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A monolithic grating surface-emitting, GaAs/AlGaAs, separate-confinement-heterostructure, single-quantum-well diode laser has been fabricated on a Si substrate using a single-step metalorganic chemical vapour deposition process. An output power of 30 mW has been obtained under pulsed operation with a peak emission wavelength of 885 nm.<> 相似文献
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Reaction of HMo(CO)3C5H5 and Sn(C5H5)2 produces the tin hydride HSn[Mo(CO)3C5H5]3 (I). Reaction of I with CCl4, CHCl3, or CH2Cl2 gives ClSn[Mo(CO)3C5H5]3 (II). With hydrogen chloride the hydride I reacts to produce the dichloride Cl2Sn[Mo(CO)3C5H5]2. The first step in this reaction is cleavage of the SnH bond to produce the chloride II. The hydride I reacts with acetic acid to produce the diacetate (CH3COO)2Sn[Mo(CO)3C5H5]2. 相似文献
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[reaction: see text] Molecular modeling was used to design mimetics of the HIV-1 matrix protein nuclear localization signal (NLS) in which a scaffold of two resorcinol units joined by a diamide linker presents 3-aminopropyl ethers in place of lysine side chains. Prospective mimetics with linkers of 6, 8, 10, or 12 atoms were synthesized and compared in a competition assay for binding to the nuclear import receptor subunit karyopherin alpha, showing the 10-atom linker to be best and shorter ones ineffective. 相似文献
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Elli S Ganazzoli F Timoshenko EG Kuznetsov YA Connolly R 《The Journal of chemical physics》2004,120(13):6257-6267
Single-chain simulations of densely branched comb polymers, or "molecular bottle-brushes" with side-chains attached to every (or every second) backbone monomer, were carried out by off-lattice Monte Carlo technique. A coarse-grained model, described by hard spheres connected by harmonic springs, was employed. Backbone lengths of up to 100 units were considered, and compared with the corresponding linear chains. The backbone molecular size was investigated as a function of its length at fixed arm size, and as a function of the arm size at fixed backbone length. The apparent swelling exponents obtained by a power-law fit were found to be larger than those for the corresponding linear polymers, indicative of stiffening of the comb backbone. The probability distribution function for the backbone end-to-end distance was also investigated for different backbone lengths and arm sizes. Analysis of this function yielded the critical exponents, which revealed an increase in the swelling exponent consistent with values found from the molecular size. The apparent persistence length of the backbone was also determined, and was found to increase with increasing branching density. Finally, the static structure factors of the whole bottle-brushes and of their backbones are discussed, which provides another consistent estimate of the swelling exponents. 相似文献
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Ngouela S Zelefack F Lenta BN Ngouamegne ET Tchamo DN Tsamo E Connolly JD 《Natural product research》2005,19(7):685-688
A xanthone derivative, 3,6,7-trihydroxy-1-methoxyxanthone has been isolated from the stem bark of Allanblackia monticola together with other known compounds, 2,6-dihydroxy-1-methoxyxanthone, allanxanthone A, epicathechin and oleanolic acid acetate. The structure of the new compound was elucidated by spectroscopic methods. 相似文献
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This review covers the isolation and structure determination of triterpenoids including squalene derivatives, lanostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, isomalabicanes and saponins. The literature from January to December 2000 is reviewed and 277 references are cited. 相似文献
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H. H. Michels R. H. Hobbs L. A. Wright J. W. D. Connolly 《International journal of quantum chemistry》1978,13(2):169-187
The electronic structure, potential energy curves, and radiative transition probabilities of excimer systems have been examined using quantum mechanical methods. These molecules are characterized by repulsive or weakly bound ground state potential curves and by bound, strongly ionic, or Rydberg, excited states. They constitute a very interesting class of molecules which offer the possibility for high power, high efficiency UV laser operation. Calculations have been carried out using the density functional SCF -Xα method, modified extensively to correct for well known errors arising from approximations to the potential and exchange terms. A limited number of ab initio calculations were also carried out for comparison purposes. For the ArF system we find that the lowest excited ionic state has symmetry 2∑ , and that the dominant laser transition observed at 1933 Å should be assigned to B 2∑ → X 2∑ . The C 2Π3/2 → X 2∑ transition is calculated to be two orders of magnitude smaller in emission intensity than the dominant transition, thus ruling out this assignment for the observed laser line in ArF. Preliminary calculations carried out for Ar2F indicate that the bound upper ionic state has 2B2 symmetry and that the most probable ground state also has 2B2 symmetry. This polyatomic system is predicted to exhibit a broadband emission spectrum with a relatively long radiative lifetime. 相似文献