Showing papers by "Tolek Tyliszczak published in 2009"

A comparison of 4f vs 5f metal-metal bonds in (CpSiMe3)3M-ECp* (M = Nd, U; E = Al, Ga; Cp* = C5Me5): synthesis, thermodynamics, magnetism, and electronic structure.

Abstract: Reaction of (CpSiMe3)3U or (CpSiMe3)3Nd with (Cp*Al)4 or Cp*Ga (Cp* = C5Me5) afforded the isostructural complexes (CpSiMe3)3M−ECp* (M = U, E = Al (1); M = U, E = Ga (2); M = Nd, E = Al (3); M = Nd, E = Ga (4)). In the case of 1 and 2 the complexes were isolated in 39 and 90% yields, respectively, as crystalline solids and were characterized by single-crystal X-ray diffraction, variable-temperature 1H NMR spectroscopy, elemental analysis, variable-temperature magnetic susceptibility, and UV−visible−NIR spectroscopy. In the case of 3 and 4, the complexes were observed by variable-temperature 1H NMR spectroscopy but were not isolated as pure materials. Comparison of the equilibrium constants and thermodynamic parameters ΔH and ΔS obtained by 1H NMR titration methods revealed a much stronger U−Ga interaction in 2 than the Nd−Ga interaction in 4. Competition reactions between (CpSiMe3)3U and (CpSiMe3)3Nd indicate that Cp*Ga selectively binds U over Nd in a 93:7 ratio at 19 °C and 96:4 at −33 °C. For 1 and 3, c...

Microbial architecture of environmental sulfur processes: a novel syntrophic sulfur-metabolizing consortia.

Abstract: Microbial oxidation of sulfur-rich mining waste materials drives acid mine drainage (AMD) and affects the global sulfur biogeochemical cycle. The generation of AMD is a complex, dynamic process that proceeds via multiple reaction pathways. The role of natural consortia of microbes in AMD generation, however, has received very little attention despite their widespread occurrence in mining environments. Through a combination of geochemical experimentation and modeling, scanning transmission X-ray microscopy, and fluorescent in situ hybridization, we show a novel interdependent metabolic arrangement of two ubiquitous and abundant AMD bacteria: chemoautotrophic sulfur-oxidizing Acidithiobacillus sp. and heterotrophic Acidiphilium sp. Highly reminiscent of anaerobic methane oxidation (AOM) consortia, these bacteria are spatially segregated within a planktonic macrostructure of extracellular polymeric substance in which they syntrophically couple sulfur oxidation and reduction reactions in a mutually beneficial arrangement that regenerates their respective sulfur substrates. As discussed here, the geochemical impacts of microbial metabolism are linked to the consortial organization and development of the pod structure, which affects cell-cell interactions and interactions with the surrounding geochemical microenvironment. If these pods are widespread in mine waters, echoing the now widespread discovery of AOM consortia, then AMD-driven CO(2) atmospheric fluxes from H(2)SO(4) carbonate weathering could be reduced by as much as 26 TgC/yr. This novel sulfur consortial discovery indicates that organized metabolically linked microbial partnerships are likely widespread and more significant in global elemental cycling than previously considered.

Time-resolved x-ray imaging of magnetization dynamics in spin-transfer torque devices

Abstract: Time-resolved x-ray imaging techniques have recently demonstrated the capability to probe the magnetic switching of nanoscale devices. This technique has enabled, for example, the direct observation of the nonuniform intermediate states assumed by the magnetic free layer during reversal by a spin-polarized current. These experiments have shown an interesting size-dependent behavior associated with the motion of vortices to mediate the magnetization reversal which cannot be explained by the macrospin picture of spin-torque switching. In this paper we present both experimental and analytical results which show the origin of the complex switching behavior. We use time-resolved x-ray microscopy to further study the switching behavior of samples with $45\ifmmode^\circ\else\textdegree\fi{}$ angle between the free and polarizing magnetic layers. A model is developed in terms of a linearized Landau-Lifshitz-Gilbert equation showing that the initial dynamics is dominated by the balance between the Oersted field and thermal fluctuations. The spin torque amplifies this dynamics, leading to a strong sensitivity to sample size, angle, and temperature. The model is in good agreement with current and previous experimental observations.

Soft X-ray beam induced current technique

Abstract: Direct mapping of the charge transport efficiency of polymer solar cell devices using a soft X-ray beam induced current (SoXBIC) method is described. By fabricating a polymer solar cell on an x-ray transparent substrate, we demonstrate the ability to map polymer composition and nanoscale structure within an operating solar cell device and to simultaneously measure the local charge transport efficiency via the short-circuit current. A simple model is calculated and compared to experimental SoXBIC data of a PFB:F8BT bulk-heterojunction device in order to gain greater insight into the device operation and physics.

Fission processes following core level excitation in closo-1,2-orthocarborane

Abstract: Time-of-flight mass analysis with multi-stop coincidence detection was used to study the multi-cation ionic fragmentation of the closo carborane cage molecule closo -1,2-orthocarborane (C2B10H12) following inner-shell excitation in or above the B 1s regime. Electron ion coincidence spectra reveal the cationic products which are formed after core level excitation. Distinct changes in fragmentation pattern are observed as a function of excitation energy. Photoelectron–photoion–photoion coincidence (PEPIPICO) spectroscopy was used to study the dominant fission routes in the core level excitation regime. Series of ion pairs are identified, where asymmetric fission dominates, leading to ion pairs of different mass. Suitable fission and fragmentation mechanisms are discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

High Velocity van de Graaf Shots of Mineral Dust : Application to in Situ Space Missions

Abstract: MINERAL DUST: APPLICATION TO IN SITU SPACE MISSIONS. F. Postberg, M. Trieloff, R. Srama, J.K. Hillier, Z. Gainsforth, A.J. Westphal, S. Bugiel, E. Grün, S. Armes, A. Kearsley, T. Tyliszczak, W.H. Schwarz, Institut für Geowissenschaften, Ruprecht-Karls-Universität Heidelberg, D69120 Heidelberg, Germany. E-mail: frank.postberg@mpihd.mpg.de. Max-Planck-Institut für Kernphysik, D-69117 Heidelberg, Germany 3 PSSRI, Open University, Milton Keynes, MK7 6AA, UK. Space Sciences Laboratory, U. C. Berkeley, USA. Dept. of Chemistry University of Sheffield, Sheffield, S3 7HF, UK IARC, Dept. of Mineralogy, The Natural History Museum, UK. Advanced Light Source, Lawrence Berkeley Laboratory, USA.