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排序方式: 共有410条查询结果,搜索用时 15 毫秒
1.
E.R. Berger M. Diehl B. Pire 《The European Physical Journal C - Particles and Fields》2002,23(4):675-689
We investigate the exclusive photoproduction of a heavy timelike photon which decays into a lepton pair, . This can be seen as the analog of deeply virtual Compton scattering, and we argue that the two processes are complementary
for studying generalized parton distributions in the nucleon. In an unpolarized experiment the angular distribution of the
leptons readily provides access to the real part of the Compton amplitude. We estimate the possible size of this effect in
kinematics where the Compton process should be dominated by quark exchange.
Received: 9 October 2001 / Published online: 5 April 2002 相似文献
2.
3.
4.
Thomas Bally Peter Diehl Edwin Haselbach Alan S. Tracey 《Helvetica chimica acta》1975,58(8):2398-2402
The NMR. spectrum of guanidinium ion 1 is studied in anisotropic liquid crystalline nematic solution. Assuming an HNH-angle of 120°, the distance ratio NH /NC = 0.784 is obtained, from which using NC = 1.330 Å (from X-ray data) NH = 1.043 Å results. An upper bound for the free energy of activation for bond rotation of ΔG+ ≤ 13 kcal/mol is deduced. The bondrotational mobility of 1 is also investigated using the MINDO/3-SCF-procedure. The results obtained for the three conceivable consecutive activation energies for bond-rotation indicate that the observed bond-rotational mobility of 1 does not involve cooperative two- or three-bond rotations. The ‘conjugative stabilization’ of 1 has been estimated to be of the order of 24–26 kcal/mol. 相似文献
5.
An artificial polypeptide scaffold composed of surface anchor and protein capture domains was designed and expressed in vivo. By using a mutant E. coli phenylalanyl-tRNA synthetase, the photoreactive amino acid para-azidophenylalanine was incorporated into the surface anchor domain. Octyltrichlorosilane-treated surfaces were functionalized with this polypeptide by spin coating and photocrosslinking. The resulting protein films were shown to immobilize recombinant proteins through association of coiled coil heterodimer. 相似文献
6.
To investigate the natural tritium content of foods a combustion apparatus was developed, in which nearly 100 ml of water are obtained in one operation from foods of any composition. To measure the tritium activity of this combustion water in the liquid scintillation spectrometer, the interfering combustion products are removed by distillation. The construction and operation of the combustion apparatus and of the water purification system are described. 相似文献
7.
Ahlen S Ambrosio M Antolini R Auriemma G Baker R Baldini A Bam BB Barbarino GC Barish BC Battistoni G Bellotti R Bemporad C Bernandini P Bilokon H Bisi V Bloise C Bower C Bussino S Cafagna F Calicchio M Campana D Campana P Carboni M Cecchini S Cei F Chiarella V Cormack R Corona A Coutu S De Cataldo G Dekhissi H De Marzo C De Vincenzi M Di Credico A Diehl E Erriquez O Favuzzi C Ficenec D Forti C Fusco P Giacomelli G Giannini G Giglietto N Giubellino P Grassi M Green P Grillo A Guarino F 《Physical review letters》1994,72(5):608-612
8.
S. Diehl 《Communications in Mathematical Physics》1996,176(1):23-44
The equation
, whereH is Heaviside's step function, appears for example in continuous sedimentation of solid particles in a liquid, in two-phase flow, in traffic-flow analysis and in ion etching. The discontinuity of the flux function atx=0 causes a discontinuity of a solution, which is not uniquely determined by the initial data. The equation can be written as a triangular 2×2 non-strictly hyperbolic system. This augmentation is non-unique and a natural definition is given by means of viscous profiles. By a viscous profile we mean a stationary solution ofu
t
+(F
)
x
=u
xx
, whereF
is a smooth approximation of the discontinuous flux, i.e.,H is smoothed. In terms of the 2×2 system, the discontinuity atx=0 is either a regular Lax, an under-or overcompressive, a marginal under- or overcompressive or a degenerate shock wave. In some cases, depending onf andg, there is a unique viscous profile (e.g. undercompressive and regular Lax waves) and in some cases there are infinitely many (e.g. overcompressive waves). The main purpose of the paper is to show the equivalence between a previously introduced uniqueness condition for the discontinuity of the solution atx=0 and the viscous profile condition. 相似文献
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10.
Qian K Diehl JW Dechert GJ DiSanzo FP 《European journal of mass spectrometry (Chichester, England)》2004,10(2):187-196
We report the first coupling of supercritical fluid chromatography (SFC) with field ionization time-of-flight high-resolution mass spectrometry (FI-ToF HRMS), in parallel with ultraviolet (UV) detection and flame ionization detection (FID), for rapid and quantitative analysis of petroleum middle distillates. SFC separates petroleum middle distillates into saturates and 1- to 3-ring aromatics. FI generates molecular ions for hydrocarbon species eluted from the SFC. The high resolution and exact mass measurements by ToF mass spectrometry provide elemental compositions of the molecules in the petroleum product. The amounts of saturates and aromatic ring types were quantified using the parallel SFC-FID assisted by SFC-UV. With a proper carbon-number calibration, the detailed composition of the petroleum middle distillate was rapidly determined. 相似文献