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  • 1
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to obtain more direct evidence for the occurrence of myoblast fusion in the developing amphibian embryo, the following transplantations were performed in vitro. The nuclei of early embryos. Ambystoma tigrinum and A. maculatum, were labeled with tritiated thymidine. Portions of prospective somite areas from these labeled donors were grafted homoplastically and orthotopically into unlabeled hosts of the same, or nearly the same, stage. The stages employed were: neurula, early tail bud, and late tail bud. Hosts were raised until they had developed into more advanced larval forms, fixed, sectioned, and prepared for radioautographic processing according to the customary procedures.The histological preparations contained varying numbers of multinucleate myotubes of a “composite” nature: that is, individual myotubes contained labeled nuclei of the donor, side by side with unlabeled nuclei of the host. There was no doubt that the mononucleate myoblasts of the grafts had fused with those of the host species to form the mutlinucleate composite myotubes.In addition to the above determinations, the method of thymidine labeling has proven to be a satisfactory method of tracing, in the context of the intact organism, somitic cell derivatives up to the feeding larval stage. Mesenchymal cells from the grafted labeled somitic tissues were consequently found in: dermatomic, sclerotomic and intermyotomic locations; the matrix of the dorsal fin; the limb bud; the abdominal muscles.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to further support the thesis that myoblast fusions lead to the formation of multinucleate myotubes during early amphibian development, prospective myoblasts from frog embryos (Rana pipiens; Xenopus laevis) were orthotopically and heterotopically transplanted into embryonic salamanders (Ambystoma maculatum; A. tigrinum). The stages employed ranged from gastrula to early tail bud. After the hosts had developed to more advanced stages, they were fixed, sectioned in the frontal plane, and prepared for histological observation. Of special interest in these xenoplastic combinations are the nuclear and cytoplasmic differences between anuran and urodele embryonic cells.In most cases, transplanted cells tended to form a tissue complex distinct from the host tissues. This naturally decreased the opportunity for cell intermingling and consequently reduced the chances for fusions between graft and host myoblasts. Thus, there was a correlation between the extent of dispersion of the transplanted cells and the frequency of chimeric myotubes. Nevertheless, in each experimental series, a number of multinucleate myotubes emerged consisting of nuclear and cytoplasmic components of both graft and host cells. These chimeric myotubes, which must have originated by multiple cell fusions of anuran and urodele cells, (1) retained their distinct nuclear differences, (2) displayed resorption of both anuran and urodele yolk platelets, and (3) contained cross-striated myofibrils. The function of these chimeric cells, their synthesis of myofibrils, and the apparent lack of free intermingling at the cellular level, are discussed.
    Additional Material: 1 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 73 (1969), S. 69-80 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Water exchange has been studied in ovarian and body cavity eggs of three Anuran species (Rana esculenta, R. pipiens and R. temporaria) with the isotope exchange method using the automatically recording diver balance. In order to estimate the rate of water diffusion in egg cytoplasm (D), a factor required to determine the rate of water permeation (= the exchange coefficient, E), three different chemical treatments (digitonin, ethanol and formaldehyde) have been used to remove the surface barrier to water flow. The obtained mean value of D, 5 × 10-6 cm2 sec-1, has been accepted as a close approximation of water diffusion in the egg cytoplasm. This value has been used to determine the exchange coefficients in the egg types of the above mentioned species. Comparisons have been made between the calculated values of E both within and between species, and some suggestions have been made concerning the influence of microvilli on the rate of water exchange. Although, on the average, water exchange proceeds at a greater rate in ovarian than in body cavity eggs, a measurable diffusion barrier at the surface can be demonstrated.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 26 (1996), S. 65-79 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2019-06-28
    Description: Structureborne noise is discussed as a contributor to propeller aircraft interior noise levels that are nonresponsive to the application of a generous amount of cabin sidewall acoustic treatment. High structureborne noise levels may jeopardize passenger acceptance of the fuel-efficient high-speed propeller transport aircraft designed for cruise at Mach 0.65 to 0.85. These single-rotation tractor and counter-rotation tractor and pusher propulsion systems will consume 15 to 30 percent less fuel than advanced turbofan systems. Structureborne noise detection methodologies and the importance of development of a structureborne noise sensor are discussed. A structureborne noise generation mechanism is described in which the periodic components or propeller swirl produce periodic torques and forces on downstream wings and airfoils that are propagated to the cabin interior as noise. Three concepts for controlling structureborne noise are presented: (1) a stator row swirl remover, (2) selection of a proper combination of blade numbers in the rotor/stator system of a single-rotation propeller, and the rotor/rotor system of a counter-rotation propeller, and (3) a tuned mechanical absorber.
