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  • 1
    Electronic Resource
    Electronic Resource
    Dielectric properties of material with random off-center defects: Monte Carlo simulation of relaxor ferroelectrics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6345-6356 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Ginzburg–Landau type theory of interaction of randomly distributed local dipoles in a paraelectric crystal is developed. The interaction is caused by the polarization of the host lattice generated by these dipoles. The obtained effective Hamiltonian of the dipole–dipole interaction is employed for the Monte Carlo simulation of ferroelectric properties of a system with off-center dopant ions producing local dipoles. The computer simulation shows that at low dopant ion concentration the paraelectric state transforms into a macroscopically paraelectric state consisting of randomly oriented polar clusters. These clusters amplify the effective dipole moment and dramatically increase the dielectric constant. The interaction between the clusters results in a spectrum of relaxation time and transition to the relaxor state. The real and imaginary parts of the susceptibility of this state are calculated. At intermediate dopant concentration, the material undergoes a diffuse phase transition into a ferroelectric state smeared within a temperature range. A further increase in the dopant concentration makes the transition sharper and closer to the conventional ferroelectric transition. The results obtained are compared with the behavior of the K1−xLixTaO3 relaxor ferroelectric. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415759
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  • 2
    Electronic Resource
    Electronic Resource
    Photoinduced current generated by subband gap optical pumping for the investigation of deep levels in semiconductor lasers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 226-230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that the measurement of photocurrents induced by optical pumping at subband gap wavelengths may be a useful technique for studying deep-level traps in semiconductor lasers. In this experiment a 1.3 μm wavelength laser is used to probe a 0.78 μm wavelength GaAs laser device. The trap density of a predegraded and postdegraded device was measured. The measurement indicates a significant increase in the trap density for the degraded device over the nondegraded device. Rate equations describing this excitation process are given and are shown to describe the experiment very well. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1327602
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  • 3
    Electronic Resource
    Electronic Resource
    Alloying of Co ultrathin films on Pt(111) with Ag buffer layers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 705-709 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure at the interfaces of Co/Ag/Pt(111) was studied by low-energy electron diffraction, ultraviolet photoelectron spectroscopy, Auger electron spectroscopy, and depth profiling. An atomic exchange occurs between Co and Ag before the formation of a Co–Pt alloy. Ag atoms start moving to the top at 425 K when the coverage of Co is one monolayer. The temperature of the complete exchange between Ag atoms and Co atoms is dependent on the thickness of the Ag buffer layer. The Co–Pt alloy develops after the atomic exchange is complete. The especially small surface free energy of Ag and large strain energy in this system are proposed as the driving force for the exchange. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373725
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  • 4
    Electronic Resource
    Electronic Resource
    Role of the tyrosine kinase JAK2 in signal transduction by growth hormone (2000)
    Springer
    Pediatric nephrology 14 (2000), S. 550-557 
    Details
    ISSN: 1432-198X
    Keywords: Key words Growth ; Growth hormone ; JAK2 ; Insulin receptor substrates ; Signal transducers and activators of transcription ; SH2-B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Chronic renal failure in children results in impaired body growth. This effect is so severe in some children that not only does it have a negative impact on their self-image, but it also affects their ability to carry out normal day-to-day functions. Yet the mechanism by which chronic renal failure causes short stature is not well understood. Growth hormone (GH) therapy increases body height in prepubertal children, suggesting that a better understanding of how GH promotes body growth may lead to better insight into the impaired body growth in chronic renal failure and therefore better therapies. This review discusses what is currently known about how GH acts at a cellular level. The review discusses how GH is known to bind to a membrane-bound receptor and activate a cytoplasmic tyrosine kinase called Janus kinase (JAK) 2. The activated JAK2 in turn phosphorylates tyrosines within itself and the associated GH receptor, forming high-affinity binding sites for a variety of signaling molecules. Examples of such signaling molecules include signal transducers and activators of transcription (Stats), which regulate the expression of a variety of GH-dependent genes, and the adapter protein Shc, which leads to activation of the Ras-Raf-MEK-MAP kinase pathway. In response to GH, JAK2 is also known to phosphorylate the insulin receptor substrates, leading to activation of phosphatidyl inositol 3’ kinase and most likely other molecules that have been implicated in the regulation of metabolism. Finally, the ability of JAK2 to bind and activate the presumed adapter protein SH2-B is discussed. SH2-B has been shown to be a potent activator of GH-promoted JAK2 activity and downstream signaling events. Presumably these and other pathways initiated by GH combine to result in its ability to regulate body growth and metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004670000366
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  • 5
    Electronic Resource
    Electronic Resource
    A local-ether model of propagation of electromagnetic wave (2001)
    Springer
    The European physical journal 21 (2001), S. 701-715 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. It is pointed out that the classical propagation model can be in accord with the Sagnac effect due to earth's rotational and orbital motions in the high-precision GPS (global positioning system) and interplanetary radar, if the reference frame of the classical propagation medium is endowed with a switchability according to the location of the wave. Accordingly, it is postulated that, as in the obsolete theory, electromagnetic waves propagate via a medium like the ether. However, the ether is not universal. It is proposed that in the region under sufficient influence of the gravity due to the earth, the sun, or another celestial body, there forms a local ether, which in turn is stationary with respect to the gravitational potential of the respective body. For earthbound and interplanetary propagation, the medium is stationary in a geocentric and a heliocentric inertial frame, respectively. An electromagnetic wave propagates at a constant speed with respect to the associated local ether, independent of the motions of source and receiver. Based on this local-ether model of wave propagation, a wide variety of earthbound, interplanetary, and interstellar propagation phenomena are accounted for. Strong evidence of this new classical model is its consistent account of the Sagnac effect due to earth's motions among GPS, the intercontinental microwave link, and the interplanetary radar. Moreover, as examined within the present precision, this model is still in accord with the Michelson–Morley experiment. To test the local-ether propagation model, a one-way-link rotor experiment is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100759
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