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  • SOLAR PHYSICS  (6)
  • AIRCRAFT PROPULSION AND POWER  (3)
  • Astronomy  (3)
  • Key words Extraocular muscle  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Extraocular muscle in merosin-deficient muscular dystrophy: cation homeostasis is maintained but is not mechanistic in muscle sparing (1998)
    Springer
    Cell & tissue research 292 (1998), S. 495-501 
    Details
    ISSN: 1432-0878
    Keywords: Key words Extraocular muscle ; Cation ; Muscular dystrophy ; Merosin ; dy Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Extraocular muscle is uniquely spared from damage in merosin-deficient congenital muscular dystrophy. Using a murine model, we have tested the hypothesis that the maintenance of calcium homeostasis is mechanistic in extraocular muscle protection. Atomic absorption spectroscopy has demonstrated a strong correlation between the perturbation of calcium homeostasis in hindlimb muscle that is severely damaged and the absence of changes in calcium in extraocular muscle. If, as in other skeletal muscles, extraocular muscle fibers are destabilized by merosin deficiency, we would expect an increase in total muscle calcium coupled with an adaptive response in the high capacity/speed of the sarcoplasmic reticulum of the eye muscle. However, we have not observed the expected increases in total muscle calcium content, Ca2+-ATPase activity, Na+/Ca2+ exchanger content, or smooth ER Ca2+-ATPase content that are predicted by this model. Instead, these results indicate that the increased membrane permeability that characterizes, and is potentially mechanistic in, myofiber degeneration in muscular dystrophy does not occur in merosin-deficient extraocular muscle. Thus, the high-capacity calcium-scavenging systems are not primarily responsible for extraocular muscle protection in muscular dystrophy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051078
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Vestibulo-ocular pathways modulate extraocular muscle myosin expression patterns (1999)
    Springer
    Cell & tissue research 295 (1999), S. 477-484 
    Details
    ISSN: 1432-0878
    Keywords: Key words Extraocular muscle ; Muscle development ; Myosin heavy chain ; Vestibular development ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The genetic and epigenetic influences that establish and maintain the unique phenotype of the extraocular muscles (EOMs) are poorly understood. The vestibulo-ocular reflex (VOR) represents an important input into the EOMs, as it stabilizes eye position relative to the environment and provides a platform for function of all other eye movement systems. A role for vestibular cues in shaping EOM maturation was assessed in these studies using the ototoxic nitrile compound 3’,3’-iminodipropionitrile (IDPN) to eliminate the receptor hair cells that drive the vestibulo-ocular reflex. Intraperitoneal injections of IDPN were followed by a 2-week survival period, after which myosin heavy chain (MyHC) analysis of the EOMs was performed. When IDPN was administered to juvenile rats, the proportion of eye muscle fibers expressing developmental and fast myosins was increased, while EOM-specific MyHC mRNA levels were downregulated. By contrast, IDPN treatment in adult rats affected only the proportion of fibers expressing developmental MyHC isoforms, leaving the EOM-specific MyHC mRNA unaltered. These data provide evidence that the VOR modulates EOM-specific MyHC expression in development. The lack of significant changes in EOM-specific MyHC expression in adult EOM following IDPN administration suggests that there may be a critical period during development when alterations in vestibular activity have significant and permanent consequences for the eye muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051253
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  • 3
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    The magnetic network location of explosive events observed in the solar transition region (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Compact short-lived explosive events have been observed in solar transition region lines with the High-Resolution Telescope and Spectrograph (HRTS) flown by the Naval Research Laboratory on a series of rockets and on Spacelab 2. Data from Spacelab 2 are coaligned with a simultaneous magnetogram and near-simultaneous He I 10,380 -A spectroheliogram obtained at the National Solar Observatory at Kitt Peak. The comparison shows that the explosive events occur in the solar magnetic network lanes at the boundaries of supergranular convective cells. However, the events occur away from the larger concentrations of magnetic flux in the network, in contradiction to the observed tendency of the more energetic solar phenomena to be associated with the stronger magnetic fields.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 370; 775-778
    Format: text
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  • 4
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    Microflares in the solar magnetic network (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Localized brightenings are found throughout the magnetic network in quiet sun image sequences obtained in the C IV 1548 A line by the SMM satellite's UV spectrometer and polarimeter. Some bright sites are short-lived, while others persist. Plots of the intensity fluctuations show that the enhancements at both short- and long-lived sites are the result of localized impulsive heating events that occur intermittently at the short-lived sites and in more rapid succession at the long-lived ones. The number of these events and their visibility in the wings of the C IV line are consistent with their identification as the explosive events seen in UV spectra.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 323; 380-390
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  • 5
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    Preflare magnetic and velocity fields (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares
    Keywords: SOLAR PHYSICS
    Type: Energetic Phenomena on the Sun: The Solar Maximum Mission Flare Workshop. Proceedings; 33 p
    Format: application/pdf
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  • 6
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    The excitation of helium resonance lines in solar flares (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Helium resonance line intensities are calculated for a set of six flare models corresponding to two rates of heating and three widely varying incident fluxes of soft X-rays. The differing ionization and excitation equilibria produced by these models, the processes which dominate the various cases, and the predicted helium line spectra are examined. The line intensities and their ratios are compared with values derived from Skylab NRL spectroheliograms for a class M flare, thus determining which of these models most nearly represents the density vs temperature structure and soft X-ray flux in the flaring solar transition region, and the temperature and dominant mechanaism of formation of the helium line spectrum during a flare.
