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  • 1
    Electronic Resource
    Electronic Resource
    Polarization dynamics of a dual-frequency laser with a nearly isotropic resonator in the presence of anisotropic feedback (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 495-502 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The polarization dynamics of a dual-frequency, nearly isotropic He-Ne laser in the presence of weak anisotropic feedback were studied. Depending on the location of the perturbed mode under the gain curve, three distinctive hysteresis characteristics were observed. These hysteresis characteristics are distinguished by the height and width of the corresponding hysterograms. These switching dynamics are explained qualitatively in terms of the stability analysis of Lamb's multimode laser theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00563589
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  • 2
    Electronic Resource
    Electronic Resource
    Discrete Alfvén waves in planar flux tubes (1986)
    Springer
    Astrophysics and space science 127 (1986), S. 265-284 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Properties of discrete Alfvén wave modes are derived, at frequencies up to the ion-cyclotron frequency, for current-carrying plasma slabs with non-uniform densities. It is shown that the essential features of the dispersion relations can be derived by examining the dominant terms in the ‘potential’ function, when the wave equation is cast in the Schrödinger equation form. Analytical predictions for a class of mass and current density profiles are compared with numerically calculated dispersion relations and wavefields for particular profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636542
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  • 3
    Electronic Resource
    Electronic Resource
    Marine diatoms grown in chemostats under silicate or ammonium limitation. II. Transient response of Skeletonema costatum to a single addition of the limiting nutrient (1976)
    Springer
    Marine biology 35 (1976), S. 187-199 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Skeletonema costatum was grown at different steady-state growth rates in ammonium or silicate-limited chemostats. The culture was perturbed from its steady-state condition by a single addition of the limiting nutrients ammonium or silicate. The transient response was followed by measuring nutrient disappearance of the liliting perturbation experiment indicate that three distinct modes of uptake of the limiting nutrient can be distinguished; surge uptake (V s ), internally controlled uptake (V i ), and externally controlled uptake (V e ). An interpretation of these three modes of uptake is given and their relation to control of uptake of the limiting nutrient is discussed. The uptake rates of the non-limiting nutrients were shown to be depressed during the surge of the uptake of the limiting nutrient. Kinetic uptake parameters, K s and V max, were obtained from data acquired during the externally controlled uptake segment, V e . The same V max value of 0. 12 h-1, was obtained under either silicate or ammonium limitation. Estimates of K s were 0.4 μg-at NH4-N l-1 and 0.7 μg-at Si l-1. Short-term 15N uptake-rate measurements conducted on nitrogen-limited cultures appear to be a combination of V s or V i , or at lower substrate concentrations V s and V e . It is difficult to separate these different uptake modes in batch or tracer experiments, and ensuing problems in interpretation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390940
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  • 4
    Electronic Resource
    Electronic Resource
    Dopant-induced excimer laser ablation of poly(tetrafluoroethylene) (1992)
    Springer
    Applied physics 55 (1992), S. 488-493 
    Details
    ISSN: 1432-0649
    Keywords: 42.55.Gp ; 78.65 ; 81.60.Jw ; 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Clean ablation of poly(tetrafluoroethylene) (PTFE) at etch rates in excess of 7µm/pulse has been achieved with an excimer laser using 308nm radiation and a 25 ns pulse width. This was accomplished by doping the ultraviolet-transparent PTFE polymer with polyimide. Ablation rates were investigated as a function of fluence in the range from 1 to 12J/cm2 and dopant levels up to 15% (wt/wt). Results show that at a given fluence there exists an optimum absorption coefficient ⇌max, for which maximum ablation rates are achieved. The value of ⇌max was found to decrease with increasing fluence. The relationship between ⇌max and fluence was determined from existing ablation rate models and found to compare favorably with empirical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332507
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  • 5
    Electronic Resource
    Electronic Resource
    Dopant-induced excimer laser ablation of Poly(tetrafluoroethylene) (1992)
    Springer
    Applied physics 54 (1992), S. 227-230 
    Details
    ISSN: 1432-0649
    Keywords: 78.65H ; 81.60J
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Poly(tetrafluoroethylene) (PTFE) does not exhibit excimer laser etching behavior at conventional, e.g., single photon absorption, emissions of 193, 248, and 308 nm, due to the lack of polymer/photon interaction. This is not surprising since the electronic transitions available to the PTFE molecule are high energy and thus require short wavelength the radiation However, by incorporating a small quantity of material into the non-absorbing fluoropolymer matrix that interacts strongly with the emitted laser energy, e.g., a dopant, successful ablation, both in terms of etch rate and structuring quality occurs. Specifically, excimer laser ablation of PTFE films containing 5, 10, and 15% polyimide (wt/wt) as a dopant was achieved at 308 nm in a fluence range of 1 to 12 J/cm2. Ablation rates for the materials increased with increasing fluence and, at the polyimide levels investigated, varied inversely with dopant concentration. All compositions exhibited excellent structuring quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325507
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  • 6
    Electronic Resource
    Electronic Resource
    Growth Responses of Indian Mustard [Brassica juncea (L.) Czern.] and Its Phytoextraction of Lead from a Contaminated Soil (1998)
    Springer
    Bulletin of environmental contamination and toxicology 61 (1998), S. 38-43 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001289900726
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  • 7
    Electronic Resource
    Electronic Resource
    An optimised method for calculating the O+-O collision parameter from aeronomical measurements (1995)
    Springer
