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  • 1995-1999  (4)
  • 1990-1994  (4)
  • 1997  (4)
  • 1992  (4)
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  • 1995-1999  (4)
  • 1990-1994  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Vibrationally enhanced inelastic atom–molecule cross sections at very low energies (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8819-8829 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants for inelastic processes in Na2 (v,j)–Ne, Ar, Na collisions are determined at a mean collision energy of the order of 1 meV in a supersonic seeded beam arrangement. The initial vibrational state v and rotational state j is varied in the range 4≤v≤35 and 5≤j≤25. The Na2 molecules are excited by Franck–Condon pumping near the transition region to free molecular flow and the flux of molecules which survive in the level (v,j) is monitored far downstream behind a small aperture. It is shown that elastic processes do not contribute to the observed signal. The magnitude of the cross section for the sum of all inelastic processes is as large as several hundred A(ring)2. It is found that the vibrational motion of the molecule, which carries an energy of up to 500 meV, strongly influences the collision dynamics. The rate constant increases with v by about 35% within the range of vibrational levels studied here. Some state-to-state rate constants are also reported. The experimental results are in good agreement with data from quasiclassical trajectory calculations on a semiempirical bond-distance-dependent potential surface. The observations can be rationalized by realizing that the long range attraction increases with vibrational excitation since the polarizability of the molecule increases. Furthermore, the vibrational excitation in combination with the relatively long interaction time due to the low collision energy enhances the probability for a change of the initial quantum state of the molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462239
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of vibrational excitation (3≤v‘≤19) on the reaction Na2 (v‘)+Cl→NaCl+Na* (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9472-9475 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The variation of the total integral cross section for the chemiluminescent channel with the vibrational excitation 3≤v‘≤19 is investigated using laser-induced fluorescence or coherent population transfer, a new method employing delayed interaction with two cw lasers to populate vibrationally excited levels. The cross section increases with v‘ by about 0.76% per vibrational level. The results are in agreement with the results of phase-space calculations, as well as with those from simple curve crossing models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463271
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  • 3
    Electronic Resource
    Electronic Resource
    Population transfer by stimulated Raman scattering with delayed pulses using spectrally broad light (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4215-4223 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The feasability of selective and complete population transfer between atomic or molecular levels by stimulated Raman scattering with delayed pulses involving spectrally broad light with characteristics typical for pulsed lasers is investigated. In extension of previous work, the effect on the transfer efficiency of phase fluctuations and of the detuning ΔR of the laser frequencies from the two-photon resonance is analyzed. The minimum pulse energy Pmin required to achieve a transfer efficiency of nearly unity is derived analytically, with some restrictions imposed on the type of phase fluctuations. Pmin increases approximately proportional to the square of the bandwidth of the laser radiation and to the square of ΔR. The conclusions are confirmed by the results of extensive numerical calculations. These studies also reveal a high sensitivity of the transfer efficiency to the autocorrelation of the fluctuating light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462840
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  • 4
    Electronic Resource
    Electronic Resource
    Triggering a radial multichannel pseudospark switch using electrons emitted from material with high dielectric constant (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1936-1938 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron emission from a field emission trigger unit was matched to the requirements for the simultaneous ignition of all channels in a radial multichannel pseudospark switch for a large parameter range of the pseudospark discharge. In such trigger unit the electrons are extracted from the surface of a high-ε material by field emission after applying a pulsed voltage. Electron emission occurs in a pressure range from 1–50 Pa, where the pseudospark discharge is operated. The access to low working gas pressures (〈10 Pa) using such trigger unit allows for achieving high hold-off voltages. The ignition of the pseudospark discharge was investigated by means of high speed photography and by a parallel observation of the electron beam of a single discharge channel, which occurs in hollow-cathode phase. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119986
