần lặp lại) để làm rõ ảnh hưởng của mật độ đến tốc độ tăng trưởng và tỷ lệ sống của cá. Kết quả sau 84 ngày thí nghiệm cho thấy có sự ảnh hưởng của mật độ nuôi đến tốc độ tăng trưởng và tỷ lệ sống của cá giai đoạn 3 tháng đầu mới nở.Cá được nuôi ở mật độ 5 con/lít có tốc độ tăng trưởng về chiều dài và trọng lượng (9,597±0,002 mm ; 11,700± 0,1 g) là tốt nhất và khác nhau đáng kể so với cá được nuôi ở mật độ 10 con/lít (9,167±0,058 mm; 11,067± 0,208 g) 15 con/lít (7,699±0,03 mm; 10,933± 0,057 g) và 20 con/lít (4,928±0,004 mm; 7,900± 0,1 g) (P0,05). Tỷ lệ sống của cá nuôi ở mật độ 5 con/lít là 85% cao nhất so với các mật độ còn lại (10 con/lít: 80,0±0,5%; 15 con/lít: 77,0±0,57% và 20 con/lít: 74,6±0,38%). Kết quả thí nghiệm cho thấy cá ông tiên mới nở đến 3 tháng tuổi nên nuôi ở mật độ 5 con/lít là tốt nhất

Physical and nutrient stimuli differentially modulate gut motility patterns, gut transit rate, and transcriptome in an agastric fish, the ballan wrasse

The effects of nutrient and mechanical sensing on gut motility and intestinal metabolism in lower vertebrates remains largely unknown. Here we present the transcriptome response to luminal stimulation by nutrients and an inert bolus on nutrient response pathways and also the response on gut motility in a stomachless fish with a short digestive tract; the ballan wrasse (Labrus berggylta). Using an in vitro model, we differentiate how signals initiated by physical stretch (cellulose and plastic beads) and nutrients (lipid and protein) modulate the gut evacuation rate, motility patterns and the transcriptome. Intestinal stretch generated by inert cellulose initiated a faster evacuation of digesta out of the anterior intestine compared to digestible protein and lipid. Stretch on the intestine upregulated genes associated with increased muscle activity, whereas nutrients stimulated increased expression of several neuropeptides and receptors which are directly involved in gut motility regulation. Although administration of protein and lipid resulted in similar bulbous evacuation times, differences in intestinal motility, transit between the segments and gene expression between the two were observed. Lipid induced increased frequency of ripples and standing contraction in the middle section of the intestine compared to the protein group. We suggest that this difference in motility was modulated by factors [prepronociceptin (pnoca), prodynorphin (pdyn) and neuromedin U (nmu), opioid neurotransmitters and peptides] that are known to inhibit gastrointestinal motility and were upregulated by protein and not lipid. Our findings show that physical pressure in the intestine initiate contractions propelling the bolus distally, directly towards the exit, whereas the stimuli from nutrients modulates the motility to prolong the residence time of digesta in the digestive tract for optimal digestion.publishedVersio

Effects of cholecystokinin (CCK) on gut motility in the stomachless fish ballan wrasse (Labrus bergylta)

Cholecystokinin (CCK) is well-known as a key hormone that inhibits stomach emptying and stimulates midgut motility in gastric species. However, the function of CCK related to gut motility in agastric fish, especially in fish with a short digestive tract such as ballan wrasse, remains unknown. Here we present a detailed description of the spatio-temporal quantification of intestinal motility activity in vitro comprising the complete intestinal tract in ballan wrasse. We show that CCK modulates intestinal motility, having multiple effects on motility patterns depending on location in the gut and types of contractions. CCK reduced propagating contractions in the foregut, but it increased both non-propagating and propagating contractions in the hindgut. CCK also altered the direction of propagating contractions, as it reduced anterograde ripples and slow propagating contractions. The velocity of propagating contractions was slowed down by CCK. CCK also reduced the amplitude of standing contractions and ripples, but it did not alter the amplitude of slow propagating contractions. The presence of CCKA receptor antagonist modulated the motility responses of ballan wrasse intestines when exposed to CCK. We also showed that CCK reduced the intestinal length and stimulated motility to empty the gallbladder. Based on our findings we hypothesize that CCK, mainly through the CCKA receptor, modulates non-propagating and propagating contractions to optimize digestion and absorption and regulate the intestinal evacuation in ballan wrasse. We also found evidence that the modulation of intestinal motility by CCK is different in agastric fish from that in gastric vertebrates. We suggest that this is an evolutionary adaptation to optimize digestion without a stomach.publishedVersio

AN INVESTIGATION INTO DIFFICULTIES IN ENGLISH LISTENING OF FRESHMEN MAJORING IN ENGLISH AT A UNIVERSITY IN THE MEKONG DELTA, VIETNAM

English is a very popular language in the world. However, learning a foreign language is not an easy process for learners, especially the English listening process. In fact, most learners believe that it is hard for them to master this skill. Therefore, the research “An Investigation into Difficulties in English Listening of Freshmen Majoring in English at a University in the Mekong Delta” was conducted with the purpose of helping these students to recognize clearly their own problems in English listening. Statistical data were collected from eighty-five English-majored freshmen. The main instrument of the study was a questionnaire. The findings of the research would point out the students’ difficulties in linguistics, including vocabulary, grammar, pronunciation, intonation and accent; background knowledge; and difficulties from their own minds. One more notable purpose of this research is that thanks to the results, students can now solve their own problems, so that they can study better. Article visualizations

