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41.
Coupling of cis-1-bromo-2-pentene and (S,S)-hydrobenzoin stannylene acetal followed by regio- and stereoselective transformations of the resulting allylic ether gave (+)-polyoxamic acid and a similar procedure was applied to the synthesis of D-sorbitol from trans-1-iodo-2-hexene. 相似文献
42.
Mattson M Alkhazov G Atamantchouk AG Balatz MY Bondar NF Cooper PS Dauwe LJ Davidenko GV Dersch U Dolgolenko AG Dzyubenko GB Edelstein R Emediato L Endler AM Engelfried J Eschrich I Escobar CO Evdokimov AV Filimonov IS Garcia FG Gaspero M Giller I Golovtsov VL Gouffon P Gülmez E Kangling H Iori M Jun SY Kaya M Kilmer J Kim VT Kochenda LM Konorov I Kozhevnikov AP Krivshich AG Krüger H Kubantsev MA Kubarovsky VP Kulyavtsev AI Kuropatkin NP Kurshetsov VF Kushnirenko A Kwan S Lach J Lamberto A 《Physical review letters》2002,89(11):112001
We observe a signal for the doubly charmed baryon Xi(+)(cc) in the charged decay mode Xi(+)(cc)-->Lambda(+)(c)K-pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence. 相似文献
43.
This paper describes a detailed study of the initial region of coaxial jets and the large scale coherent structures within this region. The coaxial jets investigated have an area ratio of 2·67 and were run at three different velocity ratios. A simple model in terms of two arrays of vortex-rings in the mixing region of the coaxial jet is proposed, and its use verified by comparisons with experimental results. Overall and spectral results of hot wire and microphone signals, obtained in the flow, support the model proposed. Evidence supporting the concept of a preferred mode, which governs the growth or decay of the vortices in the intermediate zone, is also presented. 相似文献
44.
Forty wines of Vitis Vinifera var. 'Pinot Noir' were analyzed for their elemental and organic compositions by atomic emission spectrometry and glass-capillary gas chromatography, respectively. Their sensory quality was evaluated by a panel of judges. Average overall quality scores were used to rank these wines. Stepwise regression analysis and principal component factor analysis were used to investigate correlations between objective chemical measurements and subjective sensory evaluations. Compounds which were found to be related to overall quality of wine were identified. 相似文献
45.
46.
Two external spaces of an inorganic tennis ball are a novel type of metal-centered hydrophobic pocket where two hydrophobic trans-(+/-)-1,2-diaminocyclohexane groups stand perpendicularly to and around the metal coordination plane. The space recognizes pyridine over piperidine, and a novel supramolecule was obtained using such pyridine recognition properties. 相似文献
47.
Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Copty NK Cremaldi LM Darling C Denisenko K Devmal S Fernandez A Fox GF Gagnon P Gobel C Gounder K Halling AM Herrera G Hurvits G James C Kasper PA Kwan S Langs DC Leslie J Lundberg B Magnin J Massafferri A MayTal-Beck S Meadows B de Mello Neto JR Mihalcea D Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV 《Physical review letters》2001,86(5):770-774
From a sample of 1172 +/- 61 D(+)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)-->pi(-)pi(+)pi(+))/gamma(D(+)-->K-pi(+)pi(+)) = 0.0311 +/- 0.0018(+0.0016)(-0.0026). Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478(+24)(-23) +/- 17 MeV/c(2) and width 324(+42)(-40) +/- 21 MeV/c(2) accounts for approximately half of all decays. 相似文献
48.
Single-walled carbon nanotubes (SWNTs) are used as supporting materials for palladium (Pd) nanoparticles generated in situ in ionic liquid (IL); Pd nanocatalysts on SWNTs exhibit superior reactivity for hydrogenation of aryl ketones in IL under mild conditions (1 atm of H2 (g) and room temperature) and can be reused above 10 times without any loss of catalytic activity. 相似文献
49.
A. T. Kwan M. Yu. Efremov E. A. Olson F. Schiettekatte M. Zhang P. H. Geil L. H. Allen 《Journal of Polymer Science.Polymer Physics》2001,39(11):1237-1245
We used thin‐film differential scanning calorimetry to investigate the melting of isolated polyethylene single crystals with lamellar thicknesses of 12 ± 1 nm. We observed the melting of as few as 25 crystals. Over a wide number of crystals (25–2000 crystals), the heat of fusion was 40% larger than the bulk value. The melting temperature of the isolated single crystals was 123 ± 2 °C, 9 °C lower than that of the bulk material. We also measured the heat of fusion of quenched crystals (±15%) over a wide range of heating rates (20,000–100,000 K/s). Annealing the quenched crystals resulted in shifts in the endotherm peak by as much as 15 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1237–1245, 2001 相似文献
50.
A series of crosslinked polymer electrolyte membranes were prepared by blending cellulose and sulfosuccinic acid (SA) for
fuel cell applications. The crosslinking reaction of membranes occurred via the esterification between –OH of cellulose and
–COOH of SA, as confirmed by FT-IR spectroscopy. Both the ion exchange capacity and the proton conductivity increased in proportion
to the increase of SA concentrations due to the increasing portion of charged groups in the membrane. In contrast, the water
uptake linearly increased up to 25 wt.% of SA concentration, above which it decreased abruptly. The maximum behavior of water
uptake may be a result of competitive effect between the increasing number of ionic sites and the increasing degree of crosslinking
with the SA concentrations. Wide angle X-ray scattering also showed that the crystalline structures of cellulose disappeared
upon the introduction of SA. The mechanical properties of cellulose/SA membranes, i.e., tensile strength at break and Young’s
modulus, showed a maximum at 15 wt.% of SA, as revealed by universal testing machine. These membranes exhibited good thermal
stability up to 250 °C, as revealed by thermal gravimetric analysis. 相似文献