Numerical simulation and analytical assessment of STCC columns filled with UHPC and UHPFRC

Chau V. Nguyen,An H. Le,Duc-Kien Thai 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.1

A nonlinear finite element model (FEM) using ATENA-3D software to simulate the axially compressive behavior of circular steel tube confined concrete (CSTCC) columns infilled with ultra high performance concrete (UHPC) was presented in this paper. Some modifications to the material type “CC3DNonlinCementitious2User” of UHPC without and with the incorporation of steel fibers (UHPFRC) in compression and tension were adopted in FEM. The predictions of utimate strength and axial load versus axial strain curves obtained from FEM were in a good agreement with the test results of eighteen tested columns. Based on the results of FEM, the load distribution on the steel tube and the concrete core was derived for each modeled column. Furthermore, the effect of bonding between the steel tube and the concrete core was clarified by the change of friction coefficient in the material type “CC3DInterface” in FEM. The numerical results revealed that the increase in the friction coefficient leads to a greater contribution from the steel tube, a decrease in the ultimate load and an increase in the magnitude of the loss of load capacity. By comparing the results of FEM with experimental results, the appropriate friction coefficient between the steel tube and the concrete core was defined as 0.3 to 0.6. In addition to the numerical evaluation, eighteen analytical models for confined concrete in the literature were used to predict the peak confined strength to assess their suitability. To cope with CSTCC stub and intermediate columns, the equations for estimating the lateral confining stress and the equations for considering the slenderness in the selected models were proposed. It was found that all selected models except for EC2 (2004) gave a very good prediction. Among them, the model of Bing et al. (2001) was the best predictor.

Diarylheptanoids and Flavonoids from <i>Viscum album</i> Inhibit LPS-Stimulated Production of Pro-inflammatory Cytokines in Bone Marrow-Derived Dendritic Cells

Nhiem, Nguyen X.,Kiem, Phan V.,Minh, Chau V.,Kim, Nanyoung,Park, SeonJu,Lee, Hwa Young,Kim, Eun Sil,Kim, Young Ho,Kim, Sohyun,Koh, Young-Sang,Kim, Seung Hyun American Chemical Society and American Society of 2013 Journal of natural products Vol.76 No.4

<P>Three new diarylheptanoids, (3<I>S</I>,5<I>R</I>)-3-hydroxy-5-methoxy-1,7-bis(4-hydroxyphenyl)-6<I>E</I>-heptene (<B>1</B>), (3<I>S</I>,5<I>S</I>)-3-hydroxy-5-methoxy-1,7-bis(4-hydroxyphenyl)-6<I>E</I>-heptene (<B>2</B>), and (3<I>S</I>)-3-hydroxy-1,7-bis(4-hydroxyphenyl)-6<I>E</I>-hepten-5-one (<B>3</B>), four new flavonoid glycosides, 3,7,3′-tri-<I>O</I>-methylquercetin-4′-<I>O</I>-β-<SMALL>d</SMALL>-apiofuranosyl-(1→2)-<I>O</I>-β-<SMALL>d</SMALL>-glucopyranoside (<B>4</B>), 7,3′-di-<I>O</I>-methylquercetin-4′-<I>O</I>-β-<SMALL>d</SMALL>-glucopyranosyl-3-<I>O</I>-[6‴-(3-hydroxy-3-methylglutaroyl)]-α-<SMALL>d</SMALL>-glucopyranoside (<B>5</B>), 7,3′-di-<I>O</I>-methylquercetin-4′-<I>O</I>-β-<SMALL>d</SMALL>-glucopyranosyl-3-<I>O</I>-[(6′′′′′→5′′′′)-<I>O-</I>1′′′′′-(sinap-4-yl)-β-<SMALL>d</SMALL>-glucopyranosyl-6‴-(3-hydroxy-3-methylglutaroyl)]-α-<SMALL>d</SMALL>-glucopyranoside (<B>6</B>), and (2<I>S</I>)-5-hydroxy-7,3′-dimethoxyflavanone-4′-<I>O</I>-β-<SMALL>d</SMALL>-apiofuranosyl-(1→5)-<I>O</I>-β-<SMALL>d</SMALL>-apiofuranosyl-(1→2)-<I>O</I>-β-<SMALL>d</SMALL>-glucopyranoside (<B>9</B>), and 17 known compounds were isolated from the leaves and twigs of <I>Viscum album</I>. Compounds <B>1</B>, <B>4</B>, and <B>19</B> significantly inhibited LPS-stimulated production of TNF-α, IL-6, and IL-12p40 with IC<SUB>50</SUB> values ranging from 0.09 ± 0.01 to 8.96 ± 0.45 μM. (+)-Medioresinol (<B>13</B>) showed inhibitory effects on LPS-stimulated production of IL-12p40 with an IC<SUB>50</SUB> value of 2.00 ± 0.15 μM.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jnprdf/2013/jnprdf.2013.76.issue-4/np300490v/production/images/medium/np-2012-00490v_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/np300490v'>ACS Electronic Supporting Info</A></P>

