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排序方式: 共有143条查询结果,搜索用时 15 毫秒
91.
Jaegle I Mertens T Anisovich AV Bacelar JC Bantes B Bartholomy O Bayadilov D Beck R Beloglazov YA Castelijns R Crede V Dutz H Ehmanns A Elsner D Essig K Ewald R Fabry I Fuchs M Funke Ch Gothe R Gregor R Gridnev AB Gutz E Höffgen S Hoffmeister P Horn I Junkersfeld J Kalinowsky H Kammer S Kleber V Klein F Klein F Klempt E Konrad M Kotulla M Krusche B Lang M Langheinrich J Löhner H Lopatin IV Lotz J Lugert S Menze D Messchendorp JG Metag V Morales C Nanova M Nikonov VA Novinski D Novotny R 《Physical review letters》2008,100(25):252002
Quasifree photoproduction of eta mesons off nucleons bound in the deuteron has been measured with the CBELSA/TAPS detector for incident photon energies up to 2.5 GeV at the Bonn ELSA accelerator. The eta mesons have been detected in coincidence with recoil protons and recoil neutrons, which allows a detailed comparison of the quasifree n(gamma,eta)n and p(gamma,eta)p reactions. The excitation function for eta production off the neutron shows a pronounced bumplike structure at W=1.68 GeV (E{gamma} approximately 1 GeV), which is absent for the proton. 相似文献
92.
Heinrich P. Lotz 《Israel Journal of Mathematics》2010,176(1):209-220
We consider a Dedekind σ-complete Banach lattice E whose dual is weakly sequentially complete. Suppose that E has a positive element u and a family of positive operators $
\mathcal{G}
$
\mathcal{G}
such that
(i) |
each T′, T ∈ $
\mathcal{G}
$
\mathcal{G}
, is a lattice homomorphism 相似文献
93.
The mixed convection flow and heat transfer from an exponentially stretching vertical surface in a quiescent fluid is analyzed using similarity solution technique. Wall temperature and stretching velocity are assumed to have specific exponential function forms. The influence of buoyancy along with viscous dissipation on the convective transport in the boundary layer region is analyzed in both aiding and opposing flow situations. The flow is governed by the mixed convection parameter Gr/Re2. The velocity and temperature inside the boundary layer are observed to be influenced by the parameters like Prandtl number Pr, Gebhart number Gb. Significant changes are observed in non-dimensional skin friction and heat transfer coefficients due to viscous dissipation in the medium. The flow and temperature distributions inside the boundary layer are analyzed and the results for non-dimensional skin friction and heat transfer coefficients are discussed through computer generated plots. 相似文献
94.
Gottfried T.W. Wittmann Gert N. Krynauw Simon Lotz Werner Ludwig 《Journal of organometallic chemistry》1985,293(3):c33-c37
The UV absorption bands between approximately 330 and 200 nm have been assigned to Rydberg transitions for the d6 complexes Cr(η6-C6H6)2, Cr(CO)6 and Cr(η6-C6H6)(CO)3 相似文献
95.
We extend one of the main results of Bürgisser and Cucker (http://www.arxiv.org/abs/cs/cs.CC/0312007), which asserts that the computation of the Euler characteristic of a semialgebraic set is complete in the counting complexity class . The goal is to prove a similar result over : the computation of the Euler characteristic of an affine or projective complex variety is complete in the class . To cite this article: P. Bürgisser et al., C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
96.
J. Junkersfeld A. V. Anisovich G. Anton R. Bantes O. Bartholomy R. Beck Yu. Beloglazov R. Bogendörfer R. Castelijns V. Crede A. Ehmanns J. Ernst I. Fabry H. Flemming A. Fösel M. Fuchs Ch. Funke R. Gothe A. Gridnev E. Gutz St. Höffgen I. Horn J. Hößl H. Kalinowsky F. Klein E. Klempt H. Koch M. Konrad B. Kopf B. Krusche J. Langheinrich H. Löhner I. Lopatin J. Lotz H. Matthäy D. Menze J. Messchendorp V. A. Nikonov D. Novinski M. Ostrick H. van Pee A. Radkov A. V. Sarantsev S. Schadmand C. Schmidt H. Schmieden B. Schoch G. Suft V. Sumachev T. Szczepanek U. Thoma D. Walther Ch. Weinheimer 《The European Physical Journal A - Hadrons and Nuclei》2007,31(3):365-372
Differential and total cross-sections for photoproduction of γp→pπ
0
ω and γp→Δ
+
ω were determined from measurements of the CB-ELSA experiment, performed at the electron accelerator ELSA in Bonn. The measurements
covered the photon energy range from the production threshold up to 3GeV. 相似文献
97.
