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  • 1990-1994  (31)
  • 1965-1969  (5)
  • 1940-1944  (2)
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we discuss photoluminescence (PL) and Raman excitations in the diluted magnetic semiconductors Zn1−xCoxSe and Zn1−xFexSe. The PL spectra associated with isolated crystal field d levels are found to rapidly weaken and/or broaden as the transition metal ion concentration approaches and increases beyond a critical value. In addition a Raman continuum, that overlaps with the optical phonon, is observed to develop when the PL features are modified. In the corresponding Zn1−xCoxSe samples the optical phonons acquire a characteristic Fano line shape suggestive of its coupling to the Raman continuum. It is proposed that these changes to the optical transitions arise from the enhancement of an effective p–d hybridization between low-lying d levels and band electrons with increasing x—an effect largely due to the proximity of the Co2+ and Fe2+ crystal field ground levels to the valence band maximum.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5433-5435 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the magnetic structure of the nuclear spin system in Cu below 60 nK by means of neutron scattering. The observation of the nuclear (100) superlattice reflection proves the theoretically predicted antiferromagnetic arrangement of the nuclear spins. The critical field at the lowest temperatures was 0.24 mT. Around 0.1 mT the (100) reflection could not be observed. This is taken as an indication for, possibly, a reorientation phase transitition at this field. Therefore, the phase diagram contains at least two phases. For 0.1 mT〈B〈0.24 mT strong time dependencies of the ordering were observed. At low fields (B〈0.1 mT) nucleation times of the order of 10 s have been observed. These results are discussed with respect to the cooling technique: Adiabatic demagnetization requires constant entropy, a rather unusual way to bring a system from the paramagnetic to the ordered phase.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5466-5467 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: With a newly built superconducting quantum interference device magnetometer, the time range of measurements of the thermoremanent magnetization (TRM) was extended to less than 10 ms. This new method allows a direct investigation of aging and relaxation in the spin glass region for short times. As a first example for fast TRM, the magnetization in a single crystal of the insulating spin glass CsNiFeF6 was measured in the time range −2〈log(t/s)〈3 at magnetic fields between 2 and 20 G at temperatures between 4.7 and 1.7 K. Additionally, the zero field and field cooled magnetization of this sample to temperatures up to 9 K was studied.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5593-5598 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In 1D magnets contributions to the spin dynamics which are outside the scope of spin-wave theory can be studied theoretically as well as experimentally. Two prominent examples of such effects are discussed here: solitons and the Haldane gap. We discuss inelastic polarized neutron scattering results on the stability of solitons in CsNiF3 and on the existence of the Haldane gap in CsNiCl3. In both cases, the separate determination of the different correlation functions 〈SαSα〉 with α=x,y,z is essential for definite conclusions: Solitons in CsNiF3 appear to be much more stable than expected from classical theories, and the Haldane gap is the only explanation for the observed gaps in CsNiCl3.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5266-5268 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectral quantum efficiency in ReS2 heterodiodes was measured in the wavelength region between 600 and 850 nm. Anisotropy effects in the van der Waals plane were observed by means of linearly polarized light at normal incidence to the (001) plane of ReS2 single crystals. The anisotropy in quantum efficiency reaches its maximum at λ=627 nm and therefore, ReS2 devices are well suited for detecting the angle of polarization in experiments using a HeNe laser. At wavelengths above 750 nm the sign in polarization quantum efficiency changes due to various optical transitions.
    Type of Medium: Electronic Resource
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  • 6
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    Unknown
    Provincetown, Mass., etc. : Periodicals Archive Online (PAO)
    The Journal of Genetic Psychology. 62 (1943) 119 
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Planta 79 (1968), S. 113-121 
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1. 28 marine Algen aus den Klassen der Chlorophyceen (5 Arten), Phaeophyceen (11) und Rhodophyceen (12) wurden auf das Vorkommen flüchtiger Amine untersucht. 2. Mit Hilfe papierchromatographischer und mikrokristallographischer Methoden konnten insgesamt 9 flüchtige Amine in Algen nachgewiesen werden: Methylamin (MA), Dimethylamin (DMA), Trimethylamin (TMA), Äthylamin (ÄA), Propylamin (PA), Isobutylamin (iBA), Isoamylamin (iAA), 2-Phenyläthylamin (PÄA) und das bisher aus der Natur nicht bekannte 2-Methylmercaptopropylamin (MMPA). 3. Weitverbreitet findet sich bei Algen Trimethylamin (in 23 von 28 untersuchten Arten), während Dimethylamin nur in 2 Arten sicher nachgewiesen werden konnte. Das natürliche Vorkommen von Methylamin ist nicht gesichert, da dieses Amin möglicherweise erst bei der Aufarbeitung aus instabilen Methylaminoverbindungen entsteht. 4. Primäre Amine kommen in Vertretern aller 3 Algenklassen vor, besonders verbreitet jedoch bei Rhodophyceen (7 von 12 Arten). Biogenetisch werden zumindest die primären Amine der Rhodophyceen, mit Ausnahme von Methylamin, durch enzymatische Decarboxylierung aus entsprechenden Aminosäuren gebildet.
    Notes: Summary Twenty-eight species of marine Chlorophyceae (5), Phaeophyceae (11), and Rhodophyceae (12) were examined for the occurence of simple volatile amines. The volatile alkaline constituents of the algal samples were extrated by alkaline steam destillation and separated and identified by paper chromatography and microcristallography. A total of 9 volatile amines were found to occur in the species so far examined: methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (ÄA), propylamine (PA), isobutylamine (iBA), isoamylamine (iAA), 2-phenylethylamine (PÄA), and 2-methylmercaptopropylamine (MMPA). MMPA has not previously been reported to occur in any other plant. The occurence of TMA is widespread in marine algae (23 of 28 sp.) whereas an occurrence of DMA could be demonstrated only in two species. MA, which was found in all algal samples, might be formed from labile methylamino-compounds in the course of preparation. Its coccurrence as a natural constituent of algae remains doubtful. Primary amines could be identified in species of each of the three classes of algae, but an especially widespread occurrence was found in Rhodophyceae. With the exception of MA the primary volatile amines, at least those of Rhodophyceae, arise biosynthetically from the corresponding amino acids by enzymatic decarboxylation.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 54 (1967), S. 370-371 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 55 (1968), S. 346-347 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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