Three-minute oscillations above sunspot umbra observed with SDO/AIA and NoRH

Three-minute oscillations over sunspot's umbra in AR 11131 were observed simultaneously in UV/EUV emission by SDO/AIA and in radio emission by Nobeyama Radioheliograph (NoRH). We use 24-hours series of SDO and 8-hours series of NoRH observations to study spectral, spatial and temporal variations of pulsations in the 5-9 mHz frequency range at different layers of the solar atmosphere. High spatial and temporal resolution of SDO/AIA in combination with long-duration observations allowed us to trace the variations of the cut-off frequency and spectrum of oscillations across the umbra. We found that higher frequency oscillations are more pronounced closer to the umbra's center, while the lower frequencies concentrate to the peripheral parts. We interpreted this discovery as a manifestation of variation of the magnetic field inclination across the umbra at the level of temperature-minimum. Possible implications of this interpretation for the diagnostics of sunspot atmospheres is discussed.Comment: 29 pages, 7 figures, in press ApJ, 201

Charge Imbalance Effects on Interlayer Hopping and Fermi Surfaces in Multilayered High-T_c Cuprates

We study doping dependence of interlayer hoppings, t_\perp, in multilayered cuprates with four or more CuO_2 planes in a unit cell. When the double occupancy is forbidden in the plane, an effective amplitude of t_\perp in the Gutzwiller approximation is shown to be proportional to the square root of the product of doping rates in adjacent two planes, i.e., t^eff_\perp \propto t_\perp \sqrt{\delta_1\delta_2}, where \delta_1 and \delta_2 represent the doping rates of the two planes. More than three-layered cuprates have two kinds of \cuo planes, i.e., inner- and outer planes (IP and OP), resulting in two different values of t^eff_{\perp}, i.e., t^eff_\perp 1 \propto t_\perp \sqrt{\delta_IP \delta_IP} between IP's, and t^eff_\perp 2 \propto t_\perp \sqrt{\delta_IP \delta_OP} between IP and OP. Fermi surfaces are calculated in the four-layered t-t'-t''-J model by the mean-field theory. The order parameters, the renormalization factor of t_\perp, and the site-potential making the charge imbalance between IP and OP are self-consistently determined for several doping rates. We show the interlayer splitting of the Fermi surfaces, which may be observed in the angle resolved photoemission spectroscopy measurement.Comment: Some typographical errors are revised. Journal of Physical Society of Japan, Vol.75, No.3, in pres

A systematic review of the literature on digital transformation: insights and implications for strategy and organizational change

In this article we provide a systematic review of the extensive yet diverse and fragmented literature on digital transformation (DT), with the goal of clarifying boundary conditions to investigate the phenomenon from the perspective of organizational change. On the basis of 279 articles, we provide a multi-dimensional framework synthesizing what is known about DT and discern two important thematical patterns: DT is moving firms to malleable organizational designs that enable continuous adaptation, and this move is embedded in and driven by digital business ecosystems. From these two patterns, we derive four perspectives on the phenomenon of DT: technology impact, compartmentalized adaptation, systemic shift and holistic co-evolution. Linking our findings and interpretations to existing work, we find that the nature of DT is only partially covered by conventional frameworks on organizational change. On the basis of this analysis, we derive a research agenda and provide managerial implications for strategy and organizational change.info:eu-repo/semantics/publishedVersio

Thermally-activated cation ordering in ZnGa2Se4 single crystals studied by Raman scattering, optical absorption, and ab initio calculations

