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M. I. Pech-Canul,M. Rodríguez-Reyes3,M. A. Pech-Canul,J. C. Rendón-Angeles 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.6
In this work, SiC_P and SiC_P/SiO_2 porous preforms were infiltrated without assistance in Ar→N_2 atmosphere with the alloy Al-10.3 Mg-12.04 Si (wt.%) at 1050 and 1100 °C, for 20, 40 and 60 min. It was found that a decrease in residual porosity and an increase in elastic modulus by about 22 % with respect to composites produced without SiO_2 additions to the preforms are associated with the formation of magnesium aluminate spinel (MgAl_2O_4). A concurrent increase of the matrix hardness is ascribed to a strengthening mechanism by MgAl_2O_4 formation, similar to the strengthening observed with Mg_2Si in aluminum alloys. Therefore, the spinel can be considered as a co-reinforcement of SiC_p in the aluminum matrix composites. Reactions for spinel formation and possible mechanisms for hardness enhancement are outlined.
Reyes, Alisha Wehdnesday Bernardo,Arayan, Lauren Togonon,Hop, Huynh Tan,Ngoc Huy, Tran Xuan,Vu, Son Hai,Min, WonGi,Lee, Hu Jang,Kim, Suk Elsevier 2018 Microbial pathogenesis Vol.119 No.-
<P><B>Abstract</B></P> <P>In this study, we investigated the effects of gallic acid (GA) in intracellular signaling within murine macrophages and its contribution to host immunity during <I>Brucella</I> infection<I>. In vitro</I> analysis revealed that GA treatment decreased F-actin content and suppressed p38α phosphorylation level. <I>In vivo</I> analysis showed that GA treatment reduced inflammation and proliferation of <I>Brucella</I> in spleens of mice in comparison to PBS treatment yielding a significant protection unit. For the analysis of immune response, the uninfected GA-treated mice showed increased production of IFN-γ and MCP-1, and the <I>Brucella-</I>infected GA-treated mice showed elevated levels of IL-12p70, TNF, IFN-γ, MCP-1, IL-10 and IL-6 in comparison to negative and positive control groups, respectively. These findings demonstrate the therapeutic effects of GA against <I>Brucella</I> infection through interference on intracellular signaling pathway, induction of cytokine production and protection from bacterial proliferation in spleens of mice.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Gallic acid (GA) decreased F-actin content and p38α phosphorylation level in RAW 264.7 cells. </LI> <LI> GA reduced inflammation and proliferation of <I>Brucella</I> in the spleens of mice. </LI> <LI> GA-treated mice showed increased production of IFN-γ and MCP-1. </LI> <LI> <I>Brucella</I>-infected GA-treated mice showed elevated levels of IL-12p70, TNF, IFN-γ, MCP-1, IL-10 and IL-6. </LI> <LI> GA treatment revealed potential therapeutic effects against <I>Brucella</I> infection in animals. </LI> </UL> </P>
Reyes, Alisha Wehdnesday Bernardo,Hong, Tae Gyu,Hop, Huynh Tan,Arayan, Lauren Togonon,Huy, Tran Xuan Ngoc,Min, Wongi,Lee, Hu Jang,Lee, Kang Seok,Kim, Suk Elsevier 2017 Microbial pathogenesis Vol.109 No.-
<P><B>Abstract</B></P> <P>In this study, we investigated the protective effects of tannin-derived components, gallic acid (GA) and tannic acid (TA), <I>in vitro</I> and <I>in vivo</I> against <I>Salmonella</I> infection in mice. Both GA and TA showed antibacterial effects against <I>Salmonella</I> (<I>S.</I>) Typhimurium as well as inhibitory effects on the adherence, invasion, and intracellular growth of the pathogens in macrophages. Following a lethal dose of <I>Salmonella</I> infection in mice, reduced virulence in both GA- and TA-treated groups was observed based on reduced mortality rates. In the non-infected groups, the average weights of the spleens and livers of GA- or TA-treated mice were not significantly different with the control group. In addition, the average weights of these organs in all of the <I>Salmonella</I>-infected groups were not significantly different but the numbers of bacteria in the spleens and livers in both GA- and TA-treated mice were significantly reduced. The levels of cytokine production in non-infected mice revealed that GA-treated and TA-treated mice elicited an increased level of IFN-γ, and both IFN-γ and MCP-1, respectively, as compared with the PBS-treated group. These findings highlight the potential of GA and TA as alternatives for the treatment of salmonellosis and as supplements to conventional antimicrobial food additives.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Gallic acid (GA) and tannic acid (TA) showed antibacterial effects against <I>S.</I> Typhimurium. </LI> <LI> GA and TA showed a treatment effect against <I>S.</I> Typhimurium infection in a mouse model. </LI> <LI> GA-treated and TA-treated mice elicited an increased level of IFN-γ, and both IFN-γ and MCP-1, respectively. </LI> <LI> GA and TA could be used as potential alternatives for the treatment of salmonellosis. </LI> </UL> </P>
Reyes Alisha Wehdnesday Bernardo,Kim Heejin,Huy Tran Xuan Ngoc,Nguyen Trang Thi,Min Wongi,Lee Dongho,Hur Jin,Lee John Hwa,김석 한국미생물·생명공학회 2022 Journal of microbiology and biotechnology Vol.32 No.9