    Keywords: ACOUSTICS
    Type: NASA-TM-88947 , E-3362 , NAS 1.15:88947 , AIAA PAPER 87-0530
    Format: application/pdf
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  • 7
    Publication Date: 2019-06-28
    Description: Flight tests to define the far-field tone source at cruise conditions were completed on the full-scale SR-7L advanced turboprop that was installed on the left wing of a Gulfstream 2 aircraft. This program, designated Propfan Test Assessment (PTA), involved aeroacoustic testing of the propeller over a range of test conditions. These measurements defined source levels for input into long-distance propagation models to predict en route noise. In-flight data were taken for seven test cases. Near-field acoustic data were taken on the Gulfstream fuselage and on a microphone boom that was mounted on the Gulfstream wing outboard of the propeller. Far-field acoustic data were taken by an acoustically instrumented Learjet that flew in formation with the Gulfstream. These flight tests were flown from El Paso, Texas, and from the NASA Lewis Research Center. A comprehensive listing of the aeroacoustic results from these flight tests which may be used for future analysis are presented.
    Keywords: ACOUSTICS
    Type: NASA-TM-103719 , E-6402 , NAS 1.15:103719
    Format: application/pdf
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  • 8
    Publication Date: 2019-06-28
    Description: Modern high speed propeller (advanced turboprop) aircraft are expected to operate on 50 to 60 percent less fuel than the 1980 vintage turbofan fleet while at the same time matching the flight speed and performance of those aircraft. Counterrotation turboprop engines offer additional fuel savings by means of upstream propeller swirl recovery. This paper presents acoustic sideline results for a full-scale counterrotation turboprop engine at cruise conditions. The engine was installed on a Boeing 727 aircraft in place of the right-side turbofan engine. Acoustic data were taken from an instrumented Learjet chase plane. Sideline acoustic results are presented for 0.50 and 0.72 Mach cruise conditions. A scale model of the engine propeller was tested in a wind tunnel at 0.72 Mach cruise conditions. The model data were adjusted to flight acquisition conditions and were in general agreement with the flight results.
    Keywords: ACOUSTICS
    Type: NASA-TM-101383 , E-4437 , NAS 1.15:101383
    Format: application/pdf
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  • 9
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: Structureborne noise is discussed as a contributor to propeller aircraft interior noise levels that are nonresponsive to the application of a generous amount of cabin sidewall acoustic treatment. High structureborne noise levels may jeopardize passenger acceptance of the fuel-efficient high-speed propeller transport aircraft designed for cruise at Mach 0.65 to 0.85. These single-rotation tractor and counter-rotation tractor and pusher propulsion systems will consume 15 to 30 percent less fuel than advanced turbofan systems. Structureborne noise detection methodologies and the importance of development of a structureborne noise sensor are discussed. A structureborne noise generation mechanism is described in which the periodic components or propeller swirl produce periodic torques and forces on downstream wings and airfoils that are propagated to the cabin interior as noise. Three concepts for controlling structureborne noise are presented: (1) a stator row swirl remover, (2) selection of a proper combination of blade numbers in the rotor/stator system of a single-rotation propeller, and the rotor/rotor system of a counter-rotation propeller, and (3) a tuned mechanical absorber.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 87-0530
    Format: text
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  • 10
    Publication Date: 2019-07-13
    Description: A flight program was carried out to determine the variation of noise level with distance from a model high speed propeller. Noise measurements were obtained at different distances from a SR-3 propeller mounted on a JetStar aircraft, with the test instrumentation mounted on a Lear jet flown in formation. The propeller was operated at 0.8 flight Mach number, 1.12 helical tip Mach number and at 0.7 flight Mach number, 1.0 helical tip Mach number. The instantaneous pressure from individual blades was observed to rise faster at the 0.8 M flight speed, than at the 0.7 M flight speed. The measured levels appeared to decrease in good agreement with a 6 dB/doubling of distance decay, over the measurement range of approximately 16 m to 100 m distance. Further extrapolation, to the distances represented by a community, would suggest that the propagated levels during cruise would not cause a serious community annoyance.
    Keywords: ACOUSTICS
    Type: NASA-TM-83327 , E-1574 , NAS 1.15:83327 , AIAA PAPER 83-9745 , AIAA 8th Aeroacoustics Conf.; Apr 11, 1983 - Apr 13, 1983; Atlanta
    Format: application/pdf
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