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  • 1
    Electronic Resource
    Electronic Resource
    Confinement criterion for a highly bunched beam (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 5206-5213 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonrelativistic motion is analyzed for a highly bunched beam propagating through a perfectly conducting cylindrical pipe confined radially by a constant magnetic field parallel to the conductor axis. In the present analysis, the beam is treated as either a thin rod distribution representing a continuous (unbunched) beam or periodic collinear point charges representing a highly bunched beam. Use is made of a Green's function to compute the electrostatic force on the beam due to the induced surface charge in the conductor wall. By analyzing the Hamiltonian dynamics, a criterion is derived for the confinement of unbunched and bunched beams. It is shown that for the confinement of beams with the same charge per unit length, the maximum value of the effective self-field parameter is 2ωp2/ωc2≅2a/L for a highly bunched beam with a(very-much-less-than)L. This value is significantly lower than the Brillouin density limit for an unbunched beam 2ωp2/ωc2=1. Here, a is the radius of the conducting cylinder, and L is the periodic spacing of the bunches. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319639
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  • 2
    Electronic Resource
    Electronic Resource
    Investigation of phase transition thresholds by nonlinear transient laser gratings on silicon surfaces (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3505-3510 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear transient laser gratings were excited by crossing two 180 ps Nd:YAG laser pulses (355 nm) at the silicon surface. The launched counterpropagating surface acoustic wave trains were detected outside the source with a cw laser probe-beam-deflection setup. Phase transitions occurring within the Gaussian fluence distribution of the grating induced characteristic changes in the amplitude of the corresponding grating oscillations involved and higher harmonics were found in the frequency spectrum. In the molten surface region, the amplitude decreased compared to the thermoelastic excitation, and second-harmonic generation was observed, whereas ablation generated an asymmetric profile with higher amplitudes and even the third harmonic could be detected. An accurate method is introduced to determine the ablation threshold (340 mJ/cm2 for silicon) from the transition of linear to nonlinear behavior in the distorted non-Gaussian amplitude distribution. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372373
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  • 3
    Electronic Resource
    Electronic Resource
    Effective-mass enhancement and nonparabolicity in thin GaAs quantum wells (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6945-6947 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study size quantization effects on the conduction band dispersion in GaAs/AlAs quantum wells using a semiempirical tight-binding method. For GaAs well thicknesses between 3 and 11 nm, we find a significant increase of the conduction band mass of up to 50% compared with bulk GaAs. Concomitantly, the confinement reduces the highest achievable group velocities for electrons in the Γ conduction valley of the well by up to 30%. We discuss some of the consequences for quantum-well-based devices. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321773
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative and Statistical Analysis of the Shape of Amperometric Spikes Recorded from Two Populations of Cells (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 74 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previously used methods of comparing amperometric spike characteristics from two separate groups of cells have entailed pooling all the values for a spike characteristic from each group of cells and then statistically comparing the two samples. Although this approach has indicated that there are significant differences between the spike characteristics from coloboma and control mouse chromaffin cells, the results are not consistent between experiments. We have reexamined the assumptions of the statistical tests used as well as the variability inherent in amperometric data measured from two groups of cells. Our findings indicate that when comparing amperometric spike characteristics between groups of cells, it is more appropriate to compare samples of mean spike values. This method consistently indicates that there is no difference between coloboma and control amperometric spikes. These results have been validated by using samples of mean spike characteristics to detect changes in the shape of amperometric spikes from both mouse chromaffin cells at 37°C and PC12 cells previously exposed to 50 μM L-3,4-dihydroxyphenylalanine and by the use of an additional analysis method, the nested ANOVA. Together, these results indicate that pooled samples of amperometric spike characteristics can give results that may confound the interpretation of amperometric data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.741086.x
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  • 5
    Electronic Resource
    Electronic Resource
    Electrode-sheath voltages in high-pressure mercury arcs (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1271-1275 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrode-sheath voltages (ESVs) were determined as a function of time in high-pressure ac mercury arcs running at different frequencies in the range 50 Hz–5 kHz with sinusoidal wave forms. Besides the experimental investigations, a one-dimensional model was used to describe the arc-column properties. Measurements of the voltage across the arcs were compared with model calculations for the arc-column voltage only. The calculated voltages are mostly smaller than the measured ones, and it was concluded that the difference should correspond to the ESV. This voltage drop was compared with values obtained in a completely different way, namely, by measuring the voltage at different lengths of the arcs which were otherwise identic, and extrapolating it to zero length. As had been shown before, at 50 Hz this voltage drop has a very pronounced time behavior during a half cycle. The investigations were extended to higher frequencies, and the obtained differences are discussed. The field strengths were derived from the rise of the measured voltage versus the discharge lengths; a quantitative agreement with the calculated field strengths was obtained by choosing an appropriate pressure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373814
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  • 6
    Electronic Resource
