Observation of phonon-induced magnetic deflagration in manganites

Very fast magnetic avalanches in (La, Pr)-based manganites are the signature of a phase transition from an insulating blocked charge-ordered antiferromagnetic state to a charge-delocalized ferromagnetic (CD-FM) state. We report here the experimental observation that this transition does not occur either simultaneously or randomly in the whole sample but there is instead a spatial propagation with a velocity of the order of tens of m/s. Our results show that avalanches originate from the inside of the sample, move to the outside, and occur at values of the applied magnetic field that depend on the CD-FM fraction in the sample. Moreover, upon application of surface acoustic waves at constant magnetic fields, we are able to trigger avalanches at very well-determined values of the temperature and magnetic field. Due to the interaction with the acoustic waves, the number of isolated ferromagnetic clusters in La0.225Pr0.40Ca0.375MnO3 starts to grow across the entire sample in the same way as if it were a magnetic deflagration

Insight into genetic predisposition to chronic lymphocytic leukemia from integrative epigenomics.

Genome-wide association studies have provided evidence for inherited genetic predisposition to chronic lymphocytic leukemia (CLL). To gain insight into the mechanisms underlying CLL risk we analyze chromatin accessibility, active regulatory elements marked by H3K27ac, and DNA methylation at 42 risk loci in up to 486 primary CLLs. We identify that risk loci are significantly enriched for active chromatin in CLL with evidence of being CLL-specific or differentially regulated in normal B-cell development. We then use in situ promoter capture Hi-C, in conjunction with gene expression data to reveal likely target genes of the risk loci. Candidate target genes are enriched for pathways related to B-cell development such as MYC and BCL2 signalling. At 14 loci the analysis highlights 63 variants as the probable functional basis of CLL risk. By integrating genetic and epigenetic information our analysis reveals novel insights into the relationship between inherited predisposition and the regulatory chromatin landscape of CLL

The CARMENES search for exoplanets around M dwarfs Guaranteed time observations Data Release 1 (2016-2020)

I. Ribas et al.[Context] The CARMENES instrument, installed at the 3.5 m telescope of the Calar Alto Observatory in Almería, Spain, was conceived to deliver high-accuracy radial velocity (RV) measurements with long-term stability to search for temperate rocky planets around a sample of nearby cool stars. Moreover, the broad wavelength coverage was designed to provide a range of stellar activity indicators to assess the nature of potential RV signals and to provide valuable spectral information to help characterise the stellar targets.[Aims] We describe the CARMENES guaranteed time observations (GTO), spanning from 2016 to 2020, during which 19 633 spectra for a sample of 362 targets were collected. We present the CARMENES Data Release 1 (DR1), which makes public all observations obtained during the GTO of the CARMENES survey.[Methods] The CARMENES survey target selection was aimed at minimising biases, and about 70% of all known M dwarfs within 10 pc and accessible from Calar Alto were included. The data were pipeline-processed, and high-level data products, including 18 642 precise RVs for 345 targets, were derived. Time series data of spectroscopic activity indicators were also obtained.[Results] We discuss the characteristics of the CARMENES data, the statistical properties of the stellar sample, and the spectroscopic measurements. We show examples of the use of CARMENES data and provide a contextual view of the exoplanet population revealed by the survey, including 33 new planets, 17 re-analysed planets, and 26 confirmed planets from transiting candidate follow-up. A subsample of 238 targets was used to derive updated planet occurrence rates, yielding an overall average of 1.44 ± 0.20 planets with 1 M⊕ < Mpl sin i < 1000 M⊕ and 1 day < Porb < 1000 days per star, and indicating that nearly every M dwarf hosts at least one planet. All the DR1 raw data, pipeline-processed data, and high-level data products are publicly available online.[Conclusions] CARMENES data have proven very useful for identifying and measuring planetary companions. They are also suitable for a variety of additional applications, such as the determination of stellar fundamental and atmospheric properties, the characterisation of stellar activity, and the study of exoplanet atmospheres.CARMENES is an instrument at the Centro Astronómico Hispano en Andalucía (CAHA) at Calar Alto (Almería, Spain), operated jointly by the Junta de Andalucía and the Instituto de Astrofísica de Andalucía (CSIC). CARMENES was funded by the Max-Planck-Gesellschaft (MPG), the Consejo Superior de Investigaciones Científicas (CSIC), the Ministerio de Economía y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l’Espai, Institut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft (DFG) through the Major Research Instrumentation Programme and Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. We acknowledge financial support from the Spanish Agencia Estatal de Investigación of the Ministerio de Ciencia e Innovación (AEI-MCIN) and the ERDF “A way of making Europe” through projects PID2020-117493GB-I00, PID2019-109522GB-C5[1:4], PID2019-110689RB-I00, PID2019-107061GB-C61, PID2019-107061GB-C64, PGC2018-098153-B-C33, PID2021-125627OB-C31/AEI/10.13039/501100011033, and the Centre of Excellence “Severo Ochoa” and “María de Maeztu” awards to the Institut de Ciències de l’Espai (CEX2020-001058-M), Instituto de Astrofísica de Canarias (CEX2019-000920-S), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de Astrobiología (MDM-2017-0737). We also benefited from additional funding from: the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya and the Agència de Gestió d’Ajuts Universitaris i de Recerca of the Generalitat de Catalunya, with additional funding from the European FEDER/ERDF funds, and from the Generalitat de Catalunya/CERCA programme; the DFG through the Major Research Instrumentation Programme and Research Unit FOR2544 “Blue Planets around Red Stars” (RE 2694/8-1); the University of La Laguna through the Margarita Salas Fellowship from the Spanish Ministerio de Universidades ref. UNI/551/2021-May-26, and under the EU Next Generation funds; the Gobierno de Canarias through projects ProID2021010128 and ProID2020010129; the Spanish MICINN under Ramón y Cajal programme RYC-2013-14875; the “Fondi di Ricerca Scientifica d’Ateneo 2021” of the University of Rome “Tor Vergata”; and the programme “Alien Earths” supported by the National Aeronautics and Space Administration (NASA) under agreement No. 80NSSC21K0593. TPeer reviewe

