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  • 11
    Electronic Resource
    Electronic Resource
    Heterodyne radiometer at Rijnhuizen Tokamak Project for electron cyclotron emission and absorption measurements : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 416-418 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The 20-channel heterodyne radiometer of the Rijnhuizen Tokamak Project (RTP) measures microwaves in the range between 86 and 146 GHz. The spatial resolution is ∼7–16 mm parallel and 25–1300 mm2 perpendicular to the viewing direction, depending on the position in the torus. A waveguide network gives the opportunity to do alternate measurements of X- and O-mode electron cyclotron emission (ECE) from the low-field side (LFS) and X-mode ECE from the high-field side (HFS). A backward wave oscillator is installed at the HFS, for the purpose of measuring the electron cyclotron absorption (ECA) of the plasma. This set-up also provides a possibility for fast relative calibration of the radiometer. To reduce the effects of multiple-pass reflections and standing waves, Macor viewing dumps are mounted at both sides. A comparison of HFS and LFS ECE measurements during electron cyclotron heating will be given as a first result. First results of ECA measurements were obtained but will be presented in the future. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146486
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  • 12
    Electronic Resource
    Electronic Resource
    Poloidal polarimeter system for current density measurements in ITER : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 726-729 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The polarimeter system for ITER features 10 viewing chords covering almost the full poloidal cross section of the plasma in a fan-like arrangement. The 10 laser beams all enter the plasma via 150 mm diam penetrations through the diagnostic plug at the low-field side. Small retroreflectors at the high-field side mirror the laser beams back towards the penetrations at the low-field side. Extensive feasibility calculations have led to the conclusion that the optimum wavelength for the polarimeter is around 100 μm. At this wavelength counterproductive effects like refraction and electron cyclotron absorption are negligibly small. However, the anticipated Faraday rotation angles are still very large, such that several important plasma parameters can be measured within the requirements set by the ITER team. In this article the status of the conceptual design of the polarimeter system for ITER will be presented. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149396
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  • 13
    Electronic Resource
    Electronic Resource
    The multichannel triple-laser interferometer/polarimeter system at RTP : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1217-1226 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 19-channel combined interferometer and polarimeter system has recently become operational at the Rijnhuizen Tokamak Project (a=0.164 m, R=0.72 m, Btor≤2.5 T, Ip≤150 kA, plasma pulse duration ≤500 ms), in order to determine the poloidal magnetic field and plasma density distribution simultaneously. The method is based on the separate propagation of two counter-rotating, circularly polarized probing waves, and enables high temporal resolution measurements of both the interferometric and the polarimetric phase change using only one detector per line of sight. In this article a thorough discussion of the (polarization-related) optical, electronic, and computational aspects of the system will be presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147884
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  • 14
    Electronic Resource
    Electronic Resource
    Reflectometry on ITER : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 435-438 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Reflectometry will be used on ITER to measure the density profile in the main plasma and divertor regions, and to measure the plasma position and shape in order to provide a standby reference for the magnetic diagnostics in long pulse discharges. The high temperatures of the ITER core and the resultant significant relativistic downshift of the second-harmonic electron cyclotron absorption imply that both low-field side O-mode and high-field side lower cut-off (X−l mode) systems are required to access the full plasma profile. A low-field side upper cut-off (X−u mode) system will also be required for measurements of the scrape-off layer. For measurements of the plasma position and shape, an O-mode system is optimum due to the large range of magnetic field along the plasma periphery and the wide range of possible plasma configurations achievable on ITER. A robust real-time calibration technique of the whole transmission line is required. It is likely that an accurate estimate of the position of the plasma will require the simultaneous use of signals from the profile reflectometer. For the divertor, profiles with peak densities in the range 1019–1022/m3 are to be measured with a target resolution of 3 mm. The large density range will necessitate the use of more than one system. Installing these reflectometers on ITER incurs additional difficulties such as the routing of the millimetre wave radiation around the complicated first wall and divertor structures and design of antennas able to operate through the first wall and blanket. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148220
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  • 15
    Electronic Resource
    Electronic Resource
    The multichannel triple-laser interferometer/polarimeter system at RTP (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 446-446 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 19-channel combined interferometer and polarimeter system has recently become operational at the Rijnhuizen Tokamak Project (a=0.164 m, R=0.72 m, Btor≤2.5 T, Ip≤150 kA, plasma pulse duration ≤500 ms), in order to determine the poloidal magnetic field and plasma density distribution simultaneously. The method is based on the separate propagation of two counter-rotating, circularly polarized probing waves, and enables high temporal resolution measurements of both the interferometric and the polarimetric phase change using only one detector per line of sight. In this article a thorough discussion of the (polarization-related) optical, electronic, and computational aspects of the system will be presented.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147602
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  • 16
    Electronic Resource
    Electronic Resource
    Density perturbation studies by means of pulsed radar reflectometry : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 419-421 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A four-channel pulsed radar reflectometry system has been developed for the Rijnhuizen Tokamak Project. The system combines a high spatial and temporal resolution with limited access demands to the tokamak plasma. Steady-state density profiles as measured with the pulsed radar system match very well to the profiles as measured by Thomson scattering and by interferometry. As will be illustrated in this paper, the diagnostic is able to follow fast phenomena as pellet injection and plasma disruptions as well as MHD oscillations. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146542
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  • 17
    Electronic Resource
    Electronic Resource
