Bibliothek

X
Suchhistorie löschen
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Sustained rotational stabilization of DIII-D plasmas above the no-wall beta limit : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1997-2005 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Sustained stabilization of the n=1 kink mode by plasma rotation at beta approaching twice the stability limit calculated without a wall has been achieved in DIII-D by a combination of error field reduction and sufficient rotation drive. Previous experiments have transiently exceeded the no-wall beta limit. However, demonstration of sustained rotational stabilization has remained elusive because the rotation has been found to decay whenever the plasma is wall stabilized. Recent theory [Boozer, Phys. Rev. Lett. 86, 5059 (2001)] predicts a resonant response to error fields in a plasma approaching marginal stability to a low-n kink mode. Enhancement of magnetic nonaxisymmetry in the plasma leads to strong damping of the toroidal rotation, precisely in the high-beta regime where it is needed for stabilization. This resonant response, or "error field amplification" is demonstrated in DIII-D experiments: applied n=1 radial fields cause enhanced plasma response and strong rotation damping at beta above the no wall limit but have little effect at lower beta. The discovery of an error field amplification has led to sustained operation above the no-wall limit through improved magnetic field symmetrization using an external coil set. The required symmetrization is determined both by optimizing the external currents with respect to the plasma rotation and by use of feedback to detect and minimize the plasma response to nonaxisymmetric fields as beta increases. Ideal stability analysis and rotation braking experiments at different beta values show that beta is maintained 50% higher than the no wall stability limit for durations greater than 1 s, and approaches beta twice the no-wall limit in several cases, with steady-state rotation levels. The results suggest that improved magnetic-field symmetry could allow plasmas to be maintained well above no-wall beta limit for as long as sufficient torque is provided. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1446036
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Active feedback stabilization of the resistive wall mode on the DIII-D device : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2071-2082 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A proof of principle magnetic feedback stabilization experiment has been carried out to suppress the resistive wall mode (RWM), a branch of the ideal magnetohydrodynamic (MHD) kink mode under the influence of a stabilizing resistive wall, on the DIII-D tokamak device [Plasma Phys. Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159; Phys. Plasmas 1, 1415 (1994)]. The RWM was successfully suppressed and the high beta duration above the no-wall limit was extended to more than 50 times the resistive wall flux diffusion time. It was observed that the mode structure was well preserved during the time of the feedback application. Several lumped parameter formulations were used to study the feedback process. The observed feedback characteristics are in good qualitative agreement with the analysis. These results provide encouragement to future efforts towards optimizing the RWM feedback methodology in parallel to what has been successfully developed for the n=0 vertical positional control. Newly developed MHD codes have been extremely useful in guiding the experiments and in providing possible paths for the next step. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1351823
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Feedback for High EEG Alpha Does Not Maintain Performance or Mood During Sleep Loss (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 13 (1976), S. 0 
    Details
    ISSN: 1469-8986
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin , Psychologie
    Notizen: Can performance and mood during sleep loss be maintained by self-induced high EEG alpha activity? In a previous study, most of the performance and mood measures showed sleep-loss impairment regardless of EEG alpha level, but attention and reported sleepiness were less impaired for the high-alpha group (although the differences were of doubtful significance). A constructive replication was carried out. In Group A (N=10) auditory feedback was contingent on high alpha, and in Group B (N=10) auditory feedback was contingent on low alpha and low theta. All subjects were repeatedly measured on auditory vigilance, addition, immediate recall, and feelings of sleepiness for 40 hrs during which no sleep was permitted. Sixty min of EEG feedback were given during each block of 220 min. Group A did produce significantly more alpha for the first 24 hrs but this difference was not maintained. Both groups had significant sleep-loss impairment on all measures. There were no significant differences between the groups in the amount of impairment. Self-enhanced EEG alpha activity does not prevent impairment of performance or mood during sleep loss.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1469-8986.1976.tb03338.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    Sleep During and After Gradual Sleep Reduction (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 14 (1977), S. 0 
    Details
    ISSN: 1469-8986
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin , Psychologie
