ALBERT

Description: The piezoelectric response of AlGaN/GaN circular HEMT pressure sensing device integrated on AlGaN/GaN diaphragm was experimentally investigated and supported by the finite element method modeling. The 4.2  μ m thick diaphragm with 1500  μ m diameter was loaded by the dynamic peak-to-peak pressure up to 36 kPa at various frequencies. The piezoelectric charge induced on two Schottky gate electrodes of different areas was measured. The frequency independent maximal sensitivity 4.4 pC/kPa of the piezoelectric pressure sensor proposed in a concept of micro-electro-mechanical system was obtained on the gate electrode with larger area. The measurement revealed a linear high performance piezoelectric response in the examined dynamic pressure range.

Description: Author(s): I. Loa, K. Syassen, G. Monaco, G. Vankó, M. Krisch, and M. Hanfland We have measured plasmon energies in Na under high pressure up to 43 GPa using inelastic x-ray scattering (IXS). The momentum-resolved results show clear deviations, growing with increasing pressure, from the predictions for a nearly free-electron metal. Plasmon energy calculations based on first-pr... [Phys. Rev. Lett. 107, 086402] Published Tue Aug 16, 2011

Description: We measured the spin state of iron in magnesium silicate perovskite (Mg(0.9),Fe(0.1))SiO(3) at high pressure and found two electronic transitions occurring at 70 gigapascals and at 120 gigapascals, corresponding to partial and full electron pairing in iron, respectively. The proportion of iron in the low spin state thus grows with depth, increasing the transparency of the mantle in the infrared region, with a maximum at pressures consistent with the D" layer above the core-mantle boundary. The resulting increase in radiative thermal conductivity suggests the existence of nonconvecting layers in the lowermost mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Badro, James -- Rueff, Jean-Pascal -- Vanko, Gyorgy -- Monaco, Giulio -- Fiquet, Guillaume -- Guyot, Francois -- New York, N.Y. -- Science. 2004 Jul 16;305(5682):383-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Mineralogie Cristallographie de Paris (UMR CNRS 7590), Institut de Physique du Globe de Paris, Universite Paris, 6 and 7, 4 Place Jussieu, 75252 Paris, France. james.badro@lmcp.jussieu.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15256667" target="_blank"〉PubMed〈/a〉

Description: We measured the spin state of iron in ferropericlase (Mg0.83Fe0.17)O at high pressure and found a high-spin to low-spin transition occurring in the 60- to 70-gigapascal pressure range, corresponding to depths of 2000 kilometers in Earth's lower mantle. This transition implies that the partition coefficient of iron between ferropericlase and magnesium silicate perovskite, the two main constituents of the lower mantle, may increase by several orders of magnitude, depleting the perovskite phase of its iron. The lower mantle may then be composed of two different layers. The upper layer would consist of a phase mixture with about equal partitioning of iron between magnesium silicate perovskite and ferropericlase, whereas the lower layer would consist of almost iron-free perovskite and iron-rich ferropericlase. This stratification is likely to have profound implications for the transport properties of Earth's lowermost mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Badro, James -- Fiquet, Guillaume -- Guyot, Francois -- Rueff, Jean-Pascal -- Struzhkin, Viktor V -- Vanko, Gyorgy -- Monaco, Giulio -- New York, N.Y. -- Science. 2003 May 2;300(5620):789-91. Epub 2003 Apr 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Mine Universite ralogie-Cristallographie de Paris, Universite Paris VI, Universite Paris 7, CNRS, IPGP, 4 place Jussieu, F-75252 Paris Cedex 05, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12677070" target="_blank"〉PubMed〈/a〉

Description: Although WASP-14 b is one of the most massive and densest exoplanets on a tight and eccentric orbit, it has never been a target of photometric follow-up monitoring or dedicated observing campaigns. We report on new photometric transit observations of WASP-14 b obtained within the framework of Transit Timing Variations @ Young Exoplanet Transit Initiative (TTV@YETI). We collected 19 light curves of 13 individual transit events using six telescopes located in five observatories distributed in Europe and Asia. From light-curve modelling, we determined the planetary, stellar, and geometrical properties of the system and found them in agreement with the values from the discovery paper. A test of the robustness of the transit times revealed that in case of a non-reproducible transit shape the uncertainties may be underestimated even with a wavelet-based error estimation methods. For the timing analysis, we included two publicly available transit times from 2007 and 2009. The long observation period of seven years (2007–2013) allowed us to refine the transit ephemeris. We derived an orbital period 1.2 s longer and 10 times more precise than the one given in the discovery paper. We found no significant periodic signal in the timing-residuals and, hence, no evidence for TTV in the system.

