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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 276 (1998), S. 388-394 
    ISSN: 1435-1536
    Keywords: Key words Hyaluronic acid ; degradation ; molecular weight ; metal surface ; hydroxyl radical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  When the viscosity of hyaluronic acid (HA) solution was measured with a rotational visco-meter, depolymerization occurred only by leaving the sample in the cup of the viscometer, while the solution in a glass test tube at the same temperature, 37 °C, was practically stable during the entire period of investigation. As the parts where the sample solution had contact with the viscometer are stainless steel, the participation of metal ions in the depolymerization was suspected. Therefore, experiments were carried out with stainless-steel beads in the HA solution. The results show that the molecular weight of HA decreased on exposure to the beads under aerobic conditions. The addition of 10 beads to 2 ml of a 0.1% HA solution prepared with 0.2 M NaCl reduced the molecular weight to about 75% of the initial value after 4 h. The degradation rate was proportional to the surface area of the beads. However, no dissolution of metal ion was detected, and therefore, this reaction was thought to proceed at the surface of the metal.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Gm immunoglobulin allotypes have been studied in 1157 individuals of seven Northern Selkup populations, which account for 80% of the entire population of this west Siberian tribe. This study confirms that the northern Selkup populations are a Caucasoid-Mongoloid hybrid. Restriction fragment length polymorphism (RFLP) analysis of the IGHG genes using double BamHI-SacI digests, performed on 475 DNA samples, allowed us to describe nine new BamHI-SacI haplotypes (BS47 to BS55), eight of them being characterized by IGHG gene deletion or duplication: G1 (BS49) or G4 (BS55) deletion, G4 duplication (BS51), GP-G2-G4 multigene deletion (BS50), duplication (BS48, BS53 and BS54) or triplication (BS52). A new rare Gm haplotype 15,16*;1,17;23 has been found associated with BS52. The BS51 haplotype characterized by a duplicated G4 gene (additional 7.85 kb G4 band identifying a new G4*C5 allele) was always found associated with the Gm 5*;3;23 haplotype. A high RFLP diversity has been observed for the Northern-Mongoloid haplotype Gm 15,16*;1,17;.. which was found (1) with the BS27 haplotype characterized by a 3-exon hinge G3 gene, (2) with two different GP-G2-G4 multigene duplications, BS53 and BS54 haplotypes, which differ by the size of the duplicated G4 genes, and (3) with the BS55 haplotype characterized by a G4 deletion. In the Northern Selkups, haplotypes with duplicated genes were observed at a higher frequency (24%) than haplotypes with deleted genes (6%).
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 97 (1995), S. 439-452 
    ISSN: 1434-6036
    Keywords: 61.44.+p ; 71.20.Cf ; 72.15.-v ; 79.60.-i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements with photoemission spectroscopy in the photon-energy range 35–130 eV have been used to determine the valence band of the stable icosahedral Al65Cu20Os15. Resonant photoemission near the Os 5p → 5d and 4f → 5d transitions has been employed to show that the feature in the valence band with the maximum intensity at 1.5 (1) eV below the Fermi level is predominantly of the Os 5d character. This has been additionally verified by conducting the photoemission measurements in the constant-initial-state mode and by using the effect of the Cooper minimum in the photoionization cross section of the Os 5d orbitals. The valence band feature with the maximum intensity at 3.7 (1) eV below the Fermi level has been shown as being due mainly to the states of the Cu 3d character. The Os 5d and Cu 3d empirical partial density of states have been determined from the photoemission spectra. The decrease of intensity towards the Fermi level has been interpreted as being indicative of the presence of a theoretically predicted pseudogap around the Fermi level. It has been indicated, however, that the Fermi cut-off also contributes to the observed intensity decrease. It has been demonstrated that the energy resolution of the spectroscopic measurements performed so far on quasicrystals was not high enough to unambiguously determine the presence of such a pseudogap. No unusual features in the valence band of icosahedral Al65Cu20Os15, which could be ascribed to its quasiperiodic nature, have been observed within the resolution of the experiment. High energy-resolution spectroscopic measurements were also shown to be essential to observe the theoretically predicted spikiness of the density of states in quasicrystals. A critical review of published spectroscopic data on the electronic structure of quasicrystals has also been presented.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 111 (1998), S. 453-461 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper contains three results. First, the rate constants for the tunneling reaction HD + D → H + D 2 in solid HD increase steeply with increasing temperature above 5 K, while they are almost independent of temperature below 5 K. A mechanism of a vacancy–assisted tunneling reaction is proposed to account for this temperature dependence. Second, a hydrogen atom and a hydrogen molecule form a van der Waals complex in the Ar matrix at 20 K, where the tunneling reaction HD + D →H + D 2 takes place in this complex. The analysis of well–resolved ESR spectra of the complex determined the distance between a hydrogen atom and a hydrogen molecule as 2.3 – 2.5 Å. Third, the decay rate constants of $${\text{H}}_{\text{2}}^ - $$ anions in solid parahydrogen decrease with decreasing temperature below 6.6 K, attain the minimum value at 5 K, and then increase with decreasing temperature in the range of 5 → 2.7 K. The abnormal temperature dependence of the decay rate constants below 5 K is ascribed to a phonon–scattering process of quantum diffusion.
