1,453 research outputs found
Inhibitory Mechanisms of Yc-1 and Pmc in the Induction of Inos Expression by Lipoteichoic Acid in Raw 264.7 Macrophages
No full textIn the present study, the signal pathways involved in NO formation and iNOS expression in RAW 264.7 macrophages stimulated by LTA were investigated. We also compared the relative inhibitory activities and mechanisms of PMC, a novel potent antioxidant of alpha-tocopherol derivatives, with those of YC-1, an sGC activator, on the induction of iNOS expression by LTA in cultured macrophages ill vitro and LTA-induced hypotension ill vivo. LTA induced concentration (0.1-50 mug/mL)- and time (4-24 hr)-dependent increases in nitrite (an indicator of NO biosynthesis) in macrophages. Both PMC (50 muM) and YC-1 (10 muM) inhibited NO production, iNOS protein, mRNA expression, and IkappaBalpha degradation upon stimulation by LTA (20 mug/mL) in macrophages. On the other hand, PMC (50 muM) almost completely suppressed JNK/ SAPK activation, whereas YC-1 (10 muM) only partially inhibited its activation in LTA-stimulated macrophages. Moreover, PMC (10 mg/kg, i.v.) and YC-1 (5 mg/kg, i.v.) significantly inhibited the fall in MA-P stimulated by LTA ( 10 mg/kg, i.v .) in rats. In conclusion, we demonstrate that YC-1 shows more-potent activity than PMC at abrogating the expression of iNOS in macrophages in vitro and reversing delayed hypotension in rats with endotoxic shock stimulated by LTA. The inhibitory mechanisms of PMC may be due to its antioxidative properties, with a resulting influence on JNK/ SAPK and NF- kappaB activations. YC-1 may be mediated by increasing cyclic GMP, followed by, at least partly, inhibition of JNK/SAPK and NF-kappaB activations, thereby leading to inhibition of iNOS expression. (C) 2004 Elsevier Inc. All rights reserved
Nonlinear plane-wave expansion method for analyzing dispersion properties of piezoelectric metamaterial lattices with encapsulated resonators
Full text linksquare lattices encapsulating identical nonlinear resonators in each cell are investigated through an asymptotic treatment of the wave propagation equations. The nonlinear effects of the resonators, composed of suspended piezoelectric membranes with a central mass, are investigated through the introduction of a generalized nonlinear version derived from the plane-wave expansion (PWE) method. This method leads to nonlinear wave propagation equations and the analytical derivation of nonlinear dispersion functions using the method of multiple scales. Numerical simulations verify the validity of the analytical solutions. The proposed nonlinear PWE method is shown to overcomes the limitations of the popular approach based on the enforcement of the Floquet-Bloch theorem in the context of the cell projection method. While the latter provides the dispersion curves of the fundamental propagation mode, the nonlinear PWE delivers the nonlinear dispersion curves of all modes, offering a broader perspective into the design process for semi-adaptively programmable metamaterials aimed at controlling wave propagation
Investigation of anticancer mechanism of clavulone II, a coral cyclopentenone prostaglandin analog, in human acute promyelocytic leukemia.
No full text
Somatic mutations in epidermal growth factor receptor underlying complete responsiveness to gefitinib in a taiwanese female patient with metastatic adenocarcinoma of lung.
No full textValidity of force platform measures of stance stability under varying sensory conditions. Proceedings of National Science Council, ROC: Part B
No full textOptical manipulation of metallic particles
No full textPlasmonic tweezers and optical tweezers are two techniques for trapping and manipulating particles. Plasmonic tweezers utilizes localized surface plasmon field, whilst optical tweezers utilizes focused laser beam. In this thesis, these two techniques were applied for the manipulation of metallic particles in three basic forms: single particle, particle dimer and particle trimer.
Firstly, the trapping of metallic particles was investigated through focused plasmonic tweezers when surface plasmons are excited by focused Radially Polarized Beam (RPB). The force exerted on the metallic particle is responsible for the trapping, which is found to be due to the sum of both gradient and scattering forces acting in the same direction established by the coupling between the metallic particle and focused plasmonic field. This contrasts the repulsion of metallic particles in optical tweezers. Focused plasmonic trapping of metallic particle enables actively moving metallic particle in a controlled way, which could be used for intracellular Surface Enhanced Raman Scattering (SERS) imaging.
Secondly, the trapping of horizontally-oriented metallic particle dimers was theoretically studied through focused plasmonic tweezers when surface plasmons are excited by focused linearly-polarized beam. It was found that a Surface Plasmon Virtual Probe (SP-VP) pair was generated on a metal film. A formula is derived to represent the electric field of SP-VP pair, revealing that the spacing of the two virtual probes is wavelength-dependent. Each SP-VP is able to trap a metallic particle, thus the gap between the trapped particles of the dimer can be controlled by changing the excitation wavelength. This theory was further tested by successfully trapping nanosphere and nanorod metallic dimers with 10 nm gaps. The trapped dimer showed a typical electric field enhancement of more than 103 times, which is enough for single molecule SERS detection.
