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61.
Marcus Schuetz James Murphy Robert E. Fields James M. Harnly 《Spectrochimica Acta Part B: Atomic Spectroscopy》2000,55(12):1895-1912
A single element continuum source-atomic absorption spectrometer (CS-AAS) using a two-dimensional charge coupled array detector (2D-CCD) was assembled for use with graphite furnace atomization. The two-dimensional CCD was a split-frame transfer array, was thinned and back-illuminated for high quantum efficiency at approximately 200 nm, and was capable of an 80-Hz frame rate with a read noise of <15 electrons. The transfer of charges from the integrating arrays to the storage arrays took 0.65 ms, less than 4% of the frame period (16.42 ms). The transfer of charges to the storage array was perpendicular to the wavelength axis, eliminating source flicker noise, and was implemented without masking, producing vertical smearing. The smearing was manifested as a continuum background and was corrected using pixels between orders. The two-dimensional array, in conjunction with the high-resolution echelle spectrometer, allowed measurement of absorbance with respect to wavelength and height in the furnace. Computed absorbances were corrected for stray radiation and non-specific background absorption. Detection limits were equal to those for line source AAS, with the exception of As (193.7 nm) and Se (196.0 nm). 相似文献
62.
63.
M. A. Sandhu R. D. Fields 《Journal of polymer science. Part A, Polymer chemistry》1980,18(4):1189-1202
Copolyesters of two glycols and a dicarboxylic acid moiety are frequently made to obtain specific physical properties. In the synthesis of these polymers an excess of glycol is used in the ester-exchange reaction and then removed during the polycondensation reaction to form a high-molecular-weight product. A model has been developed to predict the final polymer composition. The derivation is based on equilibria of reaction species (free glycol, polymer chain ends, and ester links) and the relative vapor pressures of the two reacting glycols. Calculated results are compared with experimental results of poly(2,2′-oxydiethylene: 2,2-dimethyl-1,3-propylene terephthalate)s. There is good agreement between calculated and experimental compositions. The model can be used to calculate the glycol concentrations that must be used to make a specific polymer composition. This model should also be useful in the calculation of other mole ratios of glycol to dicarboxylic acid that will make the same composition. 相似文献
64.
T. M. Moy M. Konas J. E. McGrath E. K. Fields 《Journal of polymer science. Part A, Polymer chemistry》1994,32(12):2377-2385
The dianhydride monomer 1,4-phenylenebis(phenylmaleic anhydride) was polymerized with various aromatic diamines in a one-step solution polymerization to afford high molecular weight, soluble polyimides containing backbone phenylmaleimide structures. The polymides were soluble in amide solvents, chlorinated hydrocarbons, and tetrahydrofuran at 25°C at a concentration of 15% (w/v), displayed molecular weight distributions (Mw/Mn) of 2.0–2.2 as determined by absolute GPC and showed Tg values of 240°C and above as measured by differential scanning calorimetry. In addition, polyimide thermosets were prepared from these materials by thermal cure at 350–360°C. The crosslinked polyimides displayed Tgs 20–25°C higher than their soluble precursors, and chloroform extraction indicated gel fractions ranging from 74–100% after cure. © 1994 John Wiley & Sons, Inc. 相似文献
65.
Yang-i Lin Thomas L. Fields Ving J. Lee S. A. Lang 《Journal of heterocyclic chemistry》1982,19(3):613-615
Reaction of N′-acyl-N,N-dimethylamidines with hydrogen sulfide in acetic acid gave N-thioacylbenzarmides in almost quantitative yields. S-Ethylation of the N-thioacylbenzamides with iodoethane gave N-aroylthio-imidates in excellent yields. Reaction of the N-aroylthioimidates with acetamidine, benzamidine, or guanidine in ethanol gave s-triazines in 60–93% yield. 相似文献
66.
Reaction of 2-methyl-2-thiopseudourea sulfate with 1-hydrazinophthalazine gave 3-amino-s-triazolo[3,4-a] phthalazine in good yield. 1-Amino-4-methyl-s-triazolo[4,3-a]quinoxaline and 1-amino-s-triazolo[4,3-a]quinoxalin-4(5H)one were similarly perpared. 相似文献
67.
68.
Huang GS Miller DH Pavlunin V Sanghi B Shipsey IP Adams GS Chasse M Cravey M Cummings JP Danko I Napolitano J He Q Muramatsu H Park CS Park W Thorndike EH Coan TE Gao YS Liu F Artuso M Boulahouache C Blusk S Butt J Dambasuren E Dorjkhaidav O Li J Menaa N Mountain R Nandakumar R Randrianarivony K Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Csorna SE Bonvicini G Cinabro D Dubrovin M Briere RA Chen GP Chen J Ferguson T Tatishvili G Vogel H Watkins ME Rosner JL Adam NE Alexander JP 《Physical review letters》2005,95(18):181801
Using data collected at the psi(3770) resonance with the CLEO-c detector at the Cornell e+e- storage ring, we present improved measurements of the absolute branching fractions of D+decays to K0e+ve, pi0e+ve, K*0e+ve, and p0e+ve, and the first observation and absolute branching fraction measurement of D+ --> omega e+ve. We also report the most precise tests to date of isospin invariance in semileptonic D0 and D+ decays. 相似文献
69.
Artuso M Boulahouache C Blusk S Butt J Dorjkhaidav O Li J Menaa N Mountain R Nandakumar R Randrianarivony K Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Csorna SE Bonvicini G Cinabro D Dubrovin M Lincoln A Briere RA Chen GP Chen J Ferguson T Tatishvili G Vogel H Watkins ME Rosner JL Adam NE Alexander JP Berkelman K Cassel DG Crede V Duboscq JE Ecklund KM Ehrlich R Fields L Gibbons L Gittelman B Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE 《Physical review letters》2005,95(25):251801
We extract a relatively precise value for the decay constant of the meson by measuring B(D+ --> mu+nu) = (4.40 +/-0.66(+0.09)(-0.12) x 10(-4) using 281 pb(-1) of data taken on phi(3770) the resonance with the CLEO-c detector. We find fD+ = (222.6 +/- 16.7(+2.8)(-3.4)) MeV, and compare with current theoretical calculations. We also set a 90% confidence upper limit on B(D+e+nu)< 2.4 x 10(-5) which constrains new physics models. 相似文献
70.
R. Singer Y. Cho T. Fields L.G. Hyman P.A. Schreiner L. Voyvodic R. Walker J. Whitmore R. Engelmann T. Kafka C. Moore M. Pratap 《Physics letters. [Part B]》1974,49(5):481-487
Using data obtained from an exposure of the 30-inch bubble chamber at NAL, inclusive and semi-inclusive two-particle rapidity correlations are analyzed for charged-charged, ??, ++, and ± particles. For the inclusive sample, positive correlations are observed in the central region. In the semi-inclusive case, the four-and six-prong events exhibit strong positive correlations near 90° CM. Selection of four-prong events with a large rapidity gap shows that the strong correlation seems to be associated with diffractive-type events. 相似文献