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981.
982.
P. Viatte S. Micek R. Müller J. Lang J. Unternährer C.M. Teodorescu L. Jarczyk 《Physics letters. [Part B]》1975,59(1):35-37
The applicability of the particle-particle correlation method to obtain spectroscopic information on unbound states is investigated. Spins, parities and partial proton widths of some levels in 41Sc have been determined from measurements of the reaction 40Ca(d,n)41Sc(p)40Ca and compared with the results from elastic proton scattering. The resonance width is an important test for the reliability of DWBA calculations. 相似文献
983.
I. G. Lang L. I. Korovin D. A. Contreras-Solorio S. T. Pavlov 《Physics of the Solid State》2001,43(6):1159-1168
The interaction between a quantum well with a large number of equidistant excited electron energy levels and light is investigated. It is shown that nonsinusoidal oscillations occur in the transmitted, reflected, and absorbed energy fluxes under exposure of the quantum well to irradiation with light pulses. For long pulses whose length γ l ?1 is one order of magnitude longer than the time ?/ΔE (where ΔE is the energy level spacing), the oscillation amplitude is small. In the case of narrow pulses when γ l ?1 ≤?/ΔE, the oscillation amplitude is comparable to the flux magnitudes. For very narrow pulses with , the decaying echo of exciting pulse should be observed at the time intervals 2π?/ΔE. Symmetric and asymmetric pulses are considered. The theory is applicable to narrow quantum wells in a strong magnetic field when the equidistant levels correspond to electron-hole pairs with different Landau quantum numbers.
相似文献
984.
We consider the weighted Hardy integral operatorT:L
2(a, b) →L
2(a, b), −∞≤a<b≤∞, defined by
. In [EEH1] and [EEH2], under certain conditions onu andv, upper and lower estimates and asymptotic results were obtained for the approximation numbersa
n(T) ofT. In this paper, we show that under suitable conditions onu andv,
where ∥w∥p=(∫
a
b
|w(t)|p
dt)1/p.
Research supported by NSERC, grant A4021.
Research supported by grant No. 201/98/P017 of the Grant Agency of the Czech Republic. 相似文献
985.
Sprengers JP Ubachs W Johansson A L'Huillier A Wahlström CG Lang R Lewis BR Gibson ST 《The Journal of chemical physics》2004,120(19):8973-8978
The lifetime of the b 1Piu(v=1) state in 14N2 has been determined experimentally using a laser-based pump-probe scheme and an exceptionally long lifetime of 2.61 ns was found. Semiempirical close-coupling calculations of the radiative lifetime, which include Rydberg-valence interactions in the singlet manifold, are consistent with this large value, giving a value of 3.61 ns and suggesting a predissociation yield of approximately 28% for this level of the b state. 相似文献
986.
Investigations on controlled transition development in a laminar separation bubble by means of LDA and PIV 总被引:1,自引:0,他引:1
When a laminar boundary layer separates because of an adverse streamwise pressure gradient, the flow is subject to increased instability with respect to small-amplitude disturbances. Laminar–turbulent transition occurs under a rapid three-dimensional (3D) development within the separated shear layer. When the following turbulent boundary layer reattaches, a laminar separation bubble is formed. To allow controlled measurements, a small-amplitude Tollmien–Schlichting wave (TS wave) was introduced into the boundary layer without (case I) and with (case II) spanwise forcing of steady 3D disturbances. Combined application of laser-Doppler anemometry (LDA) and particle image velocimetry (PIV) demonstrates the suitability of both measurement techniques to capture the development of unsteady, periodic phenomena. The transition mechanism occurring in the flow field under consideration is discussed, and results obtained by controlled measurements are compared to direct numerical simulations (DNS) and predictions from linear stability theory (LST). Flow visualizations and stereoscopic PIV measurements give better insight into the 3D breakdown of the separated shear layer.Nomenclature a
amplitude
- f0
fundamental frequency
- H12
boundary layer shape factor,
H12=1/2
- h
wavenumber coefficient in time
- k
wavenumber coefficient in the spanwise direction
- l
liter
- m
meter
- Rex
Reynolds number based on streamwise distance of the leading edge
- Re1
Reynolds number based on the displacement thickness
1
- s
second
- t
time
- u
freestream velocity
- u
velocity at the boundary layer edge
- u,v,w
velocities
- u,v
velocity fluctuations
- x
streamwise coordinate
- y
wall-normal coordinate
- z
spanwise coordinate
-
boundary layer thickness
- 1
boundary layer displacement thickness
- 2
boundary layer momentum thickness
- z
spanwise wavelength
-
phase angle 相似文献
987.