Order-disorder phase transitions induced by thermal annealing have been studied in the ordered-vacancy compound ZnGa2Se4 by means of Raman scattering and optical absorption measurements. The partially disordered as-grown sample with tetragonal defect stannite (DS) structure and I (4) over bar 2m space group has been subjected to controlled heating and cooling cycles. In situ Raman scattering measurements carried out during the whole annealing cycle show that annealing the sample to 400 degrees C results in a cation ordering in the sample, leading to the crystallization of the ordered tetragonal defect chalcopyrite (DC) structure with I (4) over bar space group. On decreasing temperature the ordered cation scheme of the DC phase can be retained at ambient conditions. The symmetry of the Raman-active modes in both DS and DC phases is discussed and the similarities and differences between the Raman spectra of the two phases emphasized. The ordered structure of annealed samples is confirmed by optical absorption measurements and ab initio calculations, that show that the direct bandgap of DC-ZnGa2Se4 is larger than that of DS-ZnGa2Se4.This study was supported by the Spanish government MEC under grants MAT2010-21270-C04-01/03/04 and MAT2010-19837-C06-06, by MALTA Consolider Ingenio 2010 project (CSD2007-00045), and by the Vicerrectorado de Investigacion y Desarrollo of the Universitat Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). EP-G, AM, and PR-H acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster. Finally, the authors would also like to acknowledge M C Moron for stimulating discussions and revision of the present manuscript.Vilaplana Cerda, RI.; Gomis Hilario, O.; Pérez-González, E.; Ortiz, HM.; Manjón Herrera, FJ.; Rodríguez-Hernández, P.; Muñoz, A.... (2013). Thermally-activated cation ordering in ZnGa2Se4 single crystals studied by Raman scattering, optical absorption, and ab initio calculations. Journal of Physics: Condensed Matter. 25(16):165802-1-165802-11. https://doi.org/10.1088/0953-8984/25/16/165802S165802-1165802-112516Bernard, J. E., & Zunger, A. (1988). Ordered-vacancy-compound semiconductors: PseudocubicCdIn2Se4. Physical Review B, 37(12), 6835-6856. doi:10.1103/physrevb.37.6835Jiang, X., & Lambrecht, W. R. L. (2004). Electronic band structure of ordered vacancy defect chalcopyrite compounds with formulaII−III2−VI4. Physical Review B, 69(3). doi:10.1103/physrevb.69.035201Yahia, I. S., Fadel, M., Sakr, G. B., & Shenouda, S. S. (2010). Memory switching of ZnGa2Se4 thin films as a new material for phase change memories (PCMs). Journal of Alloys and Compounds, 507(2), 551-556. doi:10.1016/j.jallcom.2010.08.021Yahia, I. S., Fadel, M., Sakr, G. B., Yakuphanoglu, F., Shenouda, S. S., & Farooq, W. A. (2011). Analysis of current–voltage characteristics of Al/p-ZnGa2Se4/n-Si nanocrystalline heterojunction diode. Journal of Alloys and Compounds, 509(12), 4414-4419. doi:10.1016/j.jallcom.2011.01.068Hahn, H., Frank, G., Klingler, W., St�rger, A. D., & St�rger, G. (1955). Untersuchungen �ber tern�re Chalkogenide. VI. �ber Tern�re Chalkogenide des Aluminiums, Galliums und Indiums mit Zink, Cadmium und Quecksilber. Zeitschrift f�r anorganische und allgemeine Chemie, 279(5-6), 241-270. doi:10.1002/zaac.19552790502Errandonea, D., Kumar, R. S., Manjón, F. J., Ursaki, V. V., & Tiginyanu, I. M. (2008). High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4. Journal of Applied Physics, 104(6), 063524. doi:10.1063/1.2981089Morón, M. C., & Hull, S. (2003). Order-disorder phase transition inZn1−xMnxGa2Se4: Long-range order parameter versusx. Physical Review B, 67(12). doi:10.1103/physrevb.67.125208Morón, M. C., & Hull, S. (2005). Effect of magnetic dilution in Zn1−xMnxGa2Se4 (0<x<0.5). Journal of Applied Physics, 98(1), 013904. doi:10.1063/1.1944220Morón, M. C., & Hull, S. (2007). The influence of magnetic dilution in the Zn1−xMnxGa2Se4 series with 0.5<x⩽1. Journal of Applied Physics, 102(3), 033919. doi:10.1063/1.2767273Antonioli, G., Lottici, P. P., & Razzetti, C. (1989). The structure of the defect chalcopyrite ZnGa2Se4 studied by EXAFS. physica status solidi (b), 152(1), 39-49. doi:10.1002/pssb.2221520104Haeuseler, H. (1978). FIR- und Ramanspektren von ternären Chalkogeniden des Galliums und Indiums mit Zink, Cadmium und Quecksilber. Journal of Solid State Chemistry, 26(4), 367-376. doi:10.1016/0022-4596(78)90171-8Eifler, A., Krauss, G., Riede, V., Krämer, V., & Grill, W. (2005). Optical phonon modes and structure of ZnGa2Se4 and ZnGa2S4. Journal of Physics and Chemistry of Solids, 66(11), 2052-2057. doi:10.1016/j.jpcs.2005.09.049Lottici, P. P., & Razzetti, C. (1983). A comparison of the raman spectra of ZnGa2Se4 and other gallium defect chalcopyrites. Solid State Communications, 46(9), 681-684. doi:10.1016/0038-1098(83)90506-9Razzetti, C., Lottici, P. P., & Antonioli, G. (1987). Structure and lattice dynamics of nonmagnetic defective AIIBIII2XIV4 compounds and alloys. Progress in Crystal Growth and Characterization, 15(1), 43-73. doi:10.1016/0146-3535(87)90009-8Attolini, G., Bini, S., Lottici, P. P., & Razzetti, C. (1992). Effects of Group III Cation Substitution in the Raman Spectra of Some Defective Chalcopyrites. Crystal Research and Technology, 27(5), 