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991.
Van Ornum SG Bruendl MM Cao H Reddy M Grubisha DS Bennett DW Cook JM 《The Journal of organic chemistry》2000,65(7):1957-1971
The scope of the tandem Pauson-Khand reaction has been explored for the regiospecific construction of [5.5.5.5]- and [5.6.6.5]tetracyclic systems via the photolytic method of Livinghouse. The rapid regiospecific entry into the two dicyclopentapentanoid systems 17 and 29 was accomplished from the key diene-diynes 11 and 19b. A photochemically mediated catalytic tandem Pauson-Khand cyclization was employed to prepare the parent ring systems of dicyclopenta[a,e]pentalene (from 19b) and dicyclopenta[a,f]pentalene (from 11) in regiospecific fashion in a one-pot process. Under these conditions, conversion of acyclic diene-diyne 16 into tetracyclic system 17 was achieved in 74% yield, while a similar process was employed to convert 28 into tetracycle 29 in 90% yield. This is much improved over the previous conditions that employed NMO. Six carbon-carbon bonds were generated in this process constituting up to 98% yield for each carbon-carbon bond so formed. Furthermore, tetracyclic [5.6.6.5] systems such as dicyclopenta[b,g]decalins 37, 38, and 40 were prepared from similar diene-diyne precursors via the tandem Pauson-Khand cyclization. Importantly, acetal 36 provided the desired cis-fused [5.6.6.5] system 38a (via 40a/b) in stereospecific fashion. This reaction is unique in that it provides a cis-decalin ring system; moreover, the yield of each of the six carbon-carbon bonds formed in this process was at least 89%. The structure of cis diol 38a was confirmed by X-ray crystallography. 相似文献
992.
Dennis W. Bennett Tasneem A. Siddiquee Daniel T. Haworth Manoranjan Das 《Journal of chemical crystallography》2004,34(12):865-872
The crystal and molecular structure of cis-Cu(CH3CSCHCOCH3)2 has been determined by X-ray diffraction. The complex crystallizes in the triclinic space group P
with lattice parameters a = 10.588(2) Å, b = 11.445(2) Å, c = 11.779(2) Å, = 88.13(1)°, = 63.73(2)°, = 86.57(2)°, V = 1277.6(4) Å3, Z = 4. The asymmetric unit consists of two crystallographically independent molecules. The approximate cis square planar geometry of thecomplex is consistent with the relatively large dipole moment observed in solution. Density functional calculations predict that a pseudo-tetrahedral conformation of the molecule would be on the order of 40 kJ mol–1 higher in energy than the crystallographicallydetermined conformation, while a trans conformation would have approximately the same energy. This suggests that the cis conformer observed in the solidstate coexists in equilibrium with the trans conformer in solution. 相似文献
993.
Mechelle R. Bennett Pratik Gurnani Phil J. Hill Cameron Alexander Frankie J. Rawson 《Angewandte Chemie (International ed. in English)》2020,59(12):4750-4755
The ability to harness cellular redox processes for abiotic synthesis might allow the preparation of engineered hybrid living systems. Towards this goal we describe a new bacteria‐mediated iron‐catalysed reversible deactivation radical polymerisation (RDRP), with a range of metal‐chelating agents and monomers that can be used under ambient conditions with a bacterial redox initiation step to generate polymers. Cupriavidus metallidurans, Escherichia coli, and Clostridium sporogenes species were chosen for their redox enzyme systems and evaluated for their ability to induce polymer formation. Parameters including cell and catalyst concentration, initiator species, and monomer type were investigated. Water‐soluble synthetic polymers were produced in the presence of the bacteria with full preservation of cell viability. This method provides a means by which bacterial redox systems can be exploited to generate “unnatural” polymers in the presence of “host” cells, thus setting up the possibility of making natural–synthetic hybrid structures and conjugates. 相似文献
994.
The parametrized Dirac wave equation represents position and time as operators, and can be formulated for many particles. It thus provides, unlike field-theoretic Quantum Electrodynamics (QED), an elementary and unrestricted representation of electrons entangled in space or time. The parametrized formalism leads directly and without further conjecture to the Bethe–Salpeter equation for bound states. The formalism also yields the Uehling shift of the hydrogenic spectrum, the anomalous magnetic moment of the electron to leading order in the fine structure constant, the Lamb shift and the axial anomaly of QED. 相似文献
995.
