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  • 1
    Electronic Resource
    Electronic Resource
    Spatial variation of ferroelectric properties in Pb(Zr0.3, Ti0.7)O3 thin films studied by atomic force microscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8031-8034 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Imaging of the phase and magnitude of the piezoelectric strain in Pb(Zr0.3, Ti0.7)O3 (PZT) capacitors is performed with an atomic force microscope. The imaging reveals a significant spatial dependence of the ferroelectric properties of both fatigued and unfatigued PZT films. We propose that the variation is related to the domain structure of the PZT. Through the measurement of local piezoelectric hysteresis loops and imaging of the piezoelectric strain, areas are observed in fatigued PZT that exhibit hysteresis loops shifted along the polarization axis. In some regions of fatigued samples, the hysteresis loops are shifted such that both remanent points of the hysteresis curve have the same polarization direction. These results have important implications for the scalability of nonvolatile ferroelectric random access memory to higher device densities. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373492
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of Pt heterostructure bottom electrodes on SrBi2Ta2O9 thin film properties (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 496-498 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties of SrBi2Ta2O9 (SBT) films, such as remanent polarization and leakage current density, are closely related to the film/electrode interface and surface roughness of the underlying electrode. SBT films grown on stable Pt/TiO2/SiO2/Si and Pt/ZrO2/SiO2/Si substrates exhibit high remanent polarization, low leakage current density, and low voltage saturation as compared to SBT films synthesized on Pt/Ti/SiO2/Si. It is shown that severe diffusion of Ti from the Ti interlayer onto the surface of the Pt bottom electrode and the increased surface roughness of this electrode stack play key roles in degradation of SBT properties. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125799
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  • 3
    Electronic Resource
    Electronic Resource
    Thickness effects on imprint in chemical-solution-derived (Pb, La)(Zr, Ti)O3 thin films (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2885-2887 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The film thickness-dependent imprinting behavior (voltage shift) of (Pb, La)(Zr, Ti)O3 capacitors was evaluated by a thermal stress process under a remanence bias. The remanent polarization (Pr) was found to be almost independent of the film thickness whereas in the 50–300 nm range the relative dielectric constant (cursive-epsilonr) increased linearly with the square root of the film thickness. It was found that the voltage shift, which was attributed to the accumulation of charged defects near the electrode interface, also increased linearly with increasing film thickness. In addition, the charge accumulated thickness varied with the square root of the film thickness. This was established from a simple assumption that the level of charge accumulation is determined by the product of the total amount of charged defects (total film thickness×charged defect density) and the internal field that is generated by the Pr. Therefore, the imprint is much more a bulk-related degradation phenomenon compared to the fatigue. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370989
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  • 4
    Electronic Resource
    Electronic Resource
    Thermally induced voltage offsets in Pb(Zr,Ti)O3 thin films (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3036-3038 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Voltage offset in the polarization-voltage characteristics of Pb(Zr,Ti)O3 (PZT) capacitors was evaluated by a thermal stress process. A thermally induced voltage shift occurs when heating the sample under either remanence or a saturating bias. It was found that the voltage shifts can, to a large extent, be attributed to the role of charged defects and the defect-dipole alignment throughout the films. PZT film with a high Zr/Ti ratio, i.e., rhombohedral compositions exhibited the best imprint resistance. When these films were doped wit up to 6% La, the imprint resistance was further improved. It was also found that B-site donors were more effective in minimizing the voltage shift than A-site donors. However, dopants with the same charge value as Pb, for example, Ca and Sr, did not affect the thermally induced voltage shifts of the films since they could not reduce the charged defects in the films. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1324001
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  • 5
    Electronic Resource
    Electronic Resource