685-690. doi:10.1002/crat.2170270519Takahashi, Y., Namatsu, H., Machida, K., & Minegishi, K. (1993). Measurements of Diffusion Coefficiens of Water in Electron Cryclotron Resonance Plasma SiO2. Japanese Journal of Applied Physics, 32(Part 2, No. 3B), L431-L433. doi:10.1143/jjap.32.l431Ursaki, V. V., Burlakov, I. I., Tiginyanu, I. M., Raptis, Y. S., Anastassakis, E., & Anedda, A. (1999). Phase transitions in defect chalcopyrite compounds under hydrostatic pressure. Physical Review B, 59(1), 257-268. doi:10.1103/physrevb.59.257Allakhverdiev, K., Gashimzade, F., Kerimova, T., Mitani, T., Naitou, T., Matsuishi, K., & Onari, S. (2003). Raman scattering under pressure in ZnGa2Se4. Journal of Physics and Chemistry of Solids, 64(9-10), 1597-1601. doi:10.1016/s0022-3697(03)00077-5Alonso-Gutiérrez, P., Sanjuán, M. L., & Morón, M. C. (2009). Thermally activated cation ordering in Zn0.5Mn0.5Ga2Se4single crystals studied by Raman scattering. physica status solidi (c), 6(5), 1182-1186. doi:10.1002/pssc.200881218Caldera, D., Morocoima, M., Quintero, M., Rincon, C., Casanova, R., & Grima, P. (2011). On the crystal structure of the defective ternary compound. Solid State Communications, 151(3), 212-215. doi:10.1016/j.ssc.2010.11.031Gomis, O., Vilaplana, R., Manjón, F. J., Pérez-González, E., López-Solano, J., Rodríguez-Hernández, P., … Ursaki, V. V. (2012). High-pressure optical and vibrational properties of CdGa2Se4: Order-disorder processes in adamantine compounds. Journal of Applied Physics, 111(1), 013518. doi:10.1063/1.3675162Eifler, A., Hecht, J.-D., Lippold, G., Riede, V., Grill, W., Krauß, G., & Krämer, V. (1999). Combined infrared and Raman study of the optical phonons of defect chalcopyrite single crystals. Physica B: Condensed Matter, 263-264, 806-808. doi:10.1016/s0921-4526(98)01292-7Sanjuán, M. L., & Morón, M. C. (2002). Raman study of Zn1−xMnxGa2Se4 diluted magnetic semiconductors: disorder and resonance effects. Physica B: Condensed Matter, 316-317, 565-567. doi:10.1016/s0921-4526(02)00574-4Letoullec, R., Pinceaux, J. P., & Loubeyre, P. (1988). The membrane diamond anvil cell: A new device for generating continuous pressure and temperature variations. High Pressure Research, 1(1), 77-90. doi:10.1080/08957958808202482Perdew, J. P., Burke, K., & Ernzerhof, M. (1997). Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)]. Physical Review Letters, 78(7), 1396-1396. doi:10.1103/physrevlett.78.1396Manjón, F. J., Gomis, O., Rodríguez-Hernández, P., Pérez-González, E., Muñoz, A., Errandonea, D., … Ursaki, V. V. (2010). Nonlinear pressure dependence of the direct band gap in adamantine ordered-vacancy compounds. Physical Review B, 81(19). doi:10.1103/physrevb.81.195201Santamaría-Pérez, D., Amboage, M., Manjón, F. J., Errandonea, D., Muñoz, A., Rodríguez-Hernández, P., … Tiginyanu, I. M. (2012). Crystal Chemistry of CdIn2S4, MgIn2S4, and MnIn2S4 Thiospinels under High Pressure. The Journal of Physical Chemistry C, 116(26), 14078-14087. doi:10.1021/jp303164kBaroni, S., de Gironcoli, S., Dal Corso, A., & Giannozzi, P. (2001). Phonons and related crystal properties from density-functional perturbation theory. Reviews of Modern Physics, 73(2), 515-562. doi:10.1103/revmodphys.73.515Giannozzi, P., Baroni, S., Bonini, N., Calandra, M., Car, R., Cavazzoni, C., … Wentzcovitch, R. M. (2009). QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials. Journal of Physics: Condensed Matter, 21(39), 395502. doi:10.1088/0953-8984/21/39/395502Kroumova, E., Aroyo, M. I., Perez-Mato, J. M., Kirov, A., Capillas, C., Ivantchev, S., & Wondratschek, H. (2003). Bilbao Crystallographic Server : Useful Databases and Tools for Phase-Transition Studies. Phase Transitions, 76(1-2), 155-170. doi:10.1080/0141159031000076110Loudon, R. (1964). The Raman effect in crystals. Advances in Physics, 13(52), 423-482. doi:10.1080/00018736400101051Alonso-Gutiérrez, P., & Sanjuán, M. L. (2008). Ordinary and extraordinary phonons and photons: Raman study of anisotropy effects in the polar modes ofMnGa2Se4. Physical Review B, 78(4). doi:10.1103/physrevb.78.045212Manjón, F. J., Marí, B., Serrano, J., & Romero, A. H. (2005). Silent Raman modes in zinc oxide and related nitrides. Journal of Applied Physics, 97(5), 053516. doi:10.1063/1.1856222Garbato, L., Ledda, F., & Rucci, A. (1987). Structural distortions and polymorphic behaviour in ABC2 and AB2C4 tetrahedral compounds. Progress in Crystal Growth and Characterization, 15(1), 1-41. doi:10.1016/0146-3535(87)90008-6Grzechnik, A., Ursaki, V. V., Syassen, K., Loa, I., Tiginyanu, I. M., & Hanfland, M. (2001). Pressure-Induced Phase Transitions in Cadmium Thiogallate CdGa2Se4. Journal of Solid State Chemistry, 160(1), 205-211. doi:10.1006/jssc.2001.9224Marquina, J., Power, C., Grima, P., Morocoima, M., Quintero, M., Couzinet, B., … González, J. (2006). Crystallographic properties of the MnGa2Se4 compound under high pressure. Journal of Applied Physics, 100(9), 093513. doi:10.1063/1.2358826Meenakshi, S., Vijayakumar, V., Eifler, A., & Hochheimer, H. D. (2010). Pressure-induced phase transition in defect Chalcopyrites HgAl2Se4 and CdAl2S4. 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Genome-Wide Profiling of H3K56 Acetylation and Transcription Factor Binding Sites in Human Adipocytes

The growing epidemic of obesity and metabolic diseases calls for a better understanding of adipocyte biology. The regulation of transcription in adipocytes is particularly important, as it is a target for several therapeutic approaches. Transcriptional outcomes are influenced by both histone modifications and transcription factor binding. Although the epigenetic states and binding sites of several important transcription factors have been profiled in the mouse 3T3-L1 cell line, such data are lacking in human adipocytes. In this study, we identified H3K56 acetylation sites in human adipocytes derived from mesenchymal stem cells. H3K56 is acetylated by CBP and p300, and deacetylated by SIRT1, all are proteins with important roles in diabetes and insulin signaling. We found that while almost half of the genome shows signs of H3K56 acetylation, the highest level of H3K56 acetylation is associated with transcription factors and proteins in the adipokine signaling and Type II Diabetes pathways. In order to discover the transcription factors that recruit acetyltransferases and deacetylases to sites of H3K56 acetylation, we analyzed DNA sequences near H3K56 acetylated regions and found that the E2F recognition sequence was enriched. Using chromatin immunoprecipitation followed by high-throughput sequencing, we confirmed that genes bound by E2F4, as well as those by HSF-1 and C/EBPα, have higher than expected levels of H3K56 acetylation, and that the transcription factor binding sites and acetylation sites are often adjacent but rarely overlap. We also discovered a significant difference between bound targets of C/EBPα in 3T3-L1 and human adipocytes, highlighting the need to construct species-specific epigenetic and transcription factor binding site maps. This is the first genome-wide profile of H3K56 acetylation, E2F4, C/EBPα and HSF-1 binding in human adipocytes, and will serve as an important resource for better understanding adipocyte transcriptional regulation.Singapore. Agency for Science, Technology and Research (National Science Scholarship )Massachusetts Institute of Technology (Eugene Bell Career Development Chair)National Science Foundation (U.S.) (Award No. DBI-0821391)Pfizer Inc

