Unramified -modular representations of GLn(F) and its inner forms

International audienceLet F be a non-Archimedean locally compact field of residue characteristic p and R be an algebraically closed field of characteristic ℓ different from p. Let G be the group GL(n) over F or one of its inner forms. In this article, we classify the unramified irreducible smooth R-representations of G(F): more precisely we prove that they are those representations that are irreducibly induced from an unramified character of a Levi subgroup. We deduce that any smooth irreducible unramified mod ℓ representation of G(F) can be lifted to an ℓ-adic representation, which proves a conjecture by Vignéras

Switching of Magnetic Moments of Nanoparticles by Surface Acoustic Waves

We report evidence of the magnetization reversal in nanoparticles by surface acoustic waves (SAWs). The experimental system consists of isolated magnetite nanoparticles dispersed on a piezoelectric substrate. Magnetic relaxation from a saturated state becomes significantly enhanced in the presence of the SAW at a constant temperature of the substrate. The dependence of the relaxation on SAW power and frequency has been investigated. The effect is explained by the effective ac magnetic field generated by the SAW in the nanoparticles.Comment: Accepted in Europhysics Letter

Coherent radiation by molecular magnets

The possibility of coherent radiation by molecular magnets is investigated. It is shown that to realize the coherent radiation, it is necessary to couple the considered sample to a resonant electric circuit. A theory for describing this phenomenon is developed, based on a realistic microscopic Hamiltonian, including the Zeeman terms, single-site anisotropy, and dipole interactions. The role of hyperfine interactions between molecular and nuclear spins is studied. Numerical solutions of the spin evolution equations are presented.Comment: Latex file, 11 pages, 3 figure

Absence of spin superradiance in resonatorless magnets

A spin system is considered with a Hamiltonian typical of molecular magnets, having dipole-dipole interactions and a single-site magnetic anisotropy. In addition, spin interactions through the common radiation field are included. A fully quantum-mechanical derivation of the collective radiation rate is presented. An effective narrowing of the dipole-dipole attenuation, due to high spin polarization is taken into account. The influence of the radiation rate on spin dynamics is carefully analysed. It is shown that this influence is completely negligible. No noticeable collective effects, such as superradiance, can appear in molecular magnets, being caused by electromagnetic spin radiation. Spin superradiance can arise in molecular magnets only when these are coupled to a resonant electric circuit, as has been suggested earlier by one of the authors in Laser Phys. {\bf 12}, 1089 (2002).Comment: Latex file, 14 pages, 5 figure

Upregulation of brain renin angiotensin system by 27-hydroxycholesterol in Alzheimer's disease

In spite of the fact that cholesterol does not pass the blood-brain barrier, hypercholesterolemia has been linked to increase Alzheimer's disease (AD) risk. Hypertension is another risk factor and angiotensin converting enzyme (ACE) activity is known to be increased in AD. Furthermore, a lower incidence of AD has been reported in patients taking anti-hypertensive drugs. Here we show that the levels of angiotensinogen (AGT) and ACE are increased in the cerebrospinal fluid (CSF) of patients with mild cognitive impairment and AD. Moreover, we show ACE activity in the CSF to be positively correlated with both plasma and CSF levels of 27-hydroxycholesterol (27-OH), an oxysterol known to pass through the BBB and taken up from the circulation by the brain. In addition, treatment of rat primary neurons, astrocytes, and human neuroblastoma cells with 27-OH resulted in increased production of AGT. Our results demonstrate that upregulation of renin-angiotensin system (RAS) in AD brains occurs not only at the enzymatic level (ACE) but also at the substrate level (AGT). The possibility that 27-OH is part of a mechanism linking hypercholesterolemia with increased brain RAS activity and increased AD risk is discussed

