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  • 1
    Digitale Medien
    Digitale Medien
    The role of the neutral beam fueling profile in the performance of the Tokamak Fusion Test Reactor and other tokamak plasmas : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1699-1706 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Scalings for the stored energy and neutron yield, determined from experimental data, are applied to both deuterium-only and deuterium–tritium plasmas in different neutral-beam-heated operational domains in the Tokamak Fusion Test Reactor [Nucl. Fusion 25, 1167 (1985)]. The domain of the data considered includes the Supershot, high poloidal beta, low-mode, and limiter high-mode operational regimes, as well as discharges with a reversed magnetic shear configuration. The new important parameter in the present scaling is the peakedness of the heating beam fueling profile shape. Ion energy confinement and neutron production are relatively insensitive to other plasma parameters compared to the beam fueling peakedness parameter and the heating beam power when considering plasmas that are stable to magnetohydrodynamic modes. However, the stored energy of the electrons is independent of the beam fueling peakedness. The implication of the scalings based on this parameter is related to theoretical transport models such as radial electric field shear and ion temperature gradient marginality models. Similar physics interpretation is provided for beam heated discharges on other major tokamaks.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872272
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  • 2
    Digitale Medien
    Digitale Medien
    Alpha-driven magnetohydrodynamics (MHD) and MHD-induced alpha loss in the Tokamak Fusion Test Reactor : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1610-1616 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Alpha-driven toroidal Alfvén eigenmodes (TAEs) are observed as predicted by theory in the post-neutral beam phase in high central q (safety factor) deuterium–tritium (D–T) plasmas in the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)]. The mode location, poloidal structure, and the importance of q profile for TAE instability are discussed. So far no alpha particle loss due to these modes was detected due to the small mode amplitude. However, alpha loss induced by kinetic ballooning modes (KBMs) was observed in high-confinement D–T discharges. Particle orbit simulation demonstrates that the wave–particle resonant interaction can explain the observed correlation between the increase in alpha loss and appearance of multiple high-n (n≥6, n is the toroidal mode number) modes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872363
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  • 3
    Digitale Medien
    Digitale Medien
    Local transport barrier formation and relaxation in reverse-shear plasmas on the Tokamak Fusion Test Reactor : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1736-1744 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The roles of turbulence stabilization by sheared E×B flow and Shafranov shift gradients are examined for Tokamak Fusion Test Reactor [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] enhanced reverse-shear (ERS) plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E×B and Shafranov shift effects was performed by varying the E×B shear through changes in the toroidal velocity with nearly steady-state pressure profiles. Transport and fluctuation levels increase only when E×B shearing rates are driven below a critical value that is comparable to the fastest linear growth rates of the dominant instabilities. While a turbulence suppression criterion that involves the ratio of shearing to linear growth rates is in accord with many of these results, the existence of hidden dependencies of the criterion is suggested in experiments where the toroidal field was varied. The forward transition into the ERS regime has also been examined in strongly rotating plasmas. The power threshold is higher with unidirectional injection than with balance injection. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872275
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  • 4
    Digitale Medien
    Digitale Medien
    Identification of Alfvén mode location via multichannel interferometer measurements (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. 698-698 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Quasicoherent magnetohydrodynamics modes with an Alfvén frequency scaling are seen routinely in TFTR neutral beam heated plasmas as well as some Ohmic plasmas. So far, they are only observed in external magnetic fluctuation measurement (Mirnov coils). A close correlation is observed between the changes in the mode frequency and electron density measured by the multichannel infrared interferometer. This correlation allows us to determine the location of the Alfvén modes. The result shows that they are near the plasma edge, r/a〉0.85. This method is also used to identify the location of the toroidicity-induced Alfvén eigenmode driven by fast ions in a radiowave heating experiment. The result is consistent with the location determined by the reflectometer measurement.© 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147925
