Vietnam Academy of Science and Technology: Journals Online
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TEM Study of ODS Alloy Doped with Helium Ions and Re-irradiated with Swift Xe Ions
No full textOxide dispersion strengthened (ODS) alloys are considered as candidates for fuel assembly claddings, since nano-oxides, among other things, contribute to the gas swelling suppression. However, it is still unknown that how oxides will behave in this capacity under the exposure to fission fragments. Transmission electron microscopy has been applied to study helium porosity in a ferritic EP450ODS alloy doped with helium by the ion implantation and re-irradiated with high energy Xe ions, which is used for simulating fission fragments at room temperature followed by annealing. It has been shown that helium bubbles mainly decorate the structural defects and grain boundaries both in helium doped only and in re-irradiated with Xe samples. Furthermore, we have found that there was not significant changes in the size distributions of helium bubbles in ferritic matrix due to the re-irradiation with Xe. The only effect of irradiation with swift Xe ions on the alloy structure is the amorphization of dispersed oxides in it. But, as a result of amorphization of dispersed oxides, helium bubbles were detected at the oxide-matrix (O-M) interfaces as well as inside amorphous oxides, while they have not been observed inside crystalline nano-oxides and seldom connecting to the O-M interface in the He-doped only samples. That means the nano-oxides amorphized by fission fragments can promote the better helium bubbles pinning in actual operation of the fuel assembly cladding in a nuclear reactor
Correlation Between and Concentration in Soil and Tea Tree in Luong My Farm, Hoa Binh Province, Vietnam
No full textIn this work, the correlation between 137Cs and 40K concentration in tea tree and soil in Luong My farm, Tan Thanh district, Luong Son commune, Hoa Binh province was experimentally investigated. The measurements were carried out using gamma spectroscopy with high purity germanium detector HPGe. The results showed that 40K is uniformly distributed in the soil depth while 137Cs is mainly located in 10 cm of the soil surface. Soil-plant transfer factor (TF) for 40K varies in the range of 0.491 to 0.623 and that of 137Cs is in range of 0.384 to 0.510. The concentration of these two radionuclides in tree parts is opposite to each other, while 40K is concentrated in the leave, 137Cs is mainly found in the root
MnBi Magnetic Material: A Critical Review
Get PDFManganese Bismuth (MnBi) - the ferromagnetic material attracting a great interest of the world magnetic society last years. The absence of rare-earth elements in compositions, the sizable magnetocrystalline anisotropy, the room-temperature moderate but high-temperature reasonable magnetization plus the positive temperature coefficient of coercivity and the moderate Curie temperature make MnBi bulk magnets very potential for high-temperature magnet application. This bright future is a little gray because the research results in the past were not as expected. The paper summarizes the results concerning the MnBi alloys, powders and bulk magnets investigated during past 67 years. The look on the difficulties inhibiting the development of this material is given and the proposals that might allow overcoming the difficulties and push again the efforts of research towards the goal of 12 MGOe for the energy product (BH)max of MnBi bulk magnets are discussed
Two Spot Coupled Ring Resonators
Get PDFAbstract. We consider a model of two coupled ring waveguides with constant linear gain and nonlinear absorption with space-dependent coupling. This system can be implemented in various physical situations as optical waveguides, atomic Bose-Einstein condensates, polarization condensates, etc. It is described by two coupled nonlinear Schrödinger equation. For numerical simulations, we take local two-gaussian coupling.It is found in our previous papers that, depending on the values of involved parameters, we can obtain several interesting nonlinear phenomena, which include spontaneous symmetry breaking, modulational instability leading to generation of stable circular flows with various vorticities, stable inhomogeneous states with interesting structure of currents flowing between rings, as well as dynamical regimes having signatures of chaotic behavior. This research will be associated with experimental investigation planned in Freie Universität Berlin, in the group of prof. Michael Giersig
INVESTIGATION OF APPLYING WILD BACILLUS SPECIES FOR SAND STIFFENING
Get PDFMicrobially induced calcium carbonate precipitation is a biomineralization process that has various applications in remediation and restoration of range of applications. In the present study, calcifying bacteria, Bacillus subtilis and Bacillus megaterium isolated from soil (Viet Nam). These species were investigated for sand stiffening using syringe set-up with daily nutrient addition at 7, 14 and 28 days. The stiffened sand samples were tested the physical and chemical properties. The calcium carbonate polymorphs produced by Bacillus subtilis and Bacillus megaterium were analyzed by scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD). These results show that both of the Bacillus species could make consolidation through calcite precipitation at the alkaline pH rate of 9, increased impact strength of the stiffened sand samples. Furthermore, isolated B. megaterium shows it is potential as bio-sealant to enhance the durability of low energy, green building materials (soil-cement blocks)
