Vietnam Journal of Science, Technology and Engineering

3-9

Authors: Nguyen Chi Cuong*, Trinh Xuan Thang, Lam Minh Thinh, Vuong Dinh Duy Phuc, Phan Minh Truong, Truong Huu Ly, Ngo Vo Ke Thanh, Le Quoc Cuong

At atmospheric pressure (p=101325 Pa), the effects of humidity and temperature on moist air become important when discussing the quality factor of micro-cantilever and micro-bridge resonators. The squeeze film damping (SFD) problem, the dominant damping source for micro-beam resonators, is modelled using the modified molecular gas lubrication (MMGL) equation with finite element modelling (FEM) in the eigenvalue problem. The MMGL equation is modified with the effective viscosity of moist air (μeff) to account for the effects of humidity and temperature. Other damping sources, such as thermoelastic damping (TED) and the support loss of micro-beam resonators, are also calculated. The quality factor of micro-beam resonators is then discussed over a wide range of temperatures and relative humidity levels at atmospheric pressure and gas rarefaction. The results show that the quality factor of micro-cantilever and micro-bridge resonators increases as both humidity and temperature rise in atmospheric pressure and gas rarefaction. Furthermore, the quality factor of a micro-bridge resonator with changes in humidity and temperature is significantly higher than that of a micro-cantilever resonator in atmospheric pressure and gas rarefaction.

16-23

Authors: Ngoc Danh Dang*, Xuan Thiet Nguyen

Compared to conventional mechanical transmissions, hydraulic transmission has the disadvantage of lower energy efficiency. However, it is widely employed in various working machines such as construction machines, off-road vehicles, forest logging machines, and especially agricultural machinery, owing to its flexibility in design, geometric arrangement, and simplicity in operation. In the development project for carrot harvesting machinery conjugate, hydraulic transmission is the optimal solution for the design and implementation of the carrot collecting roller system. This project is oriented towards achieving a practical result where the system structure is simple and effective, utilising hydraulic components available on the market in Vietnam. Given the myriad of hydraulic transmission circuits available, this paper undertakes an analysis based on numerical simulations of the functionality and energy efficiency of potential system design options and proposes a new practical speed control circuit. This suggested circuit uses a pressure-compensated flow control valve arranged parallel to the hydraulic motor. The study is carried out in the Matlab/Simulink simulation environment, where the circuit models are constructed using hydraulic components with practical parameter settings sourced from component suppliers. The analysis results indicate that the proposed circuit strikes a balance between functionality and economic efficiency.

34-45

Authors: Huong Ngoc Thi Dao, The Thai Nguyen, Tran Huyen Thi Nguyen, Thuy Hong Ngoc Phan, Phuong Hoang Tran*

1-(4-sulfobutyl)pyridinium chlorozincate ionic liquid was synthesised in high yield (89%) through a simple route and characterised using FT-IR, NMR, and HRMS spectroscopy. The one-pot reaction was employed for the condensation reaction of benzaldehydes, 5,5-dimethyl-1,3-cyclohexanedione, and dicyanomethane, utilising the prepared ionic liquid catalyst. The optimal conditions for the reaction were achieved with a catalyst loading of 10 mol%, a solvent mixture of water and ethanol (1:1, v/v), maintained at 100°C for 180 minutes. A broad spectrum of benzopyran-5(6H)-one derivatives was prepared, yielding moderate to good results. The notable features of this procedure include readily available substrates, short reaction times, the use of environmentally friendly solvents, and the elimination of the need for chromatography in the isolation of products. Anew acidic pyridinium-based ionic liquid was successfully synthesised and used as a catalyst in the synthetic process of 2-amino-3-cyano-4-phenyl-7,7-dimethyl-7,8-dihydro-4H-1-benzopyran-5(6H)-ones. These reactions involved a condensation reaction of aromatic benzaldehydes, 5,5-dimethyl-1,3-cyclohexanedione, and dicyanomethane in a solvent mixture of ethanol and water, resulting in the desired products in moderate to good yields. The procedure is efficient and eco-friendly, and the products can be easily obtained by recrystallisation. Thus, this protocol offers an alternative to existing methods.

53-58

Authors: Thanh Tung Truong*, John Nielsen

Fluorine holds a prominent position within the realm of drug discovery and development, substantiated by its presence in approximately 25% of drugs approved by the US Food and Drug Administration (FDA). Consequently, the advancement of new fluorination reactions stands as a pivotal area in medicinal chemistry. In particular, the monofluoro-, difluoromethyl-, and trifluoromethyl- are three groups that appear most frequently in drug structure. Quinoline, owing to its privileged structural status, plays a crucial role in drug design and synthesis. Various approaches have been documented for the direct difluoromethylation of the C-2 and C-4 positions of the quinoline ring. However, achieving direct C-3 difluoromethylation has remained an elusive objective. In this study, we introduce a novel method for effecting the direct difluoromethylation at the C-3 position of the quinoline ring.Comprehensive characterizations, including 1H-NMR, 13C-NMR, and 19F-NMR for all compounds are performed. We believe that this novel method will open a new way to access the hitherto untapped C-3-difluoromethylation active compounds.

