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121.
R. H. Warbington W. C. Crowe J. C. Seferis A. J. deVries R. Gehrke H. G. Zachmann 《Colloid and polymer science》1986,264(8):683-690
A combination of structure identifying and bulk property experiments were combined with a two-phase analytical methodology to elucidate the influence of a magnetic tape coating process on the substrate polymer film. Employing a typical tape manufacturing process that utilizes coating, drying, and calendering stages, polyethylenete-rephthalate polymer film samples with and without the magnetic coating were prepared.Experiments and modeling studies performed on these samples demonstrate that the drying and calendering processes may increase the crystallinity and noncrystalline orientation of the substrate film. In addition, dynamic mechanical experiments identified a viscoelastic transition at 50 °C for the PET substrate film sample which is near the glass transition of the magnetic coating utilized. Overall, the results of this investigation provide a basis for evaluating structure property interrelations of polymer-based magnetic tapes. 相似文献
122.
Geraldine C.B HarrimanShannon Chi Min ZhangAndrea Crowe Robert A BennettIan Parsons 《Tetrahedron letters》2003,44(18):3659-3662
The synthesis of the biologically relevant, 4-trifluoromethylpyrido[1,2-a]pyrimidin-2-one 7, is reported. Addition of substituted 2-aminopyridines 5 to activated alkynoates leads to the facile formation of a series of metabolically stable trifluoromethyl substituted pyrido[1,2-a]pyrimidines under mild conditions. 相似文献
123.
I.B. Goldberg H.R. Crowe D. Pilipovich G.R. Schneider C.J. Schack 《Chemical physics letters》1977,50(2):301-305
The reaction of iodobistrifluoromethylphosphine, P(CF3)2I, with atomic fluorine was studied by fast-flow ESR methods. The initial stage of the reaction is the abstraction of I by F, to form IF with a bimolecular rate constant of (1.0 ± 0.3) × 1014 cm3 mol?1 s?1 at 297 K. In the presence of excess F, stepwise addition to the phosphorous occurs. In the presence of excess P(CF3)2I, the reaction P(CF3)2 + IF → P (CF3)2F + I appears to take place. This reaction rate is slow relative to P(CF3)2 + F → P(CF3)2F. 相似文献
124.
Schott W. Müller S. Daniel H. Ackerbauer P. Balin D. V. Baturin V. N. Beer G. A. Breunlich W. H. Case T. Crowe K. M. Deutsch J. Egger J. von Egidy T. Govaerts J. Grigoriev Yu. S. Hartmann F. J. Kammel P. Lauss B. Maev E. M. Markushin V. Marton J. Mühlbauer M. Petitjean C. Petitjean T. Petrov G. E. Prieels R. Prymas W. Semenchuk G. G. Smirenin Yu. V. Van den Brandt B. Vorobyov A. A. Voropaev N. I. Wojciechowski P. 《Hyperfine Interactions》1996,101(1):445-449
The triton energy spectrum of the muon capture reaction µ3Het+µ where µ3He is the ground state of muonic3He, has been measured by means of a high-pressure ionization chamber in order to investigate a possible heavyv admixture into the µ flavor with high sensitivity. The upper limit of the µ-heavy vi mixing matrix element squared was obtained to be Uµi210–3 for heavy neutrino masses in the range of 25 E0V75 MeV. 相似文献
125.
Chung P Ajitanand NN Alexander JM Anderson M Best D Brady FP Case T Caskey W Cebra D Chance JL Cole B Crowe K Das A Draper JE Gilkes ML Gushue S Heffner M Hirsch AS Hjort EL Huo L Justice M Kaplan M Keane D Kintner JC Klay J Krofcheck D 《Physical review letters》2000,85(5):940-943
We have measured the sideward flow of neutral strange ( K(0)(s)) mesons in 6A GeV Au+Au collisions. A prominent antiflow signal is observed for an impact parameter range ( b less, similar7 fm) which spans central and midcentral events. Since the K(0)(s) scattering cross section is relatively small in nuclear matter, this observation suggests that the in-medium kaon vector potential plays an important role in high density nuclear matter. 相似文献
126.
Surface reflections often present a problem in the polarization difference imaging of tissue. The technique described involves illumination in a single polarization state and detection in the orthogonal polarization state. Synchronously rotating both the illumination and orthogonal detection states provides an image free from surface reflections that is sensitive to the polarization properties of the underlying tissue. Results on tissue phantoms demonstrate that polarization sensitive measurements of a test target can be made up to a depth of 12 mean free paths within a scattering medium. Preliminary images of bovine tendon are also demonstrated. 相似文献
127.
