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11.
D. L. Bowers E. A. Rhodes C. E. Dickerman 《Journal of Radioanalytical and Nuclear Chemistry》1998,230(1-2):161-165
The formation of160Er,159Dy and149Gd employing natural dysprosium as target and its irradiation with α-particles was the objective of this work. This is included
in a study performed by our group on excitation functions of induced reactions for charged particles on rare earths. A target
with metallic foils of Dy was irradiated in the Isochronous Cyclotron at Karlsruhe (Germany) with incident energy up to 88.5
MeV. Due to the contributions of the precursors in the isobaric chains, we were not able to measure the absolute cross sections.
Then, the determination of the cumulative cross sections were carried out. Thick target yields for the production of160Er,159Dy and149Gd are also presented. At present we do not know other publications about the functions studied in this work. 相似文献
12.
Absolute rate constants and approximate product distributions are presented for the reactions of He+, Ne+, Ar+, Kr+, Xe+, CO+ and CO+2 with NH3 and PH3. In all cases, electron transfer is the dominant reaction channel. Hydrogen atom transfer is observed in several systems, but only as a minor product, even when this channel is very exothermic. The magnitude of the absolute rate constants can be correlated with the Franck-Condon factors associated with the reactions in most cases. Several exceptions to this general rule are observed that could not be readily predicted a priori. It is speculated that these reactions proceed via a collision complex. 相似文献
13.
M Tuchman L D Bowers K D Fregien P J Crippin W Krivit 《Journal of chromatographic science》1984,22(5):198-202
Gas chromatographic retention indices (methylene units) are reported for 101 urinary organic acids as their trimethylsilyl and oximated trimethylsilyl derivatives on a 5% phenylmethyl silicone fused silica capillary column. Using anion exchange chromatography, organic acids were extracted from urines of five healthy individuals, seven patients with neuroblastoma, and nine patients with inherited organic acidurias. Separation of the various acids was achieved by capillary gas chromatography and identification was done by mass spectrometry using a computerized library search program. All identifications were confirmed by visual comparison with reference mass spectra. Standard deviations of the retention indices for all acids were less than 0.035 methylene units and for 46 acids less than 0.01 methylene units. Three chromatograms of urine from individuals with neuroblastoma, phenylketonuria, and propionic acidemia and one from a healthy individual are shown. 相似文献
14.
The metal binding properties of the dinucleotide duplex, dCG x dCG, were analyzed in the gas phase with ion mobility mass spectrometry. Both MALDI and ESI were used to generate [M(dCG x dCG)]+ complexes. The collision cross section of each complex was measured in helium using ion mobility based methods and compared to calculated cross sections of theoretical structures. When metal cations classified as hard acids were combined with dCG x dCG, the [M(dCG x dCG)]+ complex organized into a globular structure. However, when soft acid metal cations were examined, a structure was observed where the two C-G base pairs were Watson-Crick bound. 相似文献
15.
The authors follow up some previous work on the dynamics of pension funding by three notes. The first of these concerns contribution rates consisting of the normal cost plus a generalized amortization method for unfunded supplemental present value (actuarial accrued liability). The second note examines aggregate cost funding for active members when there exist consistent difference between the assumed and the actual rates of interest and of growth. The third note explores the operation of a variable annuity system in the context of our general model for pension funding dynamics. 相似文献
16.
Yuying Wei Robert Graf Dr. John C. Sworen Dr. Chi‐Yuan Cheng Dr. Clifford R. Bowers Prof. Dr. Kenneth B. Wagener Prof. Dr. Hans Wolfgang Spiess Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(25):4617-4620
Branching out : The mobility of linear polymers changes upon branching, which has a pronounced effect on processability and drawability. Regularly branched model polyolefins were studied by advanced solid‐state NMR spectroscopy, and twist defects around the branches in the crystalline regions are identified. For lower branch content, the twisting motions are decoupled; for higher content, collective motion is found (see picture).
17.