    A Monte Carlo simulation of polymer/polymer interface in the presence of block copolymer. I. Effects of the chain length of block copolymer and interaction energy (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 12193-12201 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A Monte Carlo simulation for the segregation behavior of symmetric diblock copolymer at the interface between immiscible homopolymers was performed on a simplified lattice model. The simulation results show that the segregation behavior of block copolymer is significantly dependent on the molecular parameters, such as the chain length Nc of block copolymer and the interaction energy εAB between A and B segments. In a weakly repulsive system with εAB=0.1, the block copolymers are more strongly segregated at the interface with increasing the chain length when the block length is shorter than and comparable to the homopolymer length. However, when the block length becomes longer than the homopolymer length, the concentration of copolymer segments at the interface rather decreases and its distribution becomes broadened. In a strongly repulsive system with εAB=0.5, the distribution of copolymer segments at the interface becomes broader as the chain length of block copolymer increases. This behavior is closely related to the stretching and orientation of block copolymer chains at the interface and to the extent of penetration of homopolymers into the copolymer layer. These simulation results are in excellent agreement with the numerical predictions by the self-consistent mean field theory. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479156
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  • 6
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of the phase separation dynamics of polymer blends in the presence of block copolymers. IV. Effects of chain length and composition of repulsive block copolymer (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4267-4281 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulation was used to study the effects of C-b-D block copolymers with repulsive interaction on the phase separation dynamics of A/B immiscible homopolymer blend. It is found that a repulsive block copolymer can significantly suppress the rate of phase separation of an immiscible binary blend when its interaction energies with the homopolymers satisfy a proper condition. It is also found that the longer the chain length of block copolymer, the better such a retardation effect. When the chain extension of block copolymer at the interface is examined, each block in the repulsive block copolymer is contracted in its corresponding homopolymer phase, whereas the attractive copolymer chain is extended at the interface. This may lead to less retardation effect of repulsive block copolymer as compared with attractive block copolymer. Unlike the attractive block copolymer, the repulsive block copolymer with an asymmetric composition (f=0.7) does not show better retardation than the symmetric one. However, in spite of some difference in retardation effect, both types of block copolymers (attractive and repulsive) obey the dynamic scaling law, and the scaled structure factors are universal with time, irrespective of copolymer structure. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475826
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  • 7
    Electronic Resource
    Electronic Resource
    Role of GSK-3β activity in motor neuronal cell death induced by G93A or A4V mutant hSOD1 gene (2005)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 22 (2005), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Point mutations such as G93A and A4V in the human Cu/Zn-superoxide dismutase gene (hSOD1) cause familial amyotrophic lateral sclerosis (fALS). In spite of several theories to explain the pathogenic mechanisms, the mechanism remains largely unclear. Increased activity of glycogen synthase kinase-3 (GSK-3) has recently been emphasized as an important pathogenic mechanism of neurodegenerative diseases, including Alzheimer's disease and ALS. To investigate the effects of G93A or A4V mutations on the phosphatidylinositol-3-kinase (PI3-K)/Akt and GSK-3 pathway as well as the caspase-3 pathway, VSC4.1 motoneuron cells were transfected with G93A- or A4V-mutant types of hSOD1 (G93A and A4V cells, respectively) and, 24 h after neuronal differentiation, their viability and intracellular signals, including PI3-K/Akt, GSK-3, heat shock transcription factor-1 (HSTF-1), cytochrome c, caspase-3 and poly(ADP-ribose) polymerase (PARP), were compared with those of wild type (wild cells). Furthermore, to elucidate the role of the GSK-3β-mediated cell death mechanism, alterations of viability and intracellular signals in those mutant motoneurons were investigated after treating the cells with GSK-3β inhibitor. Compared with wild cells, viability was greatly reduced in the G93A and A4V cells. However, the treatment of G93A and A4V cells with GSK-3β inhibitor increased their viability by activating HSTF-1 and by reducing cytochrome c release, caspase-3 activation and PARP cleavage. However, the treatment did not affect the expression of PI3-K/Akt and GSK-3β. These results suggest that the G93A or A4V mutations inhibit PI3-K/Akt and activate GSK-3β and caspase-3, thus becoming vulnerable to oxidative stress, and that the GSK-3β-mediated cell death mechanism is important in G93A and A4V cell death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2005.04191.x