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  • 5
    Digitale Medien
    Digitale Medien
    Concentration dependent photoluminescence of Te-doped In0.5Ga0.5P layers grown by liquid phase epitaxy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4024-4027 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoluminescence (PL) of Te-doped In0.5Ga0.5P epilayers grown by the liquid phase epitaxy technique has been investigated as a function of carrier concentration. The PL results are interpreted using a model taking into account nonparabolicity of the conduction band. Both the band filling as well as band tailing due to the Coulomb interaction of free carriers with ionized impurities and band shrinkage due to the exchange interaction between free carriers are considered in order to properly portray the observed features of the PL spectra. The theoretical calculations are in satisfactory agreement with the observed PL results. The PL line shape is well explained by a direct transition with a simple k-selection rule up to a carrier concentration of 2.0 ×1018 cm−3. Above the carrier concentration of 2.0 ×1018 cm−3, on the other hand, it is properly interpreted in terms of non-k-conserving transitions that arise from the indirect recombination of electrons in a highly filled conduction band. It was found that a concentration dependent gap shrinkage due to the exchange interaction in Te-doped In0.5Ga0.5P at 17 K is described by the relation Ece=2.34×10−8 n1/3 (eV). The concentration dependent effective mass has also been calculated using Kane's three band model. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.365754
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  • 6
    Digitale Medien
    Digitale Medien
    Application of microwave reflectometry to the measurement of fast magnetosonic waves in the Tokamak Fusion Test Reactor : 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. 450-453 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The application of microwave reflectometry to the study of fast magnetosonic waves in the Tokamak Fusion Test Reactor (TFTR) is investigated. Assuming the validity of geometric optics for reflectometer measurements, it is shown that linearity to the fast wave amplitude is restricted to very small density fluctuation levels (ñ/n〈10−3). Beyond this level, both phase and amplitude ambiguities occur that makes interpretation difficult. Measurements of 30 MHz fast magnetosonic waves in the core of TFTR plasmas are presented. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147604
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  • 7
    Digitale Medien
    Digitale Medien
    Rubbing-free, vertically aligned nematic liquid crystal display controlled by in-plane field (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2851-2853 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We fabricated a homeotropically aligned nematic liquid crystal display with positive dielectric anisotropy, whose on and off states are controlled by in-plane field. The rubbing-free device, dark in voltage-off state, reveals bright uniformity in all directions due to the dual domainlike director configuration in the voltage-on state. The electro-optic characteristics of one prototype with excellent viewing angles are reported herein. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.120153
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  • 8
    Digitale Medien
    Digitale Medien
    Correlation between IgA antibody and eosinophil cationic protein levels in induced sputum from asthmatic patients (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical & experimental allergy 27 (1997), S. 0 
    Details
    ISSN: 1365-2222
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Background Eosinophils are known to be main effector cells in allergic inflammation and IgA antibody has been shown to be a potent stimulus for eosinophil degranulation in in vitro conditions.Objective To evaluate the possible role of IgA antibodies on eosinophil degranulation in lower respiratory mucosa of asthmatics, we tried to find a correlation between total IgA and eosinophil cationic protein (ECP) levels in induced sputum from asthmatics.Methods We measured total IgA and albumin levels by nephelometry, and eosinophil cationic protein levels by Pharmacia CAP system in induced sputum from 23 atopic asthmatics and 12 healthy controls.Results IgA and albumin levels in induced sputum from asthmatics with sputum eosinophilia (sputum eosinophil count 5% of 200 counted non-squamous cells) were significantly higher (P 〈 0.05) than those from controls. However, IgA and albumin levels in induced sputum from asthmatics without sputum eosinophilia were not significantly different with those from controls (P 〉 0.05). In induced sputum from asthmatics, ECP levels were significantly correlated with albumin (r= 0.44, P= 0.04) and IgA levels (r= 0.67, P= 0.002). ECP/albumin ratio was also significantly correlated with IgA/albumin ratio (r= 0.61, P= 0.004).Conclusion Our results support the hypothesis that IgA antibodies in tracheobronchial secretion may be involved in eosinophil degranulation in asthma, and further study is needed to prove this hypothesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2222.1997.tb01196.x