    Notizen: To determine: 1) the minimum amounts of sleep subjects would tolerate, 2) the changes in EEG sleep measures, and 3) whether subjects would revert to baseline sleep after study termination, 4 couples gradually reduced their sleep. Three couples reduced their TST in 30-min steps from a baseline of 8 hrs and one couple from a baseline of 6.5 hrs. Subjective estimates of sleep time, sleep quality, and mood were collected daily. Home EEG sleep recordings were obtained 3 nights a week.Two of the 8-hr sleepers reduced their sleep to 5.5 hrs, 2 to 5.0 hrs, and 2 reached 4.5 hrs. These 6 subjects continued sleeping 1 to 2.5 hrs below baseline amounts a year after reduction terminated. The 6.5-hr baseline couple reached 5.0 hrs and returned to 6.5 hrs TST during follow-up.Stages W, 2, and REM decreased significantly in absolute amounts. Percentage of stages W and 2 also decreased significantly. REM percent remained constant. Stage 3 was constant while stage 4 increased in both absolute and relative amounts. REM cycle length remained constant. Stage 4 rebound on 7-hr nights was not observed during times of greatest sleep reduction. Occurrences of stage REM within 10 min of stage 1 onset were observed in 2 subjects when their TST was below 6.5 hrs.Our results are consistent with other studies of shortened sleep, indicating that TST is the major determinant of sleep-stage characteristics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1469-8986.1977.tb01168.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    Performance and Mood During and After Gradual Sleep Reduction (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 14 (1977), S. 0 
    Details
    ISSN: 1469-8986
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin , Psychologie
    Notizen: Long-term gradual sleep reduction effects were investigated on 4 young adult collegiate couples. The battery of assessment tools included a sleep log, Stanford Sleepiness Scale, Profile of Mood States, Feeling Tone Checklist, a measure of circadian oral temperature, Williams Word Memory test, Digit Span test, Wilkinson Auditory Vigilance task, Wilkinson Addition task, Minnesota Multiphasic Personality Inventory, Rapid Alternation task, psychiatric and medical examinations, and a subjective effects questionnnaire. It was concluded that 6–8 months of gradual sleep restriction, down to 4.5–5.5 hrs per night, does not result in behavioral effects measurable by the instruments used. Subjective fatigue appears to be the limiting factor in determining tolerability of gradual sleep restriction. At the end of an additional 12-month follow-up period, total sleep time was still 1–2.5 hrs below baseline, but measures of well-being had returned to baseline levels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1469-8986.1977.tb01169.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Assessment of mobility, activities and pain in different subtypes of epidermolysis bullosa (2004)
    Oxford, UK : Blackwell Science Ltd
    Clinical and experimental dermatology 29 (2004), S. 0 
    Details
    ISSN: 1365-2230
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: A standardized questionnaire was used to assess mobility, activity and pain in 140 randomly chosen children, who were representative of all major types and subtypes of inherited epidermolysis bullosa (EB). Pain status in these children was compared with 374 randomly selected adults with EB. The level of independence for each of six activities of daily living (ADL) (toileting; feeding; bathing; dressing; grooming; walking) was assessed in these EB children using conventional criteria for scoring. Whereas more than 90% of all EB simplex (EBS) and dominant dystrophic EB (DDEB) children were totally independent for each function (excluding walking), the frequency of similarly totally independent patients with junctional EB (JEB) and recessive dystrophic EB (RDEB) ranged from only 39% to 73%. No DDEB children and only 2% of EBS patients were totally dependent in their individual ADL, in comparison to 8–27% of JEB and 2–27% of RDEB children. Totally independent walking was reported in only 31%, 31%, 67%, and 24% of EBS, JEB, DDEB, and RDEB children, respectively. A daily level of EB-related pain was assessed in children by their parents using a linear scale of 0 (no pain) to 10 (unbearable pain). Whereas 14–19% of all children with EBS, JEB, and DDEB were graded with pain levels of more than 5, 32% of all RDEB children reportedly suffered this much pain. Increased frequencies of pain with scores more than 5 were most often noted in those patients having more clinically extensive or severe EB subtypes. These included JEB-Herlitz (20% vs. 14% in JEB-non-Herlitz) and RDEB-Hallopeau-Siemens (47% vs. 20% in all other RDEB subtypes). Only 5% of all RDEB children reportedly were pain-free, compared to 12–14% of those with EBS, JEB, and DDEB. Collectively, these data provide the first report of the specific impact different forms of EB have on daily living and coping with this genodermatosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2230.2004.01428.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    UPTAKE OF MANGANESE BY CHROMAFFIN GRANULES IN VITRO (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 33 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract– The distribution of metal ions in the chromaffin granule is anomalous. Calcium ions are accumulated but magnesium ions excluded. We have used the manganese ion as a convenient divalent element for following metal ion uptake because it can usefully be employed as a substitute for magnesium.The kinetics of the manganese incorporation were followed by radio tracer technique and its transport was characterized as being non-energy dependent and having a small thermal activation factor. The presence in the incubation medium of a membrane-bound ATPase inhibitor (NEM) or addition of CN− or NaN3 did not affect the metal incorporation into chromaffin granules. Little endogenous magnesium exchanges for manganese when the latter is incorporated, but magnesium competitively prevented manganese uptake. The binding of manganese inside the vesicle was strong and it was not exchangeable with magnesium even in the presence of ATP.Manganese when incorporated binds to ATP and displaces catecholamines resulting in a decrease in the CA/ATP ratio.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb09922.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    The REM Cycle in Altered Sleep/Wake Schedules (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 15 (1978), S. 0 