Boyd DR Sharma ND Bowers NI Dalton H Garrett MD Harrison JS Sheldrake GN 《Organic & biomolecular chemistry》2006,4(17):3343-3349
Biotransformations of a series of ortho-, meta- and para-substituted ethylbenzene and propylbenzene substrates have been carried out, using Pseudomonas putida UV4, a source of toluene dioxygenase (TDO). The ortho- and para-substituted alkylbenzene substrates yielded, exclusively, the corresponding enantiopure cis-dihydrodiols of the same absolute configuration. However, the meta isomers, generally, gave benzylic alcohol bioproducts, in addition to the cis-dihydrodiols (the meta effect). The benzylic alcohols were of identical (R) absolute configuration but enantiomeric excess values were variable. The similar (2R) absolute configurations of the cis-dihydrodiols are consistent with both the ethyl and propyl groups having dominant stereodirecting effects over the other substituents. The model used earlier, to predict the regio- and stereo-chemistry of cis-dihydrodiol bioproducts derived from substituted benzene substrates has been refined, to take account of non-symmetric substituents like ethyl or propyl groups. The formation of benzylic hydroxylation products, from meta-substituted benzene substrates, without further cis-dihydroxylation to yield triols provides a further example of the meta effect during toluene dioxygenase-catalysed oxidations. 相似文献
18.
Bowers A West N Taunton J Schreiber SL Bradner JE Williams RM 《Journal of the American Chemical Society》2008,130(33):11219-11222
The efficient total synthesis of the recently described natural substance largazole (1) and its active metabolite largazole thiol (2) is described. The synthesis required eight linear steps and proceeded in 37% overall yield. It is demonstrated that largazole is a pro-drug that is activated by removal of the octanoyl residue from the 3-hydroxy-7-mercaptohept-4-enoic acid moiety to generate the active metabolite 2, which is an extraordinarily potent Class I histone deacetylase inhibitor. Synthetic largazole and 2 have been evaluated side-by-side with FK228 and SAHA for inhibition of HDACs 1, 2, 3, and 6. Largazole and largazole thiol were further assayed for cytotoxic activity against a panel of chemoresistant melanoma cell lines, and it was found that largazole is substantially more cytotoxic than largazole thiol; this difference is attributed to differences in the cell permeability of the two substances. 相似文献
19.
Goodchild I Collier L Millar SL Prokes I Lord JC Butts CP Bowers J Webster JR Heenan RK 《Journal of colloid and interface science》2007,307(2):455-468
The surface, phase and aggregation behaviour of mixtures of 1-alkyl-3-methylimidazolium halide, [C(n)mim]X, where n is the alkyl chain length, with water has been explored using a variety of methods. Critical micelle concentrations (cmc) and micelle structures have been determined for aqueous [C(n)mim]Br solutions for n=2, 4, 6, 8, and 10. Small-angle neutron scattering (SANS) measurements reveal that for the n=8 and 10 systems, at concentrations just above the cmc, small near-spherical aggregates exist, which, after initial growth, possess core radii (aggregation numbers) at intermediate concentrations of 10.5+/-0.5 Angstrom (22+/-2) and 13.2+/-0.5 Angstrom (40+/-3), respectively, for n=8 and n=10. Towards higher concentrations, the aggregates appear to grow, with the aggregates in the [C(10)mim]Br system becoming increasingly elongated (prolate) with increasing concentration. No evident aggregates are formed in the systems with n=2 and 4. In the n=6 system, it appears that oblate aggregates with radius approximately 9 Angstrom form at the cmc and that the radius increases with increasing concentration. For longer alkyl chain lengths, at high concentrations lyotropic mesophases form in some systems. The mesophase region for the [C(8)mim]Cl system has been explored across the composition range using X-ray diffraction and (2)H NMR spectroscopy. Both techniques suggest that a major hexagonal phase with lattice parameter of 29.5+/-0.5 Angstrom coexists with a minor lamellar phase (23.5+/-0.3 Angstrom) or possibly a second hexagonal phase (27.1+/-0.4 Angstrom). The area per adsorbed molecule at the surface of [C(8)mim]Br solutions has been measured as a function of concentration using neutron reflectometry. A minimum in the area per molecule behaviour is coincident with a minimum identified in the surface tension isotherm occurring close to the cmc. The data suggest depletion of [C(8)mim]Br from the surface region occurs at concentrations immediately above the cmc. 相似文献
20.