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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.
Evolution pathway of CZTSe nanoparticles synthesized by microwave-assisted chemical synthesis
Reyes, Odin,Sanchez, Monica F.,Pal, Mou,Llorca, Jordi,Sebastian, P.J. Techno-Press 2017 Advances in nano research Vol.5 No.3
In this study we present the reaction mechanism of $Cu_2ZnSnSe_4$ (CZTSe) nanoparticles synthesized by microwave-assisted chemical synthesis. We performed reactions every 10 minutes in order to identify different phases during quaternary CZTSe formation. The powder samples were analyzed by x-ray diffraction (XRD), Raman spectroscopy, energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results showed that in the first minutes copper phases are predominant, then copper and tin secondary phases react to form ternary phase. The quaternary phase is formed at 50 minutes while ternary and secondary phases are consumed. At 60 minutes pure quaternary CZTSe phase is present. After 60 minutes the quaternary phase decomposes in the previous ternary and secondary phases, which indicates that 60 minutes is ideal reaction time. The EDS analysis of pure quaternary nanocrystals (CZTSe) showed stoichiometric relations similar to the reported research in the literature, which falls in the range of Cu/(Zn+Sn): 0.8-1.0, Zn/Sn: 1.0-1.20. In conclusion, the evolution pathway of CZTSe synthesized by this novel method is similar to other synthesis methods reported before. Nanoparticles synthesized in this study present desirable properties in order to use them in solar cell and photoelectrochemical cell applications.
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,Arayan, Lauren Togonon,Huy, Tran Xuan Ngoc,Vu, Son Hai,Kang, Chang Keun,Min, Wongi,Lee, Hu Jang,Lee, John Hwa,Kim, Suk Elsevier 2019 Veterinary microbiology Vol.237 No.-
<P><B>Abstract</B></P> <P>We investigated the involvement of chemokine receptor type 4 (CXCR4) signaling on the outcome of <I>Brucella</I> (<I>B.</I>) <I>abortus</I> 544 infection in murine macrophages and in a mouse model. CXCR4 manipulation were first evaluated for <I>Brucella</I> invasion and intracellular survival efficiency, mitogen-activated protein kinases (ERK1/2, JNK, p38α) activation and generation of nitric oxide (NO), and then in the splenic bacterial proliferation and cytokine production in BALB/c mice. CXCR4 blockade is involved in the successful control of <I>Brucella</I> invasion, reduction of ERK1/2 phosphorylation and inhibition of nitric oxide release from macrophages. Furthermore, using a reported CXCR4-specific antagonist AMD3100 resulted in splenomegaly but attenuated <I>Brucella</I> proliferation in these organs with elevated serum levels of MCP-1, TNF and IL-12. These findings provide insights on the contribution of CXCR4 signaling in the phagocytic pathway and immune modulation during <I>B. abortus</I> infection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CXCR4 blockade attenuated <I>B. abortus</I> invasion into RAW264.7 cells possibly via ERK pathway. </LI> <LI> CXCR4 blockade inhibited generation of NO in RAW264.7 cells during <I>B. abortus</I> infection. </LI> <LI> AMD3100 treatment in mice did not negatively affect body weight, serum ALT concentration or weight of spleens. </LI> <LI> AMD3100 treatment in mice displayed splenomegaly but reduced <I>B. abortus</I> proliferation with elevated serum levels of MCP-1, TNF and IL-12. </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 Alisha Wehdnesday Bernardo,Kim Heejin,Huy Tran Xuan Ngoc,Nguyen Trang Thi,Min Wongi,Lee Hu Jang,Hur Jin,Lee John Hwa,Kim Suk 한국미생물·생명공학회 2023 Journal of microbiology and biotechnology Vol.33 No.4
Brucellosis is a contagious zoonotic disease that infects millions of people annually with hundreds of millions more being exposed. It is caused by Brucella, a highly infectious bacterial species capable of infecting humans with an estimated dose of 10-100 organisms. Sirtuin 1 (SIRT1) has been reported to contribute to prevention of viral diseases as well as a chronic infection caused by Mycobacterium bovis. Here, we investigated the role of SIRT1 in the establishment of Brucella abortus infection in both in vitro and in vivo systems using the reported SIRT1 activators resveratrol (RES), piceatannol (PIC), and ginsenoside Rg3 (Rg3). In RAW264.7 cells, SIRT1 activators did not alter the adherence of Brucella or Salmonella Typhimurium. However, reduced uptake of Brucella was observed in cells treated with PIC and Rg3, and survival of Brucella within the cells was only observed to decrease in cells that were treated with Rg3, while PIC treatment reduced the intracellular survival of Salmonella. SIRT1 treatment in mice via oral route resulted in augmented Brucella resistance for PIC and Rg3, but not RES. PIC treatment favors Th2 immune response despite reduced serum proinflammatory cytokine production, while Rg3-treated mice displayed high IL-12 and IFN-γ serum production. Overall, our findings encourage further investigation into the complete mechanisms of action of the different SIRT1 activators used as well as their potential benefit as an effective alternative approach against intracellular and extracellular pathogens.
Dissipation of energy in steel frames with PR connections
Reyes-Salazar, Alfredo,Haldar, Achintya Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.9 No.3
The major sources of energy dissipation in steel frames with partially restrained (PR) connections are evaluated. Available experimental results are used to verify the mathematical model used in this study. The verified model is then used to quantify the energy dissipation in PR connections due to hysteretic behavior, due to viscous damping and at plastic hinges if they are formed. Observations are made for two load conditions: a sinusoidal load applied at the top of the frame, and a sinusoidal ground acceleration applied at the base of the frame representing a seismic loading condition. This analytical study confirms the general behavior, observed during experimental investigations, that PR connections reduce the overall stiffness of frames, but add a major source of energy dissipation. As the connections become stiffer, the contribution of PR connections in dissipating energy becomes less significant. A connection with a T ratio (representing its stiffness) of at least 0.9 should not be considered as fully restrained as is commonly assumed, since the energy dissipation characteristics are different. The flexibility of PR connections alters the fundamental frequency of the frame. Depending on the situation, it may bring the frame closer to or further from the resonance condition. If the frame approaches the resonance condition, the effect of damping is expected to be very important. However, if the frame moves away from the resonance condition, the energy dissipation at the PR connections is expected to be significant with an increase in the deformation of the frame, particularly for low damping values. For low damping values, the dissipation of energy at plastic hinges is comparable to that due to viscous damping, and increases as the frame approaches failure. For the range of parameters considered in this study, the energy dissipations at the PR connections and at the plastic hinges are of the same order of magnitude. The study quantitatively confirms the general observations made in experimental investigations for steel frames with PR connections; however, proper consideration of the stiffness of PR connections and other dynamic properties is essential in predicting the dynamic behavior.