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  • American Institute of Physics (AIP)  (10)
  • Chemistry Central  (2)
  • Hindawi  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Ferromagnetic resonance and exchange anisotropy in ferromagnetic/antiferromagnetic bilayers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2180-2185 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we study the in-plane ferromagnetic resonance (FMR) and exchange anisotropy in a ferromagnetic (FM)/antiferromagnetic (AFM) bilayer. In the semi-infinite limit for the AFM layer, the equilibrium energy for the system is established, and then analytical expressions are derived for FMR frequency, frequency linewidth, exchange anisotropy constant, effective exchange bias, and pinning angle. Three physical parameters are important, i.e., the classical exchange bias, the interface turning coefficient, and the applied field angle. Combining the formulas derived with numerical calculation, it is shown that there are two branches of FMR modes distinguished by critical fields which depend on the interface turning the coefficient and the applied field angle. We find that the effective exchange bias depends on the applied field angle but not on its magnitude. A comparison with previously reported theoretical results is made, and experimental measurements for physical parameters are suggested. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1433927
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  • 2
    Electronic Resource
    Electronic Resource
    Thickness and angular dependencies of exchange bias in ferromagnetic/antiferromagnetic bilayers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1009-1013 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A generalized Meiklejohn–Bean model in which the exchange coupling includes bilinear (direct exchange) and biquadratic (spin–flop) terms is proposed to study the exchange bias in ferromagnetic (FM)/antiferromagnetic (AFM) bilayers. For the strong antiferromagnetic anisotropy, an explicit formula for the exchange bias is derived and used to discuss the thickness and angular dependencies, and a lot of recent experimental results can thus be illustrated. The results show that both the critical thickness of the antiferromagnetic layer displaying the exchange bias and the saturation value of the exchange bias depend on the exchange coupling constants, the angle between the FM easy axis and AFM easy axis, as well as the orientation of an applied field. The bilinear and biquadratic terms will provide competitive contributions to the exchange bias, while the angular variation of the applied field can tune the exchange bias. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486020
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  • 3
    Electronic Resource
    Electronic Resource
    Long-range coupling interactions in ferroelectric sandwich structures (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5031-5035 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the ferroelectric system consisting of the sandwich structure (PbTiO3/BaTiO3/PbTiO3) by using the Ginzburg–Landau phenomenological theory, and emphasize the importance of the long-range coupling interaction to the ferroelectric behavior of the system. We find that after introducing the long-range coupling interaction to the ferroelectric behavior of the sandwich system, the average spontaneous polarization of the interlayer (BaTiO3) increases and a size-driven phase transition disappears. The larger the range of the long-range coupling, the larger the average spontaneous polarization. When the range of the long-range coupling is large enough, the average spontaneous polarization increases gradually with decreasing interlayer thickness, reaches one maximum at a certain finite thickness, and then decreases. The spatial distribution profile of the spontaneous polarization on the range of the coupling interaction for different values of the interlayer thickness is obtained, and the dependence of the averaged polarization on temperature is also examined. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359157
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  • 4
    Electronic Resource
    Electronic Resource
    Finite-temperature coercivity of multilayers of hard and soft magnets (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1583-1586 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss results of finite-temperature Monte Carlo simulation for the switching field of multilayers of hard and soft magnets. The maximum of the energy product as a function of the soft layer thickness is very weak and becomes weaker as the temperature is increased. However, the maximum becomes more pronounced for the energy product cost as a function of the soft layer thickness. The effect of the dipolar interaction is significant but does not change the qualitative trend of the coercive field as a function of the soft layer thickness. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373858
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  • 5
    Electronic Resource
    Electronic Resource
    Vacancy-assisted domain growth in amphiphilic systems: Monte Carlo simulation (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 6398-6403 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the phase separation of amphiphilic systems with vacancies using Monte Carlo simulation of Larson models. We try to clarify the effect of vacancy on the domain growth of a microemulsion at different quench temperatures, and obtain the phase-separating morphology, the time evolution of the structure factor, and the characteristic length scale of the system. It is found that for the deep quench case, vacancies tend to locate at interfaces and accelerate phase separation. However, for shallow quenches an amount of vacancies migrates into the bulk phase and domain growth kinetics assisted by vacancies at interfaces is balanced by the lowering interface tension of vacancies. This has been attributed to the interplay between vacancy-mediated segregation dynamics and reduction of driving force for the phase separation through vacancies at interface, depending on the quench temperatures. On the contrary, all the amphiphile molecules are still deposited onto interfaces even for high temperatures because of the chain properties of the amphiphiles. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308282
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  • 6
    Electronic Resource
    Electronic Resource
