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  • 1
    Electronic Resource
    Electronic Resource
    Ultraviolet photoemission study of oligothiophenes: π-band evolution and geometries (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4077-4092 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ultraviolet photoelectron spectroscopy (UPS) has been applied to the investigation of the electronic structure of oligothiophenes with 4–8 thiophene rings. In a series of α-linked oligomers (αn with n being the number of rings), a systematic evolution of the π band is observed. Several peaks which correspond to the π band are observed in the region of 0.7–3 eV below the Fermi level (EF), and the bandwidth becomes broader with increasing n. The nonbonding π band is observed at 3.5 eV below EF and its energy is almost independent of the number of thiophene units. UPS spectra of α7 and α8 are fairly similar to the spectra of polythiophene, showing that these oligomers are good model compounds of the polymer. The ionization threshold energy of α7 and polythiophene was observed to be 5.3 eV. The effect of irregularity on the π-electron system was also studied by using oligomers which contain a β linkage or a vinylene group at the middle of the molecule. The UPS spectra showed that the β linkages significantly affect the electronic structure of polythiophene, while the vinylene group does not. In order to analyze the UPS spectra and to investigate the electronic structures of oligomers, the orbital energies and the geometries of these oligomers are calculated by the semiempirical MNDO-SCF-MO (modified neglect of diatomic overlap self-consistent-field molecular orbital) method. Theoretically simulated spectra of these oligothiophenes derived from the obtained orbital energies by Gaussian broadening are compared with the observed ones. The agreement between the observed and calculated spectra is very good, particularly in the π region. It is shown from the optimized geometry that (1) αn 's have planar structure and π electrons are delocalized, (2) the oligomer with β linkages has nonplanar structure leading to limited delocalization of π electrons, and (3) the oligomers with a vinylene group are almost planar and the disturbance by the vinylene group on the delocalization is small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458561
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  • 2
    Electronic Resource
    Electronic Resource
    Absolute Configuration of (+)-1-Phenyl-1,2,3,4-tetrahydroisoquinoline Hydrochloride (1998)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 651-653 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270197018581
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on strongly damped components in relatively light heavy ion reaction systems (1984)
    Springer
    The European physical journal 317 (1984), S. 31-44 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Strongly damped components have been studied in relatively light heavy ion reaction systems;20Ne(E lab=93, 120 and 146MeV)+50Cr,20Ne(E lab=146MeV)+54Cr and20Ne(E lab=146MeV)+92Mo,100Mo. The kinetic energy, angular and charge distributions have been observed for those products. The yields of symmetric-mass-splitting products for20Ne+50Cr were found about three times larger than those for20Ne+54Cr. There was also observed a similar difference in the cross sections of the symmetric-mass-splitting products between20Ne+92Mo and20Ne+100Mo reactions. In order to explain the bombarding energy dependence of the cross sections of symmetric-mass-splitting products by the transport theory, it was found necessary to assume that the mean life of the composite nucleus was dependent on the bombarding energy. However, the target isotope dependence of the cross sections could not be explained by such an assumption. They could be partly explained by fission calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01420446
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  • 4
    Electronic Resource
    Electronic Resource
    Fragment mass dependence of angular anisotropy in 15 MeV proton-induced fission of 244Pu (1998)
    Springer
    The European physical journal 2 (1998), S. 153-155 
    Details
    ISSN: 1434-601X
    Keywords: PACS:25.85.-w Fission reactions – 25.85.Ge Charged-particle-induced fission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Angular distributions of fission fragments with mass number A=97-159 have been measured by the radiochemical recoil-catcher method in the proton-induced fission of 244Pu with the incident energy of 15 MeV. Angular anisotropies of extreme asymmetric mass division products even up to the fragment mass ratio of A H /A L ∼ 1.85 are found not any different from those of the typical asymmetric mass division products with A∼ 138, which indicates that no clear evidence is observed for the existence of an additional saddle point configuration in the extreme asymmetric mass division. The correlation between the saddle point state evaluated from the angular anisotropy and the mass division mode is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100500050104
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  • 5
    Electronic Resource
    Electronic Resource
    Seasonality of Great Earthquake Occurrence at the Northwestern Margin of the Philippine Sea Plate (1999)
    Springer
    Pure and applied geophysics 155 (1999), S. 689-700 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Seasonality, great earthquakes, Philippine Sea plate, atmospheric pressure, earthquake triggering.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —A significant seasonality is found in the occurrence time of past great earthquakes (M≥ 7.9) in the northwestern margin of the Philippine Sea plate. Among the thirteen earthquakes cataloged, five took place in December, and all the earthquakes are included in the seven months from August to February. The probability that such a skewed distribution occurs by chance is as small as 2.0%. This seasonal concentration of earthquakes suggests that a small stress increase may trigger an earthquake when the future focal zone is at a critical condition to release a large rupture. As a candidate factor of the earthquake triggering, we tested a possibility of stress change caused by annual variation of the atmospheric pressure. However, the incremental stress is no larger than 30 Pa, and it hardly accounts for the seasonality of the great earthquakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050283
