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41.
KB McTiernan SC Jarvis D Allen R Bol D Scholefield 《Rapid communications in mass spectrometry : RCM》1999,13(18):1803-1807
The composition of dissolved organic matter (DOM) in a soil is the product of a variety of soil processes. Changes in the composition of DOM in water discharged from soil should, therefore, give an important insight into modifications in these soil processes. We hypothesise that these processes in soils, under different grassland management regimes, would be affected to different extents by the short-term disturbance of a storm event and that evidence of this could be detected in delta(13)C and delta(15)N signatures in drainage and surface runoff waters. During a storm event we collected discharge waters from 1 ha grassland lysimeters, with or without artificial drainage, which received contrasting fertiliser inputs, and delta(13)C and delta(15)N signatures were determined. Changes in (13)C enrichment during the storm event were clearly identifiable, as were differences between plots for (13)C and (15)N, illustrating that this technique has potential to be a useful tool for identifying and investigating short- and long-term changes in soil organic matter dynamics. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
42.
43.
We derive a master equation describing the evolution of a quantum system subjected to a sequence of observations. These measurements occur randomly at a given rate and can be of a very general form. As an example, we analyse the effects of these measurements on the evolution of a two-level atom driven by an electromagnetic field. For the associated quantum trajectories we find Rabi oscillations, Zeno-effect type behaviour and random telegraph evolution spawned by mini quantum jumps as we change the rates and strengths of measurement. 相似文献
44.
D. J. Pegg H. H. Haselton R. S. Thoe P. M. Griffin M. D. Brown I. A. Sellin 《Physics letters. A》1975,50(6):447-448
The first observations of a number of optically inaccessible core-excited autoionizing states of lithium and sodium have been made. For example, the (1s2s2)2S and (1s2p2)2D states of Li have excitation energies of 56.31±0.03 and 61.04±0.03 eV, respectively. 相似文献
45.
P.A. Pegg 《Stochastic Processes and their Applications》1977,5(1):39-45
An identity is derived relating the distribution of a continuous time, skip-free process with two impenetrable barriers to the distribution of a process with one barrier. It is indicated how the methods used here can also be used to give results for related processes with different types of barriers. The identity is then used to derive explicit results giving the distribution of the process with two impenetrable barriers. 相似文献
46.
47.
E.-K.?Tan John?JeffersEmail author Stephen?M.?Barnett David?T.?Pegg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):495-499
We use retrodictive quantum theory to analyse two-photon quantum imaging systems. The formalism is particularly suitable for calculating conditional probability distributions. 相似文献
48.
K.?FritioffEmail author J.?Sandstr?m D.?Hanstorp F.?Hellberg A.?Ehlerding M.?Larsson G.?F.?Collins D.?J.?Pegg H.?Danared A.?K?llberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,27(1):23-26
Absolute cross sections for single and double electron-impact detachment of the S- ion have been investigated over collision energy ranges of 0-60 eV and 0-30 eV, respectively. The experiment was performed at the ion storage ring, CRYRING. The threshold energies were measured to be 6.6 eV for single detachment and 19.8 eV in the case of double detachment. The single detachment cross section has a maximum of 6.7 x 10-16 cm2 at 30 eV. The double detachment cross section was studied only in the threshold region. No sharp structures were observed in either of the cross sections.Received: 24 April 2003, Published online: 29 July 2003PACS:
34.80.Dp Atomic excitation and ionization by electron impact - 34.80.Kw Electron-ion scattering; excitation and ionization 相似文献
49.
D.T. Pegg 《Physics letters. A》1980,78(3):233-234
It is argued that, in the framework of Wheeler—Feynman electrodynamics objective reality and causality in the strict sense are consistent with the outcome of atomic cascade photon correlation experiments, provided this outcome is not altered by the Aspect experimental modification. 相似文献
50.
I. A. Sellin C. R. Vane S. B. Elston J. P. Forester P. M. Griffin D. J. Pegg R. S. Thoe K. -O. Groeneveld R. Laubert F. Chen 《Zeitschrift für Physik A Hadrons and Nuclei》1977,283(4):329-335
Passage of foil-excited 1.4 MeV/A S and 1.1 MeV/A Cl ions of neon charge state ~ 12+ through neon gas targets at pressure ~100 mTorr has been found to be accompanied by copious production of Ne II–VIII excited states. Comparable excitation cross-sections ~10?18 cm2 are found for a large number of levels belonging to all of these charge states and corresponding to principal quantum numbersn=2, 3, 4. Vacancy distributions very similar to those found in beam-foil excitation of ~1MeV neon beams are found. Because the Ne recoil velocities are small compared to the fast beam velocities characteristic of the beam-foil source, it is possible to reduce both Doppler shifts and spreads by 3–4 order of magnitude for equivalent collimation. It has also been found that there is an excitation cross-section change of a factor ~5 for a corresponding projectile charge state change from 6+ to 12+, that efforts to classifyK x-ray satellite spectra byLshell vacancy labels (KL 0,KL 1,...) are probably inaccurate due to extensive population ofn≧3 spectator levels, that both the recoil ion and beam-foil spectra exhibit few lines withn≧4, and that for the allowed transitions studied here, collisional excited states quenching effects due to the ~100mTorr target gas pressures used are negligible. 相似文献