Adare A Afanasiev S Aidala C Ajitanand NN Akiba Y Akimoto R Alexander J Al-Ta'ani H Andrews KR Angerami A Aoki K Apadula N Appelt E Aramaki Y Armendariz R Aschenauer EC Awes TC Azmoun B Babintsev V Bai M Bannier B Barish KN Bassalleck B Basye AT Bathe S Baublis V Baumann C Bazilevsky A Belmont R Ben-Benjamin J Bennett R Berdnikov A Berdnikov Y Blau DS Bok JS Boyle K Brooks ML Broxmeyer D Buesching H Bumazhnov V Bunce G Butsyk S Campbell S Caringi A Castera P Chen CH Chi CY Chiu M Choi IJ 《Physical review letters》2011,106(6):062001
Large parity-violating longitudinal single-spin asymmetries A(L)(e+) = -0.86(-0.14) (+0.30) and A(L)(e-) = 0.88(-0.71) (+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s] = 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e)) = 144.1 ± 21.2(stat)(-10.3) (+3.4) (syst) ± 21.6(norm) pb, and σ(pp → W- X) × BR(W- → e- ν[over ˉ](e)) = 31.7 ± 12.1(stat)(-8.2) (+10.1) (syst) ± 4.8(norm) pb. 相似文献
996.
Bennett TD Simoncic P Moggach SA Gozzo F Macchi P Keen DA Tan JC Cheetham AK 《Chemical communications (Cambridge, England)》2011,47(28):7983-7985
We report the reversible pressure-induced amorphization of a zeolitic imidazolate framework (ZIF-4, [Zn(Im)(2)]). This occurs irrespective of pore occupancy and takes place via a novel high pressure phase (ZIF-4-I) when solvent molecules are present in the pores. A significant reduction in bulk modulus upon framework evacuation is also observed for both ZIF-4 and ZIF-4-I. 相似文献
997.
R. Mitchell Parry Asiri S. Galhena Chaminda M. Gamage Rachel V. Bennett May D. Wang Facundo M. Fernández 《Journal of the American Society for Mass Spectrometry》2013,24(4):646-649
We present omniSpect, an open source web- and MATLAB-based software tool for both desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) that performs computationally intensive functions on a remote server. These functions include converting data from a variety of file formats into a common format easily manipulated in MATLAB, transforming time-series mass spectra into mass spectrometry images based on a probe spatial raster path, and multivariate analysis. OmniSpect provides an extensible suite of tools to meet the computational requirements needed for visualizing open and proprietary format MSI data. 相似文献
998.
Controlled H-aggregation of single Pc-labeled oligonucleotides is utilized as a fluorescence quenching system to discern changes in enzyme activity for the discovery of inhibitors for Long Interspersed Element 1 endonuclease (L1-EN), which is involved in genome instability and implicated in many different diseases. 相似文献
999.
Adare A Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Bataineh H Alexander J Aoki K Aphecetche L Armendariz R Aronson SH Asai J Atomssa ET Averbeck R Awes TC Azmoun B Babintsev V Baksay G Baksay L Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bazilevsky A Belikov S Bennett R Berdnikov Y Bickley AA Boissevain JG Borel H Boyle K Brooks ML Buesching H Bumazhnov V Bunce G Butsyk S Campbell S Chang BS Charvet JL Chernichenko S Chiba J Chi CY Chiu M Choi IJ Chujo T Chung P 《Physical review letters》2008,101(12):122301
Yields for J/psi production in Cu+Cu collisions at sqrt s_NN=200 GeV have been measured over the rapidity range |y|<2.2 and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data offer greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, in the range where the quark-gluon plasma transition threshold is predicted to lie. Cold nuclear matter estimates based on ad hoc fits to d+Au data describe the Cu+Cu data up to N_part approximately 50, corresponding to a Bjorken energy density of at least 1.5 GeV/fm(3). 相似文献
1000.
In this paper, we present a semi-analytical approach to obtain the DEP force generated by parallel electrodes. By solving the electric potential equation using the separation of variables method, a solution was found in the form of a Fourier series with unknown coefficients. The unknown coefficients were determined by training a linear artificial neural network with the appropriate data satisfied on the boundary. This results of calculated electric field and DEP force for both planar electrode system and 3D electrode system are validated by comparison with the numerical results obtained using the commercial software CFD-ACE+. 相似文献