The Fission Yeast Stress-Responsive MAPK Pathway Promotes Meiosis via the Phosphorylation of Pol II CTD in Response to Environmental and Feedback Cues

The RRM-type RNA-binding protein Mei2 is a master regulator of meiosis in fission yeast, in which it stabilizes meiosis-specific mRNAs by blocking their destruction. Artificial activation of Mei2 can provoke the entire meiotic process, and it is suspected that Mei2 may do more than the stabilization of meiosis-specific mRNAs. In our current study using a new screening system, we show that Mei2 genetically interacts with subunits of CTDK-I, which phosphorylates serine-2 residues on the C-terminal domain of RNA polymerase II (Pol II CTD). Phosphorylation of CTD Ser-2 is essential to enable the robust transcription of ste11, which encodes an HMG-type transcription factor that regulates the expression of mei2 and other genes necessary for sexual development. CTD Ser-2 phosphorylation increases under nitrogen starvation, and the stress-responsive MAP kinase pathway, mediated by Wis1 MAPKK and Sty1 MAPK, is critical for this stress response. Sty1 phosphorylates Lsk1, the catalytic subunit of CTDK-I. Furthermore, a feedback loop stemming from activated Mei2 to Win1 and Wis4 MAPKKKs operates in this pathway and eventually enhances CTD Ser-2 phosphorylation and ste11 transcription. Hence, in addition to starting meiosis, Mei2 functions to reinforce the commitment to it, once cells have entered this process. This study also demonstrates clearly that the stress-responsive MAP kinase pathway can modulates gene expression through phosphorylation of Pol II CTD

