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961.
Berg ER Freeman SA Green DD Ulness DJ 《The journal of physical chemistry. A》2006,110(50):13434-13446
The effects of hydrogen bonding on the ring stretching modes (both ring breathing and triangle) of pyridine are experimentally investigated using noisy light based coherent Raman scattering spectroscopy. Three systems, pyridine/formamide, pyridine/water, and pyridine/acetic acid, provide varying degrees of strength for the diluent-pyridine hydrogen bond complex. Formamide forms a relatively weaker hydrogen bond, while acetic acid essentially fully transfers a proton to pyridine. Both dilution studies and temperature studies are performed on the three systems. Together, these provide a broad context in which a very simple model for the electronic behavior of pyridine is formulated. This model is based on a molecular orbital picture and electrostatic arguments, and it well explains the observed experimental results. Additionally, a new mechanism for the line broadening of the ring breathing mode for the pyridine-water hydrogen bonded complex is proposed. 相似文献
962.
Lancaster RW Karamertzanis PG Hulme AT Tocher DA Covey DF Price SL 《Chemical communications (Cambridge, England)》2006,(47):4921-4923
A computational prediction that mixing the synthetic mirror image of progesterone with its natural form would produce a specific racemic crystal structure was validated. 相似文献
963.
The cell-permeable anthracene analog diethyl-3-3'-(9,10-anthracenediyl)bis acrylate (DADB) was recently identified as a highly selective probe for singlet oxygen ((1)O(2)). Now, we show that DADB can be used to monitor (1)O(2) formation in cell culture during photodynamic therapy. An atypical property of DADB is that fluorescence emission is decreased upon oxidation. Using photosensitizers that target specific organelles, we determined that DADB could detect (1)O(2) whether formed in ER, mitochondria or lysosomes. DADB fluorescence was not, however, significantly altered when the photosensitizing agent was the palladium bacteriopheophorbide termed WST11, an agent reported to produce mainly oxygen radicals upon irradiation in an aqueous environment, whereas singlet oxygen was formed in organic solvents. 相似文献
964.
Harry W. Gibson Michael A.G. Berg Terry L. Price Zhenbin Niu Minjae Lee Mason A. Rouser Jennifer Clifton Dickson Carla Slebodnick 《Tetrahedron》2012,68(38):8052-8067
Isoquinoline Reissert compounds (2-acyl-1,2-dihydroisoquinaldonitriles) with either 3-H (1) or 3-CH3 (2) substituents and various N-acyl groups have been examined in detail by 1H and 13C NMR spectroscopy and X-ray crystallography. In all cases the trans amide conformation, with reference to the carbonyl oxygen and the 3-position of the isoquinoline ring, predominates in solution. In the solid state the nitrile moieties are pseudo-axial and the amides exist almost exclusively in the trans form, except for the case of 2-isobutyryl-3-methyl-1,2-dihydroisoquinaldonitrile (2c), which exists exclusively as the cis amide form in the solid state. In N-aroyl 3-CH3 compounds with two ortho-aroyl substituents both amide isomerism and hindered aryl/carbonyl rotation are observed by 1H NMR spectroscopy. In other N-aroyl derivatives only hindered aryl/carbonyl rotations are observed by NMR and in N-alkanoyl compounds amide isomerism is observable only at very low temperatures. X-ray crystallography reveals the two rotamers in the solid state in four cases of ortho-substituted benzoyl compounds; with one exception, the rotamer with the larger ortho-aroyl substituent syn to the pseudo-axial cyano group is favored. Unusual solubility and reactivity patterns observed with these compounds are rationalized in terms of the interplay between steric and electronic factors. 相似文献
965.
Parmar D Matsubara H Price K Spain M Procter DJ 《Journal of the American Chemical Society》2012,134(30):12751-12757
Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI(2)-H(2)O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow "one-pot" access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl. 相似文献
966.
Kobr L Zhao K Shen Y Comotti A Bracco S Shoemaker RK Sozzani P Clark NA Price JC Rogers CT Michl J 《Journal of the American Chemical Society》2012,134(24):10122-10131
We describe an approach to regular triangular arrays of dipolar molecular rotors based on insertion of dipolar rotator carrying shafts as guests into channels of a host, tris(o-phenylenedioxy)cyclotriphosphazene (TPP). The rotor guests can either enter the bulk of the host or stay at or near the surface, if a suitable stopper is installed at the end of the shaft. Differential scanning calorimetry, solid-state NMR, and powder X-ray diffraction were used to examine the insertion of a dipolar rotor synthesized for the purpose, 1-n-hexadecyl-12-(2,3-dichlorophenyl)-p-dicarba-closo-dodecaborane, and it was found that it forms a surface inclusion compound. Rotational barriers from 1.2 to 9 kcal/mol were found by dielectric spectroscopy and were attributed to rotors inserted into the surface to different degrees, some rubbing the surface as they turn. 相似文献
967.
968.
L. F. Price C. C. Drovandi A. Lee D. J. Nott 《Journal of computational and graphical statistics》2018,27(1):1-11
Having the ability to work with complex models can be highly beneficial. However, complex models often have intractable likelihoods, so methods that involve evaluation of the likelihood function are infeasible. In these situations, the benefits of working with likelihood-free methods become apparent. Likelihood-free methods, such as parametric Bayesian indirect likelihood that uses the likelihood of an alternative parametric auxiliary model, have been explored throughout the literature as a viable alternative when the model of interest is complex. One of these methods is called the synthetic likelihood (SL), which uses a multivariate normal approximation of the distribution of a set of summary statistics. This article explores the accuracy and computational efficiency of the Bayesian version of the synthetic likelihood (BSL) approach in comparison to a competitor known as approximate Bayesian computation (ABC) and its sensitivity to its tuning parameters and assumptions. We relate BSL to pseudo-marginal methods and propose to use an alternative SL that uses an unbiased estimator of the SL, when the summary statistics have a multivariate normal distribution. Several applications of varying complexity are considered to illustrate the findings of this article. Supplemental materials are available online. Computer code for implementing the methods on all examples is available at https://github.com/cdrovandi/Bayesian-Synthetic-Likelihood. 相似文献
969.
Price D.W. Baker W.L. Beason J.D. Degnan J.H. Hall D.J. Holmes J.L. Graham J.D. Lopez E.A. Seiler S.W. Turchi P.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(1):62
Corrections are made to figures in `Enhanced load current delivery from the SHIVA Star vacuum inductive store/plasma flow switch' by D. W. Price et al. (1988) 相似文献
970.