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Đa thức độc lập của đồ thị và một số vấn đề liên quan

(2025) Phạm, Mỹ Hạnh; Đỗ, Trọng Hoàng; Đoàn, Duy Trung

Luận án tập trung nghiên cứu các bất biến tổ hợp của đồ thị corona và lớp đồ thị W p thông qua đa thức độc lập. Nghiên cứu làm rõ tính yếu vị của dãy hệ số của đa thức độc lập, đồng thời thiết lập mối liên hệ giữa đa thức độc lập của đồ thị và ℎ h-đa thức của phức độc lập. Trên cơ sở đó, luận án đề xuất công thức tính chỉ số chính quy Castelnuovo–Mumford của vành thương liên quan.

Ấn phẩm

Screening of actinomycetes from Ninh Thuan and Binh Thuan sea for antimicrobial producers

(2022-12) Vu, Thi Thu Huyen; Le, Thi Hong Minh; Nguyen, Mai Anh; Vu, Thi Quyen; Doan, Thi Mai Huong; Pham, Van Cuong

The sea is a unique ecosystem for finding secondary metabolites from marine microorganisms. Many compounds produced by marine microorganisms with antibacterial activity have been applied in life. Furthermore, microorganisms are renewable raw materials and media for drug production, thus crucial for sustainable development in our life. In this study, we screened for antibacterial activity of microbial strains isolated from tern samples from Ninh Thuan and Binh Thuan seas. The antibacterial activity of the marine microbial crude extracts was performed by the Bioassay method in a 96-well tray. The minimum inhibitory concentration (MIC) test results showed that from 86 strains of microorganisms isolated from the waters of Ninh Thuan and Binh Thuan, 68 strains were able to inhibit the growth of 1 to 6 strains of the tested microorganisms, and 27 over 86 strains had antibacterial activity against at least three strains of microorganisms tested. In which strains G631, G756, G769, and G778 inhibited 4 to 6 tested microorganisms with MIC values equal to or lower than positive controls. Morphological characteristics and molecular biological analysis identified the four most active strains. The results showed that all four strains were actinomycetes.

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Phân lập và tuyển chọn vi khuẩn quang dưỡng không lưu huỳnh màu tía cung cấp dưỡng chất, giảm phát thải CH4 trên đất phèn trồng lúa ở Bạc Liêu, Hậu Giang

(2025) Đặng, Hữu Ân; Lý, Ngọc Thanh Xuân

Nghiên cứu phân lập và tuyển chọn 52 dòng vi khuẩn quang dưỡng không lưu huỳnh màu tía (PNSB) tại Đồng Tháp và An Giang. Kết quả xác định được các dòng vi khuẩn có khả năng cố định đạm (>50 mg/L), hòa tan lân (>180 mg/L), tiết IAA, hòa tan kali và đặc biệt giảm phát thải khí metan (CH4) lên đến 49,4%. Nghiên cứu đề xuất ứng dụng các dòng PNSB (như SCS_8A, SVG_8) làm chế phẩm sinh học cho đất phèn.

Ấn phẩm

The assemblage structure of large size sea urchins (Diadematidae) in Northern Vietnam

(2022-12) Do, Hung Dang Viet; Yoko, Nozawa; Pham, Van Chien; Pham, Van Chien; Pham, Van Quang; Tran, Van Hung; Tran, Van Hung; Tran, Manh Ha; Tran, Manh Ha; Dam, Duc Tien

The large sea urchins (Diadematidae) are widely distributed worldwide, from temperate to tropical waters. Diadematidae is an important herbivore in the coral reef ecosystem through herbivore-algal-coral interaction, which maintains the reef’s health. Many studies of Diadematidae have been performed around world, but in Vietnam, there is little known about the ecology of this group. Here, we first investigated the assemblage structure of Diadematidae in Northern Vietnam. We observed 43 sites of representative coral reefs in Ba Mun - Co To, Cat Ba - Ha Long, and Hon Me. Based on the surveys, we found four species of considerable size sea urchins, of which the most common species is Diadema setosum (79.8% of the total), Enchinothrix calamaris (10.1%), E. diadema (8.3%), and D. savignyi (1.8%). Among three study regions, Hon Me is the most diverse. In addition, Hon Me also has the highest density of sea urchins. However, this value is generally low compared to that in Southern Vietnam and other neighboring countries. Further study is needed to investigate the ecology and reproductive biology of Diadematidae to provide fundamental information for sustainable exploitation and conservation.

Ấn phẩm

Phân lập, tuyển chọn vi khuẩn quang dưỡng không lưu huỳnh màu tía cung cấp dưỡng chất, giảm độc chất, phát thải CH4 trên đất phèn trồng lúa ở An Giang và Đồng Tháp

(2025) Nguyễn, Văn Minh; Lý, Ngọc Thanh Xuân

Ấn phẩm

Towards a risk-based food safety management system in the fresh produce supply chain in Da Nang, Viet Nam

(2024) Mac, Thi Thanh Ha

Food safety has emerged as a paramount concern for both Vietnamese consumers and the government. However, limited data are available on food safety management systems in Viet Nam. This study identified significant gaps in good agricultural and hygienic practices along the fresh produce chain (farmers and traditional wholesalers/market sellers) in the region of Da Nang, Viet Nam. This was achieved through a survey on good agricultural and hygienic practices for farmers (n = 100) and sellers (n = 100), which researchers further supplemented by microbiological analysis for E. coli, Salmonella spp., and Listeria monocytogenes on leafy greens, water in contact with produce and contact surfaces (hands). The results indicated that 86.0 % of farmers and 54.0 % of sellers received food safety training in the last 3 years; and women dominated both vegetable cultivation but also trading. Farm-level deficiencies included inadequate handwashing practices, lack of documentation for manure application schedules, improper washing and drying of harvest tools, failure to keep containers elevated off the ground, improper storage of vegetables, and inadequate covering of containers, with respectively 34.0 %, 30.3 %, 12.1 %, 41.7 % and 7.9 % of farmers executing the practice as prescribed by the WHO/FAO ‘5 keys of growing safer fruits and vegetables’. As for sellers, the most dominant gaps (<50.0 % compliance) were the way of handwashing and the practice of keeping containers elevated off the ground before, during, and after harvesting. The microbiological analysis confirmed that, in a total of 36 fresh produce samples including mustard greens, cucumber, lettuce, and crown daisy, the number of samples positive for E. coli, Salmonella spp., and L. monocytogenes were 12, 2, and 10 respectively. Samples of hands and the irrigation water showed high contamination with E. coli. Based on identified gaps, risk communication tools were developed and distributed amongst farmers, sellers, and Da Nang food safety management authority (governmental organisation performing inspections in the traditional food markets). As intervention, two farmers and two sellers were trained in safe agricultural practices for the cultivation of fresh vegetables (managerial intervention) and instructed to use tap water as irrigation water instead of uncontrolled surface water (technological intervention). A post-assessment was conducted, including redoing the survey on good practices and microbiological analysis. The outcome of these interventions showed positive results in terms of good agricultural and hygienic practices resulting in improved hygiene levels and safety of the fresh produce. The findings from this research have the potential to provide a model for the development of a science-based risk management strategy in alternative food chains or geographic areas in emerging countries.

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