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61.
The Claisen rearrangement of α-(thioalkoxy)-esters provided access to substituted trans-1, 6-dimethylbicyclo[4.3.0]non-2-enes characteristic of the CD rings of the cucurbitanes. 相似文献
62.
Abstract A general deformation of a smectic C liquid crystal is composed of five different distortions, each of which can be made independently. Here we show that to each of these distortions we can assign a simple vector operator. Use of these five basis operators enables us to write down the elastic free energy density as a quadratic form consisting of nine terms. We also discuss how the nine elastic constants defined by the elastic energy expansion must fulfil certain restrictions in terms of inequalities and a specific tilt angle dependence. Assuming the smectic layers to be incompressible, we examine how certain arrangements of the smectic layers can be stable due to an interplay between the incompressibility condition and the boundary conditions which we impose on the director. One such stable configuration is the wedge, where the smectic layers form parts of concentric cylinders with the common axis coinciding with the centre of the wedge. For such a system we discuss the different director configurations which can be achieved and their stability. We also discuss the possibility of inducing Frederiks transitions for some of these configurations and calculate the corresponding thresholds, thereby demonstrating the design of an experiment which would make it possible to measure those elastic constants which are related to the deformations of the smectic layers, constants which are normally difficult to determine experimentally. 相似文献
63.
Dr. Neil J. Stewart Hitomi Nakano Shuto Sugai Mitsushi Tomohiro Yuki Kase Yoshiki Uchio Dr. Toru Yamaguchi Yujirou Matsuo Dr. Tatsuya Naganuma Dr. Norihiko Takeda Dr. Ikuya Nishimura Dr. Hiroshi Hirata Dr. Takuya Hashimoto Dr. Shingo Matsumoto 《Chemphyschem》2021,22(10):915-923
Hyperpolarized [1-13C]fumarate is a promising magnetic resonance imaging (MRI) biomarker for cellular necrosis, which plays an important role in various disease and cancerous pathological processes. To demonstrate the feasibility of MRI of [1-13C]fumarate metabolism using parahydrogen-induced polarization (PHIP), a low-cost alternative to dissolution dynamic nuclear polarization (dDNP), a cost-effective and high-yield synthetic pathway of hydrogenation precursor [1-13C]acetylenedicarboxylate (ADC) was developed. The trans-selectivity of the hydrogenation reaction of ADC using a ruthenium-based catalyst was elucidated employing density functional theory (DFT) simulations. A simple PHIP set-up was used to generate hyperpolarized [1-13C]fumarate at sufficient 13C polarization for ex vivo detection of hyperpolarized 13C malate metabolized from fumarate in murine liver tissue homogenates, and in vivo 13C MR spectroscopy and imaging in a murine model of acetaminophen-induced hepatitis. 相似文献
64.
We have produced and detected molecules using a p-wave Feshbach resonance between 40K atoms. We have measured the binding energy and lifetime for these molecules and we find that the binding energy scales approximately linearly with the magnetic field near the resonance. The lifetime of bound p-wave molecules is measured to be 1.0+/-0.1 ms and 2.3+/-0.2 ms for the ml=+/-1 and ml=0 angular momentum projections, respectively. At magnetic fields above the resonance, we detect quasibound molecules whose lifetime is set by the tunneling rate through the centrifugal barrier. 相似文献
65.
James J. P. Stewart 《International journal of quantum chemistry》1996,58(2):133-146
When conventional matrix algebra is used to solve the semiempirical self-consistent field equations for large systems, the time required rises as the third power of the size of the system. A consequence of this is that self-consistent calculations of large systems such as enzymes are impractical. By using localized molecular orbitals instead of matrix methods, the time required for these systems can be made almost proportional to the size of the system. In partial geometry optimizations, the time required depends only upon the size of the fragment being optimized and is almost independent of the size of the whole system. © 1996 John Wiley & Sons, Inc. 相似文献
66.
Stephen Brown Ronald Grigg Joanne Hinsley Stewart Korn Visuvanathar Sridharan Michael D. Uttley 《Tetrahedron》2001,57(52):809-10355
A wide variety of aryl/heteroaryl iodides undergo an intermolecular Heck reaction with alkylallenes to furnish 1,3-dienes. These subsequently react in situ with various dienophiles to give Diels–Alder adducts. The chemistry has been extended to incorporate cyclisation-anion capture methodology and the stereochemistry of the products has been determined. 相似文献
67.
68.
Hui-ding Xie Louisa A. Ho Michael S. Truelove Ben Corry Scott G. Stewart 《Journal of fluorescence》2010,20(5):1077-1085
In this paper we describe a semi-empirical quantum method for predicting the wavelength of maximum fluorescence excitation
and emission for several known and new maleimide derivatives. All new maleimides, containing a N-Benzyl attachment, were successfully synthesised via a tandem Suzuki reaction with aryl boronic acids containing either an electron donating, electron withdrawing functional
groups. Absorption and emission spectra calculated using the semi-empirical AM1 method with excited state ZINDO calculations
proved more reliable than either Hartree-Fock Configuration interaction or time dependent density functional methods. Calculated
absorption and emission wavelengths were compared with 26 experimental spectra from known or newly synthesised maleimides
and found to have provide reasonable predictions, with an average deviation of less the 6% for absorption maxima and less
than 4% for emission peaks. The described method provides a strong benchmark for the accuracy that can be expected from theoretical
predictions of fluorescence spectra. 相似文献
69.
Ronald F. Stewart 《Molecular physics》2013,111(5):1577-1583
For a wide range of frequencies the time-dependent Hartree-Fock equations are solved numerically for atoms of the Ne isoelectronic sequence. From the solutions properties of each system are calculated, notably excitation energies and bound-bound oscillator strengths. Excellent agreement is observed between the TDHF oscillator strengths and the most accurate experimental and theoretical data which are currently available. 相似文献
70.