Current-driven channel switching and colossal positive magnetoresistance in the manganite-based structure

Volkov, N V,Eremin, E V,Tsikalov, V S,Patrin, G S,Kim, P D,Seong-Cho, Yu,Kim, Dong-Hyun,Chau, Nguyen Institute of Physics [etc.] 2009 Journal of Physics. D, Applied Physics Vol.42 No.6

<P>The transport and magnetotransport properties of a newly fabricated tunnel structure <I>manganite/depletion layer/manganese silicide</I> have been studied in the current-in-plane (CIP) geometry. A manganite depletion layer in the structure forms a potential barrier sandwiched between two conducting layers, one of manganite and the other of manganese silicide. The voltage–current characteristics of the structure are nonlinear due to switching conducting channels from an upper manganite film to a bottom, more conductive MnSi layer with an increase in the current applied to the structure. Bias current assists tunnelling of a carrier across the depletion layer; thus, a low-resistance contact between the current-carrying electrodes and the bottom layer is established. Below 30 K, both conducting layers are in the ferromagnetic state (magnetic tunnel junction), which allows control of the resistance of the tunnel junction and, consequently, switching of the conducting channels by the magnetic field. This provides a fundamentally new mechanism of magnetoresistance (MR) implementation in the magnetic layered structure with CIP geometry. MR of the structure under study depends on the bias current and can reach values greater than 400% in a magnetic field lower than 1 kOe. A positive MR value is related to peculiarities of the spin-polarized electronic structures of manganites and manganese silicides.</P>

Anti-inflammatory Triterpenoid Saponins from the Stem Bark of <i>Kalopanax pictus</i>

Quang, Tran H.,Ngan, Nguyen T. T.,Minh, Chau V.,Kiem, Phan V.,Nhiem, Nguyen X.,Tai, Bui H.,Thao, Nguyen P.,Tung, Nguyen H.,Song, Seok B.,Kim, Young H. American Chemical Society and American Society of 2011 Journal of natural products Vol.74 No.9