Description: Crucial to many light-driven processes in transition metal complexes is the absorption and dissipation of energy by 3d electrons. But a detailed understanding of such non-equilibrium excited-state dynamics and their interplay with structural changes is challenging: a multitude of excited states and possible transitions result in phenomena too complex to unravel when faced with the indirect sensitivity of optical spectroscopy to spin dynamics and the flux limitations of ultrafast X-ray sources. Such a situation exists for archetypal polypyridyl iron complexes, such as [Fe(2,2'-bipyridine)3](2+), where the excited-state charge and spin dynamics involved in the transition from a low- to a high-spin state (spin crossover) have long been a source of interest and controversy. Here we demonstrate that femtosecond resolution X-ray fluorescence spectroscopy, with its sensitivity to spin state, can elucidate the spin crossover dynamics of [Fe(2,2'-bipyridine)3](2+) on photoinduced metal-to-ligand charge transfer excitation. We are able to track the charge and spin dynamics, and establish the critical role of intermediate spin states in the crossover mechanism. We anticipate that these capabilities will make our method a valuable tool for mapping in unprecedented detail the fundamental electronic excited-state dynamics that underpin many useful light-triggered molecular phenomena involving 3d transition metal complexes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, Wenkai -- Alonso-Mori, Roberto -- Bergmann, Uwe -- Bressler, Christian -- Chollet, Matthieu -- Galler, Andreas -- Gawelda, Wojciech -- Hadt, Ryan G -- Hartsock, Robert W -- Kroll, Thomas -- Kjaer, Kasper S -- Kubicek, Katharina -- Lemke, Henrik T -- Liang, Huiyang W -- Meyer, Drew A -- Nielsen, Martin M -- Purser, Carola -- Robinson, Joseph S -- Solomon, Edward I -- Sun, Zheng -- Sokaras, Dimosthenis -- van Driel, Tim B -- Vanko, Gyorgy -- Weng, Tsu-Chien -- Zhu, Diling -- Gaffney, Kelly J -- P41 GM103393/GM/NIGMS NIH HHS/ -- P41 RR001209/RR/NCRR NIH HHS/ -- England -- Nature. 2014 May 15;509(7500):345-8. doi: 10.1038/nature13252. Epub 2014 May 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA. ; LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA. ; European XFEL, D-22761 Hamburg, Germany. ; Department of Chemistry, Stanford University, Stanford, California 94305, USA. ; 1] PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA [2] Department of Chemistry, Stanford University, Stanford, California 94305, USA. ; 1] Centre for Molecular Movies, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark [2] Centre for Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark. ; 1] Max Planck Institute for Biophysical Chemistry, 37077 Gottingen, Germany [2] Deutsches Elektronen Synchrotron, Notkestrasse 85, 22607 Hamburg, Germany. ; Centre for Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark. ; 1] Department of Chemistry, Stanford University, Stanford, California 94305, USA [2] SSRL, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA. ; SSRL, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA. ; Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24805234" target="_blank"〉PubMed〈/a〉

Description: Mineral properties in Earth's lower mantle are affected by iron electronic states, but representative pressures and temperatures have not yet been probed. Spin states of iron in lower-mantle ferropericlase have been measured up to 95 gigapascals and 2000 kelvin with x-ray emission in a laser-heated diamond cell. A gradual spin transition of iron occurs over a pressure-temperature range extending from about 1000 kilometers in depth and 1900 kelvin to 2200 kilometers and 2300 kelvin in the lower mantle. Because low-spin ferropericlase exhibits higher density and faster sound velocities relative to the high-spin ferropericlase, the observed increase in low-spin (Mg,Fe)O at mid-lower mantle conditions would manifest seismically as a lower-mantle spin transition zone characterized by a steeper-than-normal density gradient.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lin, Jung-Fu -- Vanko, Gyorgy -- Jacobsen, Steven D -- Iota, Valentin -- Struzhkin, Viktor V -- Prakapenka, Vitali B -- Kuznetsov, Alexei -- Yoo, Choong-Shik -- New York, N.Y. -- Science. 2007 Sep 21;317(5845):1740-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lawrence Livermore National Laboratory (LLNL), 7000 East Avenue, Livermore, CA 94550, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17885134" target="_blank"〉PubMed〈/a〉