Vietnam Academy of Science and Technology: Journals Online
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Heavy metal contamination of soil based on pollution, geo-accumulation indices and enrichment factor in Phan Me coal mine area, Thai Nguyen province, Vietnam
No full textSoil samples around the Phan Me coal mine area, Thai Nguyen province, Vietnam had been analyzed for Fe, Mn, Cu, Zn, As, Cd, Hg, Pb and Ni. Single pollution index, geo-accumulation index, enrichment factor have been determined and used for assessing the soil quality. In average by pollution index, the soil heavy metal pollution sequence is Cu(PI=4.2)Cd(3.5)Zn(3.1) Pb(1.7)Ni(1.3). High concentrations of Cu, Zn and Cd in the soil in the study area are thanks to geo-accumulation and enrichment of the metals in the soil. The soil is from moderately to heavily contaminated by Cu, Zn and Cd: Cu and Zn concentrations are 1.5-2.8 times higher than the ecological risk values, and Cd concentration is about 3.5 times higher than allowable limits. The high concentration of Pb is thanks to moderate geo-accumulation and enrichment of Pb, and the soil mostly has Pb concentration higher than the allowable limit in about 1.7 times. There is a sign that the soil is contaminated by Ni: 22% of the samples have Ni concentration higher than the threshold value, however, the enrichment of Ni is only deficient to minimal. The results of the assessment highlight the need for a comprehensive and detailed study program on heavy metal content in different soil resources in a wider area to identify the magnitude and details of the problem associated with heavy metal contamination for the development of a remediation plan and more effective pollution preventing measures
Assessment of shoreline changes for setback zone establishment from Son Tra (Da Nang city) to Cua Dai (Hoi An city), Vietnam
No full textThe most important function of the coastal setback is to minimize damage due to coastal erosion, climate change response, and sea-level rise. There are many directions and methods of researching and assessing coastal changes and coastal erosion. This study presents the results of the shoreline changes in the area from Son Tra (Da Nang City) to Cua Dai (Hoi An City), Central Vietnam based on remote sensing data from 1965 to 2019. Three methods are used to include End Point Ratio (EPR), Linear Regression Rate (LRR), and Weighted Linear Regression (WLR). The results show that the EPR method is effective when calculating the rate of shoreline changes only at two different times. For more objective and reliable calculation, it is necessary to assess the shoreline changes over time. Meanwhile, the LRR method was shown to be superior because all shoreline data were taken into account during the construction of the regression line. However, when there is much shoreline data with different reliability, the WLR method proved more superior because of limited objective errors. The results show that from 1965 to 2019, the coast of the Son Tra - Cua Dai area had quite complicated fluctuations, of which the northern area (Son Tra) tended to accretion, the central area tends to be alternate between accretion and erosion, while the south area (Cua Dai) is strong to very strong erosion. The coast with sudden changes is the Cua Dai area with the shoreline change envelope (SCE) reaching 512m. The results also allow us to divide the coast of the Son Tra - Cua Dai area into 30 segments. They are clustered into 8 groups with different levels of erosion and accretion. This is an important basis for the setback zone establishment in the study area
Vibration under variable magnitude moving distributed masses of non-uniform Bernoulli-Euler beam resting on Pasternak elastic foundation
Get PDFThe dynamic response to variable magnitude moving distributed masses of simply supported non-uniform Bernoulli-Euler beam resting on Pasternak elastic foundation is investigated in this paper. The problem is governed by fourth-order partial differential equation with variable and singular coefficients. The main objective of this work is to obtain closed form solution to this class of dynamical problem. In order to obtain the solution, a technique based on the method of Galerkin with the series representation of Heaviside function is first used to reduce the equation to second order ordinary differential equations with variable coefficients. Thereafter the transformed equations are simplified using (i) The Laplace transformation technique in conjunction with convolution theory to obtain the solution for moving force problem and (ii) finite element analysis in conjunction with Newmark method to solve the analytically unsolvable moving mass problem because of the harmonic nature of the moving load. The finite element method is first used to solve the moving force problem and the solution is compared with the analytical solution of the moving force problem in order to validate the accuracy of the finite element method in solving the analytically unsolvable moving mass problem. The numerical solution using the finite element method is shown to compare favorably with the analytical solution of the moving force problem. The displacement response for moving distributed force and moving distributed mass models for the dynamical problem are calculated for various time t and presented in plotted curves
Magnetic Lattices for Ultracold Atoms
Get PDFThis article reviews the development in our laboratory of magnetic lattices comprising periodic arrays of magnetic microtraps created by patterned magnetic films to trap periodic arrays of ultracold atoms. Recent achievements include the realisation of multiple Bose-Einstein condensates in a 10 m-period one-dimensional magnetic lattice; the fabrication of sub-micron-period square and triangular magnetic lattice structures suitable for quantum tunnelling experiments; the trapping of ultracold atoms in a sub-micron-period triangular magnetic lattice; and a proposal to use long-range interacting Rydberg atoms to achieve spin-spin interactions between sites in a large-spacing magnetic lattice
Absorption of Electromagnetic Waves by FeO/Paraffin Composite Materials
Get PDFElectromagnetic pollution in general and the harmful effects of microwave radiation in particular on environment is currently in the urgent stage. To eliminate the effect of electromagnetic energy the most common methods relies on the use of absorbing materials with large absorption capacities in wide frequency band. In this paper, we investigate the capability of absorption of electromagnetic waves of Fe3O4 nanoparticles in paraffin basis. The Fe3O4/paraffin composite materials were prepared with a weight ratio of 35%/65%. The dielectric constant (εr) and the magnetic permeability (μr) in the frequency (f) range from 8 to 18 GHz were measured for various sample thicknesses. The results indicated a large dielectric loss and strong thickness dependence of absorption capacity. The maximum absorption coefficient (RL) is of order -13.6 dB, corresponding to the achieved absorbance of 96,9% for the 2.6 mm of sample thickness. The experimental results are consisted with our simulation calculation
Isolation and characterization of a c-repeat binding factor gene from Tevang-1 maize cultivar
Get PDFC-repeat binding factor (CBF) proteins are transcription factors involved in plant response to abiotic stresses, especially low-temperature condition. In this research, a CBF3-coding gene was isolated from a cold-acclimation maize variety, Zea mays var. Tevang-1 and denoted as ZmCBF3tv. The isolated gene shared 96.49% homology with the B73-reference gene and had no intron in the coding sequence. By using bioinformatic tools, a number of variations in the nucleotide and amino acid sequences were identified. An alignment between ZmCBF3tv and other CBF/DREB1 proteins from various species revealed functional regions and typical features, such as nuclear localization signal (NLS), the AP2 DNA-binding domain, and acidic-amino-acid-rich segments. Additionally, a phylogenetic analysis based on the AP2 domain showed that the maize CBF3 transcription factor had the highest similarity with that from rice and closely related to other DREB1/CBF protein of monocots. The function of the ZmCBF3tv product is suggested to be a CBF/DREB1 transcription factor.