    Double pulse Thomson scattering system at RTP : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 721-724 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article a double pulse multiposition Thomson scattering diagnostic, under construction at RTP, is discussed. Light from a double pulsed ruby laser (pulse separation: 10–800 μs, max. 2×12.5 J) is scattered by the free electrons of the tokamak plasma and relayed to a Littrow polychromator for spectral analysis. The spectrally resolved light is recorded by two ICCD detectors. Simulations show that the system sensitivity will be such that electron temperatures in the range of 100 eV–7 keV can be determined with an accuracy as good as 2%–3% for electron densities of 1020 m−3, with a spatial resolution down to 2.6 mm. With this diagnostic the dynamics of small scale structures in the electron temperature profile will be studied. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147685
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  • 18
    Electronic Resource
    Electronic Resource
    High spatial resolution interferometry and polarimetry in hot plasmas (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3407-3423 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Interferometry is a standard technique for measuring the line-integrated electron density of magnetically confined plasmas. It is based on the fact that an electromagnetic wave, on its passage through a plasma, experiences a phase change with respect to the vacuum situation. Moreover, the plane of polarization of the wave will in general rotate because the plasma is birefringent. The total (Faraday) rotation angle of the wave, which can be measured by polarimetric techniques, is proportional to the line-integrated value of the magnetic field component parallel to the beam. The optimum wavelength for interferometry/polarimetry, for diagnosing magnetically confined plasmas is in the far-infrared and infrared spectral region. To invert the line-integrated data of the electron density and magnetic field component to local values, without using too stringent assumptions on the plasma symmetry, it is necessary to probe the plasma along multiple chords. In many confinement devices this is done by using a limited number of discrete probing chords. In recent years much attention has been devoted to the development of multichannel interferometer/polarimeter systems with a much better coverage of the plasma, which could be achieved by expanding the probing beam either to a slab- or a fanlike beam, covering almost the complete minor cross section of the plasma. A much higher number of detectors can be implemented in this way, thus substantially improving the spatial resolution of the measurements. In this paper the present status of interferometer/polarimeter systems featuring slablike or fanlike probing beams will be reviewed. Results of detailed measurements that have been performed to study the effect of magnetohydrodynamic activity (in particular sawteeth), disruptions, additional heating, and pellet injection on the electron density distribution, will be used to illustrate the merits of interferometry/polarimetry with high spatial resolution. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145516
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  • 19
    Electronic Resource
    Electronic Resource
    The agonistic binding site at the histamine H2 receptor. II. Theoretical investigations of histamine binding to receptor models of the seven α-helical transmembrane domain (1996)
    Springer
    Journal of computer aided molecular design 10 (1996), S. 479-489 
    Details
    ISSN: 1573-4951
    Keywords: G-protein-coupled receptor ; Hartree-Fock calculations ; Histamine H2 receptor ; Molecular mechanics ; Receptor models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In the first part (pp. 461–478 in this issue) of this study regarding the histamine H2 receptor agonistic binding site, the best possible interactions of histamine with an α-helical oligopeptide, mimicking a part of the fifth transmembrane α-helical domain (TM5) of the histamine H2 receptor, were considered. It was established that histamine can only bind via two H-bonds with a pure α-helical TM5, when the binding site consists of Tyr182/Asp186 and not of the Asp186/Thr190 couple. In this second part, two particular three-dimensional models of G-protein-coupled receptors previously reported in the literature are compared in relation to agonist binding at the histamine H2 receptor. The differences between these two receptor models are discussed in relation to the general benefits and limitations of such receptor models. Also the pros and cons of simplifying receptor models to a relatively easy-to-deal-with oligopeptide for mimicking agonistic binding to an agonistic binding site are addressed. Within complete receptor models, the simultaneous interaction of histamine with both TM3 and TM5 can be analysed. The earlier suggested three-point interaction of histamine with the histamine H2 receptor can be explored. Our results demonstrate that a three-point interaction cannot be established for the Asp98/Asp186/Thr190 binding site in either of the investigated receptor models, whereas histamine can form three H-bonds in case the agonistic binding site is constituted by the Asp98/Tyr182/Asp186 triplet. Furthermore this latter triplet is seen to be able to accommodate a series of substituted histamine analogues with known histamine H2 agonistic activity as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00124477
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  • 20
    Electronic Resource
    Electronic Resource
    Hybrid-hybrid matrix structural refinement of a DNA three-way junction from 3D NOESY-NOESY (1999)
    Springer
    Journal of biomolecular NMR 14 (1999), S. 209-221 
    Details
    ISSN: 1573-5001
    Keywords: MORASS ; NOESY-NOESY ; relaxation matrix analysis ; three-way junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Homonuclear 3D NOESY-NOESY has shown great promise for the structural refinement of large biomolecules. A computationally efficient hybrid-hybrid relaxation matrix refinement methodology, using 3D NOESY-NOESY data, was used to refine the structure of a DNA three-way junction having two unpaired bases at the branch point of the junction. The NMR data and the relaxation matrix refinement confirm that the DNA three-way junction exists in a folded conformation with two of the helical stems stacked upon each other. The third unstacked stem extends away from the junction, forming an acute angle (∼60° ) with the stacked stems. The two unpaired bases are stacked upon each other and are exposed to the solvent. Helical parameters for the bases in all three strands show slight deviations from typical values expected for right-handed B-form DNA. Inter-nucleotide imino-imino NOEs between the bases at the branch point of the junction show that the junction region is well defined. The helical stems show mobility (± 20° ) indicating dynamic processes around the junction region. The unstacked helical stem adjacent to the unpaired bases shows greater mobility compared to the other two stems. The results from this study indicate that the 3D hybrid-hybrid matrix MORASS refinement methodology, by combining the spectral dispersion of 3D NOESY-NOESY and the computational efficiency of 2D refinement programs, provides an accurate and robust means for structure determination of large biomolecules. Our results also indicate that the 3D MORASS method gives higher quality structures compared to the 2D complete relaxation matrix refinement method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008330011425
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