Synthesis, Stability, and Reactivity of High-Oxidation-State Pentamethylcyclopentadienyl Acetamidinate Beta-Hydride- or Beta-Methide-Bearing Alkyl Complexes of Zirconium, Titanium, and Tantalum

In the course of study into the stability and reactivity of early transition metal (TM) complexes, it has been further confirmed that the pentamethylcyclopentadienyl acetamidinate ligand set is particularly apt for the stabilization of early TM-alkyl species. The first examples of a solid state structure of cyclobutylmethyl complexes were obtained, after pentamethylcyclopentadienylacetamidinatezirconium (Cp*ZA) cyclobutylmethyl compounds were prepared via hydrozirconation of methylenecyclobutane. The ring opening of neutral and cationic cyclobutylmethyl Cp*ZAs and the conformation of the product pendant olefin pentenyl cation were studied via selective neuclear Overhouser effect (nOe) confirming that the pendant olefin was coordinated to the cationic Zr center. To further study the properties of pendant olefin complexes, a methyl butenyl Cp*ZA complex was prepared, and was observed to convert to a Cp*ZA butadiene complex, presumably via a beta-H abstraction by the metal-based methyl group. The reactivity of the first known non-base stabilized n2-styrene zirconium complex, supported by the Cp* acetamidinate ligands, was studied with olefins, 1,3-butadienes, and 2-butyne. It was shown that the initial products of α-olefin insertion into the n2-styrene complex are saturated zirconacyclopentanes that can then undergo a dehydrogenation producing H2 and a Cp*ZA butadiene complex. The reaction of the n2-styrene Cp*ZA with 2-butyne was shown to produce a Cp*ZA butadiene complex via a sequential butyne insertion followed by a formal 1,3-hydride shift, and the reaction with 1,3-butadienes yielded Cp*ZA butadiene complexes with loss of styrene. The chemistry of pentamethylcyclopentadienylacetamidinatetitanium (Cp*TiA) was pursued, and the reaction of the Cp*TiA dichloride with 2 equiv. of MeLi yielded the dimethyl Ti(IV) complex, while the reaction with 2 equiv. of EtLi yielded the Ti(III) ethyl complex. Studies were carried out with Cp* acetamidinate compounds of Ta (Cp*TaAs). The reactions of Cp*TaA trichloride with EtLi, nBuLi, iBuLi, NpLi produced a series of new Ta(V), Ta(IV), and Ta(III) complexes. The Ta(IV) dichloride was also accessed via a Na/Hg reduction allowing further access to Ta(IV) alkyl compounds.The thermal decomposition of the Ta(IV) diisobutyl yielded a Ta(IV) TMM complex and a diamagnetic Ta(IV) dimeric dihydride

Enhancement of Solid Fuel Combustion in a Hybrid Rocket Motor Using Amorphous Ti–Al–B Nanopowder Additives

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Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN

Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns