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Phan, T. L.,Nguyen, V. D.,Ho, T. A.,Khiem, N. V.,Thanh, T. D.,Phuc, N. X.,Thang, P. D.,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.6
<P>The magnetic properties of polycrystalline ceramic samples (Nd1-xYx)(0.7)Sr0.3MnO3 with x = 0.21 - 0.35 were studied by means of dc magnetization and ac susceptibility measurements. Experimental results reveal a strong decrease of the ferromagnetic (FM)-paramagnetic phase-transition temperature (T-C) from 97 to 65 K as increasing x from 0.21 to 0.35, respectively. There is magnetic inhomogeneity associated with short-range FM order. Particularly, the samples undergo a spin-glass (SG) phase transition at the so-called blocking temperature (T-B) below T-C, which shifts toward lower temperatures with increasing the applied field, Hex; T-B -> T-g (the SG phase-transition temperature) as H-ex -> 0. The existence of the SG behavior in these samples was also confirmed by frequency (f) dependences of the ac susceptibility. For the in-phase/real component, chi' (T), it shows a frequency-dependent peak at the SG freezing temperature (T-f); T-f -> T-g as f -> 0. Dynamics of this process were analyzed by means of the slowing down scaling law, tau/tau(0) proportional to (T-f/T-g - 1)(-zv), where tau(0) and zv are the characteristic time and critical exponent, respectively. Fitting the experimental T-f(f) data to the scaling law gave the results of zv = 10.1-12.3 and tau(0) = 10(-21)-10(-15)s. These values are different from those expected for canonical SG systems with zv = 10 and tau(0) = 10(-13)s, revealing the cluster-SG behavior of (Nd1-xYx)(0.7)Sr0.3MnO3 samples. Notably, the increase in Y content leads to the shift of tau(0) and zv values toward those of canonical SG systems, which is ascribed to an expansion of SG clusters.</P>
Phan, T. L.,Thanh, T. D.,Ho, T. A.,Thang, P. D.,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.4
<P>We prepared BaTi<SUB>1-x</SUB>Mn<SUB>x</SUB>O<SUB>3</SUB> samples (x = 0 and 0.05) by standard solid-state reaction at 700°C and 900°C in an Ar ambient to change oxidation number of Mn dopants. The fabricated samples were then studied structural characterization and electronic structures by means of X-ray diffraction and absorption, and Raman scattering and electron-spin-resonance spectrometers. We found oxidation numbers 2+ and 3+ of Mn ions coexisting in BaTi<SUB>1-x</SUB>Mn<SUB>x</SUB>O<SUB>3</SUB> with x = 0.05, where the Mn<SUP>2+</SUP>/Mn<SUP>3+</SUP> ratio is about one for the sample annealed at 700°C. These Mn ions prefer locating at the Ti site in the tetragonal BaTiO<SUB>3</SUB> host lattice. In particular, there is a change in the oxidation number of Mn<SUP>2+</SUP> → Mn<SUP>3+</SUP> when the annealing temperature changes from 700°C to 900°C. Their magnetic properties are accordingly changed. Meanwhile, annealing pure BaTiO<SUB>3</SUB> in an Ar ambient at 700°C and 900°C does not lead to ferromagnetic (FM) order; they are almost diamagnetic. With the obtained results, we believe that FM order in Mn-doped BaTiO<SUB>3</SUB> annealed in an Ar ambient is associated with exchange interactions of Mn<SUP>2+</SUP> ions mediated by oxygen vacancies rather than associated with Mn<SUP>3+</SUP> ions.</P>
Ferromagnetic Order in Rapidly Cooled Nd-Fe-Co-Al Alloy Ribbons
Phan, T. L.,Zhang, Y. D.,Dan, N. H.,Thang, D. D.,Thanh, T. D.,Zhang, P.,Yu, S. C. IEEE 2013 IEEE transactions on magnetics Vol.49 No.7
<P>We have studied the magnetic properties of Nd<SUB>45</SUB>Fe<SUB>30</SUB>Co<SUB>15</SUB>Al<SUB>10</SUB> alloy ribbons with various thicknesses of about 120 (N<SUB>1</SUB>) and 50 μm (N<SUB>2</SUB>) prepared by melt-spinning. Structural analyses based on an X-ray diffractometer and a high-resolution transmission electron microscope revealed an existence of nanocrystals with sizes of 10 ~ 20 nm surrounded by an amorphous host matrix. With decreasing ribbon thickness and nanocrystalline size, magnetic studies upon a vibrating sample magnetometer indicated the decrease of the Curie temperature (T<SUB>C</SUB>), coercive force (H<SUB>c</SUB>), and magnetic entropy change (ΔS<SUB>m</SUB>). In the ferromagnetic region, however, magnetization values determined for N<SUB>2</SUB> are greater than those determined for N<SUB>1</SUB>. These results are related to the differences in the critical exponents of N<SUB>1</SUB> (β=0.418 and γ=1.173), and N<SUB>2</SUB> (β=0.512 and γ=1.077), which are characteristic for the ferromagnetic nature existing in the alloy ribbons with different thicknesses.</P>
Oleanane-type saponins from Glochidion glomerulatum and their cytotoxic activities
Thu, V.K.,Van Thang, N.,Nhiem, N.X.,Tai, B.H.,Nam, N.H.,Kiem, P.V.,Minh, C.V.,Anh, H.L.T.,Kim, N.,Park, S.,Kim, S.H. Pergamon Press 2015 Phytochemistry Vol.116 No.-
Eight oleanane-type saponins, glomerulosides A-H, were isolated from leaves of Glochidion glomerulatum. All isolated compounds were evaluated for cytotoxic activity on four human cancer cell lines, A-549, HT-29, OVCAR, and MCF-7. Glomerulosides C and E, which contain a benzoyloxy group at C-22, showed significant cytotoxic activities against the A-549, HT-29, and OVCAR cancer cell lines with IC<SUB>50</SUB> values ranging from 5.9 to 9.8μM. Glomeruloside A showed cytotoxicity on HT-29 and OVCAR cell lines with IC<SUB>50</SUB> values of 7.3 and 6.6μM, respectively. Moreover, glomeruloside B exhibited significant activity on A-549 and HT-29 cancer cell lines with IC<SUB>50</SUB> values of 9.7 and 7.5μM. In contrast, glomerulosides F-H, lacking a benzoyloxy group, showed only moderate cytotoxic activity.