Allaus magnètiques en Òxids amb efectes Magnetoresistius Colossals

Aquest és un projecte d’investigació en Ciència de Materials. En aquest projecte s’han intentat caracteritzar de la forma més complerta possible les allaus magnètiques en una família d’òxids amb efectes Magnetoresistius Colossals coneguts com a Manganites. En concret s’ha treballat sobre mostres de La0.225Pr0.4Ca0.375Mn03 i s’han utilitzat aparells de mesura i caracterització magnètica d’alta tecnologia (magnetòmetre SQUID). D’aquesta primera caracterització s’ha conclòs que al refredar les mostres sense camp aplicat s’arriba a un estat metastable. En l’estat metastable hi ha presents dues fases, la fase Antiferromagnètica amb ordenament de càrrega (CO-AFM) i la fase Ferromagnètica sense ordenament de càrrega (CD-FM). La fase CD-FM es la minoritària i es troba en forma de clústers nanomètrics distribuïts al dins de la fase majoritària, fase CD-AFM. S’ha observat que l’aplicació d’un camp magnètic intens provoca una transició de primer ordre (FOPT) en la que el clústers de fase CD-FM creixent ràpidament, quan la transició ha tingut lloc la mostra es totalment CD-FM. Aquest estat es estable en el sentit que un cop es retira el camp la mostra no retorna a l’estat inicial. També s’ha observat que la forma en què té lloc la transició depèn de l’historia magnètica del material. Acte seguit s’ha procedit a l’estudi espacial i temporal de la transició mitjançant bobines collectores col.locades al llarg de la mostra. Per a la caracterització espacial de les allaus s’han construir un dispositiu format per 3 bobines i un termoparell. Amb les bobines situades al llarg d’una mostra policristal.lina de Manganita per a detectar els canvis de magnetització locals al llarg de la mostra. El senyal del termoparell indica l’instant d’inici de l’allau. Els resultats d’aquesta segona experiència determinen que la transició te lloc en mil.lèsimes de segons i que es propaga des de l’interior de la mostra cap als extrems. En aquesta memòria es troba resumit tot el procés seguit per a la realització del projecte, inclosa la recerca a la literatura prèvia als experiments. Al llarg del projecte s’han utilitzat les unitats de mesura del sistema centímetre-gram-segon (cgs). Primer perquè els aparells de mesura utilitzats en el nostre laboratori utilitzen aquest sistema i segon perquè les expressions matemàtiques es simplifiquen. Els lectors interessats poden trobar una taula de conversió a unitats del Sistema Internacional a l’Apèndix A

