Vietnam Journal of Science, Technology and Engineering

5-9

Authors: Nhan Ba Dam, Van Tuan Chu, Anh Tuan Do, Quyet Thang Le

In this work, we study the influence of the substitution Si for Ni for the magnetic properties of LaNi5-xSix (x = 0-0.5) alloys. The structure of the alloy was tested by X-ray diffraction (XRD) measurements. The magnetic properties of the samples were carried out using a vibrating sample magnetometer (VSM) system. The results showed that when Ni was substituted for Si in alloys and after hydrogen absorption, LaNi5-xSix alloys retained their CaCu5 structure. The susceptibility (χ) of the alloys decreased when substituting Ni by Si increased. The original bulk samples showed a Pauli paramagnetism state after hydrogen absorption transformed into a superparamagnetic state. The results obtained showed that although measurements of magnetic characteristics are relatively simple, quantitative information about the microscopic processes occurring in the material was used as the negative electrode in Ni-MH rechargeable battery.

14-21

Authors: The Anh Nguyen, Truong Giang Vu, Thi Lan Nguyen, Quang Trung Pham, Thi Thao Ta

Honey is a natural, sweet, and syrupy fluid which has been used in Vietnam in a variety of ways; as a food supplement, beauty product, and natural drug. However, quality control and characterization of honey are blind problems. Consumers, and even market management committees, must believe in the producer’s quality standards without using any special techniques to evaluate the botanical origins of honey in the Vietnamese market. The chemical composition and physical properties of natural honey vary per plant species of which the honey bees scrounged. Longan flower-honey has a high price and is commercially produced in Yen Bai, Bac Giang, and the more well-known Hung Yen Province in Vietnam, and now is being confused with original flower honey. In this work, a total of 57 honey samples (longan and non-longan) from different geographic and botanical origins have been analysed in terms of 1H-NMR spectroscopy, coupled also with multivariate statistical analysis methods. Principal component analysis followed by icoshift algorithm analysis comes about as a proficient device in recognising 1H-NMR spectra of longan honey samples.

30-33

Authors: Chi Buu Bui, Thi Lang Nguyen

Although Vietnam is the second largest rice exporter in the world, the country has only recently met the demand for sustainable food supply at a national level, and not yet at a household one. In the early 1970s, the average rice yield in the Mekong River Delta (MRD) was 1.9 tons/ha and the annual production weighed 4 million tons. The current rice productivity and production has gained over 6 tons/ha and 24 million tons/year, respectively. This is a substantial increase. This progress in the MRD is in brief, due mostly to (1) Governmentpolicy, (2) Water management, and (3) Technological innovation and application with an emphasis on varietal improvement. As an impact of the ongoing El Nino Southern Oscillation (ENSO) phenomenon, severe droughts and salinity intrusion has been occurring in Vietnam’s MRD and has caused varying degrees of damage to agriculture, fisheries and the livelihoods of people in the region. New rice genotypes have been released via both conventional breeding and marker-assisted selection. The introgression of target genes from wild species viz. Oryza officinalis, O. australiensis, O. rufipogon into cultivars has been conducted successfully. Commercial rice varieties, which are currently growing in the MRD for export, are listed as Jasmine 85, OM3536, OM4900, IR64, OM6162, ST3, ST5...

39-42

Authors: Huu Hung Nguyen, Van Vang Luong, Thi Minh Tam Ngo, Hoai Son Vu, Xuan Thang Nguyen

This study was conducted at the Maize Research Instituteof Vietnam using 24 maize hybrids, identified as STM1 to STM24, at five different salt concentrations, which were 0, 50, 100, 150, and 200 mM NaCl. After seven days of germination at room temperature, seedlings were transplanted to nutrient-rich solutions salinized with salt. 17 day-old seedlings were then harvested to calculate their growth parameters of the day to seedlings fully wilt and degradation, root and shoot length, seedling dry matter production, and content. As the study results show, salt stress caused the reduction of plant growth in all hybrids, however, the STM10 and STM21 varieties showed the best salt tolerance, while STM17 and STM18 presented most salt-sensitive. The analyzed results for Na+ and K+ showed that among the hybrids, STM21 had lower Na+ and higher K+ contents in both roots and shoots of the seedlings than others.

