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M. Della Negra D. Drijard H.G. Fischer G. Fontaine H. Frehse P. Frenkiel C. Chesquiere R. Gokieli P. Hanke W. Hofmann W. Isenbeck E.E. Kluge V. Korbel D. Linglin A. Minten A. Norton A. Putzer R. Sosnowski D. Wegener 《Physics letters. [Part B]》1976,65(4):394-396
The reaction pp→ppπ+π? at √s=31GeV was studied at the Split Field Magnet Facility of the CERN-ISR. Selecting events with two leading protons of x>0.9 and a rapidity gap Δy>2 between the protons and both pions a sample of 720 events is obtained representing a cross section of 25±10μb. The mass distribution of the dipion system, x and pT distributions for the protons are presented and analyzed for the presence of double pomeron exchange. 相似文献
34.
Long pulse laser action has been achieved at 3378.28 and 3481.96 Å in an electron beam excited supersonic flow. These laser emissions, attributed to NeII transitions, have been obtained when a mixture of Ne and NF3 at a pressure of 0.2 atm. and aerodynamically cooled to 80 K was excited by a medium intensity electron beam. Laser pulse duration, about 350 ns fwhm for both lines, was only limited by the electron beam pulse length. The second of these laser lines had not been previously reported. 相似文献
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Ayad T Faugeroux V Génisson Y André C Baltas M Gorrichon L 《The Journal of organic chemistry》2004,69(25):8775-8779
We developed a stereocontrolled route allowing potential access to the eight isomers of 4-benzylaminohex-5-ene-1,2,3-triol in two or four steps and ca. 50% yield from readily available chiral nonracemic cis- or trans-alpha,beta-epoxyimine precursors. A new (NH(4))(2)CO(3)-based carboxylation/intramolecular cyclization sequence allowed regio- and stereocontrolled C-3 epoxide opening while neat C-2 hydrolysis was ensured by simple aqueous acidic treatment. 相似文献
38.
Meallet-Renault R Pansu R Amigoni-Gerbier S Larpent C 《Chemical communications (Cambridge, England)》2004,(20):2344-2345
A fluorescent sensor for Cu(2+) at the nanomolar level in water has been designed by associating a BODIPY fluorophore and a selective ligand (cyclam) in ultrafine polymer nanoparticles. 相似文献
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The frequency dependence of the ultrasound signal backscattered by blood in shear flow was studied using a simulation model. The ultrasound backscattered signal was computed with a linear model that considers the characteristics of the ultrasound system and tissue acoustic properties. The tissue scattering properties were related to the position and shape of the red blood cells (RBCs). A 2D microrheological model simulated the RBC dynamics in a Couette shear flow system. This iterative model, described earlier [Biophys. J. 82, 1696-1710 (2002)], integrates the hydrodynamic effect of the flow, as well as adhesive and repulsive forces between RBCs. RBC aggregation was simulated at 40% hematocrit and shear rates of 0.05-2 s(-1). The RBC aggregate sizes ranged, on average, from 3.3 RBCs at 2 s(-1) to 33.5 cells at 0.05 s(-1). The ultrasound backscattered power was studied at frequencies between 5-120 MHz and insonification angles between 0-180 degrees. At frequencies below approximately 30 MHz, the ultrasound backscattered power increased as the shear rate was decreased and the size of the aggregates was raised. A totally different scattering behavior was noted above 30 MHz. Typical spectral slopes of the backscattered power (log-log scale) between 5-25 MHz equaled 3.8, whereas slopes down to 0.6 were measured at 0.05 s(-1), between 40-60 MHz. The ultrasound backscattered power was shown to be angle dependent at low frequencies (5-25 MHz). The anisotropy persisted at high frequencies (>25 MHz) for small aggregates (at 2 s(-1)). In conclusion, this study sheds some light on the blood backscattering behavior with an emphasis on the non-Rayleigh regime. Additional experimental studies may be necessary to validate the simulation results, and to fully understand the relation between the ultrasound backscattered power, level of RBC aggregation, shear rate, frequency, and insonification angle. 相似文献
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Bonfim M Ghiringhelli G Montaigne F Pizzini S Brookes NB Petroff F Vogel J Camarero J Fontaine A 《Physical review letters》2001,86(16):3646-3649
We have developed a new original technique to study the magnetization reversal dynamics of thin films with element selectivity in the nanosecond time scale. X-ray magnetic circular dichroism measurements in pump-probe mode are carried out taking advantage of the time structure of synchrotron radiation. The dynamics of the magnetization reversal of each of the layers of complex heterostructures (like spin valves or tunnel junctions) can be probed independently. The interlayer coupling in the studied systems has been shown to play a key role in the determination of the magnetization reversal of each individual layer. 相似文献