Acoustically driven arrayed waveguide grating

“© 2015 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"We demonstrate compact tunable phased-array wavelength-division multiplexers driven by surface acoustic waves (SAWs) in the low GHz range. The devices comprise two couplers, which respectively split and combine the optical signal, linked by an array of single-mode waveguides (WGs). Two different layouts are presented, in which multi-mode interference couplers or free propagating regions were separately employed as couplers. The multiplexers operate on five equally distributed wavelength channels, with a spectral separation of 2 nm. A standing SAW modulates the refractive index of the arrayed WGs. Each wavelength component periodically switches paths between the output channel previously asigned by the design and the adjacent channels, at a fixed applied acoustic power. The devices were monolithically fabricated on (Al, Ga) As. A good agreement between theory and experiment is achieved.The authors thank W. Seidel, and S. Rauwerdink for preparation of the devices. This research has been supported by the international campus of excellence VLC/CAMPUS and by the program INNCIDE from the Spanish Ministry of Economy and Competitiveness (MINECO), through the program "Valoritza i Transfereix" from the Vice-Principal of Research and Scientific Policy of the Universitat de Valencia and through the program INNOVA (grant SP20120860) from the Universitat Politecnica de Valencia. Financial support by the Spanish MINECO Projects TEC2010-21337 and MAT2012-33483 is gratefully acknowledged. A. Crespo-Poveda and B. Gargallo acknowledge financial support through FPI grants BES-2010-036846 and BES-2011-046100, respectively.Crespo-Poveda, A.; Hernandez-Minguez, A.; Gargallo Jaquotot, BA.; Biermann, K.; Tahraoui, A.; Santos, PV.; Munoz, P.... (2015). Acoustically driven arrayed waveguide grating. Optics Express. 23(16):21213-21231. https://doi.org/10.1364/OE.23.021213S21213212312316Dragone, C. (1991). An N*N optical multiplexer using a planar arrangement of two star couplers. IEEE Photonics Technology Letters, 3(9), 812-815. doi:10.1109/68.84502Talahashi, H., Oda, K., Toba, H., & Inoue, Y. (1995). Transmission characteristics of arrayed waveguide N×N wavelength multiplexer. Journal of Lightwave Technology, 13(3), 447-455. doi:10.1109/50.372441Smit, M. K., & Van Dam, C. (1996). PHASAR-based WDM-devices: Principles, design and applications. IEEE Journal of Selected Topics in Quantum Electronics, 2(2), 236-250. doi:10.1109/2944.577370Munoz, P., Pastor, D., & Capmany, J. (2002). Modeling and design of arrayed waveguide gratings. Journal of Lightwave Technology, 20(4), 661-674. doi:10.1109/50.996587Paiam, M. R., & MacDonald, R. I. (1997). Design of phased-array wavelength division multiplexers using multimode interference couplers. Applied Optics, 36(21), 5097. doi:10.1364/ao.36.005097Nakamura, S., Ueno, Y., & Tajima, K. (2001). Femtosecond switching with semiconductor-optical-amplifier-based Symmetric Mach–Zehnder-type all-optical switch. Applied Physics Letters, 78(25), 3929-3931. doi:10.1063/1.1379790Wurtz, G. A., Pollard, R., Hendren, W., Wiederrecht, G. P., Gosztola, D. J., Podolskiy, V. A., & Zayats, A. V. (2011). Designed ultrafast optical nonlinearity in a plasmonic nanorod metamaterial enhanced by nonlocality. Nature Nanotechnology, 6(2), 107-111. doi:10.1038/nnano.2010.278Li, X., Xu, H., Xiao, X., Li, Z., Yu, Y., & Yu, J. (2014). Fast and efficient silicon thermo-optic switching based on reverse breakdown of pn junction. Optics Letters, 39(4), 751. doi:10.1364/ol.39.000751Ishii, M., Hibino, Y., Hanawa, F., Nakagome, H., & Kato, K. (1998). Packaging and environmental stability of thermally controlled arrayed-waveguide grating multiplexer module with thermoelectric device. Journal of Lightwave Technology, 16(2), 258-264. doi:10.1109/50.661019Watanabe, T., Ooba, N., Hayashida, S., Kurihara, T., & Imamura, S. (1998). Polymeric optical waveguide circuits formed using silicone resin. Journal of Lightwave Technology, 16(6), 1049-1055. doi:10.1109/50.681462Xiao, G. Z., Zhao, P., Sun, F. G., Lu, Z. G., Zhang, Z., & Grover, C. P. (2004). Interrogating fiber Bragg grating sensors by thermally scanning a demultiplexer based on arrayed waveguide gratings. Optics Letters, 29(19), 2222. doi:10.1364/ol.29.002222Stabile, R., Rohit, A., & Williams, K. A. (2014). Monolithically Integrated 8 × 8 Space and Wavelength Selective Cross-Connect. Journal of Lightwave Technology, 32(2), 201-207. doi:10.1109/jlt.2013.2290322Asakura, H., Hashimoto, M., Nashimoto, K., Tsuda, H., & Kudzuma, D. (2012). High-speed wavelength selective operation of PLZT-based arrayed-waveguide grating. Electronics Letters, 48(16), 1009-1010. doi:10.1049/el.2012.1292Gorecki, C., Chollet, F., Bonnotte, E., & Kawakatsu, H. (1997). Silicon-based integrated interferometer with phase modulation driven by surface acoustic waves. Optics Letters, 22(23), 1784. doi:10.1364/ol.22.001784De Lima, M. M., Beck, M., Hey, R., & Santos, P. V. (2006). Compact Mach-Zehnder acousto-optic modulator. Applied Physics Letters, 89(12), 121104. doi:10.1063/1.2354411Beck, M., de Lima, M. M., Wiebicke, E., Seidel, W., Hey, R., & Santos, P. V. (2007). Acousto-optical multiple interference switches. Applied Physics Letters, 91(6), 061118. doi:10.1063/1.2768889Beck, M., de Lima, M. M., & Santos, P. V. (2008). Acousto-optical multiple interference devices. 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Cerebrospinal fluid neurogranin in an inducible mouse model of neurodegeneration: A translatable marker of synaptic degeneration