Zhaofu Fei Holger Thnnessen Peter G. Jones Lindsey Crowe Robin K. Harris Reinhard Schmutzler 《无机化学与普通化学杂志》2000,626(8):1763-1772
The reaction of the bis‐chlorophosphines 1 a – 1 d with bis(2‐chloroethyl)amine hydrochloride in the presence of triethylamine and with various trimethylsilylamines led to a new class of bis‐phosphorus ligands 2 a – 2 c and 3 a – 3 g . 31P‐NMR studies suggested that the bis‐phosphorus ligands undergo rotation reactions about the alkyl bridge in polar solvents. Compounds 2 a – 2 c showed initially only one sharp singlet each in their 31P‐NMR spectra. After a few days at room temperature, two signals were observed. Similar results were observed for 3 a – 3 g . In the solid state, the two phosphorus atoms in 2 c are not equivalent, as was confirmed by the observation of two signals in the solid state 31P‐NMR spectrum. Oxidation reactions of 2 a – 2 c by the hydrogen peroxide‐urea 1 : 1 adduct (NH2)2C(:O) · H2O2 led to the formation of the corresponding phosphoryl compounds 4 a – 4 c . Reaction of 2 a and 3 a with Pt[COD]Cl2 (COD = 1.5‐Cyclooctadiene) furnished the complexes 5 and 6 . The NMR spectra suggested that the two chlorine atoms are in cis position. X‐ray structure analyses were conducted for 2 a , which exhibits twofold symmetry; 2 c , which is linked into dimers by hydrogen bonds C–H…O; and 6 , confirming the cis configuration. 相似文献
128.
E. M. Maev V. A. Andreev T. A. Case K. M. Crowe P. U. Dick A. Dijksman J. Egger D. Fahrni A. A. Fetisov V. A. Ganzha F. J. Hartmann P. Kammel A. G. Krivchitch O. E. Maev C. Petitjean G. E. Petrov R. Prieels S. M. Sadetsky G. N. Schapkin R. Schmidt G. G. Semenchuk M. Soroka A. A. Vorobyov N. I. Voropaev 《Hyperfine Interactions》2001,138(1-4):451-457
A new experiment is under preparation with the aim to improve considerably the present knowledge of the rate Λ
s
, which should be measured on a level of 1% or better, for the basic electroweak capture reaction of a negative muon on the
free proton μp
1s
→ n + νμ. The capture rate will be determined by measuring the lifetime of μ− stopped in ultra pure hydrogen at 10 bar pressure and comparing it with the lifetime of the unbound μ+. A new experimental method was developed for this project which should allow measuring the μ− lifetime with at least 10 ppm precision. The basic element of the detector is operating in the hydrogen gas time projection
chamber (TPC) surrounded by multi-wire proportional chambers (MWPCs) and scintillator counters. The arrival times and trajectories
of the incoming muons and the outgoing decay electrons are measured with this device providing effective suppression of background.
Using the TPC as an active target, we can monitor on-line the protium contamination by impurities with a sensitivity better
than 10−8. This can be done by detecting the charged products of the muon capture reaction on these impurities. It was demonstrated
that the TPC and MWPCs can operate in pure hydrogen under 10 bar pressure providing gas gain up to 10 000.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
129.
T. Case D.V. Balin W.H. Breunlich K.M. Crowe H. Daniel B. Gartner F.J. Hartmann P. Kammel B. Lauss E.M. Maev V.E. Markushin M. Mühlbauer C. Petitjean G.E. Petrov W. Prymas G.N. Schapkin W. Schott G.G. Semenchuk Yu.V. Smirenin A.A. Vasiliev A.A. Vorobyov N.I. Voropaev J. Zmeskal 《Hyperfine Interactions》1999,118(1-4):197-202
Data from the recent PSI high statistics experiment on d μ d fusion are used to measure the stripping process in d μ d→
n+μ,3He and test current calculations of the stripping process. The PSI results in μ3He capture are also used to remove a troubling background from this measurement. Combination of these results with the old
dμ t sticking analysis slightly raise and improve that result to ωs= (0.58± 0.04)% and indicate that theory and experiment can meet if theoretical stripping is increased only at the beginning
of the track. This conclusion is in accord with the new stripping calculations where excited state stripping is increased
significantly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
130.
A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based
on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin
(TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase.
The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence
enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic
amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation
with the theoretically derived equation in the range 1.0 × 10–6 to 8.0 × 10–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity
of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine
in water samples containing interferents with satisfactory recovery.
Received: 21 November 1999 / Revised: 10 January 2000 / Accepted: 15 January 2000 相似文献