Allaus magnètiques en Òxids amb efectes Magnetoresistius Colossals

Aquest és un projecte d’investigació en Ciència de Materials. En aquest projecte s’han intentat caracteritzar de la forma més complerta possible les allaus magnètiques en una família d’òxids amb efectes Magnetoresistius Colossals coneguts com a Manganites. En concret s’ha treballat sobre mostres de La0.225Pr0.4Ca0.375Mn03 i s’han utilitzat aparells de mesura i caracterització magnètica d’alta tecnologia (magnetòmetre SQUID). D’aquesta primera caracterització s’ha conclòs que al refredar les mostres sense camp aplicat s’arriba a un estat metastable. En l’estat metastable hi ha presents dues fases, la fase Antiferromagnètica amb ordenament de càrrega (CO-AFM) i la fase Ferromagnètica sense ordenament de càrrega (CD-FM). La fase CD-FM es la minoritària i es troba en forma de clústers nanomètrics distribuïts al dins de la fase majoritària, fase CD-AFM. S’ha observat que l’aplicació d’un camp magnètic intens provoca una transició de primer ordre (FOPT) en la que el clústers de fase CD-FM creixent ràpidament, quan la transició ha tingut lloc la mostra es totalment CD-FM. Aquest estat es estable en el sentit que un cop es retira el camp la mostra no retorna a l’estat inicial. També s’ha observat que la forma en què té lloc la transició depèn de l’historia magnètica del material. Acte seguit s’ha procedit a l’estudi espacial i temporal de la transició mitjançant bobines collectores col.locades al llarg de la mostra. Per a la caracterització espacial de les allaus s’han construir un dispositiu format per 3 bobines i un termoparell. Amb les bobines situades al llarg d’una mostra policristal.lina de Manganita per a detectar els canvis de magnetització locals al llarg de la mostra. El senyal del termoparell indica l’instant d’inici de l’allau. Els resultats d’aquesta segona experiència determinen que la transició te lloc en mil.lèsimes de segons i que es propaga des de l’interior de la mostra cap als extrems. En aquesta memòria es troba resumit tot el procés seguit per a la realització del projecte, inclosa la recerca a la literatura prèvia als experiments. Al llarg del projecte s’han utilitzat les unitats de mesura del sistema centímetre-gram-segon (cgs). Primer perquè els aparells de mesura utilitzats en el nostre laboratori utilitzen aquest sistema i segon perquè les expressions matemàtiques es simplifiquen. Els lectors interessats poden trobar una taula de conversió a unitats del Sistema Internacional a l’Apèndix A

Topological magnetic irreversibility in superconducting Pb samples of various shapes

The magnetic-field dependence of the magnetization of cylinders, disks, and spheres of pure type-I superconducting lead was investigated by means of isothermal measurements of first magnetization curves and hysteresis cycles. Depending on the geometry of the sample and the direction and intensity of the applied magnetic field, the intermediate state exhibits different irreversible features that become particularly highlighted in minor hysteresis cycles. The irreversibility is noticeably observed in cylinders and disks only when the magnetic field is parallel to the axis of revolution and is very subtle in spheres. When the magnetic field decreases from the normal state, the irreversibility appears at a temperature-dependent value whose distance to the thermodynamic critical field depends on the sample geometry. The irreversible features in the disks are altered when they are submitted to an annealing process. These results agree well with very recent high-resolution magneto-optical experiments in similar materials that were interpreted in terms of transitions between different topological structures for the flux configuration in the intermediate state. A discussion of the relative role of geometrical barriers for flux entry and exit and pinning effects as responsible for the magnetic irreversibility is given

