Vietnam Journal of Science, Technology and Engineering

7-14

Authors: Quang Minh Do, Ngoc Tri Huynh Nguyen, Thi Hong Hoa Huynh, Hong Lien Pham, Thi Thu Ho, Do Trung Kien Kieu, Ngoc Minh Huynh

Glass ionomer cement (GIC) is a particular type of cement used in dentistry. One of the most critical properties of GIC is the ability to release fluoride, which can prevent recurrent tooth decay. This study simultaneously investigated the release of fluoride, the compressive strength, and the apparent density of three GICs in deionized water (DW) and artificial saliva (AS) environments. GICs with 3 different types of glass powders were used to study. Powder B (the original) was the glass powder based on the SiO2-Al2O3-CaF2-AlPO4-Na3AlF6 system, powder HA5 was powder B supplemented with 5 wt. % hydroxyapatite powder (HA), and powder Si2 was powder B surface-treated with 2 wt. % silane JH-S69. The results of this study showed the amount of fluoride ion (F-) released during 28 days in AS was lower in comparison to the DW environment, and the rate slowed down significantly after 1 d. The F- release rate at 1-d age tended to be high as the compression strength was low. In AS, the powder supplemented with 5 wt.% HA improved the compressive strength and the cumulative amount of F- released by the GIC. After 28 d, the F- release of the GIC materials were able to be recharged in a NaF solution with 1,018 ppm F- concentration for 3 min and further fluoride ions were released in both the DW and AS environments

21-29

Authors: Hoang-Quan Dinh*, Thanh-Bang Nguyen

Geopolymers are a class of new binder manufactured by activating aluminosilicate source materials in a highly alkaline medium. This binder is considered “environmentally friendly” due to the recycling of industrial waste sources such as fly ash and blast furnace slag. However, in order to be widely used, this binder has to ensure both quality and economic efficiency. This paper focuses on the optimization of the composition of ground granulated blast-furnace slag and fly ash-based geopolymers activated by sodium silicate and sodium hydroxide solutions. Statistical models are developed to predict the compressive strength and cost of 1 ton of binder using Response Surface Methodology (RSM). In this regard, the effects of three principal variables (%Na2O, Ms and %GGBS) were investigated in which: %Na2O - mass ratio of Na2O in the alkali-activated solution and total solids; Ms - mass ratio of SiO2 and Na2O in the activated solution; %GGBS - mass ratio of ground granulated blast-furnace slag (GGBS), and total binder. Quadratic models were proposed to correlate the independent variables for the 28-d compressive strength and cost of 1 ton of binder by using the Central Composite Design (CCD) method. The study reveals that Ms has a minor effect on the strength of mortar in comparison with %Na2O and %GGBS. The optimized mixture proportions were assessed using the multi-objective optimization technique. The optimal values found were %Na2O=5.18%, Ms=1.16, and %GGBS=50%, with the goals of maximum compressive strength, the largest amount of fly ash, and reasonable cost for one ton of binder. The experimental results show that the compressive strength of the samples ranged between 62.95-63.54 MPa and were consistent with the optimized results (the variation between the predicted and the experimental results was obtained less than 5%).

36-41

Authors: Nguyen Quang Thinh

Black gram (Vigna mungo L.) is a high nutrient pulse crop. Its seed quickly and easily deteriorates after harvest, resulting in poor planting material production that must be improved accordingly by seed enhancement methods. The blue-green microalgaeSpirulina platensis contains variously beneficial substances, including macro and micro nutrients, vitamins, amino acids and antioxidants. The aim of this study is to improve the vigour and germination of black gram by priming its seeds with Spirulina platensisextract to prevent seed deterioration. Medium vigour black gram seeds were subjected to hydropriming for three hours (T2); other seeds were primed with Spirulina platensis extract at 1.5% for three hours (T3) while unprimed seeds served as control (T1). Then, the seeds were artificially aged under 40±1oC and 95±5% relative humidity for five days. The results revealed that the hydropriming and control of black gram seeds were significantly lower in all physiological and biochemical seed quality parameters than seeds primed with Spirulina platensis extract at 1.5% for three hours. Consequently, Spirulina platensis extract can effectively enhance black gram seeds and use agents in.

