The topology of fluid flow past a sequence of cylinders

AbstractThis paper analyzes conditions under which dynamical systems in the plane have indecomposable continua or even infinite nested families of indecomposable continua. Our hypotheses are patterned after a numerical study of a fluid flow example, but should hold in a wide variety of physical processes. The basic fluid flow model is a differential equation in R2 which is periodic in time, and so its solutions can be represented by a time-1 map F:R2→R2. We represent a version of this system “with noise” by considering any sequence of maps Fn:R2→R2, each of which is ε-close to F in the C1 norm, so that if p is a point in the fluid flow at time n, then Fn(p) is its position at time n+1. We show that indecomposable continua still exist for small ε

Ultrasensitive vibrational resonance induced by small disturbances

We have found two kinds of ultra-sensitive vibrational resonance in coupled nonlinear systems. It is particularly worth pointing out that this ultra-sensitive vibrational resonance is a transient behavior caused by transient chaos. Considering long-term response, the system will transform from transient chaos to periodic response. The pattern of vibrational resonance will also transform from ultra-sensitive vibrational resonance to conventional vibrational resonance. This article focuses on the transient ultra-sensitive vibrational resonance phenomenon. It is induced by a small disturbance of the high-frequency excitation and the initial simulation conditions, respectively. The damping coefficient and the coupling strength are the key factors to induce the ultra-sensitive vibrational resonance. By increasing these two parameters, the vibrational resonance pattern can be transformed from an ultra-sensitive vibrational resonance to a conventional vibrational resonance. The reason for different vibrational resonance patterns to occur lies in the state of the system response. The response usually presents transient chaotic behavior when the ultra-sensitive vibrational resonance appears and the plot of the response amplitude versus the controlled parameters shows a highly fractalized pattern. When the response is periodic or doubly-periodic, it usually corresponds to the conventional vibrational resonance. The ultra-sensitive vibrational resonance not only occurs at the excitation frequency, but it also occurs at some more nonlinear frequency components. The ultra-sensitive vibrational resonance as a transient behavior and the transformation of vibrational resonance patterns are new phenomena in coupled nonlinear systems

CpG-induced tyrosine phosphorylation occurs via a TLR9-independent mechanism and is required for cytokine secretion

Toll-like receptors (TLRs) recognize molecular patterns preferentially expressed by pathogens. In endosomes, TLR9 is activated by unmethylated bacterial DNA, resulting in proinflammatory cytokine secretion via the adaptor protein MyD88. We demonstrate that CpG oligonucleotides activate a TLR9-independent pathway initiated by two Src family kinases, Hck and Lyn, which trigger a tyrosine phosphorylation–mediated signaling cascade. This cascade induces actin cytoskeleton reorganization, resulting in cell spreading, adhesion, and motility. CpG-induced actin polymerization originates at the plasma membrane, rather than in endosomes. Chloroquine, an inhibitor of CpG-triggered cytokine secretion, blocked TLR9/MyD88-dependent cytokine secretion as expected but failed to inhibit CpG-induced Src family kinase activation and its dependent cellular responses. Knock down of Src family kinase expression or the use of specific kinase inhibitors blocked MyD88-dependent signaling and cytokine secretion, providing evidence that tyrosine phosphorylation is both CpG induced and an upstream requirement for the engagement of TLR9. The Src family pathway intersects the TLR9–MyD88 pathway by promoting the tyrosine phosphorylation of TLR9 and the recruitment of Syk to this receptor