    Annales geophysicae 13 (1995), S. 541-550 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A study has been made of the interaction between the thermosphere and the ionosphere at high latitudes, with particular regard to the value of the O+-O collision parameter. The European incoherent scatter radar (EISCAT) was used to make tristatic measurements of plasma parameters at F-region altitudes while simultaneous measurements of the neutral wind were made by a Fabry-Perot interferometer (FPI). The radar data were used to derive the meridional neutral winds in a way similar to that used by previous authors. The accuracy of this technique at high latitudes is reduced by the dynamic nature of the auroral ionosphere and the presence of significant vertical winds. The derived winds were compared with the meridional winds measured by the FPI. For each night, the value of the O+-O collision parameter which produced the best agreement between the two data sets was found. The precision of the collision frequency found in this way depends on the accuracy of the data. The statistical method was critically examined in an attempt to account for the variability in the data sets. This study revealed that systematic errors in the data, if unaccounted for by the analysis, have a tendency to increase the value of the derived collision frequency. Previous analyses did not weight each data set in order to account for the quality of the data; an improved method of analysis is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-995-0541-x
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  • 8
    Electronic Resource
    Electronic Resource
    On the longitudinal extent of magnetopause reconnection pulses (1996)
    Springer
    Annales geophysicae 14 (1996), S. 865-878 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The open magnetosphere model of cusp ion injection, acceleration and precipitation is used to predict the dispersion characteristics for fully pulsed magnetic reconnection at a low-latitude magnetopause X-line. The resulting steps, as would be seen by a satellite moving meridionally and normal to the ionospheric projection of the X-line, are compared with those seen by satellites moving longitudinally, along the open/closed boundary. It is shown that two observed cases can be explained by similar magnetosheath and reconnection characteristics, and that the major differences between them are well explained by the different satellite paths through the events. Both cases were observed in association with poleward-moving transient events seen by ground-based radar, as also predicted by the theory. The results show that the reconnection is pulsed but strongly imply it cannot also be spatially patchy, in the sense of isolated X-lines which independently are intermittently active. Furthermore they show that the reconnection pulses responsible for the poleward-moving events and the cusp ion steps, must cover at least 3 h of magnetic local time, although propagation of the active reconnection region may mean that it does not extend this far at any one instant of time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-0865-1
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  • 9
    Electronic Resource
    Electronic Resource
    Predicted signatures of pulsed reconnection in ESR data (1997)
    Springer
    Annales geophysicae 14 (1997), S. 1246-1256 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Early in 1996, the latest of the European inco-herent-scatter (EISCAT) radars came into operation on the Svalbard islands. The EISCAT Svalbard Radar (ESR) has been built in order to study the ionosphere in the northern polar cap and in particular, the dayside cusp. Conditions in the upper atmosphere in the cusp region are complex, with magnetosheath plasma cascading freely into the atmosphere along open magnetic field lines as a result of magnetic reconnection at the dayside magnetopause. A model has been developed to predict the effects of pulsed reconnection and the subsequent cusp precipitation in the ionosphere. Using this model we have successfully recreated some of the major features seen in photometer and satellite data within the cusp. In this paper, the work is extended to predict the signatures of pulsed reconnection in ESR data when the radar is pointed along the magnetic field. It is expected that enhancements in both electron concentration and electron temperature will be observed. Whether these enhancements are continuous in time or occur as a series of separate events is shown to depend critically on where the open/closed field-line boundary is with respect to the radar. This is shown to be particularly true when reconnection pulses are superposed on a steady background rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-1246-5
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  • 10
    Electronic Resource
    Electronic Resource
    Possible configurations of the magnetic field in the outer magnetosphere during geomagnetic polarity reversals (1999)
    Springer
    Annales geophysicae 18 (1999), S. 11-27 
    Details
    ISSN: 0992-7689
    Keywords: Geomagnetism and paleomagnetism (reversals-process, time scale, magnetostratigraphy) ; Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetospheric configuration and dynamics)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Possible configurations of the magnetic field in the outer magnetosphere during geomagnetic polarity reversals are investigated by considering the idealized problem of a magnetic multipole of order m and degree n located at the centre of a spherical cavity surrounded by a boundless perfect diamagnetic medium. In this illustrative idealization, the fixed spherical (magnetopause) boundary layer behaves as a perfectly conducting surface that shields the external diamagnetic medium from the compressed multipole magnetic field, which is therefore confined within the spherical cavity. For a general magnetic multipole of degree n, the non-radial components of magnetic induction just inside the magnetopause are increased by the factor 1 + [(n + 1)/n] relative to their corresponding values in the absence of the perfectly conducting spherical magnetopause. An exact equation is derived for the magnetic field lines of an individual zonal (m = 0), or axisymmetric, magnetic multipole of arbitrary degree n located at the centre of the magnetospheric cavity. For such a zonal magnetic multipole, there are always two neutral points and n – 1 neutral rings on the spherical magnetopause surface. The two neutral points are located at the poles of the spherical magnetopause. If n is even, one of the neutral rings is coincident with the equator; otherwise, the neutral rings are located symmetrically with respect to the equator. The actual existence of idealized higher-degree (n 〉 1) axisymmetric magnetospheres would necessarily imply multiple (n + 1) magnetospheric cusps and multiple (n) ring currents. Exact equations are also derived for the magnetic field lines of an individual non-axisymmetric magnetic multipole, confined by a perfectly conducting spherical magnetopause, in two special cases; namely, a symmetric sectorial multipole (m = n) and an antisymmetric sectorial multipole (m = n – 1). For both these non-axisymmetric magnetic multipoles, there exists on the spherical magnetopause surface a set of neutral points linked by a network of magnetic field lines. Novel magnetospheric processes are likely to arise from the existence of magnetic neutral lines that extend from the magnetopause to the surface of the Earth. Finally, magnetic field lines that are confined to, or perpendicular to, either special meridional planes or the equatorial plane, when the multipole is in free space, continue to be confined to, or perpendicular to, these same planes when the perfectly conducting magnetopause is present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-000-0011-4
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