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  • 1
    Electronic Resource
    Electronic Resource
    Determination of the crystallographic orientation of a single crystal using resonant ultrasound spectroscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2139-2140 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Using resonant ultrasound spectroscopy (RUS) we have determined the crystallographic orientation of a tantalum single crystal from a measurement of its mechanical resonance spectrum. This accomplishment is significant not only because it reduces the sample requirements for RUS but also because it is the simplest method for simultaneous determination of a crystal's elastic constants and microscopic crystallographic orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144712
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  • 2
    Electronic Resource
    Electronic Resource
    Paced Electrogram Fractionation Analysis of Arrhythmogenic Tendency in ΔKPQ Scn5a Mice (2005)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 16 (2005), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Gain-of-function mutations within Scn5a, including the ΔKPQ 1505-1507 deletion in the inactivation domain compromising myocardial repolarization, are implicated in human long QT 3 syndrome (LQT3), associated with ventricular arrhythmogenesis and sudden death. Methods and Results: Patch clamp studies on isolated ventricular Scn5a+/Δ myocytes from ΔKPQ mice produced by homologous recombination in embryonic stem (ES) cells confirmed such altered electrophysiological properties of the mutant channel. Programmed electrical stimulation (PES) with decremental pacing from the basal right ventricular epicardial surface and paced electrogram fractionation analysis (PEFA) of electrograms recorded from the basal left ventricular epicardial surface of Langendorff-perfused whole heart preparations demonstrated ventricular tachycardia (VT) in 8 of 9 Scn5a+/Δ mutant (but no Scn5a+/+ (wild-type (WT)) controls; n = 17), with increased electrogram durations (EGD) and more dispersed conduction curves. Isoproterenol (100 nM) was without effect on tachycardic Scn5a+/Δ hearts (n = 9) yet propranolol (1 μM) prevented VT in all isoproterenol-infused WT control (n = 4) but no Scn5a+/Δ hearts (n = 4). Furthermore propranolol itself increased EGD and dispersion in Scn5a+/Δ hearts. In contrast, mexiletine (10 μM) suppressed VTs in 4 of 5 Scn5a+/Δ hearts without altering EGD or dispersion. Conclusion:β-adrenoreceptor blockade does not confer an antiarrhythmic effect and may even enhance arrhythmogenesis by increasing reentrant substrate in Scn5a+/Δ hearts while mexiletine protects against VT without modifying conduction characteristics. Together these findings permit a scheme where VT in LQT3 is initiated by triggered mechanisms but propagated by reentry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2005.00200.x
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  • 3
    Electronic Resource
    Electronic Resource
    Torsion modulus and internal friction of a fiber-reinforced composite (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3212-3213 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By a kilohertz-frequency resonance method, we determined the torsion modulus and internal friction of a uniaxially fiber-reinforced composite. The composite was composed of glass fibers in an epoxy-resin matrix. We studied three fiber contents: 0, 41, and 49 vol %. The internal friction failed to fit a classical free-damped-oscillator model where one assumes a linear rule-of-mixture for three quantities: oscillator mass, force constant, and mechanical-resistance constant. The torsion modulus approximately fits a plane-wave-scattering ensemble-average model. The microstructure showed strong fiber-distribution nonhomogeneity. Considering this nonhomogeneity yielded a better agreement between model and observation. Thus, torsion-modulus measurements provide a method to detect and quantify fiber-distribution nonhomogeneity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358455
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  • 4
    Electronic Resource
    Electronic Resource
    Elastic constants of a material with orthorhombic symmetry: An alternative measurement approach (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2738-2741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An alternative approach to measuring the complete anisotropic elastic constants cij(sij) of an orthorhombic-symmetry material is proposed. This approach requires measurements along only principal directions: 〈100〉. In this approach, a pulse-echo (megahertz-frequency) method was used to measure c11, c22, c33, c44, c55, and c66. A resonance (kilohertz-frequency) method was used to measure three elastic compliances: s11, s22, and s33. Combining the cii with the sii, the complete sets of cij and sij were obtained. This approach avoids the troublesome, error-prone determination of off-diagonal cij(sij) by the usual measurements along nonprincipal directions. The approach was applied to a boron-aluminum composite where the off-diagonal terms remain uncertain. In principle, the approach applies to any orthorhombic-symmetry material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357577
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetoresistance oscillation in window-coupled wire systems (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7036-7040 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a theoretical investigation of electron magnetotransport characteristics of a window-coupled quantum wire system which is treated as a four-terminal device. Different shapes and sizes of the coupling region are studied and various four-terminal Büttiker resistances are computed as a function of an external magnetic field. Our results are consistent with those of the experimental measurements of Hirayama, Tokura, Wieck, Koch, Haug, von Klitzing, and Ploog [Phys. Rev. B 48, 7991 (1993)] on similar device structures. In particular we have observed the fine interference pattern in the magnetoresistance and negative values of certain four-terminal resistance at low-magnetic-field strength. These features are found to be sensitive to the incoming electron energy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361470
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  • 6
    Electronic Resource
    Electronic Resource
    Young modulus and internal friction of a fiber-reinforced composite (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 1972-1976 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By a kilohertz-frequency resonance method we determined the Young modulus and internal friction of a uniaxially fiber-reinforced composite. The composite comprised glass fibers in an epoxy-resin matrix. We studied three fiber contents: 0, 41, and 49 vol %. The Young modulus fit a linear rule of mixture. The internal friction fit a classical free-damped-oscillator model where one assumes a linear rule of mixture for three quantities: mass, force constant, and mechanical-resistance constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336375
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  • 7
    Electronic Resource
    Electronic Resource
    THE VARIATION OF CRACK OPENING STRESS INTENSITY WITH TIME (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 8 (1985), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: It was found that crack opening stress intensities are not constant after holding for various times in the unloaded state for iron and a sequence of Fe-Si binary alloys. The crack opening level decreased with time first because of asperity creep and substructure relaxation, and then increased again with time due to reverse plastic zone relaxation allowing a new set of asperities to come into contact. It is demonstrated that the crack closure phenomenon is not only a result of residual plasticity, oxidation and asperities, but also is due to asperity creep and reverse plastic zone relaxation at the crack tip for low strength materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1985.tb00421.x
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  • 8
    Electronic Resource
    Electronic Resource
    The POT1–TPP1 telomere complex is a telomerase processivity factor (2007)
    [s.l.] : Nature Publishing Group
    Nature 445 (2007), S. 506-510 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Telomeres were originally defined as chromosome caps that prevent the natural ends of linear chromosomes from undergoing deleterious degradation and fusion events. POT1 (protection of telomeres) protein binds the single-stranded G-rich DNA overhangs at human chromosome ends and suppresses unwanted ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05454
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  • 9
    Electronic Resource
    Electronic Resource
    Intrinsic motions along an enzymatic reaction trajectory (2007)
    [s.l.] : Nature Publishing Group
    Nature 450 (2007), S. 838-844 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The mechanisms by which enzymes achieve extraordinary rate acceleration and specificity have long been of key interest in biochemistry. It is generally recognized that substrate binding coupled to conformational changes of the substrate–enzyme complex aligns the reactive groups in an optimal ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06410
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  • 10
    Electronic Resource
    Electronic Resource
    A hierarchy of timescales in protein dynamics is linked to enzyme catalysis (2007)
    [s.l.] : Nature Publishing Group
    Nature 450 (2007), S. 913-916 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The synergy between structure and dynamics is essential to the function of biological macromolecules. Thermally driven dynamics on different timescales have been experimentally observed or simulated, and a direct link between micro- to milli-second domain motions and enzymatic function has ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06407
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