Analysis of reproductive traits and laying egg rhythm of maize weevil sitophilus zeamais (motschulsky)
Get PDFThe maize weevil, Sitophilus zeamais (Motschulsky), is a serious pest affecting a wide range of cereal crops, such as maize, rice, beans and other stored dried grains. As a S. zeamais female can keep laying eggs for a long time throughout its life after chewing its way into the grains, most development stages of the maize weevil, such as eggs, larvae and pupae, can always be found in stored maize grains. Our experiment with S. zeamais on long grain rice showed that 10 days after eclosion and mating, maize weevil females started laying eggs for a period of 145 days. On average, a S. zeamais female laid 38.67 eggs, of which, up to 62.81% were laid in the first 7–8 weeks (with the remaining 37.19% in the latter half of the 145 day period), and 55.07% were laid within day 55–95. The egg laying pattern of S. zeamais was modeled using cubic polynomials, which described the maximum percentages of eggs laid at day 15, 35, 75, 95 and 105.
Formulation and application of nanosilver-infused cream in prevention and treatment of mastitis in dairy cows
Get PDFResearch on formulation of nanosilver-infused cream was carried out at the Institute of Environmental Technology and the effects of this cream in prevention and treatment of mastitis in dairy cows were assessed at Bavi Cattle and Forage Research Center. Cream with 0.4% carbomer was infused with silver nanoparticles for high uniformity and long-term stability. At concentrations of 50–250 ppm, nanosilver-infused cream proved to be effective against mastitis pathogens such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa. Nanosilver cream at concentrations of 150 ppm had the best effect on clinical and subclinical mastitis prevention in dairy cows. Combining nanosilver cream with ceftiofer antibiotic achieved excellent treatment rate, up to 93.33%. For prevention of dairy mastitis, silver cream can be used at a concentration of 150 ppm 15 days before calving and for the whole milking period. Using nanosilver cream in combination with antibiotics led to highly effective mastitis treatment.
The significance of zircon U-Pb ages in the Ba river basin to the timing of major tectonic stages of Kontum massif
No full textBa River originates from the Ngoc Linh mountain ranges, NW of Kontum massif and flows into the East Sea from the Da Rang estuary. The Ba River basin (Da Rang river) is considered as the means of transport and storage of products from the Kontum massif resulted following weathering, erosion or deformation processes either by natural causes or the regional thermo-tectonic events. A total of 122 zircon grains separated from the Ba River basin sediments are selected for U-Pb isotopic age dating by LA-ICP-MS method. Among the 122 samples, 114 are concordant, forming 3 major age groups, including middle-Late Cretaceous (105–85 Ma), Middle Permian - Late Triassic (270–211 Ma), Late Ordovician - Early Silurian (455–424 Ma). A few samples show ages scattering from 1470 to 970 Ma (Mesoproterozoic), and one sample shows a value of 2383±24 Ma (Paleoproterozoic). The acquired U-Pb zircon ages may reflect 3 major thermo- tectonic stages in the formation and evolution of the Kontum Massif from the Early Paleoproterozoic till middle-Late Cretaceous, with the most significant time being Middle Permian (270 Ma)-Late Triassic (211 Ma) (97 over 122 samples, e.g., 79,5%), corresponding to the period of convergence, collision and orogeny of the Indosinian block.
BIOCOMPATIBILITY OF HAp/CNTs COATING ON Ti6Al4V ALLOY INTO THE SIMULATED BODY FLUID SOLUTION
No full textHydroxyapatite doped carbon nanotubes (HAp/CNTs) was synthesized successfully as a coating on the surface of titanium alloy (Ti6Al4V) by a scanning potential method. The biocompatibility of the materials soaked into a simulated body fluid solution (SBF) were investigated. SEM images are observed that the formation of new apatite crystals on the surface of Ti6Al4V with HAp or HAp/CNTs coating is better than that of Ti6Al4V. The formed apatite crystals are confirmed by XRD result of Ti6Al4V after 21 soaked days in SBF solution. These results indicated that the coatings of HAp or HAp/CNTs have a good biocompatibility