    Keywords: SOLAR PHYSICS
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  • 7
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    Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection Against Icing. 1: Unpartitioned Blades (1948)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation to determine the effectiveness of icing protection afforded by air-heating hollow steel unpartitioned propeller blades has been conducted In the NACA Cleveland icing research tunnel. The propeller used was a production model modified with blade shank and tip openings to permit internal passage of heated air. Blade-surface and heated-air temperatures were obtained and photographic observations of Ice formations were made with variations In icing intensity and heating rate to the blades. For the conditions of Icing to which the propeller was subjected, it was found that adequate ice protection was afforded with a heating rate of 40 1 000 Btu per hour per blade. With less than 40,000 Btu per hour per blade, ice protection failed because of significant ice accretions on the leading edge. The chordwise distribution of heat was unsatisfactory with most of the available heat dissipated well back of the leading edge on both the thrust and camber face's instead of at the leading edge where it was most needed. A low utilization of available heat for icing protection is indicated by a beat-exchanger effectiveness of approximately 47 percent.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NACA-TN-1586
    Format: application/pdf
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  • 8
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    Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection Against Icing. 3: 25% Partitioned Blades (1948)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The icing protection obtained from an internally air-heated propeller blade partitioned to confine the heated air forward of 25-percent chord was investigated in the NACA Cleveland icing research tunnel. A production-model hollow steel propeller was modified with an Internal radial partition at 25-percent chord and with shank and tip openings to admit and exhaust the heated air. Temperatures were measured on the blade surfaces and in the heated-air system during tunnel icing conditions. Heat-exchanger effectiveness and photographs of Ice formations on the blades were obtained. Surface temperature measurements indicated that confining the heated air forward of the 25-percent chord gave.a more economical distribution of the applied heat as compared with unpartitioned and 50-percent partitioned blades, by dissipating a greater percentage of the available heat at the leading edge. At a propeller speed of 850 rpm, a heating rate of 7000 Btu per hour per blade at a shank air temperature of 400 F provided adequate Icing protection at ambient-air temperatures of 23 F but not at temperatures as low as 15 F. With the heating rate used, a heat-exchanger effectiveness of 77 percent was obtained as compared to 56 percent for 50-percent partitioned and 47 percent for unpartitioned blades.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NACA-TN-1588
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  • 9
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    Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection Against Icing. 2: 50% Impartitioned Blades (1948)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The icing protection afforded an internal air-heated propeller blade by radial partitioning at 50-percent chord to confine the heated air to the forward half of the blade was determined in the NACA Cleveland icing research tunnel. A modified production-model hollow steel propeller, was used for the investigation. Temperatures of the blade surfaces for several heating rates were measured under various tunnel Icing' conditions. Photographic observations of ice formations on blade surfaces and blade heat-exchanger effectiveness were obtained. With 50-percent partitioning of the blades, adequate icing protection at 1050 rpm was obtained with a heating rate of 26,000 Btu per hour per blade at the blade shank using an air temperature of 400 F with a flow rate of 280 pounds per hour per blade, which is one-third less heat than was found necessary for similar Ice protection with unpartitioned blades. The chordwise distribution of the applied heat, as determined by surface temperature measurements, was considered unsatisfactory with much of the heat dissipated well back of the leading edge. Heat-exchanger effectiveness of approximately 56 percent also Indicated poor utilization of available heat. This effectiveness was, however, 9 percent greater than that obtained from unpartitioned blades.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NACA-TN-1587
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  • 10
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    Chandra Observations of Magnetic White Dwarfs and Their Theoretical Implications (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Observations of cool DA and DB white dwarfs have not yet been successful in detecting coronal X-ray emission but observations of late-type dwarfs and giants show that coronae are common for these stars. To produce coronal X-rays, a star must have dynamo-generated surface magnetic fields and a well-developed convection zone. There is strong observational evidence that the DA star LHS 1038 and the DB star GD 358 have weak and variable surface magnetic fields. Since these fields are likely to be generated by dynamo action and since both stars have well-developed convection zones, theory predicts detectable levels of coronal X-rays from these white dwarfs. However, we present analysis of Chandra observations of both stars showing no detectable X-ray emission. The derived upper limits for the X-ray fluxes provide strong constraints on theories of formation of coronae around magnetic white dwarfs.
    Keywords: Astronomy
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