The impact of the COVID-19 pandemic on the stressful relationship between parents and children

The stressful relationship between children and parents is the pain both go through when they find themselves unable to cope as a parent or a child. In order to find out the status, causes, and impacts of the COVID-19 pandemic and suggest some solutions to reduce stress between parents and children, we surveyed the impact of the COVID-19 pandemic on stressful relationships between parents and children at high school age in Da Nang city. The findings of a survey conducted on 550 randomly selected parents and 550 high school students using the Perceived Stress Scale reveal a high rate of tension between parents and their children, particularly up to 51.1% and 38.5%, respectively. In reality, many factors are affecting the stressful relationship between parents and their children at this age, in which psychological fear about health; social distancing policy; closed schools; students staying at home 24 hours a day and learning online; the disruption in children's daily routine; excessive use of electronic devices are major causes of stress in the relationship between parents and their children. From this practice, our research team has proposed such solutions as participating in creative activities and consulting the handbook instructing parents' behaviour rules toward children and vice versa, designing extra-curricular activities, and organizing training courses on life values for both parents and children to increase happiness and reduce stress in the parent-child relationship

Determinants Influencing Entrepreneurial Intention in Hanoi, Vietnam

This research employed survey data from 204 students between two groups of  economics and technical majors in Hanoi city for assessing the impact levels of determinants on entrepreneurial intention. The results show that a number of determinants including Need for achievement, Self-efficacy, and Instrumental readiness have positive impacts on student’s entrepreneurial intention. Besides, this study is also to create a basis for  comparative students among different economics and technical majors, work exoperience, and gender. These findings are the basis to recommend policies and solutions to promote entrepreneurship movement in Vietnam. Keywords: Entrepreneurial intention, need for achievement, self-efficacy, instrumental readiness. DOI: 10.7176/EJBM/12-15-10 Publication date:May 31st 2020

Factors affecting the creativity of high school students

Creativity is a vital personality quality of each individual. Each person has their potential for creativity, and it can be nurtured and developed in an appropriate and safe environment. The purpose of the study was to find out which factors from schools and students themselves affect creativity as well as the association between creativity and age, gender and giftedness of students, which then a basis to adjust and establish appropriate methods from schools, families, and students themselves to develop elements and their creativity. The study was conducted on 108 high school students in three grades from giftedness and non-giftedness schools. The data was collected through a survey method using a self-constructed questionnaire and drawing creativity test TCT-DP to determine students' creativity levels and personal information. The study's finding, which uses mathematical methods and one-way analysis of variance, reveals that factors affecting elements and creativity level are objective factors including education environment from school; behavior of teachers, and subjective factors including interests, perspectives, and thoughts of students. It was also found that there were no significant differences in the components of creativity and creativity among students in different grades, gender, and groups of giftedness schools

Tin Dioxide Nanocrystals as an Effective Sensitizer for Erbium Ions in Er-Doped SnO 2

Undoped SnO2 and erbium-doped SnO2 powders were successfully prepared by precipitation method. The effect of the heat treatment and doping contents on the structure of tin oxide and optical properties was also studied. The XRD data and Raman spectra indicate that the SnO2 crystals have formed after being heat-treated at 400°C and the average size of grains is about 8 nm for doping content of 1 mol%. An increase of doping concentration has controlled the growth of nanocrystals. The principle of the visible and infrared emissions of SnO2 and SnO2:Er is also discussed. All photoluminescence study shows that the Er3+ ions can be located in SnO2 nanocrystals and that there is energy transfer from defect levels of SnO2 nanoparticles to neighboring Er3+ ions of crystals

Antibacterial Nanocomposites Based on Fe 3

For the vulcanized natural rubber (NR), incorporation of silver nanoparticles (AgNPs) into the NR matrix did not exhibit the bactericidal property against Escherichia coli (E. coli). However, incorporation of AgNPs into polyethylene (PE) matrix showed good antibacterial activities to both Gram-negative and Gram-positive bacteria. In the present work, NR/PE (85/15) blends have been prepared by melt blending with presence of compatibilizer in an internal mixer. To possess antibacterial property, AgNPs (5–10 nm) or Fe3O4–Ag hybrid nanoparticles (FAgNPs, 8 nm/16 nm) were added into PE matrix before its blending with NR component. The tensile test indicated that the presence of compatibilizer in NR/PE blend significantly enhanced the tensile strength and elongation at break (up to 35% and 38% increases, resp.). The antibacterial activity test was performed by monitoring of the bacterial lag-log growth phases with the presence of nanocomposites in the E. coli cell culture reactor. The antibacterial test showed that the presence of FAgNPs in NR/PE blend had a better antibacterial activity than that obtained with the lone AgNPs. Two similar reasons were proposed: (i) the faster Ag+ release rate from the Fe3O4–Ag hybrid nanoparticles due to the electron transfer from AgNP to Fe3O4 nanoparticle and (ii) the fact that the ionization of AgNPs in hybrid nanostructure might be accelerated by Fe3+ ions