77-83

Authors: Tien Hai Ly, Le Hoang Vu, Ly Van Khanh, Nguyen Thi Ngoc Anh*

This study was conducted to assess the effects of stocking densities on the water quality, survival and growth of the freshwater prawn Macrobrachium rosenbergii postlarvae (PL) cultured in a biofloc system integrated with red seaweed (Gracilaria tenuistipitata). Postlarvae prawns weighing 0.012±0.001 g were stocked at densities of 1,000, 1,500, 2,000, and 2,500 PL/m3, noted as D1, D1.5, D2, and D2.5, respectively. Each density treatment was replicated three times and randomly assigned to 12 plastic tanks of 150 l at a salinity of 10 ppt. Red seaweed was added at a rate of 1.5 kg/m3, and molasses was used as a carbon source to maintain a C:N ratio of 15:1. No water exchange occurred during the 30-day rearing period. Results indicated that water quality parameters, including TAN and NO2-, biofloc volume, total heterotrophic bacteria, and Vibrio spp. counts, increased at higher prawn densities but remained within the appropriate range for prawn performance. Growth rate in weight and survival of prawns decreased as stocking density increased, with D1 and D1.5 showing comparable and significantly higher results compared to D2 and D2.5. Prawn production increased with rising stocking density, with a significant difference among treatments (p<0.05). Furthermore, prawns in D1 and D1.5 exhibited significantly higher feed efficiency than those in D2 and D2.5. These findings suggest that nursery rearing of prawn PL at a density of 1,500 ind/m3 in a biofloc system integrated with red seaweed offers optimal growth and feed efficiency, while maintaining good water quality and conserving water resources.

90-95

Authors: Nguyen Hoang Giang, Nguyen Trong Ha, Nguyen Thi Xuan*

Lymphoma represents a heterogeneous group of cancers affecting the lymphatic system, encompassing non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL). The majority of NHL cases originate from B cells. HL is characterized by the presence of rare Hodgkin and Reed-Sternberg cells. Within the context of the inflammatory response, two SH2 domain-containing protein tyrosine phosphatases (SHPs), namely SHP-1 and SHP-2, serve as negative regulators. Deubiquitinating enzymes (DUBs) play a crucial role in inhibiting NF-κB activation in response to various stimuli. This study focuses on the DUBs OTUB1, OTUB2, and Cezanne. Blood samples were collected from 50 NHL patients, 26 HL patients, and 50 healthy individuals. Quantitative RT-PCR was employed to assess the mRNA expression of OTUB1, OTUB2, Cezanne, SHP-1,and SHP-2, while ELISA was used to determine IL-6 and CA125 concentrations. The results revealed that the mRNA level of OTUB1 was significantly downregulated in NHL patients but not in HL patients. Notably, Cezanne expression was downregulated in lymphoma patients, with significantly lower levels observed in HL compared to NHL patients. Furthermore, SHP-1 mRNA expression was significantly lower in the NHL group compared to the HL group or healthy individuals. Conversely, SHP-2 gene expression was upregulated in NHL patients but remained unchanged in HL patients. In conclusion, these findings highlight significant differences in the expressions of DUB and SHP genes and the inflammatory response in lymphoma patients. This study provides a foundation for further investigation into the roles of DUBs and tyrosine phosphatases in regulating the functional activation of lymphoma cells.

104-110

Authors: Chinh Nghia Nguyen, Hang Ngan Dinh, Thu Trang Nguyen, Ha Trang Nguyen, Thi Trang Nguyen, Giang Hoang, Ky Son Chu, Thu Trang Vu*

In recent years, cheese consumption in Vietnam is markedly rising, leading to the attention of local milk processors on cheese making. Quark-type cheese, a traditional food in Central Europe, is a type of well-known acid-coagulated cheese product. Milk coagulation properties (MCPs) play an important role to the success of the cheese-making process and are influenced by different parameters. In this study, the quality of raw milk for cheese making and the coagulation conditions in quark-type cheese processing were investigated. Raw milk collected from Phu Dong dairy farm met the requirement of Vietnamese standard for cheese making. The appropriate conditions for coagulation were identified: the heat treatment of milk at 60°C for 15 minutes, coagulation temperature at 40oC and pH 5.5, CaCl2 concentration at 0.04g/l. Under these conditions, a short coagulation time (72.33 seconds) and high curd yields (50.70%) were obtained. These results suggested that quark-type cheese using raw milk in Vietnam could be successfully developed at larger scale.

120-128

Authors: Linh-Thy Le, Khanh-Bang V. Quang, Trieu-Vi Vo, Thanh-Mai T. Nguyen, Thi-Viet-Huong Dao, Xuan-Thanh Bui*

Air pollution is one of the leading risk factors for death but also a significant contributor to the global disease burden, affecting quality of life. According to a World Health Organisation (WHO) report, seven million people die from air pollution every year, and 9 out of 10 people worldwide breathe polluted air. Any person can be affected by exposure to polluted air, especially the elderly, children, pregnant women, and people with comorbidities. Some studies indicate that the diseases most affected by air pollution are respiratory infections, chronic obstructive pulmonary disease (COPD), lung cancer, and cardiovascular diseases. The degree of effect on the body depends on the pollutant composition, source and dose, level and duration of exposure to polluted air. Particulate matter (PM10 and PM2.5), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2) could lead to air pollution. Long-term exposure to air pollution can affect every organ in the body and worsen existing health conditions. Short-term exposure to contaminants can include unpleasant sensations such as coughing, wheezing, shortness of breath, eye, nose, and throat irritation, headache, dizziness, and fatigue. Community and individual solutions such as using clean fuel, wearing personal masks, filtering indoor air, and ventilating need to be taken to reduce the impact of air pollution.