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91.
Adam Walters Holger S.P. Müller Frank Lewen Stephan Schlemmer 《Journal of Molecular Spectroscopy》2009,257(1):24-28
Measurements of the rotational spectrum of diethyl ether have been extended up to 903 GHz for the aa-conformer and up to 638 GHz for the ag-conformer. These measurements supplement previous ones up to 366 GHz and improve predictions into the THz region to be used in particular for astronomical searches for this species using the next-generation of radio-astronomy instruments such as the Atacama Large Millimeter Array. 相似文献
92.
S. Civiš A.N. Imenkov A.P. Danilova N.M. Kolchanova V.V. Sherstnev Y.P. Yakovlev A.D. Walters 《Applied physics. B, Lasers and optics》2000,71(4):481-485
A new type of multimode semiconductor laser, based on InAsSb/InAsSbP heterostructures, is described. This continuous laser
working in a broad range of temperatures (30–100 K) was tested using a closed-cycle He-cryostat and its quality was demonstrated
using the laser spectroscopy of gases absorbing in the 2800 cm-1 region. Two different laser modes were used to increase the spectral range. The spectral characteristics and tunability of
the laser were explored as a function of heat-sink temperature and drive current with the aim of developing its use for high–resolution
spectroscopy. The laser has potential applications in the field of chemistry, atmospheric research and the study of the kinetics
of reactive species.
Received: 18 October 1999 / Revised version: 10 May 2000 / Published online: 16 August 2000 相似文献
93.
Let P be a Poisson process of intensity 1 in a square Sn of area n. We construct a random geometric graph Gn,k by joining each point of P to its k nearest neighbours. For many applications it is desirable that Gn,k is highly connected, that is, it remains connected even after the removal of a small number of its vertices. In this paper we relate the study of the s-connectivity of Gn,k to our previous work on the connectivity of Gn,k. Roughly speaking, we show that for s=o(logn), the threshold (in k) for s-connectivity is asymptotically the same as that for connectivity, so that, as we increase k, Gn,k becomes s-connected very shortly after it becomes connected. 相似文献
94.
Michelle A. Meierhoefer Matthew J. Walters S. Patrick Dunn Jarrett H. Vella Bonnie J. Grant Carolyn L. Sober Nidhi S. Patel Laela M. Hajiaghamohseni Sara B. Lioi Clyde R. Metz Charles F. Beam William T. Pennington Donald G. Vanderveer N. Dwight Camper 《Journal of heterocyclic chemistry》2006,43(2):307-313
95.
We present two new variants of Schur complement domain decompositionpreconditioners suitable for 2D anisotropic problems. Thesevariants are based on adaptations of the probing idea, describedby Chan et al (1992 Fifth Int. Symp. on Domain DecompositionMethods for Partial Differential Equations, Philadelphia: SIAM,pp 236-249), used in conjunction with a coarse grid approximationas introduced by Bramble et al (1986 Math. Comput. 47, 103-134).The new methods are specifically designed for situations wherethe coupling between neighbouring interfaces is stronger thanthe coupling within an interface. Taking into account this strongcoupling, one variant uses a multicolour probing technique toavoid distortion in the probe approximations that appear whenusing the method proposed by Chan et al. The second techniqueuses additional probe matrices to approximate not only the couplingwithin the interfaces but also the coupling between interfacepoints across the subdomains. This latter procedure looks somewhatlike an alternating line relaxation method for anisotropic problems,see Brandt (1977 Math. Comput.. 31, 333-390). To assess therelevance of the new preconditioners, we compare their numericalbehaviour with well known robust preconditioners such as thebalanced Neumann-Neumann method proposed by Mandel (1993 Commun.Numer. Methods Eng.. 9, 233-241). 相似文献
96.
