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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>
Kang, S.W.,Doan, H.T.T.,Noh, J.H.,Choe, S.E.,Yoo, M.S.,Kim, Y.H.,Reddy, K.E.,Nguyen, T.T.D.,Van Quyen, D.,Nguyen, L.T.K.,Kweon, C.H.,Jung, S.C. Elsevier 2013 Parasitology international Vol.62 No.6
Toxoplasma gondii and Trichinella spiralis are important zoonotic pathogens with worldwide distributions. In Korea, several outbreaks of human toxoplasmosis and trichinellosis due to the consumption of infected wild animals have been reported. The purpose of this study was to determine the seroprevalence of T. gondii and T. spiralis infections in wild boars killed in Korea from December 2009 to October 2011. A total of 521 wild boars hunted in eight provinces were examined for antibodies to T. gondii and T. spiralis by using commercial ELISA kits. Overall, 25.1% of serum samples from individual boars were seropositive for T. gondii and 1.7% were seropositive for T. spiralis. Seropositive for T. gondii was found in the boars in all the eight provinces investigated and for T. spiralis in four provinces. This is the first report on the seroprevalence of T. gondii and T. spiralis infections in wild boars in Korea. The consumption of undercooked wild boar meat may expose humans to a high risk of infection.
Tran Dang Thanh,Phan, T. L.,Pham Thi Thanh,Nguyen Hai Yen,Nguyen Huy Dan,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.4
<P>This paper presents the magnetocaloric effect and critical behavior of alloy ingot and ribbon samples of Ni<SUB>50</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> doped with 8% Ag, which were prepared by an arc-melting and rapidly quenched melt-spinning methods, respectively. Experimental results reveal that a partial replacement of Ag for Ni leads to stamping out the antiferromagnetic martensitic phase. This means that there is only the austenitic phase with a ferromagnetic-paramagnetic (FM-PM) phase-transition temperature of T<SUB>C</SUB> ≈ 295 K. Detailed studies and analyses around the phase transition region prove both samples undergoing a second-order magnetic phase transition. Basing on magnetic field dependences of magnetization, we have determined the magnetic-entropy change (ΔS<SUB>m</SUB>) of the samples. Under a field change of 10 kOe, the maximum magnetic-entropy change (|ΔS<SUB>max</SUB>|) reaches values 0.54 and 0.69 J · kg<SUP>-1</SUP> · K<SUP>-1</SUP> for the alloy ingot and ribbon, respectively. Using Landau's phase-transition theory, and careful analyses of the magnetic data around the FM-PM transition region, we have determined the critical parameters (T<SUB>C</SUB>, β, γ, and δ) in the low field range (below 10 kOe) with T<SUB>C</SUB> = 294.8 K, β = 0.469 ± 0.011, γ = 1.149 ± 0.060, and δ = 3.4 ± 0.1 for the alloy ingot, and with T<SUB>C</SUB> = 294.4 K, β = 0.449 ± 0.005, γ = 1.319 ± 0.040, and δ = 3.9 ± 0.1 for the alloy ribbon. One can see that β values fall in between those expected for the 3-D Heisenberg model (β = 0.365) and mean-field theory (β = 0.5). This indicates a coexistence of short-range and long-range FM interactions in both the samples. The nature of changes in value related to the critical parameters and maximum ΔS<SUB>m</SUB> is thoroughly discussed by means of structural analyses.</P>
Tran Dang Thanh,Phan, T. L.,Nguyen Van Chien,Do Hung Manh,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.4
<P>In this paper, we present a detailed study of the magnetocaloric effect and critical properties around the ferromagnetic-paramagnetic (FM-PM) phase transition of La<SUB>0.7</SUB>Ca<SUB>0.3-x</SUB>Sr<SUB>x</SUB>MnO<SUB>3</SUB> nanoparticles with x = 0.10, 0.11, and 0.12. The samples were synthesized by a combination of reactive milling and thermal processing. The average crystallite size of nanoparticles estimated from the linewidth of X-ray diffraction peaks by using the Williamson-Hall method is about 50 nm. Under a magnetic field change of 10 kOe, the maximum magnetic entropy change (|ΔS<SUB>max</SUB>|) reaches values of 1.47, 1.42, and 1.38 J·kg<SUP>-1</SUP>·K<SUP>-1</SUP> for x = 0.10, 0.11, and 0.12, respectively, at around 300 K. The refrigerant capacity is thus in between 44 and 54 J·kg<SUP>-1</SUP>. Particularly, the M<SUP>2</SUP> versus H/M curves prove that all the samples exhibit a second-order magnetic phase transition. Based on Landau's phase-transition theory and careful analyses of the magnetic data around the FM-PM transition region, we have determined the critical exponents β, y, δ, and T<SUB>C</SUB>. Here, the β values obtained are 0.397, 0.453, and 0.456 for x = 0.10, 0.11, and 0.12, respectively, which are in between those expected on the basis of the mean-field theory (β = 0.5) and value of the 3-D Heisenberg model (β = 0.365). The result proves the coexistence of shortand long-range FM interactions in La<SUB>0.7</SUB>Ca<SUB>0.3-x</SUB>Sr<SUB>x</SUB>MnO<SUB>3</SUB> nanoparticles. The nature of this phenomenon is discussed thoroughly.</P>
Sorting CD4+ T Cells in Blood by Using Magnetic Nanoparticles Coated with Anti-CD4 Antibody
N. T. Khuat,V. T. A. Nguyen,T. N. Phan,L. H. Hoang,C. V. Thach,N. H. Hai,N. Chau 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
We used Fe3O4 magnetic nanoparticles (MNPs) which are coated with antiCD4 monoclonal antibody to bind selectively onto membranes of CD4+ T cells (hereafter antiCD4-MNPs). The antiCD4-MNPs were prepared through direct covalent interaction between the carboxyl group of the antiCD4 antibody and the amino group of amino-modified MNPs. The antiCD4-MNPs were mixed with human blood cells, followed by bursting the red blood cells with hypotonic buffer; then, the antiCD4-MNPs coated cells were separated by using a magnet. We observed the number of cells bound with magnetite clusters and particles. When fluorescence isothiocyanate labeled antiCD4- MNPs was used to observe the CD4+ T cells, the fluorescent intensity was improved by about two times compared to that when cells were labeled with the antiCD4 antibody only. This is a potential method to sort helper CD4+ T cells for observation under conventional microscopes. We used Fe3O4 magnetic nanoparticles (MNPs) which are coated with antiCD4 monoclonal antibody to bind selectively onto membranes of CD4+ T cells (hereafter antiCD4-MNPs). The antiCD4-MNPs were prepared through direct covalent interaction between the carboxyl group of the antiCD4 antibody and the amino group of amino-modified MNPs. The antiCD4-MNPs were mixed with human blood cells, followed by bursting the red blood cells with hypotonic buffer; then, the antiCD4-MNPs coated cells were separated by using a magnet. We observed the number of cells bound with magnetite clusters and particles. When fluorescence isothiocyanate labeled antiCD4- MNPs was used to observe the CD4+ T cells, the fluorescent intensity was improved by about two times compared to that when cells were labeled with the antiCD4 antibody only. This is a potential method to sort helper CD4+ T cells for observation under conventional microscopes.