A Buoyancy-Based Screen of Drosophila Larvae for Fat-Storage Mutants Reveals a Role for Sir2 in Coupling Fat Storage to Nutrient Availability

Obesity has a strong genetic component, but few of the genes that predispose to obesity are known. Genetic screens in invertebrates have the potential to identify genes and pathways that regulate the levels of stored fat, many of which are likely to be conserved in humans. To facilitate such screens, we have developed a simple buoyancy-based screening method for identifying mutant Drosophila larvae with increased levels of stored fat. Using this approach, we have identified 66 genes that when mutated increase organismal fat levels. Among these was a sirtuin family member, Sir2. Sirtuins regulate the storage and metabolism of carbohydrates and lipids by deacetylating key regulatory proteins. However, since mammalian sirtuins function in many tissues in different ways, it has been difficult to define their role in energy homeostasis accurately under normal feeding conditions. We show that knockdown of Sir2 in the larval fat body results in increased fat levels. Moreover, using genetic mosaics, we demonstrate that Sir2 restricts fat accumulation in individual cells of the fat body in a cell-autonomous manner. Consistent with this function, changes in the expression of metabolic enzymes in Sir2 mutants point to a shift away from catabolism. Surprisingly, although Sir2 is typically upregulated under conditions of starvation, Sir2 mutant larvae survive better than wild type under conditions of amino-acid starvation as long as sugars are provided. Our findings point to a Sir2-mediated pathway that activates a catabolic response to amino-acid starvation irrespective of the sugar content of the diet

Structural and vibrational properties of CdAl2S4 under high pressure: Experimental and theoretical approach

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jp5037926.”The behavior of defect chalcopyrite CdAl2S4 at high pressures and ambient temperature has been investigated in a joint experimental and theoretical study. High-pressure X-ray diffraction and Raman scattering measurements were complemented with theoretical ab initio calculations. The equation of state and pressure dependences of the structural parameters of CdAl2S4 were determined and compared to those of other AB(2)X(4) ordered-vacancy compounds. The pressure dependence of the Raman-active mode frequencies is reported, as well as the theoretical phonon dispersion curves and phonon density of states at 1 atm. Our measurements suggest that defect chalcopyrite CdAl2S4 undergoes a phase transition above 15 GPa to a disordered-rocksalt structure, whose equation of state was also obtained up to 25 GPa. In a downstroke from 25 GPa to 1 atm, our measurements indicate that CdAl2S4 does not return to the defect chalcopyrite phase; it partially retains the disordered-rocksalt phase and partially transforms into the spinel structure. The nature of the spinel structure was confirmed by the good agreement of our experimental results with our theoretical calculations. All in all, our experimental and theoretical results provide evidence that the spinel and defect chalcopyrite phases of CdAl2S4 are competitive at 1 atm. This result opens the way to the synthesis of spinel-type CdAl2S4 at near-ambient conditions.Financial support from the Spanish Consolider Ingenio 2010 Program (Project CSD2007-00045) is acknowledged. This work was also supported by Spanish MICCIN under Project MAT2010-21270-C04-03/04 and by Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia under Projects UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11. Supercomputer time was provided by the Red Espanola de Supercomputacion (RES) and the MALTA cluster. J.A.S. acknowledges the Juan de la Cierva fellowship program for financial support. AM. and P.R.-H. acknowledge S. Munoz Rodriguez for providing a data-parsing application.Sans Tresserras, JÁ.; Santamaría Pérez, D.; Popescu, C.; Gomis, O.; Manjón Herrera, FJ.; Vilaplana Cerda, RI.; Muñoz, A.... (2014). Structural and vibrational properties of CdAl2S4 under high pressure: Experimental and theoretical approach. Journal of Physical Chemistry C. 118(28):15363-15374. https://doi.org/10.1021/jp5037926S15363153741182