A conceptually new type of electronic spark source is described. A parallel combination of a hydrogen thyratron and a diode is used as the switch element. The switch operates by providing parallel paths for current oscillating from capacitors discharging through inductive loads. The same principle is used to route current through the analytical spark gap. Either the switch current or the spark current can be adjusted in waveform from fully oscillatory to fully unidirectional simply by changing the value of a single inductor, without changing capacitance, resistance, or the voltage at which the source operates.The electrical circuitry is singularly simple, thus producing a source that is characterized by reliable, long term operation, precise ignition with low time jitter (ca. 5 nsec) and low conducted or radiated radio-frequency interference. Because of the latter, modern electronic devices (such as microprocessors and minicomputers) can be used in conjunction with and in direct control of the spark source, i.e., while the spark is conducting current. The source functions equally well for industrial spectrochemical analysis and for basic research on optical emission phenomena.A partial circuit analysis is included here. The current commutation between the hydrogen thyratron and shunt diode is characterized. Electronic circuitry appropriate for source operation at variable repetition rate is described. The types of spark current waveforms that can be obtained under electronic control are illustrated. 相似文献
97.
D.B. Walters W.J. Chamberlain F.J. Akin M.E. Snook O.T. Chortyk 《Analytica chimica acta》1978,99(1):143-150
Large-scale fractionation of cigarette smoke condensate (CSC) was carried out by gel filtration and silicic acid column chromatography, and selected fractions and their subfractions were tested for tumorigenicity by mouse-skin bioassay. The weak-acid fraction was separated into four subfractions, the polynuclear aromatic hydrocarbon (PAH) fraction into two subfractions, and the polar neutral lipid fraction into three subfractions. Also, combinations of subfractions were examined for synergic effects and portions of all active material were subjected to chemical analyses by gel filtration, column, thinlayer and gas chromatography, and ultraviolet and mass spectrometry. A weak-acid subfraction (F-63) in which catechol was concentrated, and which comprized 3.27% CSC was shown to be tumorigenic, as were combinations of this sub fraction with the active PAH (F-67) sub fraction and a polar, neutral lipid (F-70) sub fraction, representing 0.01 and 0.05% CSC, respectively. The results indicated that catechol may be a potent cocarcinogen and that the PAH in CSC interact with other components to exert a tumorigenic effect. 相似文献
98.
H. R. J. Walters H. Ast C. T. Whelan R. M. Dreizler H. Graf C. D. Schröter J. Bonfert W. Nakel 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,23(4):353-357
We report here on an (e, 2e) experiment at relativistic electron energies (E 0=300 keV and 500 keV) in coplanar symmetric geometry. Absolute triple differential cross section measurements forK-shell ionisation of gold, silver and copper are compared with a number of simple first order approximations. Appreciable discrepancies between theory and experiment are found, which reduce with decreasingZ and increasing primary energy. The theoretical calculations show that spin flip effects are important in symmetric geometry, in earlier works these had been neglected. 相似文献
99.
M.?KamppEmail author S.?Kawano P.?J.?P.?Roche J.?Rasch D.?H.?Madison H.?R.?J.?Walters C.?T.?Whelan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,29(1):17-19
The spin asymmetry arising in an (e,2e) process using spin-polarized incoming electrons with non-relativistic energies is shown to be dominated by the fine structure effect if a suitable kinematical regime is chosen. Calculations in the distorted wave Born approximation (DWBA) for both the triple differential cross-section and the spin asymmetry are presented for the inner shell ionization of argon. This process would provide an accessible target for existing experimental set-ups. 相似文献
100.
Dillmann I Kratz KL Wöhr A Arndt O Brown BA Hoff P Hjorth-Jensen M Köster U Ostrowski AN Pfeiffer B Seweryniak D Shergur J Walters WB;ISOLDE Collaboration 《Physical review letters》2003,91(16):162503
First beta- and gamma-spectroscopic decay studies of the N=82 r-process "waiting-point" nuclide 130Cd have been performed at CERN/ISOLDE using the highest achievable isotopic selectivity. Several nuclear-physics surprises have been discovered. The first one is the unanticipatedly high energy of 2.12 MeV for the [pi g(9/2) multiply sign in circle nu g(7/2)] 1(+) level in 130In, which is fed by the main Gamow-Teller transition. The second surprise is the rather high Q(beta) value of 8.34 MeV, which is in agreement only with recent mass models that include the phenomenon of N=82 shell quenching. Possible implications of these new results on the formation of the A approximately 130 r-process abundance peak are presented. 相似文献