Spatial Determination of Magnetic Avalanche Ignition Points

Using time-resolved measurements of local magnetization in the molecular magnet Mn12-ac, we report studies of the propagation of magnetic avalanches (fast magnetization reversals) that originate from points inside the crystals rather than at the edges. The curved nature of the fronts produced by avalanches is reflected in the time-of-arrival at micro-Hall sensors placed at the surface of the sample. Assuming that the avalanche interface is a spherical bubble that grows with a radius proportional to time, we are able to locate the approximate ignition point of each avalanche in a two-dimensional cross-section of the crystal. For the samples used in these studies, avalanches in a given crystal are found to originate in a small region with a radius of roughly 150 microns.Comment: 3 pages, 4 figure

Las Autoridades Europeas de Supervisión: estructura y funciones

This study looks into the basic lines of the institutional structure and functions of the new European Supervisory Authorities (ESF): the European Banking Authority (EBA), the European Securities Markets Authority (ESMA) and the European Insurance and Occupational Pensions Authority (EIOPA). Within the framework of the reforms adopted in reaction to the financial crisis, the creation of the ESF is a step forward in the process of progressive comunitarisation of supervision and regulation in the EU, going clearly beyond the cooperation schemes of the former European committees of supervision which they replace assuming their aquis. Within the taxonomy of EU entities and institutions, the ESF may be labeled «regulatory agencies». As agencies, their regulatory powers are limited and, by definition, delegated. Notwithstanding, their formal patterns may lead to underestimating their importance, as there may be no doubt about their future salient role as primary material sources of financial law. Their coordination capabilities place them clearly supra partes with regard to National authorities in their respective scopes. They are also an essential part of what may now properly be named the European regulatory, supervisory and crisis management architecture, distinguishable from a mere network of National authorities.El presente trabajo aborda las líneas básicas de la estructura institucional y las funciones de las nuevas Autoridades Europeas de Supervisión (AES): la Autoridad Bancaria Europea (ABE), la Autoridad Europea de Valores y Mercados (AEVM) y la Autoridad Europea de Seguros y Pensiones de Jubilación (AESPJ). Inscrita en el marco de las reformas adoptadas en respuesta a la crisis financiera, la creación de las AES supone un paso adelante en el proceso de comunitarización progresiva de la regulación y supervisión en el ámbito de la UE, superando claramente el esquema de cooperación de los antiguos comités europeos de supervisores, a los que sustituyen y cuyo acervo heredan. Dentro de la taxonomía de entidades e instituciones de la UE, las AES pueden calificarse de «agencias reguladoras». Como tales agencias, sus potestades regulatorias son limitadas y, por naturaleza, delegadas. No obstante, los rasgos formales pueden llevar a minusvalorar su importancia, puesto que no cabe duda de que van a erigirse en fuentes materiales primordiales del Derecho financiero futuro. Sus capacidades de coordinación las sitúan, asimismo, claramente supra partes respecto a las autoridades nacionales en sus respectivos ámbitos. Son asimismo, parte integrante esencial de lo que ya puede denominarse la arquitectura regulatoria, supervisora y de gestión de crisis europea, distinguible de una mera red de autoridades nacionales.This study looks into the basic lines of the institutional structure and functions of the new European Supervisory Authorities (ESF): the European Banking Authority (EBA), the European Securities Markets Authority (ESMA) and the European Insurance and Occupational Pensions Authority (EIOPA). Within the framework of the reforms adopted in reaction to the financial crisis, the creation of the ESF is a step forward in the process of progressive comunitarisation of supervision and regulation in the EU, going clearly beyond the cooperation schemes of the former European committees of supervision which they replace assuming their aquis. Within the taxonomy of EU entities and institutions, the ESF may be labeled «regulatory agencies». As agencies, their regulatory powers are limited and, by definition, delegated. Notwithstanding, their formal patterns may lead to underestimating their importance, as there may be no doubt about their future salient role as primary material sources of financial law. Their coordination capabilities place them clearly supra partes with regard to National authorities in their respective scopes. They are also an essential part of what may now properly be named the European regulatory, supervisory and crisis management architecture, distinguishable from a mere network of National authorities

How cyclical do cyclically-adjusted balances remain? An EU study

Observed budget balances are an imperfect indicator of the fiscal policy stance, because fluctuations in economic activity induce automatic changes in the balance, hence the use of cyclically-adjusted balances (CAB). However, this paper shows that CABs (as measured through one of the two methods currently used by the Commission) tend to be systematically overestimated during downturns and underestimated during expansions. The dominant source of this distortion arises from the filtering of revenues deemed to be cyclical, possibly signalling a problem with the computation of elasticities. The effect of the items which are assumed not to move with the cycle is non significant, but this overall result conceals offseting effects: public investment turns to be significantly procyclical and interest payments and transfers to firms are countercyclical.Structural balances, output gap

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

Tuning Magnetic Avalanches in Mn12-ac

Using micron-sized Hall sensor arrays to obtain time-resolved measurements of the local magnetization, we report a systematic study in the molecular magnet Mn$_{12}$-acetate of magnetic avalanches controllably triggered in different fixed external magnetic fields and for different values of the initial magnetization. The speeds of propagation of the spin-reversal fronts are in good overall agreement with the theory of magnetic deflagration of Garanin and Chudnovsky \cite{Garanin}.Comment: 8 pages, 7 figures; discussion expanded and revise

Field induced magnetic transition and metastability in Co substituted Mn2SbMn_{2}Sb

A detailed investigation of first order ferrimagnetic (FRI) to antiferromagnetic (AFM) transition in Co (15%) doped $Mn_2Sb$ is carried out. These measurements demonstrate anomalous thermomagnetic irreversibility and glass-like frozen FRI phase at low temperatures. The irreversibility arising between the supercooling and superheating spinodals is distinguised in an ingenious way from the irreversibility arising due to kinetic arrest. Field annealing measurements shows reentrant FRI-AFM-FRI transition with increasing temperature. These measurements also show that kinetic arrest band and supercooling band are anitcorrelated i.e regions which are kinetically arrested at higher temperature have lower supercooling temperature and vice versa.Comment: 10 pages, 8 figure

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

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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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

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