Vietnam Academy of Science and Technology: Journals Online
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Optimizing conditions for treatment and extraction of collagen from fan-bellied leatherjacket skin Monacanthus chinensis (Osbeck, 1765)
No full textThe fan-bellied leatherjacket skin was treated to extract collagen by chemical method. The non-collagenous substances and the pigment in the skin were removed with NaOH and H2O2, respectively. Collagen was extracted with acetic acid. The treatment and extraction conditions were optimized by response surface methodology. The concentrations, skin/solution ratios (g/ml) and times were surveyed. The optimum conditions to remove the non-collagenous substances were as follows: the concentration of NaOH at 0.15M, the ratio (g/ml) at 1/13.9, time at 56.9 hours. Using H2O2 with the concentration at6%, the skin/solution ratio (g/ml) at 1/2, time at 10 minutes were suitable values for skin pigmentation removal. For collagen extraction, the concentration of acetic acid at 0.53M, skin/solution ratio at 1/9.6 g/ml and time in 59.6 hours were optimal
The numerical calculation of statically admissible slip-line field for plane strain compression of a three-layer symmetric strip between rigid plates
No full textThis paper present a method to build up statically admissible slip-line field (the field of characteristics) and, as a result, the field of statically admissible stresses of the compression of a three-layer symmetric strip consisting of two different rigid perfectly plastic materials between rough, parallel, rigid plates (for the case: the shear yield stress of the inner layer is greater than that of the outer layer). Under the conditions of sticking regime at bi-material interfaces and sliding occurs at rigid surfaces with maximum friction, the appropriate singularities on the boundary between the two materials have been assumed, then a standard numerical slip-line technique is supplemented with iterative procedure to calculate characteristic and stress fields that satisfy simultaneously the stress boundary conditions as well as the regime of sticking on the bi-material interface
Multiband Metamaterial Absorber in a Ring Structure Base on High-order Magnetic Resonance
No full textWe proposed a multi-band metamaterial absorber (MA) based on high-order magnetic resonance using ring-shaped structures. We obtained three absorption peaks at 4.71 GHz (the fundamental resonance), 13.39 GHz (the third-order behavior), and 19.91 GHz (the fifth-order behavior) with correspondent absorptions of 90%, 100%, and 99.33%, respectively. Therefore, these high-order perfect absorptions are the potential to make the easier fabrication for the next generation of MAs, especially in high-frequency regions. Particular, the obtained results are further controlled using the LC circuit model. Besides, by scaling down the unit-cell size, the third- and fifth-order absorptions are created in the THz frequency band
Simulation of Angle-insensitive Microwave Metamaterial Absorbers Operating at Transmission Mode
No full textMetamaterial absorbers with the resonator/dielectric/metallic-mirror conventional design are often angle-dependent and completely reflective outside the absorption band. Herein we have proposed a novel solution to achieve an angle-insensitive bidirectional absorber operating at transmission mode using a simple metamaterials system. The proposed system is composed of two symmetric disk-pair layers, called the disk-pair dimer, that exhibited two identical but coupled magnetic resonances at the same frequency. This unique design allows to absorb the electromagnetic energy at the transmission mode, which is rarely achieved in the conventional modes. By optimizing the coupling strength between two disk-pair layers, a total absorptivity could be enhanced up to 90%
High-dimensional Private Quantum Channels and Regular Polytopes
No full textAs the quantum analog of the classical one-time pad, the private quantum channel (PQC) plays a fundamental role in the construction of the maximally mixed state (from any input quantum state), which is very useful for studying secure quantum communications and quantum channel capacity problems. However, the undoubted existence of a relation between the geometric shape of regular polytopes and private quantum channels in the higher dimension has not yet been reported. Recently, it was shown that a one-to-one correspondence exists between single-qubit PQCs and three-dimensional regular polytopes (i.e., regular polyhedra). In this paper, we highlight these connections by exploiting two strategies known as a generalized Gell-Mann matrix and modified quantum Fourier transform. More precisely, we explore the explicit relationship between PQCs over a qutrit system (i.e., a three-level quantum state) and regular 4-polytopes. Finally, we attempt to devise a formula for such connections on higher dimensional cases
STUDIES ON THE ANTIOXIDANT ACTIVITY OF APIGENIN, LUTEOLIN AND NEVADENSIN USING DFT
No full textThe molecular properties of apigenin, luteolin and nevadensin which are three naturally flavonoid compounds have been studied theoretically by DFT method at 6-311++G(d,p) level. Both FMO analysis, mechanism, and kinetics studied suggested that compound Luteolin (compound 3) was a promising antioxidant agent. The results indicated that HAT is thermodynamically preferred in the gas phase, and SPLET is the thermodynamically favorable pathway in methanol and wate
Bioinformatic approaches for analysis of coral-associated bacteria using R programming language
