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  • Electronic Resource  (5)
  • 1995-1999  (5)
  • PMMA  (3)
  • Amino acids  (2)
  • Pheochromocytoma
  • 1
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; Osmoregulation ; Cell size ; Cell shape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Taurine is a very important organic osmolyte in most adult cells. Because of this property it has been proposed that large changes in the intracellular content of taurine can osmotically stress the cell, causing changes in its size and shape. This hypothesis was examined by measuring cell dimensions of taurine deficient cardiomyocytes using confocal microscopy. Incubation of isolated neonatal rat myocytes with medium containing 5mMβ-alanine led to a 55% decrease in intracellular taurine content. Associated with the loss of taurine was a reduction in cell size. Two factors contributed to the change in cell size. First, there was a shift in cell shape, favoring the smaller of the two cellular configurations commonly found in the myocyte cell culture. Second, the size of the polyhedral configuration was reduced after ßalanine treatment. These same two events also contributed to size reduction in cardiomyocytes incubated with medium containing 30mM mannitol. Nonetheless, some qualitative differences exist between cells osmotically stressed by increasing the osmolality of the incubation medium and decreasing intracellular osmolality. The results support a role for taurine in the regulation of osmotic balance in the neonatal cardiomyocyte.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; Calcium paradox ; Cultured myocardial cell ; Intracellular free calcium ; Beating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of taurine on the cellular distribution of [Ca2+]i, during the calcium paradox was examined by digital imaging of a single fura-2-loaded cell. Cardiomyocytes superfused with control medium containing 2mM Ca2+ exhibited typical transients associated with spontaneous beating. When the cells were exposed to Ca2+-free buffer, immediate cessation of both spontaneous contractions and calcium transients was observed as [Ca2+]; rapidly fell to a level of 3–6 × 10−8M. Subsequent restoration of medium calcium increased [Ca2+]i to level 4–7 times normal. Large increases in [Ca2+]i were observed in most cells and were associated with the development of contracture and bleb formation. Taurine pretreatment (20mM) caused no significant effect on [Ca2+]i during Ca2+ depletion. However, it inhibited excessive accumulation of [Ca2+]i during the Ca2+ repletion. Moreover, taurine treated cells recovered their Ca2+-transients and beating pattern earlier than non-treated cells. Finally morphological abnormalities commonly associated with calcium overload were attenuated by taurine treatment.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 83 (1997), S. 305-313 
    ISSN: 1573-2673
    Keywords: dynamic crack propagation ; stress intensity factor ; crack velocity ; a cceleration ; polymers ; PMMA ; expoxy ; caustic method.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dynamic crack propagations in PMMA and epoxy specimens were studied using the method of caustics in combination with a Cranz-Schardin type high-speed camera. Single-edge-cracked tensile specimens were fractured under pin-loading conditions so that cracks could experience acceleration, deceleration and re-acceleration stages in one fracture process. The dynamic stress intensity factor K ID, crack velocity a and acceleration a were evaluated in the course of crack propagation to examine the effects of a and a on K ID. Results showed that a and a were important factors in changing the values of K ID, and for constant a the decelerating crack had a larger value of K ID than the accelerating or re-accelerating crack. Also, it was found that K ID could be expressed as two parametric functions of and a for PMMA and epoxy specimens.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 96 (1999), S. 347-360 
    ISSN: 1573-2673
    Keywords: Dynamic crack propagation ; unloading behavior ; stress intensity factor ; crack velocity ; unloading rate ; brittle polymers ; epoxy ; PMMA ; homalite-100 ; caustic method.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The method of caustics in combination with a Cranz–Schardin high-speed camera was utilized to study dynamic crack propagation and unloading behavior of epoxy, PMMA and Homalite-100 specimens. Dynamic stress intensity factor K ID and crack velocity $$\dot a$$ were evaluated in the course of crack propagation. Caustic patterns at the loading points were also recorded to estimate load P applied to the specimen. Unloading rate $$\dot P$$ , the time derivative of P, was determined as a function of time t, and its time correlation with K ID or $$\dot a$$ was examined. The findings showed that the change in $$\dot P$$ was qualitatively in accord with the change in K ID or $$\dot a$$ . However, there existed slight differences among the values of t giving the maximum $$\dot P$$ , $$\dot a$$ and K ID, so that their order was $$\dot a$$ , $$\dot P$$ and K ID.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 86 (1997), S. 289-300 
    ISSN: 1573-2673
    Keywords: Polymers ; crack tip ; displacement fields ; moiré interferometry ; PMMA ; PA6/PPE/SBS alloy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Moiré interferometry was utilized to experimentally determine displacement fields around a crack tip in single-edge-cracked tensile PMMA and PA6/PPE/SBS alloy specimens. Vertical displacement v was expressed as functions of distance r and angle θ from the crack tip, and compared with the approximate solution of linear elastic fracture mechanics to study its applicability to polymers. The results showed that the solution agreed with the experiments in the vicinity of a crack tip in the PMMA specimens, but it yielded a discrepancy as r increased. For the alloy specimens, however, the solution gave much smaller values than the experiments. The principle of superposition was employed to determine the values of v*(=v-v′), i.e. the difference between two displacements v and v′ which was related to a uniform strain field without a crack. The expressions for v* and v were also introduced to analyze the effects of r, θ and load P applied to the specimen. v* was found to be an important factor in increasing the displacements near the crack tip, and the v expression well represented the experimental results for both the PMMA and alloy specimens.
    Type of Medium: Electronic Resource
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