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  • 5
    Electronic Resource
    Electronic Resource
    Predictability of early atopy by cord blood-IgE and parental history (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical & experimental allergy 27 (1997), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Atopic family history and cord blood IgE have been used as predictors of atopic disease in newborns for about 20 years, but at least for cord blood IgE the sensitivity has been shown to be very low. The objective of this paper was to evaluate whether parental history and cord blood-IgE were more accurate predictors for the appropriate atopic phenotypes in the infants rather than for any atopy.Methods A total of 1314 newborn infants was recruited in six German obstetric departments in 1990 and followed-up for 2 years. Four hundred and ninty-ninc (38%) were at high risk for atopy with at least two first degree atopic family members and/or elevated cord-blood IgE concentrations.Results The cumulative incidence of atopic dermatitis over the first 2 years of life (AD24) amounted to 20. 1%, and there was a significant association with AD history of the mother (OR 2.5, 95%-Cl 1.46–4.26) and of the father (OR 3.53, 95%cC1 1.90–6.54). The cumulative incidence of recurrent wheezing in the first 2 years of life (RW24) amounted to 16.1%, and was positively associated with asthma history (OR 2.11, 95%CI 1.33–3.60) and sensitization history (OR 1.64, 95%C1 1.34–2.36) of the mother, but with neither for the father. RW24 was less prevalent in girls than in boys (OR 0.64. 95%Cl 0.47–0.89). Thirty-one per cent of infants were sensitized (CAP test value 〉 0.35 kU/L) against at least one of nine food or inhalative allergens (S24) and this was signilicantly associatcd with cord blood-IgE value (OR 2.43, 95%C1 1.69–3.49). and sensitization history of the mother (OR 1.64, 95%CI 1.18–2.41). Using multiple logistic regression analysis, the prediction of AD24 by AD of parents, of RW24 by asthma of parents, and of sensitization by cord blood IgE was of low accuracy.Conclusion The predictive capacity of parental history and cord blood IgE is not high enough to recommend them as screening instruments for primary prevention. The majority of atopic manifestations and of sensitization occur in infants with no demonstrable risk at birth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2222.1997.310899.x
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  • 6
    Electronic Resource
    Electronic Resource
    Ozone increases group 5 allergen content of Lolium perenne (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Allergy 52 (1997), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1398-9995.1997.tb02163.x
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  • 7
    Electronic Resource
    Electronic Resource
    Mite fauna of German farms (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Allergy 52 (1997), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Storage mites are important sources of airborne allergens, especially on farms. A mite survey was conducted in the working environments of 121 farms in five regions of Germany. Of 859 samples, 743 (86.4%) contained mites, representing 547 857 astigmatic mites in 723 g of dust and 34 501 prostigmatic mites in 469 g of dust. Dust samples from nine sites of each farm were collected and analyzed. Ninety-three percent of all mites belonged to the order Astigmata (storage- and house-dust-mite species); 35 Astigmata and 14 Prostigmata mite species were identified. According to the abundance and steadiness of the important astigmatic mite species, the following order was found: Lepidoglyphus destructor 〉 Glycyphagus domesticus 〉 Acarus siro 〉 Tyrophagus longior 〉 Blomia tjibodas 〉 Chortoglyphus arcuatus 〉 Thyreophagus entomophagus 〉 Tyrophagus putrescentiae 〉 Euroglyphus longior 〉 Tyrophagus palmarum 〉 Acarus farris 〉 Acarus immobilis 〉 Gohieria fusca. Blomia tjibodas was described for the first time as an abundant species of farms in Germany.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1398-9995.1997.tb02529.x
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  • 8
    Electronic Resource
    Electronic Resource
    Coherent population transfer: Stimulated raman adiabatic passage and the Landau-Zener picture (1992)
    Springer
    The European physical journal 23 (1992), S. 33-39 
    Details
    ISSN: 1434-6079
    Keywords: 32.80.Bx ; 32.80.Wr ; 42.50.Hz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We show that three-state coherent excitation by pulsed lasers, sometimes termed Stimulated Raman Adiabatic Passage (STIRAP), can be regarded as a limiting case of four-state excitation involving pairs of two-state transitions (pump and Stokes) that couple coherently. A complementary limiting case of our four-state model is recognizable as a pair of Landau-Zener curve crossings. In each of these regimes it is possible to have complete population transfer by adiabatic passage. With the aid of analytical expressions and numerical computations we show the differences between these two mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01436700
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