This study investigated the contribution of lipoxygenase (LOX) inhibitors, nordihydroguaiaretic acid (NDGA), tetra-O-methyl nordihydroguaiaretic acid (M4N) and zileuton (ZIL), and thromboxane A2 (TXA2) inhibitor 4,5-diphenylimidazole (DPI) in the proliferation of Brucella abortus infection. None of the compounds affected the uptake of Brucella into the macrophages. We determined the effect of neutralizing leukotriene B4 (LTB4) receptor and showed that the uptake of the bacteria was inhibited at 30 min post-infection. M4N treatment attenuated intracellular survival of Brucella at 2 h post-incubation but it was not observed in the succeeding time points. DPI treatment showed reduced survival of Brucella at 24 h post-incubation while blocking LTB4 receptor was observed to have a lower intracellular growth at 48 h post-incubation suggesting different action of the inhibitors in the course of the survival of Brucella within the cells. Reduced proliferation of the bacteria in the spleens of mice was observed in animals treated with ZIL or DPI. Increased serum cytokine level of TNF-α and MCP-1 was observed in mice treated with M4N or ZIL while a lower IFN-γ level in ZIL-treated mice and a higher IL-12 serum level in DPI-treated mice were observed at 7 d postinfection. At 14 d post-infection, ZIL-treated mice displayed reduced serum level of IL-12 and IL-10. Overall, inhibition of 5-LOX or TXA2 or a combination therapy promises a potential alternative therapy against B. abortus infection. Furthermore, strong ligands for LTB4 receptor could also be a good candidate for the control of Brucella infection.
Reyes-Salazar, Alfredo,Soto-Lopez, Manuel Ernesto,Bojorquez-Mora, Eden,Lopez-Barraza, Arturo Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.2
Several issues regarding the structural idealization of steel buildings with perimeter moment resisting steel frames (MRSFs) and interior gravity frames (GFs) are studied. Results indicate that the contribution of GFs to the lateral structural resistance may be significant. The contribution increases when the stiffness of the connection of the GFs is considered and is larger for inelastic than for elastic behavior. The interstory shears generally increase when the connections stiffness is taken into account. Resultant stresses at some base columns of MRSFs also increase in some cases but to a lesser degree. For columns of the GFs, however, the increment is significant. Results also indicate that modeling the building as planes frames may result in larger interstory shears and displacements and resultant stresses than those obtained from the more realistic 3-D formulation. These differences may be much larger when semi-rigid (SR) connections are considered. The conservativism is more for resultant stresses. The differences observed in the behaviour of each structural representation are mainly due to a) the elements that contribute to strength and stiffness and b) the dynamics characteristics of each structural representation. It is concluded that, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis, the GFs should be considered as part of the lateral resistance system, and the stiffness of the connections should be included in the design of the GFs. Otherwise, the capacity of gravity frames may be overestimated while that of MRSFs may be underestimated.
Ductility and ductility reduction factor for MDOF systems
Reyes-Salazar, Alfredo Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.13 No.4
Ductility capacity is comprehensively studied for steel moment-resisting frames. Local, story and global ductility are being considered. An appropriate measure of global ductility is suggested. A time domain nonlinear seismic response algorithm is used to evaluate several definitions of ductility. It is observed that for one-story structures, resembling a single degree of freedom (SDOF) system, all definitions of global ductility seem to give reasonable values. However, for complex structures it may give unreasonable values. It indicates that using SDOF systems to estimate the ductility capacity may be a very crude approximation. For multi degree of freedom (MDOF) systems some definitions may not be appropriate, even though they are used in the profession. Results also indicate that the structural global ductility of 4, commonly used for moment-resisting steel frames, cannot be justified based on this study. The ductility of MDOF structural systems and the corresponding equivalent SDOF systems is studied. The global ductility values are very different for the two representations. The ductility reduction factor $F_{\mu}$ is also estimated. For a given frame, the values of the $F_{\mu}$ parameter significantly vary from one earthquake to another, even though the maximum deformation in terms of the interstory displacement is roughly the same for all earthquakes. This is because the $F_{\mu}$ values depend on the amount of dissipated energy, which in turn depends on the plastic mechanism, formed in the frames as well as on the loading, unloading and reloading process at plastic hinges. Based on the results of this study, the Newmark and Hall procedure to relate the ductility reduction factor and the ductility parameter cannot be justified. The reason for this is that SDOF systems were used to model real frames in these studies. Higher mode effects were neglected and energy dissipation was not explicitly considered. In addition, it is not possible to observe the formation of a collapse mechanism in the equivalent SDOF systems. Therefore, the ductility parameter and the force reduction factor should be estimated by using the MDOF representation.