Credé V Bartholomy O Anisovich AV Anton G Bantes R Beloglazov Y Bogendörfer R Castelijns R Ehmanns A Ernst J Fabry I Flemming H Fösel A Freiesleben H Fuchs M Funke Ch Gothe R Gridnev A Gutz E Höffgen SK Horn I Hössl J Joosten R Junkersfeld J Kalinowsky H Klein F Klempt E Koch H Konrad M Kopf B Krusche B Langheinrich J Löhner H Lopatin I Lotz J Matthäy H Menze D Messchendorp J Morales C Novinski D Ostrick M van Pee H Radkov A Reinnarth J Sarantsev AV Schadmand S Schmidt Ch Schmieden H Schoch B 《Physical review letters》2005,94(1):012004
Total and differential cross sections for the reaction p(gamma,eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into peta. At medium energies we find evidence for a new resonance N(2070)D15 with (M,Gamma)=(2068+/-22, 295+/-40) MeV. At gamma energies above 1.5 GeV, a strong peak in the forward direction develops, signaling the exchange of vector mesons in the t channel. 相似文献
98.
Trnka D Anton G Bacelar JC Bartholomy O Bayadilov D Beloglazov YA Bogendörfer R Castelijns R Crede V Dutz H Ehmanns A Elsner D Ewald R Fabry I Fuchs M Essig K Funke Ch Gothe R Gregor R Gridnev AB Gutz E Höffgen S Hoffmeister P Horn I Hössl J Jaegle I Junkersfeld J Kalinowsky H Klein F Klein F Klempt E Konrad M Kopf B Kotulla M Krusche B Langheinrich J Löhner H Lopatin IV Lotz J Lugert S Menze D Messchendorp JG Mertens T Metag V Morales C Nanova M Novotny R Ostrick M Pant LM van Pee H Pfeiffer M 《Physical review letters》2005,94(19):192303
The photoproduction of omega mesons on nuclei has been investigated using the Crystal Barrel/TAPS experiment at the ELSA tagged photon facility in Bonn. The aim is to study possible in-medium modifications of the omega meson via the reaction gamma + A --> omega + X --> pi(0)gamma + X('). Results obtained for Nb are compared to a reference measurement on a LH2 target. While for recoiling, long-lived mesons (pi(0), eta, and eta;(')), which decay outside of the nucleus, a difference in the line shape for the two data samples is not observed, we find a significant enhancement towards lower masses for omega mesons produced on the Nb target. For momenta less than 500 MeV/c an in-medium omega meson mass of M(medium) = [722(+4)(-4)(stat)+35-5(syst)] MeV/c(2) has been deduced at an estimated average nuclear density of 0.6rho(0). 相似文献
99.
C. Mathieu A. Thierry J. C. Wittmann B. Lotz 《Journal of Polymer Science.Polymer Physics》2002,40(22):2504-2515
Nucleating agents with an ≈6.5 Å lattice parameter induced the α phase of isotactic polypropylene (iPP, α‐iPP). A 6.5 Å periodicity is also involved in the nucleating agents for the β phase of iPP (β‐iPP). The similarity in substrate periodicities suggests that some nucleating agents may induce either the α or β phase under different crystallization conditions. 4‐Fluorobenzoic acid, dicyclohexylterephthalamide, and γ‐quinacridone (the latter two are known as β‐iPP nucleators) were tested over a wide range of crystallization temperatures [up to crystallization temperature (Tc) > 145 °C]. The two former nucleating agents induce exclusively α‐iPP and β‐iPP, respectively. γ‐Quinacridone on the contrary is a versatile agent with respect to the crystal phase generated. More specifically, the same crystal face of γ‐quinacridone induces either β‐iPP or α‐iPP when Tc is below or above ≈140 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2504–2515, 2002 相似文献
100.
Blends of isotactic polypropylene and polyethylene or polyamides often display highly unusual crystalline morphologies in which the chain axes of the helical and linear polymers are at large angles to each other. These crystalline morphologies are explained on the basis of a specific epitaxial relationship that rests on the existence, in the (010) plane of iPP, of rows of methyl groups nearly 5-Å apart. The structural basis of all the observed morphologies is the parallel alignment of the aliphatic segments of the PE or polyamides and of the iPP methyl rows (or vice versa) and matching of the near 5-Å distances between PE or PA chains and iPP methyl rows. The implications of this unusual epitaxial relationship with respect to the apparent “universality” of polymer nucleating agents are examined. 相似文献
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