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  • 1
    Electronic Resource
    Electronic Resource
    Electrically controlled elasticity utilizing piezoelectric coupling (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 863-868 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical control of elasticity was performed in piezoelectric polymer films by connecting an electric circuit parallel to the sample electrodes. A polyvinylidene fluoride film and a vinylidene fluoride tetrafluoroethylene copolymer (73/27) film were used. Electrical circuits acting as a variable negative capacitor or a variable inductor were constructed using operational amplifiers. Theoretically, when the value of the external negative capacitance is increased, the observed elastic constant increases from that at an open circuit to positive infinity at around the value of the sample, turns to negative infinity, and then increases through zero to that at a short circuit. If the inductance of the external circuit is changed around the electrical resonant frequency, the elastic constant exhibits resonance and antiresonance against frequency. Experimental observations of the characteristics of the dynamic elastic constant agreed well with these theoretical predictions. By coupling the negative capacitance, the elastic constant changed between 0.5 and 2 times the original value, and the elastic loss increased to tan δ=0.7. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371954
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  • 2
    Electronic Resource
    Electronic Resource
    Piezoelectric Effect in Poly-γ-methyl- L -glutamate (1966)
    [s.l.] : Nature Publishing Group
    Nature 211 (1966), S. 1079-1079 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It has been recently established that a number of high polymeric substances show a piezoelectric effect1'2. The substances so far investigated have been naturally occurring polymers such as cellulose, keratin, silk fibroin and collagen. Actual specimens used in the study have been taken from ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2111079a0
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of thrombopoietin on peroxidase activity of cryopreserved peripheral blood stem cells (1997)
    Springer
    Medical molecular morphology 30 (1997), S. 194-201 
    Details
    ISSN: 1860-1499
    Keywords: Thrombopoietin (TPO) ; Peripheral blood stem cell (PBSC) ; Ultrastructural peroxidase activity ; Cryopreserved sample
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transplantation of mobilized peripheral blood stem cells is increasingly used to facilitate hematological recovery following high-dose chemotherapy. In general, peripheral blood stem cells can be maintained by cryopreservation, e.g., at −80°C, until the day of transplantation. We investigated the effect of thrombopoietin (c-Mpl ligand) on cryopreserved peripheral blood stem cells obtained from 10 patients with malignant disease by assessing peroxidase activity by ultrastructual technique. Leukocyte surface markers wre evaluated by flow cytometry. After peripheral blood stem cells had been purified by use of CD34 monoclonal antibody, cells whose size resembled that of monocytes showed low levels of positivity for CD7, CD41a, and CD42b, but high levels of positivity for CD13, CD14, and HLA-DR. The lymphocyte-size cells showed high levels of positivity for CD7 only. Recombinant human thrombopoietin, administered alone and in combination with various cytokines, promoted the expression of CD41a by CD34-positive progenitor cells. No increase in the expression of CD7, CD13, CD14, and HLA-DR was detected following exposure to cytokines. However, the expression of CD41a and CD42b was enhanced by thrombopoietin. Ultrastructural study of peroxidase activity detected CD41a-positive cells. as well as platelet peroxidase-positive cells, following stimulation with thrombopoietin. Stimulation by other cytokines failed to yield platelet peroxidase-positive cells. Results thus suggest that thrombopoietin may be useful for increasing the recovery of platelets following transplantation of cryopreserved peripheral blood stem cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01545770
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  • 4
    Electronic Resource
    Electronic Resource
    Piezoelectric effect of cyanoethylated hydroxyethylcellulose (1998)
    Springer
    Journal of wood science 44 (1998), S. 35-39 
    Details
    ISSN: 1611-4663
    Keywords: Cyanoethylated hydroxyethylcellulose ; High piezoelectric material ; Functional cellulose derivative ; Electromechanical coupling factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The piezoelectricity of cyanoethylated hydroxyethylcellulose was investigated. Elastic, piezoelectric, and dielectric relaxations were observed at −80° to −60°C and 0° to 20°C at a frequency of 10Hz. The activation energy is about 9–15 kcal/mol in the low temperature region and about 30–45 kcal/mol at room temperature. These relaxations in the low temperature region may be caused by the motion of the cyanoethyl group and those at room temperature mostly by the motions of the main chain. Cyanoethylated hydroxyethylcellulose has a high piezoelectric strain constant (d 25), which is the largest value among the cellulose derivatives and is almost the same as the value for polyvinylidene fluoride. The electromechanical coupling factor for cyanoethylated hydroxyethylcellulose was small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00521872
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature variation of piezoelectric moduli in oriented poly(γ-methyl L-glutamate) (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 61-70 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The real and imaginary components of the complex piezoelectric strain constant, which relates the polarization to the applied stress, have been determined for elongated films of poly(γ-methyl L-glutamate) over the temperature range -170°C to +170°C at a frequency of 20 Hz. The variation of the piezoelectric constant with temperature is similar for both α-helical and β-form molecular conformations. The sign of piezoelectric polarization is opposite for L and D polymers. A simple model, representing the piezoelectric crystallites as embedded in nonpiezoelectric amorphous regions, is proposed to account for the piezoelectric temperature dispersion curves.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080105
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