<P>Five new compounds, 16,23,29-trihydroxy-3-oxo-olean-12-en-28-oic acid (<B>1</B>), 4,23,29-trihydroxy-3,4-<I>seco</I>-olean-12-en-3-oate-28-oic acid (<B>2</B>), 3β,6β,23-trihydroxyolean-12-en-28-oic acid 28-<I>O</I>-β-<SMALL>d</SMALL>-glucopyranoside (<B>3</B>), 3-<I>O</I>-[2,3-di<I>-O</I>-acetyl-α-<SMALL>l</SMALL>-arabinopyranosyl]hederagenin 28-<I>O</I>-α-<SMALL>l</SMALL>-rhamnopyranosyl-(1→4)-β-<SMALL>d</SMALL>-glucopyranosyl-(1→6)-β-<SMALL>d</SMALL>-glucopyranoside (<B>4</B>), and 3-<I>O</I>-[3,4-di-<I>O</I>-acetyl-α-<SMALL>l</SMALL>-arabinopyranosyl]hederagenin 28-<I>O</I>-α-<SMALL>l</SMALL>-rhamnopyranosyl-(1→4)-β-<SMALL>d</SMALL>-glucopyranosyl-(1→6)-β-<SMALL>d</SMALL>-glucopyranoside (<B>5</B>), as well as 10 known compounds (<B>6</B>–<B>15</B>), were isolated from the stem bark of <I>Kalopanax pictus</I>. Compounds <B>1</B>–<B>5</B> and <B>7</B>–<B>14</B> inhibited TNFα-induced NF-κB transcriptional activity in HepG2 cells in a dose-dependent manner, with IC<SUB>50</SUB> values ranging from 0.6<B></B>to 16.4 μM. Furthermore, the transcriptional inhibitory function of these compounds was confirmed on the basis of decreases in COX-2 and iNOS gene expression in HepG2 cells. The structure–activity relationship of the compounds with respect to anti-inflammatory activity is also discussed.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jnprdf/2011/jnprdf.2011.74.issue-9/np200382s/production/images/medium/np-2011-00382s_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/np200382s'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/np200382s'>ACS Electronic Supporting Info</A></P>

Sorting CD4⁺ T Cells in Blood by Magnetic Nanoparticles Coated with Anti-CD4 Antibody

N.T. Khuat,V.A.T. Nguyen,T.N. Phan,C.V. Thach,N.H. Hai,N.H. Luong,N. Chau 한국자기학회 2007 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

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.

Extension of the Inhibitory Effect of Chloramphenicol on Bacteria by Incorporating It into Fe3O4 Magnetic Nanoparticles

H. T. Khuat,N. H. Hai,C. V. Thach,N. Chau,T. N. Phan,V. T. Nguyen 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

Magnetite Fe$_3$O$_4$ nanoparticles were prepared by using a co-precipitation method, then functionalized by double layers of surfactants (core/oleic acid (OA)/sodium dodecyl sulfate (SDS)). For application as a drug carrier, the double-layer-coated magnetic nanoparticles were fully loaded with the antibiotic chloramphenicol (Cm) to investigate the effect of the drug release process on the bacteria {\it Escherichia coli} (E. coli). The water-soluble Cm and Cm-coated magnetic nanoparticles (Cm-NPs) (equivalent to 50 $\mu$l of 5 -- 200 $\mu$g/ml Cm) were poured into small holes on agar plates spread with E. coli, after which the plates were incubated overnight. The diameters of the non-bacteria circles were shown to gain their maximal values after 14 h, then to gradually decrease in almost all samples. Nevertheless, the circles created by Cm-NPs were about 1.5 times larger than those for the control Cm. The speed of bacterial lawn re-grown in the case of the Cm-NPs was obviously slower than that of the controlled Cm. We conclude that the magnetic nanoparticles gradually release the antibiotic, thereby maintaining the stability and the effect of the antibiotic longer than that of the conventional water-soluble antibiotic.

Simplified stress-strain model for circular steel tube confined UHPC and UHPFRC columns

An H. Le,Fehling Ekkehard,Duc-Kien Thai,Chau V. Nguyen 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.1

The research on the confinement behavior of ultra high performance concrete without and with the use of steel fibers (UHPC and UHPFRC) has been extremely limited. In previous studies, authors experimentally investigated the axially compressive behavior of circular steel tube confined concrete (STCC) short and intermediate columns with the employment of UHPC and UHPFRC. Under loading on only the concrete core, the confinement effect induced by the steel tube was shown to significantly enhance the utimate stress and its corresponding strain of the concrete core. Therefore, this paper develops a simplified stress – strain model for circular STCC columns using UHPC and UHPFRC with compressive strength ranging between 150 MPa and 200 MPa. Based on the regression analysis of previous test results, formulae for predicting peak confined stress and its corresponding strain are proposed. These proposed formulae are subsequently compared against some previous empirical formulae available in the literature to assess their accuracy. Finally, the simplified stress . strain model is verified by comparison with the test results.