Ho, T. A.,Phan, T. L.,Thang, P. D.,Yu, S. C. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.5
<P>We used the modified Arrott plot method to analyze the magnetic field dependence of the magnetization, M(H), for a perovskite-type manganite (La0.9Dy0.1)(0.8)Pb0.2MnO3, and determined the critical parameter values T (C) = 248.4 K, beta = 0.484 +/- A 0.002, gamma = 0.961 +/- A 0.012, and delta = 2.90 +/- A 0.01. With these exponent values, the M(H) data around T (C) fall on two universal branches of a scaling function M(H,epsilon) = |epsilon| (beta) f (+/-)(H/|epsilon| (beta + gamma) ), where epsilon = (T - T (C))/T (C) is the reduced temperature, f (+) for T > T (C) and f (-) for T < T (C). Comparing with theoretical models, the exponent values obtained in our work are quite close to those expected from mean-field theory (with beta = 0.5, gamma = 1, and delta = 3). This reveals nearly long-range ferromagnetic order existing in (La0.9Dy0.1)(0.8) Pb0.2MnO3. From the M(H) data, we also found that, around the ferromagnetic-paramagnetic phase-transition temperature (T (C)), the magnetic entropy change reaches a maximum value (|delta S (max)|) of about 1.1 J kg(-1) K-1 for H = 10 kOe, corresponding to relative cooling power (RCP) of 50 J/kg. In addition to the above investigation, the temperature dependence of the magnetization, remanent magnetization (M (r)), and coercivity (H (c)) were recorded to learn about the physical processes taking place in (La0.9Dy0.1)(0.8)Pb0.2MnO3.</P>
Phan, The-Long,Ho, T.A.,Thang, P.D.,Tran, Q.T.,Thanh, T.D.,Phuc, N.X.,Phan, M.H.,Huy, B.T.,Yu, S.C. Elsevier 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.615 No.-
<P><B>Abstract</B></P> <P>We have determined the values of critical exponents of two polycrystalline samples (Nd<SUB>1−</SUB> <I> <SUB>x</SUB> </I>Y<I> <SUB>x</SUB> </I>)<SUB>0.7</SUB>Sr<SUB>0.3</SUB>MnO<SUB>3</SUB> (<I>x </I>=0 and 0.07) from the magnetization data versus temperature and magnetic field, <I>M</I>(<I>H</I>, <I>T</I>), to learn about their magnetic and magnetocaloric (MC) properties. The results reveal the samples exhibiting the crossover of first-order and second-order phase transitions, where the exponent values <I>β </I>=0.271 and <I>γ </I>=0.922 for <I>x </I>=0, and <I>β </I>=0.234–0.236 and <I>γ </I>=1.044–1.063 for <I>x </I>=0.07 determined by using modified Arrott plots and static-scaling hypothesis are close to those expected for the tricritical mean-field theory (<I>β </I>=0.25 and <I>γ </I>=1.0). Particularly, the <I>T</I> <SUB>C</SUB> of <I>x </I>=0 and 0.07 can be any value in the temperature ranges of 240–255K and 170–278K, respectively, depending on the magnitude of applied magnetic field and determination techniques. Around the <I>T</I> <SUB>C</SUB>, studying the MC effect of the samples has revealed a large magnetic-entropy change (Δ<I>S</I> <SUB>m</SUB>) up to ∼8J/kgK for the applied field interval Δ<I>H </I>=50kOe, corresponding to refrigerant capacity values of 200–245J/kg. These phenomena are related to the crossover nature and the persisting of FM/anti-FM interactions even above the <I>T</I> <SUB>C</SUB>, as further confirmed by electron-spin-resonance data, Curie–Weiss law-based analyses, and an exponential parameter characteristic of magnetic order <I>n </I>=dLn|Δ<I>S</I> <SUB>m</SUB>|/dLn<I>H</I>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Tricritical point in Y-doped Nd<SUB>0.7</SUB>Sr<SUB>0.3</SUB>MnO<SUB>3</SUB> manganites. </LI> <LI> A large magnetic-entropy change. </LI> <LI> Magnetic inhomogeneity and phase separation. </LI> </UL> </P>
Adaptive streaming of audiovisual content using MPEG DASH
Thang, T. C.,Quang-Dung Ho,Jung Won Kang,Pham, A. T. IEEE 2012 IEEE transactions on consumer electronics Vol.58 No.1
<P>HTTP streaming has become a cost effective means for multimedia delivery nowadays. In this paper, we study the use of MPEG DASH standard to stream audiovisual content. We first describe a novel estimation method for connection throughput. Then, employing the extensibility feature of DASH syntax, we present a systematic method for selecting the best audio and video alternatives given the estimated throughput. The experiments show that our solution is stable to short-term fluctuations while responding quickly to large fluctuations.</P>