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- 저자 : N. Tran (검색결과 147 건)
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Chi K. Hoang,Cuong H. Le,Dat T. Nguyen,Hang T. N. Tran,Chinh V. Luu,Huong M. Le,Ha T. H. Tran 한국균학회 2023 Mycobiology Vol.51 No.4
Genus Penicillium comprising the most important and extensively studied fungi has beenwell-known as a rich source of secondary metabolites. Our study aimed to analyze andinvestigate biological activities, including in vitro anti-cancer, anti-inflammatory and anti-diabeticproperties, of metabolites from a marine-derived fungus belonging to P. levitum. Thechemical compounds in the culture broth of P. levitum strain N33.2 were extracted withethyl acetate. Followingly, chemical analysis of the extract leaded to the isolation of threeergostane-type steroid components, namely cerevisterol (1), ergosterol peroxide (2), and(3b,5a,22E)-ergosta-6,8(14),22-triene-3,5-diol (3). Among these, (3) was the most potent cytotoxicagainst human cancer cell lines Hep-G2, A549 and MCF-7 with IC50 values of 2.89,18.51, and 16.47 mg/mL, respectively, while the compound (1) showed no significant effectagainst tested cancer cells. Anti-inflammatory properties of purified compounds were evaluatedbased on NO-production in LPS-induced murine RAW264.7 macrophages. As a result,tested compounds performed diverse inhibitory effects on NO production by the macrophages,with the most significant inhibition rate of 81.37 ± 1.35% at 25 mg/mL by the compound(2). Interestingly, compounds (2) and (3) exhibited inhibitory activities againstpancreatic lipase and a-glucosidase enzymes in vitro assays. Our study brought out newdata concerning the chemical properties and biological activities of isolated steroids from aP. levitum fungus.
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Electronic structure and magnetic properties of BaTi1-xMnxO3
N.V. Dang,N.T. Dang,T.A. Ho,N. Tran,T. L. Phan 한국물리학회 2018 Current Applied Physics Vol.18 No.2
The electronic structure and magnetic properties of polycrystalline BaTi1-xMnxO3 (x ¼ 0e0.1) compounds prepared by solid-state reactions were studied. The results revealed that the increase in Mn content (x) did not change the oxidation numbers of Ba (þ2) and Ti (þ4) in BaTi1-xMnxO3. However, there is the change in Mn valence that Mn3þ,4þ ions coexist in the samples with x ¼ 0.01e0.04 while Mn4þ ions are almost dominant in the samples with x ¼ 0.06e0.1. We also point out that Mn3þ and Mn4þ ions substitute for Ti4þ and prefer locating in the tetragonal and hexagonal BaTiO3 structures, respectively, in which the hexagonal phase constitutes soon as x ¼ 0.01. Particularly, all the samples exhibit roomtemperature ferromagnetism. Ferromagnetic order increases with increasing x from 0 to 0.02, but decreases as x 0.04. We think that ferromagnetism in BaTi1-xMnxO3 is related to lattice defects and/or exchange interactions between Mn3þ and Mn4þ ions.
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Tran Aimee N.,Chang Seung Ho 한국체육학회 2022 International journal of human movement science Vol.16 No.1
Athletes are often faced with tasks that demand high levels of focus, success, and performance. Professional athletes, specifically, are expected by many people to be the best and perform exceptionally well. Their lives often revolve around their sport, with long hours of training, strict nutrition, and different types of therapy. However, these athletes are human and experience stress from various factors. Athletes can experience external stress (e.g., from the audience or coaches), or internal stress (e.g., negative thoughts or anxiety). These are only a few examples of the stressors that athletes face throughout their careers. Numerous other factors may cause athletes to stress, and consequently, perform poorly. Therefore, athletes may have low levels of confidence, experience anxiety, or lose focus during high stake moments. However, there is a great body of research that shows mental skills training helps athletes overcome stressors and perform better. Self-talk is one example of an intervention for the mental skills found to help individuals perform better through relaxation, goal setting, self-regulation, self-reflection, flow, and self-efficacy. To better understand the effects of self-talk on sports performance, there is a need to identify how self-talk affects athletes in certain sport skills and situations, as there may be important differences or similarities to discover. Therefore, the purpose of this paper was to explore the effectiveness of self-talk on collegiate athletes’ performance across various sports. The findings of this paper suggest that the self-talk is a positive aspect of improving flow, self-efficacy, motivation and stopping general competitive anxiety and a nervousness. In addition, the fact that pairing a challenging statement to negative self-talk would be the effective way to promote athletes’ performance in some situation was found.
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N. Tran,Y.J. Choi,T. L. Phan,D. S. Yang,B.W. Lee 한국물리학회 2019 Current Applied Physics Vol.19 No.12
Crystal, electronic structures and the magnetic and electromagnetic wave absorption properties of BaFe12- xCoxO19 (x=0–2) M-type hexaferrites prepared by a co-precipitation technique were studied. The analyses of Xray diffraction patterns indicated that the samples mainly crystallized in the P63/mmc hexagonal structure, with the additional constitution of Y-type hexaferrite as x > 0. The replacement of Co2+ for Fe3+ in BaFe12-xCoxO19 changed the lattice constants and caused lattice distortions. Particularly, Co2+ doping also reduced magnetization and hard magnetic property of BaFe12-xCoxO19. This is ascribed to magnetic moment of Co2+ smaller than that of Fe3+ and to the decrease of magnetocrystalline anisotropy. Having studied electromagnetic wave absorption properties in the frequency range f=0.1–18 GHz, we found BaFe12-xCoxO19 showing high reflection loss (RL) values at frequencies of 0.1–15 GHz, but fairly low RL values at higher frequencies. These features suggest that BaFe12-xCoxO19 can be suitable to electronic devices working at GHz frequencies.
