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  • 1
    Electronic Resource
    Electronic Resource
    X-ray Tomography Study on Green State Joining of Silicon Carbide Using Polymer Precursors (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: X-ray tomography has been used to investigate the density variations in SiC joints formed using polymer pastes. It has been demonstrated that X-ray tomography provides accurate bulk density measurements and volumetric density gradients. The results suggest that the magnitude of the applied pressure after green state joining and the amount of polymer (polycarbosilane, PCS) in the joining pastes influence the green density of the joints. All joints are prepared and applied in air atmosphere and at room temperature. The green densities of the joints increase from 54% to 66% of theoretical with the increase of the applied pressure from ambient to 138 MPa. Highest joint density without applied pressure is achieved using paste containing 50 vol% PCS. Furthermore, allylhydridopopolycarbosilane- (AHPCS-) containing pastes resulted in higher densities at the joint–matrix interface, indicating infiltration of polymer into the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00943.x
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  • 2
    Electronic Resource
    Electronic Resource
    Green State Joining of Silicon Carbide Using Polycarbosilane (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Green state joining of SiC was investigated using a paste consisting of polycarbosilane polymer and SiC powder. The joining process and densification were described. Initial experiments resulted in the formation of symmetrical black bands and cracks on both sides of the joint. However, with modifications in processing conditions, the cracks were eliminated and the resulting joints were indistinguishable from the matrix. The flexural strength of joined samples was measured to be 234 MPa, which was comparable to that of the control sample with similar density. As the applied pressure during joining was increased from 34 to 138 MPa, the strength of the joined samples increased from 180 to 250 MPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01450.x
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  • 3
    Electronic Resource
    Electronic Resource
    A new cylindrical photoacoustic cell with improved performance (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 404-410 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report a new design for an acoustically resonant photoacoustic cell with high performance. A cylindrical cell with suitable size was selected so that the resonant frequency of the first radial mode was equal to that of a longitudinal higher mode. The ends of the cell have a pair of thin coaxial tubes which lengths are 1/2 and 1/4 of acoustic wavelength λ, respectively. The λ/4 acoustic resonance makes a coupling between the first radial resonance and the higher longitudinal resonance, then leads to an acoustic energy concentrating in the middle of the cell. Thus, the surface loss was decreased, the acoustic quality factor and pressure amplitude increased obviously as compared with conventional radial resonant cylindrical cell. The ability to measure absorption coefficients as low as 2.43×10−9 cm−1 (1:1 signal to noise level) has been achieved. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427306
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  • 4
    Electronic Resource
    Electronic Resource
    The stretching vibrational overtone spectra of PH3: Local mode vibrational analysis, dipole moment surfaces from density functional theory and band intensities (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 7018-7026 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The infrared spectra of PH3 molecule were recorded on a Bruker IFS 120HR Fourier transform spectrometer from 4000 to 9500 cm−1. The P–H stretching vibrational frequencies and intensities were derived from the experimental data. The Morse oscillator parameters De and α in the anharmonically coupled anharmonic oscillator local mode model were determined by the least-squares fitting with the observed vibrational band centers. The ab initio three-dimensional P–H stretching dipole moment surfaces were calculated by the density functional theory method. The dipole moment vectors were projected to three kinds of molecule-fixed reference systems. The corresponding dipole moment components were fitted to polynomial functions in terms of the P–H bond length displacements with the molecular symmetry taken into account. The absolute band intensities were obtained and then compared with the experimental data. The results showed that a proposed improved bond dipole model can predict the absolute band intensities within a factor of 2 for most of the observed transitions, indicating a reasonably good agreement. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352038
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  • 5
    Electronic Resource
    Electronic Resource
    Extracellular ATP-Induced Ca2+ Transients in Cardiac Myocytes Are Potentiated by an Increase in Cellular cAMP (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 603 (1990), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1990.tb37701.x
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  • 6
    Electronic Resource
    Electronic Resource
    The Growth-Hormone-Releasing Hormone Receptor: Signal Transduction, Gene Expression, and Physiological Function in Growth Regulation (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 805 (1996), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1996.tb17483.x
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  • 7
    Electronic Resource
    Electronic Resource
    In situ Growth of SiC Whisker in Pyrolyzed Monolithic Mixture of AHPCS and SiC (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In situ whisker growth was observed during heat treatment of allylhydridopolycarbosilane (AHPCS) and SiC powder in the temperature range of 1250°–1350°C. TEM equipped with an electron energy loss spectrometer (EELS) verified that the banded whiskers are twinned single-grained β-SiC. Convergent beam electron diffraction patterns (CBED) of the whisker tips were consistent with formation by a vapor–solid (VS) mechanism. The effects of process variables on whisker growth were addressed. The mechanism of whisker growth was discussed and attributed to the reaction between the gaseous products of the polymers AHPCS and polycarbosilane (PCS). Thermal decomposition behavior of the polymers was followed to relate gas evolution to whisker formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01667.x
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  • 8
    Electronic Resource
    Electronic Resource
    Green State Joining of SiC without Applied Pressure (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: External pressure (uniaxial or isostatic) is usually necessary to form a thin and defect-free joint in green state joining of SiC ceramics. A successful method of joining SiC in the green state using a liquid polymer precursor, allylhydridopolycarbosilane (AHPCS), without applied pressure, is described. The thermal decomposition behavior of the polymer was examined, and defect formation during joint evolution was investigated by interrupting the heat treatment at various stages. Cracks and pores were observed in the joints formed by pure AHPCS during the pyrolysis of the polymer precursor. Adding SiC powder to the joining paste eliminated defect formation. Optimum SiC loading in the paste was determined to be in the range of 25–35 vol%. Joints formed by AHPCS + (SiC + 5 wt% B) paste were essentially indistinguishable from the matrix and had an average strength of 323 MPa, comparable to that of the control sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01039.x
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  • 9
    Electronic Resource
    Electronic Resource
    Prestin is the motor protein of cochlear outer hair cells (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 405 (2000), S. 149-155 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The outer and inner hair cells of the mammalian cochlea perform different functions. In response to changes in membrane potential, the cylindrical outer hair cell rapidly alters its length and stiffness. These mechanical changes, driven by putative molecular motors, are assumed to produce ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35012009
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  • 10
    Electronic Resource
    Electronic Resource
    Phase separated domain structure of poly(vinyl butyral) (1988)
    Springer
    Polymer bulletin 20 (1988), S. 487-491 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A morphological study of poly(vinyl butyral) is performed on the thin films prepared by evaporation of polymer solutions. It is shown by transmission electron microscopy that there are many domains of dimensions 0.02 to 1 μm in this amorphous random copolymer. The image contrast of the electron micrographs is improved significantly by RuO4 staining technique. It is suggested that the domain structure can be mainly attributed to the hetrogeniety of the polymer as a result of microphase separation in the polymer solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01153442
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