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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 64-66 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrafast relaxation dynamics of light and heavy holes in GaAs following femtosecond valence-to-conduction-band excitation are measured by probing the light- and heavy-to-split-off hole transitions at different midinfrared wavelengths using the recently developed broadly tunable femtosecond optical parametric oscillator. The initial relaxation times are less than 75 fs, and a spectral hole-burning effect is seen. The results suggest that carrier–carrier and optical-phonon scattering, in particular, polar optical-phonon scattering, are the primary processes leading to the initial redistribution of heavy and light holes. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6098-6100 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stage 2 CocMn1−cCl2-graphite intercalation compounds (0≤c≤1) approximate two-dimensional site-random XY spin systems with a competition between ferromagnetic [J(Co–Co) and J(Co–Mn)], and antiferromagnetic exchange interactions [J(Mn–Mn)]. The magnetic phase diagram and critical behavior of these compounds are studied by means of ac and dc magnetic susceptibility. For c≥ (R18)0.45 the phase transition occurs between the paramagnetic phase and the ferromagnetic phase. The critical exponents of γ and β do not change with dilution of Mn atoms: γ=2.31 and β=0.085 for c=0.90.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5749-5751 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of a quasi-two-dimensional mixed ferromagnetic and antiferromagnetic system, stage-2 CocMn1−cCl2 -graphite intercalation compounds (GICs), have been studied by dc magnetic susceptibility measurements. The Curie–Weiss temperature determined as a function of Co concentration indicates that the intraplanar exchange interaction between Co2+ and Mn2+ is ferromagnetic and that J(Co-Mn)=1.3 [J(Co-Co)||J(Mn-Mn)||]1/2. With decreasing Co concentration c, the transition temperature tends to decrease to zero as c approaches 0.5 (the percolation concentration for the triangular lattice sites), but is not reduced to zero even below c=0.5. There may be a possibility of a spin-glass phase for 0≤c〈0.4 arising from the competition between J(Mn-Mn), J(Co-Mn), and J(Mn-Mn).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 3247-3257 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of a vertical magnetic field on the integral heat transfer and the temporal dynamics of liquid metal Rayleigh–Bénard convection is studied in an experiment using a small Prandtl number (Pr(approximate)0.02) sodium potassium alloy Na22Kr78 as a test fluid. The test section is a rectangular box of large aspect ratio 20 : 10 : 1 that covers a parameter range of Rayleigh numbers, 103〈Ra〈105, and Chandrasekhar numbers, 0〈Q〈1.44×104. The integral heat transfer across the layer is evaluated from the measured temperatures at the upper and the lower boundary and the applied heat flux. Local, time-dependent temperatures are obtained from a four-element temperature probe placed in the middle of the liquid metal layer. The noncoplanar arrangement of the thermocouples enables the evaluation of the time-dependent temperature gradient vector that allows us to estimate the local isotropy properties of the time-dependent flow. From the damping effect of Joule dissipation, the convective heat transport decreases monotonically with increasing Chandrasekhar numbers. Fluctuations of the temperature field are damped significantly by the magnetic field. However, this effect is selective with respect to frequency. Long period fluctuations are strongly damped whereas short period fluctuations are less damped or may even be amplified. The observations show that significant convective heat transport is practically always associated with time-dependent flow. The fluctuating part of the local temperature gradient confirms the horizontal isotropy of the velocity field; no predominant orientation of time-dependent flow structures is established either with or without a magnetic field. © 2001 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3566-3569 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe fast recovery at a wavelength of 1550 nm in a multiple-quantum-well (MQW) saturable absorber with InGaAsP quaternary wells and barriers using electric-field-induced carrier sweepout. The MQW SA is integrated with a distributed Bragg reflector in a p-type–intrinsic–n-type structure. Pump–probe measurements show that the recovery time can be reduced from 〉900 to 28 ps by application of a 151 kV/cm sweepout field. We measure the dependence of the recovery time on the energy of the saturating pulse and explain our results in terms of carrier dynamics in the sweepout field. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1442-1444 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A prominent theme in inorganic materials research is the creation of uniformly flat thin films and heterostructures over large wafers, which can subsequently be lithographically processed into functional devices. This letter proposes an approach that will lead to thin film topographies that are directly counter to the above-mentioned philosophy. Recent years have witnessed considerable research activity in the area of self-assembly of materials, stimulated by observations of self-organized behavior in biological systems. We have fabricated uniform arrays of nonplanar surface features by a spontaneous assembly process involving the oxidation of simple metals, especially under constrained conditions on a variety of substrates, including glass and Si. In this letter we demonstrate the pervasiveness of this process through examples involving the oxidation of Pd, Cu, Fe, and In. The feature sizes can be controlled through the grain size and thickness of the starting metal thin film. Finally, we demonstrate how such submicron scale arrays can serve as templates for the design and development of self-assembled, nanoelectronic devices. © 2001 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1664-1666 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the switch-off and recovery dynamics of a vertical-cavity surface-emitting semiconductor laser induced by injection of near-infrared or midinfrared femtosecond optical pulses. The laser is switched off by carrier-density depletion or carrier-heating effects, depending on the spectral range of the injected pulses. In both cases, the recovery of the laser output can be described by standard rate equations. © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1734-1736 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ultrafast relaxation dynamics of split-off holes in GaAs are studied using a time-resolved two-wavelength excitation luminescence technique. Following valence-to-conduction-band transitions that are excited by near-infrared femtosecond pulses, delayed midinfrared femtosecond pulses are used to promote holes from the heavy-hole band to the split-off-hole band. The subsequent conduction-to-split-off-hole luminescence indicates that the room-temperature lifetime of split-off holes in GaAs is approximately 50 fs. The accompanying changes in conduction-to-heavy-hole-and-light-hole luminescence when holes are transferred to the split-off band are also observed. © 1999 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3341-3343 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A high-repetition-rate, femtosecond optical parametric oscillator based on bulk periodically poled lithium niobate is described. This optical parametric oscillator is continuously tunable from 1.12 to 1.50 μm in the signal branch, and signal pulses as short as 60 fs have been observed. The corresponding turning range for the idler branch is from 1.68 to 2.72 μm. Modifications which should result in a femtosecond optical parametric oscillator with a pumping threshold of less than 50 mW are discussed. © 1997 American Institute of Physics.
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  • 10
    Publication Date: 2011-06-24
    Description: Peelle’s Pertinent Puzzle (PPP) was described in 1987 in the context of estimating fundamental parameters that arise in nuclear interaction experiments. In PPP, generalized least squares (GLS) parameter estimates fell outside the range of the data, which has raised concerns that GLS is somehow flawed and has led to suggested alternatives to GLS estimators. However, there have been no corresponding performance comparisons among methods, and one suggested approach involving simulated data realizations is statistically incomplete. Here we provide performance comparisons among estimators, introduce approximate Bayesian computation (ABC) using density estimation applied to simulated data realizations to produce an alternative to the incomplete approach, complete the incompletely specified approach, and show that estimation error in the assumed covariance matrix cannot always be ignored.
    Electronic ISSN: 1999-4893
    Topics: Computer Science
    Published by MDPI Publishing
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