Single trace terahertz spectroscopic ellipsometry

© 2019 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited"[EN] A new technique for terahertz time-domain ellipsometry is presented. Information of reflection coefficients of the sample in two orthogonal polarizations is encoded on the same terahertz trace by using a birefringent medium. This allows for single measurement refractive index extraction without the need for a moving analyzer. A comparison of the complex refractive index measurements of optical grade fused silica and non birefringent sapphire are carried out both in reflection ellipsometry and with a standard terahertz transmission spectrometer showing good agreement. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing AgreementMinisterio de Ciencia, Innovación y Universidades (TEC2016-80906-R).Báez-Chorro, MÁ.; Vidal Rodriguez, B. (2019). Single trace terahertz spectroscopic ellipsometry. Optics Express. 27(24):35468-35474. https://doi.org/10.1364/OE.27.035468S35468354742724Bockelt, A., Palaci Lopez, J., & Vidal, B. (2015). All-Fiber Centralized Architecture for Parallel Terahertz Sensors. IEEE Transactions on Terahertz Science and Technology, 5(1), 137-144. doi:10.1109/tthz.2014.2373313Khazan, M., Meissner, R., & Wilke, I. (2001). Convertible transmission-reflection time-domain terahertz spectrometer. Review of Scientific Instruments, 72(8), 3427-3430. doi:10.1063/1.1384433Liu, H.-B., Chen, Y., Bastiaans, G. J., & Zhang, X.-C. (2006). Detection and identification of explosive RDX by THz diffuse reflection spectroscopy. Optics Express, 14(1), 415. doi:10.1364/opex.14.000415Sanjuan, F., Bockelt, A., & Vidal, B. (2014). Birefringence measurement in the terahertz range based on double Fourier analysis. Optics Letters, 39(4), 809. doi:10.1364/ol.39.000809Nagashima, T., & Hangyo, M. (2001). Measurement of complex optical constants of a highly doped Si wafer using terahertz ellipsometry. Applied Physics Letters, 79(24), 3917-3919. doi:10.1063/1.1426258Matsumoto, N., Hosokura, T., Nagashima, T., & Hangyo, M. (2011). Measurement of the dielectric constant of thin films by terahertz time-domain spectroscopic ellipsometry. Optics Letters, 36(2), 265. doi:10.1364/ol.36.000265Galuza, A. A., Kiseliov, V. K., Kolenov, I. V., Belyaeva, A. I., & Kuleshov, Y. M. (2016). Developments in THz-Range Ellipsometry: Quasi-Optical Ellipsometer. IEEE Transactions on Terahertz Science and Technology, 6(2), 183-190. doi:10.1109/tthz.2016.2525732Morris, C. M., Aguilar, R. V., Stier, A. V., & Armitage, N. P. (2012). Polarization modulation time-domain terahertz polarimetry. Optics Express, 20(11), 12303. doi:10.1364/oe.20.012303Iwata, T., Uemura, H., Mizutani, Y., & Yasui, T. (2014). Double-modulation reflection-type terahertz ellipsometer for measuring the thickness of a thin paint coating. Optics Express, 22(17), 20595. doi:10.1364/oe.22.020595Byrne, M. B., Shaukat, M. U., Cunningham, J. E., Linfield, E. H., & Davies, A. G. (2011). Simultaneous measurement of orthogonal components of polarization in a free-space propagating terahertz signal using electro-optic detection. Applied Physics Letters, 98(15), 151104. doi:10.1063/1.3579258Guo, Q., Zhang, Y., Lyu, Z., Zhang, D., Huang, Y., Meng, C., … Yuan, J. (2019). THz Time-Domain Spectroscopic Ellipsometry With Simultaneous Measurements of Orthogonal Polarizations. IEEE Transactions on Terahertz Science and Technology, 9(4), 422-429. doi:10.1109/tthz.2019.2921200Pupeza, I., Wilk, R., & Koch, M. (2007). Highly accurate optical material parameter determination with THz time-domain spectroscopy. Optics Express, 15(7), 4335. doi:10.1364/oe.15.004335Grischkowsky, D., Keiding, S., van Exter, M., & Fattinger, C. (1990). Far-infrared time-domain spectroscopy with terahertz beams of dielectrics and semiconductors. Journal of the Optical Society of America B, 7(10), 2006. doi:10.1364/josab.7.002006Kim, Y., Yi, M., Kim, B. G., & Ahn, J. (2011). Investigation of THz birefringence measurement and calculation in Al_2O_3 and LiNbO_3. Applied Optics, 50(18), 2906. doi:10.1364/ao.50.002906Chen, X., Parrott, E. P. J., Huang, Z., Chan, H.-P., & Pickwell-MacPherson, E. (2018). Robust and accurate terahertz time-domain spectroscopic ellipsometry. Photonics Research, 6(8), 768. doi:10.1364/prj.6.000768Neshat, M., & Armitage, N. P. (2012). Terahertz time-domain spectroscopic ellipsometry: instrumentation and calibration. Optics Express, 20(27), 29063. doi:10.1364/oe.20.029063Van Exter, M., Fattinger, C., & Grischkowsky, D. (1989). Terahertz time-domain spectroscopy of water vapor. Optics Letters, 14(20), 1128. doi:10.1364/ol.14.00112