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Evaluation of horizontal and moment bearing capacities of tripod bucket foundations in sand
Tran, N.X.,Hung, L.C.,Kim, S.R. Pergamon Press 2017 Ocean engineering Vol.140 No.-
Bearing capacities of tripod bucket foundations differ from those of single bucket foundations because of the interaction among individual buckets of the tripod. This study analyzed the bearing capacities of tripod bucket foundations in medium and dense sands by performing a series of 3D finite element analyses. The sandy soil was modeled by using an elasto-plastic model following the Mohr-Coulomb failure criterion. The Young's modulus of the sands increased with depth because of the stress-dependency of the modulus. Parametric studies were performed, in which the spacing between each bucket, the embedded depth of the bucket, the bucket diameter, and the magnitude of vertical loading were varied. Results showed that the horizontal bearing capacities of tripod bucket foundations reached the maximum values at a spacing ratio of S/D=1.5 to 3.5 for the foundation with an embedment ratio of L/D=0.5 to 1 (where S is the bucket spacing, D is the bucket diameter, and L is the skirt length of the tripod bucket). However, the moment bearing capacities increased linearly as the S/D ratios increased. Finally, bearing capacity equations were proposed in consideration of bucket spacing, embedment depth, effect of foundation diameter and vertical load, and soil density.
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Joint Rate and Power Control in Wireless Network: A Novel Successive Approximations Method
Tran, N H,Choong Seon Hong IEEE 2010 IEEE communications letters Vol.14 No.9
<P>The conventional method of joint rate and power control (JRPC) relies on high signal-to-interference ratio (SIR) assumption which achieves only suboptimal results. By using a novel successive convex approximations method, we can attain the global optimal source rates and link powers in a distributed fashion exploiting message passing. Through simulations, our method converges faster than the previous work based on logarithm successive convex approximations.</P>
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Tran, N.,Kim, D.H.,Phan, T.L.,Dang, N.T.,Bach, T.N.,Manh, D.H.,Lee, B.W. North-Holland 2018 Physica. B, Condensed matter Vol.532 No.-
<P><B>Abstract</B></P> <P>Our studies on the crystal characterization and magnetic property of CoFe<SUB>2</SUB>O<SUB>4</SUB> nanoparticles (NPs) point out their instability in a specific temperature range. While as-prepared NPs exhibit single phase in a cubic spinel structure, annealing at temperatures <I>T</I>=673–1273K leads to the development of an impurity phase of Fe<SUB>2</SUB>O<SUB>3</SUB>. Interestingly, annealing at higher temperatures re-creates the single phase of NPs. This strongly influences their magnetic property. The magnetic inhomogeneity and/or multiple phase exist in as-prepared NPs and in those annealed below 1273K, better magnetic property is found in the samples with annealing temperature (<I>T</I> <SUB>an</SUB>) higher than 1273K. Ferromagnetic-paramagnetic phase transition temperatures of these samples are located around 815–850K, and are less dependent on <I>T</I> <SUB>an</SUB>. At room temperature, their saturation magnetization is located in the range of 41–55emu/g, while the coercivity can be changed from 600 to ~3200Oe. These results are related to microstructures, structural phases, and exchange interactions between Fe and Co ions situated in the <I>A</I> and <I>B</I> sites of the spinel structure, which are modified by heat treatment.</P>
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Fracture energy of ultra-high-performance fiber-reinforced concrete at high strain rates
Tran, N.T.,Tran, T.K.,Jeon, J.K.,Park, J.K.,Kim, D.J. Pergamon Press ; Elsevier Science Ltd 2016 Cement and concrete research Vol.79 No.-
The fracture energy of ultra-high-performance fiber-reinforced concrete (UHPFRC) at high strain rates (5-92s<SUP>-1</SUP>) was investigated, and specimens with 1-1.5% fibers exhibited very high fracture energy (28-71kJ/m<SUP>2</SUP>). Evaluation of the rate effects on the UHPFRC fracture resistance, including fracture strength (f<SUB>t</SUB>), specific work-of-fracture (W<SUB>S</SUB>), and softening fracture energy (W<SUB>F</SUB>), indicated that f<SUB>t</SUB> and W<SUB>S</SUB> were highly sensitive to strain rate, whereas W<SUB>F</SUB> was not. The effects of fiber type, volume content, specimen shape and fiber blending on the fracture resistance at high and static strain rates differed significantly: 1) smooth fibers exhibited higher f<SUB>t</SUB> and W<SUB>S</SUB> at high rates than twisted fibers; 2) higher fiber volume content did not clearly generate higher W<SUB>S</SUB> and W<SUB>F</SUB> at high rates; 3) notched specimens generally exhibited higher fracture resistance than un-notched samples at both static and high rates; and 4) UHPFRC blending two fibers produced higher W<SUB>S</SUB> and W<SUB>F</SUB> than UHPFRC with mono fiber at high rates.
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