    Stripe patterns in frustrated spin systems (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 1686-1691 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the effects of the long-range dipolar interaction on the formation of the stripe patterns in two-dimensional (2D) spin systems with competing short- and long-range interactions by using the continuous time Monte Carlo technique. We find that there exists an optimal temperature region at which the best stripe patterns are prone to be formed, and the stability and the orientational ordering of striped structures mainly depend on the temperature T, while the width of the striped domains is determined by the strength of the long-range dipolar interaction g. Furthermore, a complete T-g phase diagram is obtained. The results provide a simple and universal picture to account for striking and substantial physics revealed in the prevalent striped morphologies of 2D spin systems. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487817
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  • 7
    Electronic Resource
    Electronic Resource
    Controlling structural organization of binary phase-separating fluids through mobile particles (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 7719-7723 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structural organization in binary immiscible fluids is studied in the presence of mobile particles. We show that the particles, which are included in the favorable phase due to a selective affinity and assemble therein, can drive the favorable phase to self-organize into cluster, interconnected, and network structures, depending on the particle concentration. The detailed studies enable us to confirm the physical origin of the morphology transitions: At low particle concentration, the assembly of particles would amplify the spatial heterogeneity by depleting the favorable phase in the particle-free region, where the hydrodynamic flows further accelerate the dropletlike formation of favorable phase; with increasing the particle concentration, the assembly of particles becomes energetically unfavorable due to the considerably excluded volume effect of particles and they tend to stabilize the percolated structure of the favorable phase. Furthermore, the respective crossover behaviors of the growth dynamics are also observed, corresponding to different structure formations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467344
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  • 8
    Electronic Resource
    Electronic Resource
    Ordering stripe structures of nanoscale rods in diblock copolymer scaffolds (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 7783-7786 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report a simulation on the formation of ordered stripe structures of nanoscale rods driven by symmetric diblock copolymer melts. Due to the preferential adsorption of one species of the diblock onto the mobile rods, the phase ordering process will couple with the movement of rods. We find that the self-assembly of rods on the copolymer scaffold produces the highly ordered nanowires of rods, and copolymer blends in turn form the well-oriented lamellar structure. This is due to the interplay among the micro-phase separating dynamics in the diblock copolymer, the wetting interaction between rods and diblock copolymer, and the nematic ordering dynamics of rods. We examine the influence of the domain size, the wetting strength, and the rod number density on the formation of such a nanoscale structure. Additionally, we indicate that the orientation of the pattern can be well controlled by external fields acting on the rods. The results suggest that our model system may provide a novel and simple way to control and design the ordering nanowire structure. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1476313
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  • 9
    Electronic Resource
    Electronic Resource
    Domain patterns in ternary mixtures with different interfacial properties (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3734-3738 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Numerical simulation of the phase separation kinetics in ternary mixtures with different interfacial properties is performed by means of the cell dynamics approach. We discuss the effects of the competition between the phase separation and the wetting phenomena on the system morphology and growth dynamics. Morphological changes and domain growth due to different interfacial properties including wetting and interface tension difference between two interfaces are observed in the late stage of spinodal decomposition. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343838
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  • 10
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    Ultrasound-assisted lipase-catalyzed synthesis of D-isoascorbyl Palmitate: process optimization and Kinetic evaluation (2013)
    Chemistry Central
    Details
    Publication Date: 2013-12-10
    Description: Background: D-isoascorbic acid is a food antioxidant additive and used in accordance with Good Manufacturing Practice (GMP). High solubility in water (about 150 g/L at 25[degree sign]C) reduces its effectiveness in stabilizing fats and oils. Our research group had successfully synthesized D-isoascorbyl palmitate using immobilized lipase Novozym 435 as a biocatalyst. Low production efficiency of D-isoascorbyl palmitate is still a problem for industrial production due to the long reaction time of over 24 h. In the present work, ultrasonic treatment was applied for accelerating the reaction process. The operation parameters were optimized to obtain the maximum D-isoascorbyl palmitate conversion rate by using a 5-level-4-factor Central Composite Design (CCD) and Response Surface Methdology (RSM). The reaction apparent kinetic parameters under the ultrasound treatment and mechanical shaking conditions were also determined and compared. Results: Results showed that ultrasound treatment decreased the reaction time by over 50%. D-isoascorbyl palmitate yielded to 94.32 +/- 0.17% and the productivity reached to 8.67 g L-1 h-1 under the optimized conditions as: 9% of enzyme load (w/w), 61[degree sign]C of reaction temperature, 1:5 of D- isoascorbic-to-palmitic acid molar ratio, and 137 W of the ultrasound power. The immobilized lipase Novozym 435 could be reused for 7 times with 65% of the remained D-isoascorbyl palmitate conversion rate. The reaction kinetics showed that the maximum apparent reaction rate (vmax) of the ultrasound-assisted reaction was 2.85 times higher than that of the mechanical shaking, which proved that ultrasound treatment significantly enhanced the reaction efficiency. Conclusion: A systematic study on ultrasound-assisted enzymatic esterification for D-isoascorbyl palmitate production is reported. The results show a promising perspective of the ultrasound technique to reduce the reaction time and improve the production efficiency. The commercial D-isoascorbyl palmitate synthesis will be potentially realized due to this ultrasound-promoted esters synthesis method.
    Electronic ISSN: 1752-153X
    Topics: Chemistry and Pharmacology
    Published by Chemistry Central
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