Thirdly, a vertically-oriented dimer structure was proposed based on trapping of metallic nanoparticle by focused plasmonic tweezers. The vertically-oriented dimer can effectively make use of the dominant longitudinal component of the SP-VP thus providing much stronger electric field in the gap. Furthermore, for practical application the top nanoparticle of the dimer can be replaced with the tip of an atomic force microscope which enables the precise control of the gap distance of the dimer. Therefore the proposed vertically-oriented dimer structure provides both the scanning capability and the extremely-high electric field enhancement necessary for the high sensitivity Raman imaging.
Lastly, the stable trapping and steady rotation of a metallic particle trimer were experimentally achieved by optical tweezers with optical vortex. The trimer particles are found to be confined inside the maximum intensity ring of a focused circularly polarized optical vortex. Theoretical analysis suggests that a large proportion of the radial scattering force pushes the particles together, whilst the remaining portion provides the centripetal force necessary for the rotation. The achieved steady rotation of the metallic particle trimer may lead to the development of microfluidics devices such as micro-rotor
Yc-1-Inhibited Proliferation of Rat Mesangial Cells through Suppression of Cyclin D1—Independent of Cgmp Pathway and Partially Reversed by P38 Mapk Inhibitor
No full textThis study was designed to investigate the effect of 1- benzyl-3-(5′- hydroxymethyl-2′-furyl) indazole (YC-1), a guanylate cyclase activator, upon the proliferation of rat mesangial cells and its underlying mechanism . YC-1 inhibited cell proliferation and DNA synthesis in a dose- and time- dependent manner. Flow cytometry cell-cycle studies revealed that YC-1 prevented the entry of cells from G1 into S phase . The expression of cyclin D1 and the kinase activity of cyclin D1/cyclin-dependent kinase ( CDK)4 were lower within YC-1-treated cells, revealed by Western blotting, Northern blotting and kinase assays. YC-1 did not increase the intracellular cGMP concentration in mesangial cells. Inhibitors of soluble guanylate cyclase, protein kinase G, or protein kinase A also did not reverse the inhibitory effect elicited by YC-1, while co-treatment with p 38 mitogen -activated protein kinase (MAPK) inhibitor could partially reverse the suppressive effect. YC-1 inhibited proliferation of mesangial cells and induced cell-cycle arrest by the reduction of cyclin D1 synthesis and cyclin D1/CDK4 kinase activity. This effect acts partially through p38 MAPK signal transduction activation and is independent of cGMP - signaling pathways
Rock Physical Properties of Longmaxi Shale Gas Formation in South Sichuan Province, China
No full textDeep shale gas (burial depth > 3500 m) in the Longmaxi Formation of southern Sichuan Province will be the primary target for exploration and development in China for a relatively long period. However, the lack of a physical basis for the “sweet-spots” seismic and well-logging prediction is caused by uncertainty in the rock physical properties of deep shale gas in the research area. Acoustic and hardness measurements were performed on shale samples from a deep layer of the Longmaxi Formation in southern Sichuan. Microtextural characteristics of the shale samples were also analyzed by conventional optical microscopy and scanning electron microscopy. Based on these measurements, the rock physical properties of the shale samples and control factors are discussed. It is shown that the deep shale samples have similar properties to the shallow shale in mineral composition, microtexture, and pore type. However, the organic pore in deep shale samples is relatively undeveloped, while the dissolved pores are more developed. For high-quality shale samples (total organic content > 2%), crystal quartz of biological origin forms the framework of rock samples, resulting in effective dynamic and static properties, reflecting the elastic behavior of rigid quartz aggregates. For organic-lean samples (total organic content < 2%), orientated detrital clay particles take the role of load-bearing grains. Therefore, these shale samples’ overall rock physical properties are mainly controlled by the elastic properties of “soft” clay. The load-bearing grain variation from organic-rich shale samples to organic-lean samples results in an overturned “V”-type change in terms of velocity versus content. Organic-rich shale samples also show an apparent low Poisson’s ratio. Organic-rich shale has a slight velocity–porosity trend, while organic-lean shale shows a significant velocity–porosity trend. In addition, due to the difference in rock microtexture between organic-rich and organic-lean shale, these two kinds of reservoir rocks can be discriminated in cross plots of P-wave impedance versus Poisson’s ratio and Young’s modulus versus Poisson’s ratio. Change in hardness also reflects the control of microtexture, and shale samples with biological-origin quartz as load-bearing grains show higher hardness and brittleness. However, the variation in quartz content has less of an impact on hardness and brittleness in shale samples with clay as the load-bearing grain. Our results provide an experimental basis for the geophysical identification and prediction of deep shale gas layers.</p
- …