No full textRecent advances in metagenomics and bioinformatics allow the robust analysis of the composition and abundance of microbial communities, functional genes, and their metabolic pathways. So far, there has been a variety of computational/statistical tools or software for analyzing microbiome, the common problems that occurred in its implementation are, however, the lack of synchronization and compatibility of output/input data formats between such software. To overcome these challenges, in this study context, we aim to apply the DADA2 pipeline (written in R programming language) instead of using a set of different bioinformatics tools to create our own workflow for microbial community analysis in a continuous and synchronous manner. For the first effort, we tried to investigate the composition and abundance of coral-associated bacteria using their 16S rRNA gene amplicon sequences. The workflow or framework includes the following steps: data processing, sequence clustering, taxonomic assignment, and data visualization. Moreover, we also like to catch readers’ attention to the information about bacterial communities living in the ocean as most marine microorganisms are unculturable, especially residing in coral reefs, namely, bacteria are associated with the coral Acropora tenuis in this case. The outcomes obtained in this study suggest that the DADA2 pipeline written in R programming language is one of the potential bioinformatics approaches in the context of microbiome analysis other than using various software. Besides, our modifications for the workflow execution help researchers to illustrate metagenomic data more easily and systematically, elucidate the composition, abundance, diversity, and relationship between microorganism communities as well as to develop other bioinformatic tools more effectively
A comparative study on the two vibration driven locomotion systems in various friction levels
No full textThis paper presented comparison results of two locomotion models: a pure-vibration driven and a vibro-impact driven system. In experiments, the friction force can be varied without changing the internal and the body masses. The mathematical models of the two systems were developed and experimentally verified. Using dimensionless models, the results can be expanded to other sizes in practice. The two models were compared in the following aspects: the progression rate, the motion direction and the dynamics response. The effect of friction as an important variable on the dynamic response of the two scaled models were examined and compared by means of bifurcation analysis and basin of attraction. It has been found that, the pure-vibration can provide forward motion better than the vibro-impact does. The highest progression rate of the vibro-impact was less than that of the pure-vibration system in the investigated ranges of input parameters. Besides, the pure-vibration always has period-1 motion, whereas the vibro-impact system has a rich and complex dynamic response, including period-1, period-2 as well as chaotic motions. The results obtained would be useful for design and operating the self-propelled locomotion systems
Polymorphism of the TMPRSS2 gene relating to COVID-19 subceptibility in Vietnamese population
No full textRecently, a contagious lung disease named coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), rapidly spread worldwide and has many serious consequences for human health. Human genetic polymorphisms may contribute to the variation of incidence, mortality as well as severity of COVID-19. To date, this factor in the Vietnamese population remains unknown. A cellular protease termed transmembrane protease serine 2 (TMPRSS2) was found to play a vital role in the entry of SARS-CoV-2 into host cells. In this study, we investigated polymorphisms in the TMPRSS2 gene from 270 whole exome sequencing data of Vietnamese peoples. We also employed bioinformatics tools including SIFT, Polyphen-2, and PROVEAN to predict the possible function of missense variants. A total of 34 TMPRSS2 variants were identified, of which, 29 were in non-coding regions and 14 were in coding regions. Variants found in exons included seven synonymous and seven non-synonymous point mutations, one of which was novel mutation (c.A1336C/p.R446R). Mutation c.G589A/p.V197M (rs12329760) possesses the highest frequency and was predicted to have the ability to damage protein by SIFT and Polyphen-2. In addition, the damaging possibility was also found in c.T244G/p.Y82D and c.C896T/p.A299V variants. This study contributes to the understanding of Vietnamese genetic variation databases relating to susceptibility to COVID-19.
Assessment of effective coral rehabilitated in Marine Protected Areas of south Vietnam
No full textMore than 20,300 fragment corals belonging to 24 species, eight genera and six families were rehabilitated in marine protected areas of south Vietnam. Mean survival rates of coral fragments ranged from 60–97.7%, the average growth rate of the branched corals was 4.8 mm/month meanwhile the foliose coral was 1.9 mm/month. The survival and growth rate of corals are different among areas because each coral species has different biological characteristics, structure colonies and due to differences in natural conditions each area. The results showed that the growth rate of corals will return to normal after 4 months rehabilitation. The factors affected the effective coral rehabilitation including: Coral reef predators, spatial competition among species, environmental conditions change due to human’s activities; and other factors such as hydrodynamic regimes, cutting fragment corals cause its injury damage. The rehabilitation and protection activities of coral reefs in marine protected areas should be continued and expanded, contributing to the protection of biodivesity, marine resource and sustainable coral reefs ecosystem development