van Buuren LD Szczerba D Alarcon R Boersma DJ van den Brand JF Bulten HJ Ent R Ferro-Luzzi M Harvey M Heimberg P Higinbotham DW Klous S Kolster H Lang J Militsyn BL Nikolenko D Norum BE Passchier I Poolman HR Rachek I Simani MC Six E de Vries H Zhou ZL 《Physical review letters》2002,89(1):012001
We report on measurements of the cross section and provide first data on spin correlation parameters A(TT') and A(TL') in inclusive scattering of longitudinally polarized electrons from nuclear-polarized hydrogen. Polarized electrons were injected into an electron storage ring operated at a beam energy of 720 MeV. Polarized hydrogen was produced by an atomic beam source and injected into an open-ended cylindrical cell, located in the electron storage ring. The four-momentum transfer squared ranged from Q2 = 0.2 GeV(2)/c(2) at the elastic scattering peak to Q2 = 0.11 GeV(2)/c(2) at the Delta(1232) resonance. The data provide a stringent test of pion electroproduction models. 相似文献
988.
Ahrens J Altieri S Annand JR Anton G Arends HJ Aulenbacher K Beck R Bradtke C Braghieri A Degrande N D'Hose N Drechsel D Dutz H Goertz S Grabmayr P Hansen K Harmsen J Von Harrach D Hasegawa S Hasegawa T Heid E Helbing K Holvoet H Van Hoorebeke L Horikawa N Iwata T Jahn O Jennewein P Kageya T Kamalov S Kiel B Klein F Kondratiev R Kossert K Krimmer J Lang M Lannoy B Leukel R Lisin V Matsuda T McGeorge JC Meier A Menze D Meyer W Michel T Naumann J Panzeri A Pedroni P Pinelli T Preobrajenski I 《Physical review letters》2002,88(23):232002
The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes. 相似文献
989.
Measurement of the conductance of a hydrogen molecule 总被引:8,自引:0,他引:8
Recent years have shown steady progress towards molecular electronics, in which molecules form basic components such as switches, diodes and electronic mixers. Often, a scanning tunnelling microscope is used to address an individual molecule, although this arrangement does not provide long-term stability. Therefore, metal-molecule-metal links using break-junction devices have also been explored; however, it is difficult to establish unambiguously that a single molecule forms the contact. Here we show that a single hydrogen molecule can form a stable bridge between platinum electrodes. In contrast to results for organic molecules, the bridge has a nearly perfect conductance of one quantum unit, carried by a single channel. The hydrogen bridge represents a simple test system in which to understand fundamental transport properties of single-molecule devices. 相似文献
990.
Zhang F Wolff MW Williams D Busch K Lang SC Murhammer DW Linhardt RJ 《Applied biochemistry and biotechnology》2001,90(2):125-136
Human secreted alkaline phosphatase (SEAP) was produced in a stablytransformed Spodoptera frugiperda Sf-9 insect cell line (Sfb4GalT) following infection with a recombinant Autographa californica multiple nuclear polyhedrovirus containing the SEAP gene under control of the polyhedrin promoter. An affinity chromatographic
column prepared by linking 4-aminobenzylphosphonic acid to histidyl-expoxy-Sepharose was used to isolate SEAP from the cell
supernatant following removal of cells and virus and 10-fold concentration through ultrafiltration. We found that the binding
of SEAP on the affinity matrix follows the Langmuir isotherm model. In addition, either recycling SEAP sample through the
column for 24 h or loading high SEAP concentrations resulted in a high-purity product. Some nonspecific binding of protein
on the matrix occurred when low concentrations of SEAP sample were loaded. Finally, we found that SEAP binding occurs rapidly,
i.e., within 30 min of adding the SEAP sample to the affinity matrix. 相似文献