ASSESSMENT OF ANTIBIOTIC RESISTANCE AND BACTERIAL CONTAMINATION OF ICE SOLD IN CANTHO CITY, VIETNAM
No full textThis study aimed to investigate the bacterial contamination of flake and cube ice being used dailyin the community. Thirty-one ice samples were collected from different areas in the city of Can Tho city, Vietnam. The enumeration of total aerobic mesophilic counts, the presence of coliforms and Escherichia coli (E. coli) and determination of antibiotics resistance of E. coli isolates were examined. The results indicated that total aerobic mesophilic counts ranged from 2.5 to 6.2 log CFU/mL and significant differences of total aerobic mesophilic counts were found between flake ice and cube ice (p 0.05). Coliforms and E. coli were present on the ice samples of 93.55% and 58.06%, respectively. A total of 39 E. coli isolates were tested their resistance to 15 different antibiotics. The E. coli isolates of 74.36% were multi-resistance from three to thirteen antibiotics. The high prevalance was resistant to Ampicillin (79.49%), Cefotaxime (69.23%), Ceftazidime (46.15%), Tetracycline (56.41%), Sulfamethoxazole/Trimethoprime (46.15%), Colistin (20.51%), etc. As E. coli is an hygiene indicator and a candidate vehicle for the transfer of antibiotic resistance gene, it is highly recommended using clean and probable water in ice making as well as preventing the spread of antibiotic resistant bacteria
Antioxidant, anti-inflammatory and hepatoprotective activities on carbon tetrachloride - induced hepatic damage in mice of trang to (ixora duffii) leaf extract
No full textTrang To (Ixora duffii) belongs to the genus Ixora in the family Rubiaceae. The in vitro total antioxidant and anti-inflammatory capacity of the methanol extract of Trang To leaf was investigated using the phosphomolypdenum method and the bovine serum albumin denaturation test, respectively. The results showed that the methanol extract of Trang To leaf possessed relatively high antioxidant activity (OD0,5 = 15,551 ± 0,344 μg/mL) compared to that of the standard, trolox (OD0,5=2,315±0,083 μg/mL). The anti-inflammatory effect using bovine serum albumin denaturation test showed that the activity of the methanol extract of Trang To leaf (EC50= 6,03±0,12 μg/mL) was comparable to that of the reference drug, diclofenac sodium (EC50=0,57±0,21µg/mL). To evaluate the hepatoprotective activity of the methanol extract of Trang To leaf, the liver damage was induced in mice given with carbon tetrachloride (CCl4) mixed in olive oil (1: 4) at a dose of 2.5 mL/kg body weight/day. As a control, the standard hepatoprotective agent, silymarin, was used at the dose of 16 mg/kg body weight for 4 consecutive weeks. Trang To leaf extract was given at three different doses 100, 200 and 400 mg/kg body weight. The results showed the effective dose-dependent reduction of transaminase enzyme (ALT and AST) levels in sera. In addition, Trang To leaf extract also improved the oxidative stress status of the liver through effective reduction of MDA level and increase of GSH level in the liver. Histopathological examination of the liver tissue revealed that the mice treated with Trang To leaf extract showed significant improvement of liver tissue damages similar to silymarin treatment compared to the non-treated control group. The present results demonstrated that Trang To leaf extract has potent antioxidant and hepatoprotective activity.
TECHNOLOGY OF MUSHROOM CULTIVATION
Get PDFMushroom cultivation has been developed by two ways, i. e., one based on cultivation by wood-log and another based on cultivation by non-wood-log. Non-wood-log cultivation would be categorized into two aspects. Mushroom cultivation under non-aseptic condition, i. e., one characterized by the processes of fermentation (composting) and casing, and another characterized by using sterilized media followed by cultivation process associated with strict control of environmental factors such as light, temperature, humidity, and CO2 concentration
KINEMATIC AND DYNAMIC ANALYSIS OF MULTIBODY SYSTEMS USING THE KRONECKER PRODUCT
Get PDFThis paper employ Khang’s definition of the partial derivative of a matrix with respect to a vector and the Kronecker product to define translational and rotational Hessian matrices. With these definitions, the generalized velocities in the expression of a linear acceleration or an angular acceleration are collected into a quadratic term. The relations of Jacobian and Hessian matrices in relative motion are then established. A new matrix form of Lagrange’s equations showing clearly the quadratic term of generalized velocities is also introduced
LAYERED O3-NaFe0.5Co0.5O2 AS HIGH CAPACITY AND LOW- COST MATERIAL FOR SODIUM ION BATTERIES
Get PDFO3-NaFe0.5Co0.5O2 layered cathode material was synthesized by solid state reaction at 900 oC followed by a quenching step in argon atmosphere. The chemical composition and morphology of synthesized material were analyzed by Atomic Absorption Spectroscopy (AAS) and Scanning Electron Microscopy (SEM). The electrochemical properties were evaluated by Cyclic Voltammetry (CV) and charge-discharge cycling. The material NaFe0.5Co0.5O2 shows the sloped discharge curves with high flat voltage plateau and excellent cycling stability. The reversible capacity of about 120 mAh/g at rate C/10 and good capacity retention after 100 cycles were obtained