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  • 6
    Electronic Resource
    Electronic Resource
    Prognostic significance of posterior subtalar joint arthrography following fractures of the calcaneus (1995)
    Springer
    Archives of orthopaedic and trauma surgery 114 (1995), S. 257-259 
    Details
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Nineteen patients with 22 intra-articular fractures of the calcaneus were investigated by posterior subtalar joint arthrography after 6 (2–15) months following injury, and their clinical symptoms were compared with the arthrography findings. The arthrograms were classified into four types based on the findings of the joint space of the posterior subtalar joint in Anthonsen's view. The classification correlated significantly (P = 0.03) with the clinical results which were assessed after 23 (9–41) months following injury. We conclude that posterior subtalar joint arthrography has prognostic value in assessing patients with fractures of the calcaneus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00452082
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  • 7
    Electronic Resource
    Electronic Resource
    Uniform oligomers as reference materials for molecular weight determination of polymers (1997)
    Springer
    Accreditation and quality assurance 2 (1997), S. 137-139 
    Details
    ISSN: 1432-0517
    Keywords: Key words Uniform oligomer ; Reference materials ; Supercritical fluid chromatography ; Size exclusion chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Uniform oligomers are special oligomers having no molecular weight distribution. They have been used as reference materials for polymer characterization, especially for accurate molecular weight determination in lower molecular weight ranges. These oligomers are used for different purposes. First, they are used in the calibration for chromatographic or spectroscopic data. Second, they are applied to identifying peaks appearing in chromatographies such as supercritical fluid chromatography (SFC) of oligomeric mixtures. Finally, they could give accurate instrumental or physicochemical constants used in polymer characterizations. The uniform oligomers have been prepared by using preparative chromatographies as separation methods. In some cases, step-wise syntheses have been applied together with the chromatographic methods. Recently, we prepared uniform oligostyrenes and oligo(oxyethylene)s whose molecular weights are greater than 1000 by using preparative size exclusion chromatography. More recently, using preparative SFC, some Japanese researchers have prepared high molecular weight and uniform oligomers such as oligo(methylmethacrylate)s. In this article, we briefly review recent progress mainly made by Japanese researchers in the field of preparation, analysis and applications of these pure oligomers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007690050118
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of the change of nuclear charge radius of the119Sn Mössbauer transition by internal conversion (1984)
    Springer
    Hyperfine interactions 20 (1984), S. 305-325 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Radioactive119Sb was implanted into six host matrices (CaSnO3, Pt, Y, Au,Β-Sn, Pb) and internal conversion electrons of the 23.87 keV transition in119Sn were measured with an iron-free magnetic spectrometer as well as Mössbauer spectra. In the analysis of the conversion spectra of outermost electrons, the overlapping K-LM Auger lines were subtracted using the Auger spectrum of tin measured with another source of117mSn, and the shake-off effect accompanying the conversion process was considered. From the correlation between the Mössbauer isomer shifts and the intensity ratios of O-shell to N1-shell conversion electrons, the change of the nuclear charge radius of the 23.87 keV transition of119Sn was deduced to be δR/R=(0.87 ± 0.25) × 10−4 for a uniform charge distribution ofR= 1.2 ×A 1/3 fm or, equivalently, δ 〈r2〉—=(3.6 ± 1.0) ×10−3 fm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02069379
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  • 9
    Electronic Resource
    Electronic Resource
    Development of Si-B-O-N fibres from polyborosilazane (1994)
    Springer
    Journal of materials science 29 (1994), S. 2238-2244 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A polyborosilazane, which is a precursor of ceramic fibre, was synthesized from perhydropolysilazane and trimethyl borate. The polyborosilazane was dry-spun and then pyrolysed to produce amorphous Si-B-O-N fibre. The Si-B-O-N fibre retained its high tensile strength to higher temperatures (about 1600 °C). The fibre has a density of 2.4 g cm−3, tensile strength of 2.5 GPa and an elastic modulus of 180 GPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01154704
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  • 10
    Electronic Resource
    Electronic Resource
    Conversion mechanism of polyborosilazane into silicon nitride-based ceramics (1995)
    Springer
    Journal of materials science 30 (1995), S. 410-416 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The pyrolysis of polyborosilazane in anhydrous ammonia has been studied up to 1200 °C through the analysis of the gas phase and the characterization of the solid residue by elemental analyses, thermogravimetric analysis, Fourier transform-infrared analysis, X-ray photoelectron spectroscopy, X-ray diffraction and 29Si cross-polarization/magic angle spinning-nuclear magnetic resonance. The pyrolysis mechanism involves four main steps: (1) below 400 °C, an evaporation of residual solvent and reaction with ammonia leading to an increase of nitrogen content; (2) from 400–600 °C, reaction with ammonia leading to an increase of nitrogen content and formation of preceramic polymer-ceramics intermediate solid with a three-dimensional network along with evolution of gaseous species; (3) from 600–800 °C, completion of loss of C-H functionalities and progress of formation of an amorphous ceramic, accompanied by evolution of CH4 and H2; (4) from 800–1200 °C, completion of formation of an amorphous hydrogenated Si-B-O-N solid composed of SiN4−x Ox(x=0,1,2,3) and BN3−y O y (y=0, 1), along with evolution of H2
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00354405
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