48-52

Authors: Nhu Hiep Pham*, Huu Thien Ho, Anh Vu Pham, Hai Thanh Phan, Thanh Xuan Nguyen, Xuan Dong Pham, Tien Nhan Van, Nghiem Trung Tran, Trung Vy Pham, Si Doan Diem Tran, Trung Hieu Mai, Le Minh Chau Dao

Objective: Natural Orifice Transluminal Endoscopic Surgery (NOTES) is an important evolution in minimally invasive surgery (MIS) nowaday. This paper presents the techniques and early results of the pure transanal and transvaginal laparoscopies (NOTES) used for the treatment of colorectal cancer.Material and method: Prospective studies were conductedat Hue Central Hospital, Vietnam.Patients: From December 2013 to September 2015, 22 cololorectal cancer patients (18 rectum, 3 sigmoid tumors and 1 descending colon), adenocarcinoma, T≤ T3N1M0. Methods:The patients were placed in lithotomy and Trendelenburg positions, and the lone-star retractor was placed in the anus (rectum cancer) or vagina (sigmoid cancer). The surgical cavity was then inflated with CO2 and set at 12 mm/Hg. Dissection was continued until inside of the abdominal cavity (transanal technique). After that, the rectum was pushed into the abdominal cavity. The IMA and IMV were divided (TME included) in both techniques. After finishing dissection, the specimens were pulled out through the anus or vagina to prepare anastomosis. Coloanal and colorectal anastomosis were either hand-sewn (6 cases) or sealed with EEA staplers (16 cases). Results: 2 patients needed one more 5 mm umbilical port in RLQ, 2 patients needed two 5 mm trocars (post radiation hemorrhage, and urethral perforation). One patient converted to open and 1 patient converted to the HYBRID-NOTES procedure. The operation time was 258±40 (190-300) minutes. All patients required minimal analgesia. Bowel movement returned on the first day to 16 patients (average: two days, maximum: three days). The hospital stay was 7±2.8 (4-14) days. Kirwan classification (sphincter function) was very good (stage I: 18). Conclusions: Pure transanal and transvaginal laparoscopies for the treatment of colorectal cancer are feasible and safe. We believe that this is the first pure transvaginal laparoscopy (NOTES) for human in the world. A multicentric study in a large numbers of patients and a long follow-up is necessary.

56-61

Authors: Thi My Yen Nguyen, Xuan Quang Ngo*

Sub-tidal free-living nematodes in 12 stations along the Saigon River were investigated in both dry and rainy seasons during 2014 and 2015. In total, 157 nematode genera were found to belong to 59 families, and 11 orders of two classes of Enoplea and Chromadorea were identified. The trophic structure of free-living nematode communities was analysed spanning the overall seasons to see that deposit-feeders developed dominantly in the Saigon River indicating their association with food types including particles, bacteria, diatom, etc.. The dominance of deposit-feeders was contributed to a high abundance of genera in each station, including Theristus, Teschellingia, Monhystera, Thalassomonhystera, Paraplectonema, Daptonema, Aphanonchus, Sphaerotheristus, and Geomonhystera. Epistrate-feeder types were found as the second most abundant group. The remaining feeding types, such as chewers and suction-feeders, were in rather low proportion at most stations.

76-82

Authors: Hong Thien Van, Phi Nga Nguyen, Ngoc Toan Tran, Hong Truong Luu*

Alocasia rivularis (Araceae) is proposed as a new species from central Vietnam. The new species is morphologically similar to those of the Cuprea Group of Alocasia, but according to results of the trnL-trnF IGS and matK sequences, and based on morphological differences, it is clearly different from the closest congeners. Phylogenetic analysis, descriptions, and illustrations are provided.

88-91

Authors: Duc Ngu Nguyen*

This paper presents a summary of the results of a study into the effects of ENSO (El Niño and La Niña) on the frequency of cold fronts and tropical cyclones affecting Vietnam. The results show that, during the ENSO periods, cold air activities affecting Vietnam were reduced. The ratio of total positive anomalies to negative anomalies of front frequency was 68% in the case of El Niño, and 60% in the case of La Niña. The frequency of tropical cyclones affecting Vietnam decreased by 28% in the case of El Niño, and increased to 38% in comparison with the multi-year average in the case of La Niña. During the El Niño period, hurricanes affecting Vietnam were often evenly distributed or concentrated in the first half of the typhoon season, but during the La Niña period, hurricanes were concentrated in the second half of the hurricane season.