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of PARP inhibitor on ischaemic cell death, its related inflammation and survival signals (2004)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 20 (2004), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Poly(ADP-ribose) polymerase (PARP) plays an important role in ischaemic cell death, and 3-aminobenzamide (3-AB), one of the PARP inhibitors, has a protective effect on ischaemic stroke. We investigated the neuroprotective mechanisms of 3-AB in ischaemic stroke. The occlusion of middle cerebral artery (MCA) was made in 170 Sprague–Dawley rats, and reperfusion was performed 2 h after the occlusion. Another 10 Sprague–Dawley rats were used for sham operation. 3-AB was administered to 85 rats 10 min before the occlusion [3-AB group (n = 85) vs. control group without 3-AB (n = 85)]. Infarct volume and water content were measured, brain magnetic resonance imaging, terminal deoxynucleotidyltransferase (TdT)-mediated dUTP-biotin nick end-labelling (TUNEL) and Cresyl violet staining were performed, and immunoreactivities (IRs) of poly(ADP-ribose) polymer (PAR), cleaved caspase-3, CD11b, intercellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2), phospho-Akt (pAkt) and phospho-glycogen synthase kinase-3 (pGSK-3) were compared in the peri-infarcted region of the 3-AB group and its corresponding ischaemic region of the control group at 2, 8, 24 and 72 h after the occlusion. In the 3-AB group, the infarct volume and the water content were decreased (about 45% and 3.6%, respectively, at 24 h), the number of TUNEL-positive cells was decreased (about 36% at 24 h), and the IRs of PAR, cleaved caspase-3, CD11b, ICAM-1 and COX-2 were significantly reduced, while the IRs of pAkt and pGSK-3 were increased. These results suggest that 3-AB treatment could reduce the infarct volume by reducing ischaemic cell death, its related inflammation and increasing survival signals. The inhibition of PARP could be another potential neuroprotective strategy in ischaemic stroke.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2004.03632.x
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  • 9
    Electronic Resource
    Electronic Resource
    Lead Zirconate Titanate Thin Films on Base-Metal Foils: An Approach for Embedded High-Permittivity Passive Components (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An approach for embedding high-permittivity dielectric thin films into glass epoxy laminate packages has been developed. Lead lanthanum zirconate titanate (Pb0.85La0.15(Zr0.52Ti0.48)0.96O3, PLZT) thin films were prepared using chemical solution deposition on nickel-coated copper foils that were 50 μm thick. Sputter-deposited nickel top electrodes completed the all-base-metal capacitor stack. After high-temperature nitrogen-gas crystallization anneals, the PLZT composition showed no signs of reduction, whereas the base-metal foils remained flexible. The capacitance density was 300–400 nF/cm2, and the loss tangent was 0.01–0.02 over a frequency range of 1–1000 kHz. These properties represent a potential improvement of 2–3 orders of magnitude over currently available embedded capacitor technologies for polymeric packages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01029.x
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  • 10
    Electronic Resource
    Electronic Resource
    Preparation and oil-absorptivity of crosslinked polymers containing stearylmethacrylate, 4-t-butylstyrene, and divinylbenzene (2000)
    Springer
    Polymer bulletin 44 (2000), S. 17-24 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The crosslinked polymers, poly(stearylmethacrylate-co-divinylbenzene) [CP(SMA-co-DVB)] and poly(t-butylstyrene-co-divinylbenzene) [CP(tBS-co-DVB)], and CP(SMA-co-DVB)/PtBS IPNs, were prepared by the polymerization of corresponding monomer pairs in the presence of BPO. The structures and thermal properties of CP(SMA-co-DVB), CP(tBS-co-DVB), and the IPN were determined by FT-IR, DSC, and TGA. The oil-absorptivities of CP(SMA-co-DVB) and CP(SMA-co-DVB)/PtBS IPN decreased with increasing concentrations of DVB and tBS, respectively. The highest oil-absorptivities of CP(SMA-co-DVB) and the IPN(PtBS: 25%) were 615 % and 330 %, respectively. The toluene absorptivity of the synthesized polymers decreased in following order: CP(tBS-co-DVB) 〉 CP(SMA-co-DVB) 〉 IPN(PtBS: 25 %) 〉 IPN(PtBS: 50 %) 〉 IPN(PtBS: 75 %) at immersion above 60 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050568
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