47-53

Authors: Le Nhat Minh, Vo Trong Nhan, Thi Thao Do, Tran Thu Huong, Le Tri Vien, Phung Thi Kim Hue*

Cancer stem cells (CSCs) are the cancer cells that have abilities to self-renew, differentiate into defined progenies, and to initiate and maintain tumour growth. They also contribute to cancer metastasis and therapeutic resistance, both of which are the principal causes of cancer mortality. Therefore, finding efficient fluorescent materials for CSC labelling and basic research is an urgent need. Thus, this research is focused on using a rare-earth element, which is the fluorescent Tb3+ nano-ion, and the CD133 monoclonal antibody to create a CSC-targeting nanocomplex (LV3). Tb3+ nanorods were silica-surface treated and -NH2 activated before being conjugated with the monoclonal antibody (mAb) against CD133, a typical CSC surface marker. The use of robust fluorescent Tb3+nanorods was to decrease the toxicity of a high-dose prober while the CD133 mAb would increase the CSC’s specific binding capacity of the LV3. The fluorescent properties of the coupled LV3 complex were measured and CSC-targeting label activities on the pluripotent human embryonal carcinoma cell line (NTERA-2) were observed. The obtained results presented fluorescent images of LV3 exposed to NTERA-2 cells under microscopy. LV3 also demonstrated that it effectively labelled up to 99.68% of the tested NTERA-2 cells. By contrast, LV3 only labelled 1.44% of the CCD-18Co human healthy cells. On the other hand, LV3 exhibited anti-CSC activity, which inhibited 11.14% in vitro and 30.5% tumourspheroid growth of NTERA-2 cells. In conclusion, LV3 showed its efficiency in specific CSC target labelling and inhibition, which could be further applied to fundamental and preclinical research.

59-63

Authors: Hang Thi Nguyet Pham*, Hong Nguyen Tran, Xoan Thi Le, Khoi Minh Nguyen, Hiep Tuan Nguyen, Lap Thi Nguyen, Folk R. William

Centella asiatica (L.) Urb. is a nootropic that has been used medicinally for centuries. The present study investigates the anti-dementia effect of an n-butanol extract of Centella asiatica in a mouse model of neurodegeneration caused by trimethyltin (TMT). Mice were administered Centella asiatica extract (150 and 540 mg/kg) or a reference drug, tacrine (2.1 mg/kg), daily for one week before TMT injection and during tests to analyse spatial short-term and spatial working memory. The treatment of mice with TMT caused deficits in short-term spatial working memory and decreased the number of pyramidal cells in the hippocampal CA1 and CA3 regions elucidated by Nissl staining at 28 d post-TMT treatment. The administration of Centella asiatica extract or tacrine significantly attenuated the behavioural and histochemical changes caused by TMT. These results suggest that Centella asiatica extract improved memory deficits partly by protecting hippocampal neurons from TMT-induced damage

71-76

Authors: Hong Ha Bui, Lan Huong Nguyen*, Thanh Tri Nguyen, Phuoc Dan Nguyen

In this study, a co-digestion pilot scale study of a mixture of domestic wastewater and the organic fraction of food waste using an anaerobic membrane bioreactor was developed. The results show that the removal efficiencies of the chemical oxygen demand (COD) and total suspended solids (TSS) were high and reached more than 90%. However, the removal of nitrogen and phosphate was not remarkable. The daily biogas yield reached 2.12 m3/d. The obtained biogas per COD removed was 0.22 m3/kgCODremoved. The average generated methane yield was 1.33 m3/d, which is equivalent to 0.14 m3/kgCODremoved. A high efficiency of organic compound removal combined with a large amount of retained nutrients and high biogas yield suggests the results of this pilot scale study can be practically applied to the recovery of nutrients for agricultural use along with biogas for cooking. These benefits remarkably reduce environmental pollution, especially for decentralized residential areas and independent-stationed military units located far from concentrated wastewater treatment plants.

83-89

Authors: Nguyen Thanh Tung, Wilai Chiemchaisri, Chart Chiemchaisri*, Samunya Sanguanpak

A biofilter using organic (compost) and inorganic (pumice, porous silica pellet or poremat) media was applied to the removal of methane (CH4) and nitrous oxide (N2O) to minimize the impact of off-gasses from municipal solid waste disposal global. The objective was to determine the appropriate biofilter media for CH4 oxidation and N2O conversion. The off gas (59.6% CH4, 1.0% N2O) was fed simultaneously with air (1:3 ratio) into the biofilter. CH4 oxidation and N2O conversion rates were observed over a 101-day period through the analysis of gas concentration along the biofilter’s depth using gas chromatography. Higher CH4 oxidation in the biofilters containing organic and inorganic media was achieved, especially for the compost-poremat biofilter with 70.1 g CH4/m3/d realised. The most active methane oxidation zone was found near the gas inlet at the bottom of the biofilter. The presence of inorganic material helped promote aerobic conditions for CH4 oxidation, especially during the initial period. N2O was also more completely removed with the biofilter containing inorganic media. Higher methanotrophic activities in matured biofilter media and the presence of methanotrophs type I, which prefer oxygen-rich conditions, were confirmed.