High nonlinear figure-of-merit amorphous silicon waveguides

The nonlinear response of amorphous silicon waveguides is reported and compared to silicon-on-insulator (SOI) samples. The real part of the nonlinear coefficient gamma is measured by four-wave-mixing and the imaginary part of gamma is characterized by measuring the nonlinear loss at different peak powers. The combination of both results yields a two-photon-absorption figure of merit of 4.9, which is more than 7 times higher than for the SOI samples. Time-resolved measurements and simulations confirm the measured nonlinear coefficient $\gamma$ and show the absence of slow free-carrier effects versus ns free-carrier lifetimes in the SOI samples.We acknowledge financial support from the Spanish Ministry of Science and Innovation SINADEC (TEC2008-06333) and PROMETEO/2010/087 NANOFOTONICA projects and Universidad Politecnica de Valencia for PAID2011/1914 and J. Matres' doctoral grant.Matres Abril, J.; Ballesteros García, G.; Gautier, P.; Fedeli, J.; Martí Sendra, J.; Oton Nieto, CJ. (2013). High nonlinear figure-of-merit amorphous silicon waveguides. Optics Express. 21(4):3932-3940. https://doi.org/10.1364/OE.21.003932S39323940214Almeida, V. R., Barrios, C. A., Panepucci, R. R., & Lipson, M. (2004). All-optical control of light on a silicon chip. Nature, 431(7012), 1081-1084. doi:10.1038/nature02921Lee, B. G., Biberman, A., Turner-Foster, A. C., Foster, M. A., Lipson, M., Gaeta, A. L., & Bergman, K. (2009). Demonstration of Broadband Wavelength Conversion at 40 Gb/s in Silicon Waveguides. IEEE Photonics Technology Letters, 21(3), 182-184. doi:10.1109/lpt.2008.2009945Kuyken, B., Clemmen, S., Selvaraja, S. K., Bogaerts, W., Van Thourhout, D., Emplit, P., … Baets, R. (2011). On-chip parametric amplification with 265 dB gain at telecommunication wavelengths using CMOS-compatible hydrogenated amorphous silicon waveguides. Optics Letters, 36(4), 552. doi:10.1364/ol.36.000552Mizrahi, V., Saifi, M. A., Andrejco, M. J., DeLong, K. W., & Stegeman, G. I. (1989). Two-photon absorption as a limitation to all-optical switching. Optics Letters, 14(20), 1140. doi:10.1364/ol.14.001140Narayanan, K., & Preble, S. F. (2010). Optical nonlinearities in hydrogenated-amorphous silicon waveguides. Optics Express, 18(9), 8998. doi:10.1364/oe.18.008998O’Leary, S. K., Johnson, S. R., & Lim, P. K. (1997). The relationship between the distribution of electronic states and the optical absorption spectrum of an amorphous semiconductor: An empirical analysis. Journal of Applied Physics, 82(7), 3334-3340. doi:10.1063/1.365643Kuyken, B., Ji, H., Clemmen, S., Selvaraja, S. K., Hu, H., Pu, M., … Baets, R. (2011). Nonlinear properties of and nonlinear processing in hydrogenated amorphous silicon waveguides. Optics Express, 19(26), B146. doi:10.1364/oe.19.00b146Vallaitis, T., Bogatscher, S., Alloatti, L., Dumon, P., Baets, R., Scimeca, M. L., … Leuthold, J. (2009). Optical properties of highly nonlinear silicon-organic hybrid (SOH) waveguide geometries. Optics Express, 17(20), 17357. doi:10.1364/oe.17.017357Tsu-Te Kung, Ching-Ten Chang, Jeng-Cherng Dung, & Sien Chi. (2003). Four-wave mixing between pump and signal in a distributed raman amplifier. Journal of Lightwave Technology, 21(5), 1164-1170. doi:10.1109/jlt.2003.810929Wu, M., & Way, W. I. (2004). Fiber Nonlinearity Limitations in Ultra-Dense WDM Systems. Journal of Lightwave Technology, 22(6), 1483-1498. doi:10.1109/jlt.2004.829222Mas, S., Matres, J., Marti, J., & Oton, C. J. (2012). Accurate Chromatic Dispersion Characterization of Photonic Integrated Circuits. IEEE Photonics Journal, 4(3), 825-831. doi:10.1109/jphot.2012.2199294Vallaitis, T., Koos, C., Bonk, R., Freude, W., Laemmlin, M., Meuer, C., … Leuthold, J. (2008). Slow and fast dynamics of gain and phase in a quantum dot semiconductor optical amplifier. Optics Express, 16(1), 170. doi:10.1364/oe.16.000170Lin, Q., Painter, O. J., & Agrawal, G. P. (2007). Nonlinear optical phenomena in silicon waveguides: modeling and applications. Optics Express, 15(25), 16604. doi:10.1364/oe.15.016604Matres, J., Lacava, C., Ballesteros, G. C., Minzioni, P., Cristiani, I., Fédéli, J. M., … Oton, C. J. (2012). Low TPA and free-carrier effects in silicon nanocrystal-based horizontal slot waveguides. Optics Express, 20(21), 23838. doi:10.1364/oe.20.023838Koos, C., Jacome, L., Poulton, C., Leuthold, J., & Freude, W. (2007). Nonlinear silicon-on-insulator waveguides for all-optical signal processing. Optics Express, 15(10), 5976. doi:10.1364/oe.15.005976Rukhlenko, I. D., Premaratne, M., & Agrawal, G. P. (2012). Effective mode area and its optimization in silicon-nanocrystal waveguides. Optics Letters, 37(12), 2295. doi:10.1364/ol.37.002295Koos, C., Vorreau, P., Vallaitis, T., Dumon, P., Bogaerts, W., Baets, R., … Leuthold, J. (2009). All-optical high-speed signal processing with silicon–organic hybrid slot waveguides. Nature Photonics, 3(4), 216-219. doi:10.1038/nphoton.2009.2

