Stereospecific and chemoselective copper-catalyzed deaminative silylation of benzylic ammonium triflates

A method for the synthesis of benzylsilanes starting from the corresponding ammonium triflates is reported. Silyl boronic esters are employed as silicon pronucleophiles, and the reaction is catalyzed by copper(I) salts. Enantioenriched benzylic ammonium salts react stereospecifically through an SN2‐type displacement of the ammonium group to afford α‐chiral silanes with inversion of the configuration. A cyclopropyl‐substituted substrate does not undergo ring opening, thus suggesting an ionic reaction mechanism with no benzyl radical intermediate.DFG, 388910461, Ionische und radikalische Kreuzkupplungen zur Kohlenstoff‒Silicium-BindungsknüpfungTU Berlin, Open-Access-Mittel - 201

Variation and fractionation of lithium isotopes within single tourmaline crystals in the pegmatites of the Black Hills, South Dakota

"May 2014."Thesis supervisor: Dr. Peter I. Nabelek.Extremely large elongated crystals, attributed to low nucleation rates and rapid growth during fast cooling (Nabelek et al., 2010), are just one example of the intriguing and unusual disequilibrium features found in granitic pegmatites. Lithium isotope ratios are no exception. Previous studies have shown pegmatites to have signicantly elevated [delta]?�?Li compared to normal crustal values and large variations across individual pegmatite intrusions (Teng et al., 2006, Maloney et al., 2008). Variable and extreme isotope fractionation has been linked to kinetics of crystallization, dierential diusion of [delta]?�?Li and [delta]?�?Li, fractional crystallization, and interaction with fluids. Although a number of isotopic studies of pegmatites exist at the outcrop scale, studies on single crystals are rare. A study by Ludwig et al. (2011) showed a roughly homogenous isotope profile in a tourmaline using secondary ion mass spectroscopy. If, however, Li isotope ratios are in fact variable within individual crystals, the variability has implications for crystallization processes in leucogranite and pegmatite dikes. For this study, tourmaline crystals were collected from several texturally different pegmatite localities in the large, Proterozoic leucogranite-pegmatite field in the Black Hills, SD. Lithium concentrations and isotope ratios were measured at numerous points along the lengths of individual tourmaline crystals. Slices of tourmalines, cut perpendicular to the crystal's long axis, were dissolved by an alkali fusion technique. Concentrations were determined at the University of Missouri using a Perkin-Elmer Optima 3300 ICP-OES. Isotope measurements were performed at University of Maryland-College Park using a Nu Plasma Multi-collector ICP-MS. Purication followed the three-column cation exchange chromatography method (Moriguti and Nakamura, 1998). Mapping of major elements was performed on slices of one sample using the JEOL JXA-8200 Superprobe at Washington University in St. Louis. Results reveal extIncludes bibliographical references (pages 64-72)

Rigorous Derivation of the Gross-Pitaevskii Equation

The time dependent Gross-Pitaevskii equation describes the dynamics of initially trapped Bose-Einstein condensates. We present a rigorous proof of this fact starting from a many-body bosonic Schroedinger equation with a short scale repulsive interaction in the dilute limit. Our proof shows the persistence of an explicit short scale correlation structure in the condensate.Comment: 4 pages, 1 figur

Biodistribution and PET Imaging of pharmacokinetics of manganese in mice using Manganese-52

<div><p>Manganese is essential to life, and humans typically absorb sufficient quantities of this element from a normal healthy diet; however, chronic, elevated ingestion or inhalation of manganese can be neurotoxic, potentially leading to <i>manganism</i>. Although imaging of large amounts of accumulated Mn(II) is possible by MRI, quantitative measurement of the biodistribution of manganese, particularly at the trace level, can be challenging. In this study, we produced the positron-emitting radionuclide ⁵²Mn (<i>t</i>_<i>1/2</i> = 5.6 d) by proton bombardment (<i>E</i>_<i>p</i><15 MeV) of chromium metal, followed by solid-phase isolation by cation-exchange chromatography. An aqueous solution of [⁵²Mn]MnCl₂ was nebulized into a closed chamber with openings through which mice inhaled the aerosol, and a separate cohort of mice received intravenous (IV) injections of [⁵²Mn]MnCl₂. <i>Ex vivo</i> biodistribution was performed at 1 h and 1 d post-injection/inhalation (p.i.). In both trials, we observed uptake in lungs and thyroid at 1 d p.i. Manganese is known to cross the blood-brain barrier, as confirmed in our studies following IV injection (0.86%ID/g, 1 d p.i.) and following inhalation of aerosol, (0.31%ID/g, 1 d p.i.). Uptake in salivary gland and pancreas were observed at 1 d p.i. (0.5 and 0.8%ID/g), but to a much greater degree from IV injection (6.8 and 10%ID/g). In a separate study, mice received IV injection of an imaging dose of [⁵²Mn]MnCl₂, followed by <i>in vivo</i> imaging by positron emission tomography (PET) and <i>ex vivo</i> biodistribution. The results from this study supported many of the results from the biodistribution-only studies. In this work, we have confirmed results in the literature and contributed new results for the biodistribution of inhaled radiomanganese for several organs. Our results could serve as supporting information for environmental and occupational regulations, for designing PET studies utilizing ⁵²Mn, and/or for predicting the biodistribution of manganese-based MR contrast agents.</p></div

Efficient growth of complex graph states via imperfect path erasure

Given a suitably large and well connected (complex) graph state, any quantum algorithm can be implemented purely through local measurements on the individual qubits. Measurements can also be used to create the graph state: Path erasure techniques allow one to entangle multiple qubits by determining only global properties of the qubits. Here, this powerful approach is extended by demonstrating that even imperfect path erasure can produce the required graph states with high efficiency. By characterizing the degree of error in each path erasure attempt, one can subsume the resulting imperfect entanglement into an extended graph state formalism. The subsequent growth of the improper graph state can be guided, through a series of strategic decisions, in such a way as to bound the growth of the error and eventually yield a high-fidelity graph state. As an implementation of these techniques, we develop an analytic model for atom (or atom-like) qubits in mismatched cavities, under the double-heralding entanglement procedure of Barrett and Kok [Phys. Rev. A 71, 060310 (2005)]. Compared to straightforward postselection techniques our protocol offers a dramatic improvement in growing complex high-fidelity graph states.Comment: 15 pages, 10 figures (which print to better quality than when viewed as an on screen pdf