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  • American Institute of Physics (AIP)  (29)
  • National Academy of Sciences  (12)
  • 2005-2009
  • 1990-1994  (41)
  • 1930-1934
  • 1990  (41)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1622-1628 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a new ultrasonic method for measuring the phase velocity of longitudinal and shear waves in self-supporting thin films. The film is bonded at one end to an interdigital transducer (IDT) which emits a continuous wave signal. The film is supported at the other end and maintained flat under a weak tension. A receiving IDT detects the in-phase and quadrature components of the sound waves as they propagate. A liquid bond is used between the receiving IDT and the film to allow a continuous variation of the path length. From the longitudinal and shear wave velocities, we can deduce the flexural and shear moduli of the film. For films of uniaxial or higher symmetry, the Young's and biaxial moduli can be expressed as combinations of the flexural and shear moduli. We applied this technique to Cu-Pd composition modulated thin films. Contrary to previous reports, we have not observed the supermodulus effect in either the flexural, shear, Young's or biaxial moduli for modulation wavelengths between 13 and 36 A(ring).
    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 67 (1990), S. 4616-4618 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous melt-spun Pr2(Fe1−xCox)14B has been prepared to test the concept of magnetic-field-induced crystallite alignment. Crystallization temperatures (Tx) of alloys with x=0.5, 0.6, and 1.0 were determined to be 622, 646, and 507 °C, respectively. These temperatures are all lower than the Curie temperatures (Tc) of the crystallized 2:14:1 phase. The glasses were then heat treated at a temperature Tt(Tx〈Tt〈Tc), either in no field or in a magnetic field of 0.3 T applied parallel to the long edge of the ribbon. The degree of alignment was investigated by means of x-ray diffraction and magnetization measurements. A texture was found where the c axes tend to lie in the ribbon plane in zero field, which is slightly modified when a magnetic field is applied during the heat treatment.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5087-5098 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We construct a free-energy density-functional approximation for the primitive model of the electrical double layer. The hard-sphere term of the free-energy functional is based on a nonlocal generic model functional proposed by Percus. This latter model functional, which is a generalization of the exact solution for the nonuniform hard-rod model, requires as input the free energy of a homogeneous hard-sphere mixture. We choose the extension of the Carnahan–Starling equation of state to mixtures. The electrostatic part of the nonuniform fluid ion–ion correlations present in the interface is approximated by that of a homogeneous bulk electrolyte. Using the mean spherical approximation for a neutral electrolyte, we apply the theory to symmetrical 1:1 and 2:2 salts in the restricted primitive model. We present comparisons of density profiles and diffuse layer potentials with Gouy–Chapman theory and Monte Carlo data. We also compare our results with data from other recent theories of the double layer. For highly charged surfaces, the profiles show the layering of counterions and charge inversion effects, in agreement with Monte Carlo data.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4308-4319 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Means are presented for using stationary points in two ways. One, for well-understood potentials, elucidates relations between the form of the surface and the dynamics that it supports, including the determination of the effective molecular symmetry group. The other, for potentials of uncertain quality, provides a test for unphysical characteristics and suggests how the surface might be improved if it is found to be unsatisfactory in some respect. Our approach involves comparison of transition state calculations using the slowest slide and Cerjan–Miller algorithms for two example systems: the Lennard-Jones Ar7 cluster and the Handy–Carter many-body-expansion potential for the ground state of formaldehyde.
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3427-3431 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Flow of fluids confined in molecularly narrow pores is studied by molecular dynamics. Strong density variations across the pore render the usual dependence of the local viscosity on local density inappropriate. At separations greater than four molecular diameters flow can be described by a simple redefinition of local viscosity. In narrower pores a dramatic increase of effective viscosities is observed and is due to the inability of fluid layers to undergo the gliding motion of planar flow. This effect is partially responsible for the strong viscosity increases observed experimentally in thin films that still maintain their fluidity.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1720-1731 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic quenching of BrCl B 3Π(O+) was studied in pulsed and steady-state laser induced fluorescence experiments. BrCl(B) deactivation rate coefficients were determined as a function of vibrational quantum number for the following collision partners: He, Ne, Ar, Kr, N2, O2, and Cl2. Quenching from a vibrationally thermalized, 300 K BrCl(B,v') distribution by the noble gases N2, and Cl2 was slow with all rate coefficients less than 4.3±0.7×10−13 cm3 molecule−1 s−1 . The quenching by O2 was much faster with a rate coefficient of 6.5±0.6×10−12 cm3 molecule−1 s−1 . The quenching of BrCl(B), under single collision conditions, depends strongly on vibrational quantum number of BrCl(B), with rate coefficients ranging from 4.3±0.1×10−13 cm3 molecule−1 s−1 for v'=0 to 1.4±0.3×10−10 cm3 molecule−1 s −1 for v'=6 under collisions with Cl2 and with rate coefficients ranging from 1.5±0.3×10−13 cm3 molecule−1 s−1 for v'=0 to 1.0± 0.4×10−10 cm3 molecule−1 s−1 for v'=6 under collisions with He. Several mechanisms for the electronic deactivation of BrCl(B) are discussed. The radiative lifetime of BrCl(B) was determined to be 38.7±1.7 μs, independent of vibrational level for v'≤6.
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1661-1671 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A cw laser-induced fluorescence experiment is described in which state-to-state rate coefficients for rotation-to-translation energy transfer have been determined from J'=72, v'=6 in IF B 3Π(0+). Using the collision partners He, Ne, Ar, Kr, Xe, N2, and CF4, nearly 500 individual rate coefficients have been measured. The rare-gas atoms display a characteristic behavior with the heavier collision partners more efficiently exchanging large amounts of angular momentum in a single collision.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4339-4344 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The density distribution functions of a confined one-dimensional fluid of particles obeying the Tonks–Takahashi nearest neighbor two-body potential are reduced to simple functions of the grand canonical ensemble partition function. The resulting formulas are analogous to those found by Robledo and Rowlinson for a hard-rod fluid. In the absence of an external field the partition functions can be evaluated by the method of Laplace transforms. The dependence of the pressure P on the separation L of the confining walls is investigated for three model potentials: (i) hard rod, (ii) square well, and (iii) triangle well. P is an oscillating function of L in all three cases. The oscillations arise from the ordering effect of the repulsive forces between particles. The attractive interactions of the triangle-well potential reinforces the ordering whereas those of the square-well potential diminishes the ordering. Results for semiconfined and homogeneous fluids are also presented.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1488-1490 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Degenerate four-wave mixing was used to evaluate third-order nonlinearities in Ag-Na exchange waveguides. Guided wave linear absorption analysis was used to correlate metallic Ag content with nonlinear properties. Measured conjugate reflectivities approached 4%.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1281-1288 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple form of the electrodynamic balance, suitable for a wide range of microparticle measurements, is described and analyzed. The ac electrode of the device consists of a pair of parallel rings, and the dc endcaps are either simple disks or they can be eliminated entirely by applying suitable dc bias voltages to the rings. The stability characteristics of the device are determined by extension of well-established stability theory, and experiments are compared with that theory. The device is particularly well-suited for detection of radioactive aerosols, for it has significant advantages over the bihyperboloidal device for radioactivity measurement. The detection of radioactivity levels of less than 20 pCi is feasible. Coupled with a Raman spectrometer the balance serves as a stable "platform'' for the study of the chemistry of microparticles, and both qualitative and quantitative analysis of microdroplet chemistry are demonstrated for binary droplets of 1-octadecene and 1-bromoctadecane.
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