Magnetic fingerprints of the very fast jumps of colossal magnetoresistance in the phase-separated manganite La0.225Pr0.40Ca0.375MnO3

We found that colossal variations of resistance in La 0.225 Pr 0.40 Ca 0.375 Mn O 3 in about 100 μ s occur simultaneously with magnetic avalanches that last about 1 ms . These findings are interpreted as macroscopic fingerprints of the percolative phase separation upon application of the external magnetic field. Depending on the fraction of the ferromagnetic phase x , the colossal magnetoresistance jumps appear to be caused either by fluctuations of x , accompanied by fast propagation of the magnetic avalanches through the sample, or by a phase transition from charge ordered antiferromagnetic phase to charge delocalized ferromagnetic phase

IAA : Información y actualidad astronómica (45)

Sumario : Cinco décadas estudiando cuásares.-- Un deseo llamado gravedad cuántica.-- DECONSTRUCCIÓN Y otros ENSAYOS. SKA.-- EL “MOBY DICK” DE... Guillem Anglada (IAA).-- CIENCIA EN HISTORIAS...La controvertida historia de los tasaday.-- ACTUALIDAD.-- SALA LIMPIA.-- CIENCIA: PILARES E INCERTIDUMBRES. Galaxias luminosas en el infrarrojo.N

Optical phase characterization of photonic integrated devices

We propose a relatively simple experimental setup, capable of accurately characterizing the optical phase response of an integrated photonic circuit. The setup is based on a phase-noise reduction scheme using an external heterodyne Mach Zehnder interferometer. In particular, we characterize the phase response of different silicon photonic components: under- and over-coupled ring resonators, and a slow-light corrugated waveguide.This work was supported by the Spanish Ministry of Science and Innovation through SINADEC (TEC2008-06333), LEOMIS (TEC2012-38540), and PROMETEO/2010/087 NANOFOTONICA Contracts, Universidad Politecnica de Valencia for PAID2011/1914 and Joaquin Matres FPI Doctoral Grant, and Transatlantic partnership for Excellence in Engineering funded by EU Commission under the Erasmus Mundus Action 2 program.Matres Abril, J.; Ballesteros García, G.; Mas Gómez, SM.; Brimont, ACJ.; Sanchis Kilders, P.; Martí Sendra, J.; Oton Nieto, CJ. (2014). Optical phase characterization of photonic integrated devices. IEEE Journal of Selected Topics in Quantum Electronics. 20(4). https://doi.org/10.1109/JSTQE.2013.2292511S20