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  • 9
    Digitale Medien
    Digitale Medien
    Prognostic factors for toluene diisocyanate-induced occupational asthma after removal from exposure (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical & experimental allergy 27 (1997), S. 0 
    Details
    ISSN: 1365-2222
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Background The outcome of isocyanatc-induced occupational asthma remains to be further defined. There have been few studies on the role of specific antibodies in prognosis of toluene diisocyanate (TDI) induced occupational asthma. Moreover, to the best of our knowledge, there have been no studies on the improvement pattern of airway hyper-responsiveness (AH). We analysed the prognostic factors that affected the outcome of 35 toluene diisocyanate-induced occupational asthma.Objectives To define clinical and laboratory parameters predicting favourable prognosis for TDI-induced occupational asthma.Methods and results After confirmation of bronchial sensitivity by TDI hronchoprovocation test (BPT), 35 patients were recommended to avoid exposure to TDI; they were also given anti-asthmatic medications including inhaled steroids and monitored for 2 years. Seventeen (49%) recovered completely with disappearance of airway hyperresponsiveness (AH) to methacholine during the follow-up period (mean duration: 12 months, range of 3–30 months). Eleven (31%) showed a significant improvement in AH for first year, which improvement stabihzed in the next year with mild symptoms. Seven (20%) patients did not show any evidence of improvement in AH and had persistent symptoms. Favourable prognosis was associated with a short duration of asthmatic symptoms before diagnosis (P 〈 0.05), immediate cessation of exposure after diagnosis (P 〈 0.05), milder degree of AH at diagnosis (P 〈 0.05), and the presence of specific IgE antibodies to TDI-human serum albumin conjugate (0.05 〈 P 〈 0.1). No association was found with atopic and smoking status, age, exposure duration, or length of latent period (P 〉 0.05).Conclusion These data suggest that early detection of TDI-induced asthma and immediate cessation of exposure are important factors for a favourable prognosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2222.1997.tb01151.x
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  • 10
    Digitale Medien
    Digitale Medien
    Cerebral cortex blood flow and vascular smooth muscle contractility in a rat model of ischemia: a correlative laser Doppler flowmetric and scanning electron microscopic study (1997)
    Springer
    Acta neuropathologica 93 (1997), S. 354-368 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Key words Reperfusion ; Cerebral blood flow ; Vascular smooth muscle cell ; Pericyte ; Scanning ; electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The present study was undertaken to ascertain the role of smooth muscles and pericytes in the microcirculation during hyperperfusion and hypoperfusion following ischemia in rats. Paired external carotids, the pterygopalatine branch of the internal carotids and the basilar artery were exposed and divided. Reversible inflatable occluders were placed around the common carotids. After 24 h, the unanesthetized rat underwent 10-min ischemia by inflating the occluders. Continuous cortical cerebral blood flow (c-CBF) was monitored by laser Doppler flowmetry. The measured c-CBF was below 20% of control (P 〈 0.001) during ischemia. A c-CBF of 227.5 ± 54.1% (P 〈 0.001) was obtained during reperfusion hyperemia. A c-CBF of 59.7 ± 8.8% (P 〈 0.001) occurred at the nadir of postischemic hypoperfusion, and this was followed by a second hyperemia. The cytoarchitecture of the vascular smooth muscles and pericytes was assessed by scanning electron microscopy. Samples were prepared using a KOH-collagenase digestion method. In control rats, arteriolar muscle cells showed smooth surfaces. Capillary pericytes were closely apposed to the endothelium. Immediately after reperfusion, transverse membrane creases were observed on the smooth muscle surfaces. During maximal hyperemia the creases disappeared. When c-CBF started to decrease the creases became visible again. Throughout the postischemic hypoperfusion the creases remained. Capillary endothelial walls became tortuous in the late phase of hypoperfusion. During the second hyperemia most arteriolar muscle cells showed smooth surfaces. Some pericytes appeared to have migrated from the vascular wall. The morphological changes of smooth muscle membranes suggest that they are related to specific perfusional disturbances during ischemia and reperfusion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004010050627
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