    Details
    ISSN: 1469-8986
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin , Psychologie
    Notizen: The length and rhythmicity of the REM cycle was studied using data from three laboratories. In the three studies, 25 subjects obtained their sleep in naps under three different sleep/wake schedules: 60/160 min (N =8), 30/60 min (N =10), and 60/120 min (N =7), over a period of 40 hrs to 10 days. Previous results from these subjects (Moses, Lubin, Johnson, & Naitoh, 1977) indicated that the REM cycle is sleep-dependent, rather than an expression of an ongoing Basic Rest-Activity Cycle (BRAC). As a further test of the sleep-dependent hypothesis, autocorrelation and r2 analysis was applied to the compressed sleep (i.e., all wake time between and within sleep periods subtracted) of the baseline, nap, and recovery conditions. Compared to baseline, there were no significant differences in nap REM cycle length in the 60/160 and 60/120 groups; the 30/60 group had significantly shorter cycles. It appeared that this REM cycle shortening was due to the significantly shorter REM episodes in this group. The nap r2 values were significantly lower than baseline in the 30/60 and 60/120 groups, indicating increased variability in the timing of REM episodes during naps. All the nap r2 values, however, were significantly larger than those obtained from a random distribution of sleep stages.To further examine the effects of the degree of sleep fragmentation on REM cycle rhythmicity, two additional groups of subjects whose sleep was fragmented by either REM or SWS deprivation were compared to the nap groups. REM deprivation was the most disruptive of REM cycle rhythmicity; the r2 values for REM deprivation were significantly less than those for napping or SWS deprivation.These data offer further support that the REM cycle is a sleep-dependent rhythm and is not an expression of an ongoing BRAC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1469-8986.1978.tb03112.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Sleep Stage Deprivation and Total Sleep Loss: Effects On Sleep Behavior (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 12 (1975), S. 0 
    Details
    ISSN: 1469-8986
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin , Psychologie
    Notizen: The combined effects of total sleep loss and the deprivation of stage 4 or stage REM were studied in I two separate experiments. Two full nights or sleep loss preceded stage 4 deprivation or stage REM deprivation in Experiment 1 (N=12); 1 full night of sleep loss followed 3 nights or stage 4 deprivation or stage REM deprivation in Experiment 2 (N=I4).Total sleep loss before sleep stage deprivation significantly increased the number of attempts to enter stage 4, but had little influence on stage REM. A significant REM rebound was found in only one of the REM-deprived groups, but there was a significant stage 4 rebound in all groups on the first full recovery night, supporting the hypothesis from other studies that stage 4 has priority over REM in terms of recovery from sleep loss. The results suggested that stages 2, 3, and 4 partially overlap in their recuperative functions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1469-8986.1975.tb01264.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    Effect of Self-Enhanced EEG Alpha on Performance and Mood After Two Nights of Sleep Loss (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Psychophysiology 12 (1975), S. 0 
    Details
    ISSN: 1469-8986
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin , Psychologie
    Notizen: Can the deleterious effects of acute sleep loss on performance and mood be ameliorated by self-enhanced alpha activity? Fourteen Naval volunteers were divided equally into an experimental (alpha-contingent auditory feedback) group and a yoked control (pseudo feedback) group. All subjects received feedback plus performance and mood tests during 3 baseline days and following 2 days and 2 nights without sleep. Feedback was given for 45 min in the morning and 45 mm in the afternoon, preceding performance and mood tests. The self-enhanced alpha (experimental) subjects did produce more alpha than the yoked controls during all feedback sessions except for one pair that was discarded. Of eleven measures that were sensitive to deep loss, two performance scores and one mood score showed significantly less sleep-loss decrement for the self-enhanced alpha group (at the usual univariate. 05 level). Two recall scores and an anxiety score showed more impairment for the self-enhanced alpha group following sleep loss. The differences were not significant, however, by (he conservative Dunn-Bonferroni multivariate criterion, so our results are not conclusive.Alpha enhancement may help maintain performance that requires continuous attention, such us counting and auditory discrimination, but does not ameliorate the sleep-loss effect for anxiety, memory, and addition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1469-8986.1975.tb00051.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...