    Electronic Resource
    Improved algorithm for modeling collision broadening through a sequence of scattering events in semiclassical Monte Carlo (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 303-311 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improved, more physically accurate algorithm is presented for modeling collision broadening in semiclassical Monte Carlo. More specifically, the method of connecting a sequence of collision broadened scattering events is addressed. Sequences of collision broadened scattering events are analyzed via basic theory and illustrated via first-principles simulations using the quantum transport simulator Schrödinger Equation Monte Carlo in which, in contrast to semiclassical Monte Carlo, real scattering and collision broadening are inseparable processes. It is demonstrated that the requirement for energy conservation in the coupled carrier-phonon system prohibits the accumulation of the uncertainty in the carrier energy associated with collision broadening through a sequence of scattering events, accumulation that is possible with the conventional treatment of collision broadening in semiclassical Monte Carlo. Based on this analysis, basic changes to the treatment of collision broadening in semiclassical Monte Carlo are suggested. The potential significance of these changes is then assessed via simplified semiclassical Monte Carlo simulations. In particular, the exaggeration of the high-energy tail of the carrier distribution possible with the conventional treatment of collision broadening in semiclassical Monte Carlo is demonstrated to be an artifact of the above described nonphysical accumulation of the collision broadening contributions, not of the form of the collision broadening used (Lorentzian, etc.) as often assumed; with this more physically accurate new algorithm, well-behaved high-energy tails of the carrier distribution are obtained even with full Lorentzian broadening. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371861
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  • 7
    Electronic Resource
    Electronic Resource
    Maintaining nonvoluntary relationships with disliked partners: an investigation into the use of distancing behaviors (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Human communication research 26 (2000), S. 0 
    Details
    ISSN: 1468-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Media Resources and Communication Sciences, Journalism
    Notes: Theory in interpersonal communication usually assumes that people maintain their relationships voluntarily and that they like their relational partners. Neither assumption is necessarily correct. This research examines nonvoluntary relationship with disliked partners (NR/Ds). Heider's balance theory predicts that when people dislike their relational partners they will feel discomfort. It was hypothesized that people would try to attenuate this discomfort by increasing psychological distance between themselves and their disliked partners. Participants (n = 185 in Study 1, n = 158 in Study 2) responded to questionnaires about their maintenance of voluntary and nonvoluntary relationships with liked and disliked partners. The results showed that people use distance to attenuate the discomfort created by an NR/D. Thirty-six distancing behaviors were found through content analysis. Using hierarchical cluster analysis, these behaviors were grouped into clusters that suggested 3 basic profiles of regulating distance in NR/Ds - expressing detachment, avoiding involvement, and showing antagonism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1468-2958.2000.tb00765.x
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  • 8
    Electronic Resource
    Electronic Resource
    Quality Changes in Fresh-cut Pear Slices as Affected by Cultivar, Ripeness Stage, Fruit Size, and Storage Regime (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 65 (2000), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fresh-cut fruit slices prepared from partially ripened Bartlett pears had longer shelf life than those from Bosc, Anjou, and Red Anjou pears. Pear fruit ripeness, based on flesh firmness of 44 to 58 N, is optimal for fresh-cut pear slice processing. Pear slices derived from smaller size fruit (122 to 135 g) have greater cut surface discoloration and deteriorate more rapidly than slices derived from larger fruit (152 g). Recently harvested Bartlett pear fruit and whole pears held at –1 °C in a controlled atmosphere of 2%O2+ 98%N2 had a longer post-cutting shelf life than those held in air at –1 °C for the same duration. Cut surface browning, flesh softening, and surface dehydration of the slice cut surface were all contributors to loss of product quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2000.tb16044.x
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  • 9
    Electronic Resource
    Electronic Resource
    Relativistic all-electron coupled-cluster calculations on Au2 in the framework of the Douglas–Kroll transformation (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1809-1813 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report relativistic all-electron coupled-cluster calculations on the gold dimer, using methods based on the Douglas–Kroll transformation. We use basis sets comprising up to i-type functions and study the dependence of Re, De, and ωe on basis set size, correlation method, and basis set superposition error. It is found that the dispersion interaction (electron correlation) between the gold d shells is described satisfactorily only if basis sets with angular momenta up to at least h functions are used. Møller–Plesset calculations up to fourth order tend to underestimate the bond distance, while averaged coupled-pair functional and coupled-cluster calculations including perturbative triples converge to molecular parameters close to experiment. Correlating the 5p semicore of the gold atoms is found to have a non-negligible contribution. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480744
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  • 10
    Electronic Resource
    Electronic Resource
    Comment on "An ab initio cluster study of the structure of the Si(001) surface" [J. Chem. Phys. 112, 2994 (2000)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 9353-9354 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This recent paper uses multiconfiguration self-consistent field (MCSCF) wave functions to study the structure of Si(001). The results are at odds with density functional theory predictions and experiment. This comment shows that dynamic correlation, which is neglected in MCSCF calculations, is essential for reliable predictions of the geometry of Si(001). © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1320058
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