Synapse impairment is thought to be an early event in Alzheimer's disease (AD); dysfunction and loss of synapses are linked to cognitive symptoms that precede neuronal loss and neurodegeneration. Neurogranin (Ng) is a somatodendritic protein that has been shown to be reduced in brain tissue but increased in the cerebrospinal fluid (CSF) of AD patients compared to age-matched controls. High levels of CSF Ng have been shown to reflect a more rapid AD progression. To gauge the translational value of Ng as a biomarker, we developed a new, highly sensitive, digital enzyme-linked immunosorbent assay (ELISA) on the Simoa platform to measure Ng in both mouse and human CSF. We investigated and confirmed that Ng levels are increased in the CSF of patients with AD compared to controls. In addition, we explored how Ng is altered in the brain and CSF of transgenic mice that display progressive neuronal loss and synaptic degeneration following the induction of p25 overexpression. In this model, we found that Ng levels increased in CSF when neurodegeneration was induced, peaking after 2 weeks, while they decreased in brain. Our data suggest that CSF Ng is a biomarker of synaptic degeneration with translational value

Immigration and Human Development: Evidence from Lebanon

This paper takes Lebanon as a case study to examine the relationship between human development and immigration. It examines this issue from both ends: the sending and the receiving countries. The author suggests that by developing the concept of a diasporic civil society and a diasporic public sphere, a significant aspect of the relationship between human development and immigration is illuminated especially at the level of political, social and cultural capitals. The paper also argues that the double impact of the home country and that of destination has a lot to say about the influence of immigration on human development in Lebanon. In examining Australia as a destination country, the paper shows the particular impact that globalisation and September 11 have lately had on the capacity of the Lebanese migrants for human development. Finally, the paper concludes by showing the extent to which the diasporic civil society compensates for the ‘negligent’ character of the Lebanese state in the context of human development