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  • 5
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present experimental observations and study of $${\text{H}}_{\text{2}}^ - $$ in solid parahydrogen. Since the parahydrogen molecule does not produce local magnetic fields, high–resolution ESR spectra of trapped radicals can be observed in the solid parahydrogen matrices. Using this high–resolution ESR spectroscopy, new quartet ESR signals were observed in γ–rays irradiated solid parahydrogen and assigned as $${\text{H}}_{\text{2}}^ - $$ In addition, para– $${\text{H}}_{\text{2}}^ - $$ was observed to convert into ortho– $${\text{H}}_{\text{2}}^ - $$ on the storage at 4.2 K. On the other hand, ortho–H 2 molecule converts into para– $${\text{H}}_{\text{2}}^ - $$ at cryogenic temperatures. The difference in the conversion between the H 2 molecule and the $${\text{H}}_{\text{2}}^ - $$ anion is explained by the parity conservation law of wavefunctions on exchanging the protons in homonuclear diatomic molecules such as the $${\text{H}}_{\text{2}}^ - $$ anion and H 2 molecule.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 114 (1999), S. 413-429 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Decay mechanism of H 2 - anions in X(γ)-irradiated solid para-H2 (p-H 2 ) has been studied using high-resolution ESR spectroscopy in the temperature range between 1.3–6.6 K. The results are summarized as follows. First,the decay rate constant of the 2 - anions is not proportional to initial yields of reactive species such as cations and H atoms but proportional to the concentration of less-reactive species of HD molecules in p-H2 . This result shows that the decay of the 2 - anion is due to the reaction neither with cations nor H atoms but with HD molecules originally contained in the p-H2 sample at natural abundance. Second,the decay rate constant of the 2 - anions increases proportionally with the increase in temperature below 3 K and decreases with the increase in temperature between 3–5 K,although it increases exponentially with the increase in temperature above 5 K. This result indicates that the decay rate constant of the 2 - anions is controlled by the rate constant for the diffusion of the 2 - anions via one-phonon assisted quantum tunneling below 3 K,two-phonon scattered or assisted quantum tunneling between 3–5 K,and thermally-activated process above 5 K.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 5797-5804 
    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 computer simulation, based on the Khachaturyan diffusion equation, is presented to develop the kinetics of the morphological evolution of the A2/B2 second-order phase transition in a binary solid solution. The evolution of the occupation probability, as a function of composition, shows a good similarity to the actual micrographs experimentally obtained based on the macroscopic composition gradient method. These results are used in parallel with the results of the evolution of the long-range order parameter as a function of the ageing time, to verify a new concept of the ordering behaviour inside the ordered phase.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 30 (1995), S. 5056-5064 
    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 phase separation in iron-rich Fe-Si-Ge ternary alloys was investigated by means of transmission electron microscopy. The phase separations into A2 and D03 were recognized in several alloys in addition to the phase separation into B2 and D03 which has already been found in Fe-Si and Fe-Ge binary systems. On the basis of TEM observations, isothermal section diagrams are proposed for the iron-rich corner at 823, 873, 923 and 973 K. The A2 + D03 two-phase field exists in a band-shaped region at 823 K. With increase in temperature,the A2 + D03 field gradually shrinks and is eventually replaced at 973 Kwith the B2 + D03 field, which extends from both the Fe-Si and Fe-Ge binary sides. The phase diagrams were well reproduced by the calculations based on the so-called Bragg-Williams-Gorsky approximation, taking account of the chemical and magnetic pair interactions up to the second nearest neighbour. The effects of the magnetism on the equilibria are discussed.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 34 (1999), S. 3901-3908 
    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 effect of retained austenite (γ) on the microstructure and mechanical properties of a martensitic precipitation hardening stainless steel was experimentally investigated, whose chemical composition was Fe-1.8Cu-15.9Cr-7.3Ni-1.2Mo-0.08Nb-low C, N (mass %). The microstructures of all specimens consist of a typical lath martensite with interlath films of the retained γ, which is not reverted with aging. Cu-rich precipitates which may contribute to precipitation hardening can not clearly be observed. The tensile properties and Charpy absorbed energy are linearly approximated to the amount of retained γ as follows: 0.2% Y.S. (MPa) = 1192.3 − 13.6 × γ%, T.S. (MPa) = 1250.1 − 9.3 × γ%, El. (%) = 12.16 + 0.43 × γ%, R.A. (%) = 64.25 + 0.14 × γ%, and A.E. (J) = 72.5 + 0.8 × γ%. The introduction of retained γ is not beneficial to the fatigue limit. An excellent combinations of strength, ductility and toughness obtained in the present work is attributed to the introduction of retained γ and also to the chemical composition of the specimen used.
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  • 10
    Publication Date: 1995-10-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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