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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4857-4859 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Twin screw extruder is employed as a mechanical dispersion tool in the processing of particulate media incorporating high specific surface area (SSA) pigments. In this study, the effectiveness of a typical screw configuration used in the processing of formulations containing acicular iron particles of SSA=50 m2/g was experimentally investigated. During a steady state mixing operation, the extruder was brought to a dead stop, the screws were pulled out and material samples were collected from nine different screw sections. These samples were analyzed to determine the progress of the mixing process as the dispersion flows from section to section. Using SEM micrographs of the material samples, magnetic particle distributions corresponding to different screw sections were identified. The microstructure was observed to change from a granular appearance of aggregates and voids to a coagulated but relatively more uniform distribution of magnetic particles. The state of the dispersion was also magnetically evaluated by probing the magnetostatic interaction in the dispersion samples. Both hysteresis curves and remanence curves of the samples were utilized for this purpose. Interaction parameters associated with the hysteresis curves, such as coercivity, did not exhibit clear trends from section to section. The remanence curves were found to be more appropriate to analyze the state of the dispersion.Peak ΔM values calculated from the remanence curves followed the changes that were observed in the microstructure. It was concluded from the overall results that the extrusion process could be further improved by changes in the screw configuration. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6269-6271 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetic properties of Sm1−xPrxCo4−yFeyB with various values of x and y have been observed mainly from the viewpoint of permanent magnet material. Pr substitution for SmCo4B results in an increase of the saturation moment; however, it leads to a decrease of the anisotropy field. The Curie temperature remains constant. On the other hand, the Fe substitution increases both the Curie temperature and the saturation moment significantly, and does not give vital damage to the original huge anisotropy field of SmCo4B. A possibility of the above system for a candidate of permanent magnet material is discussed in addition to discussion of the fundamental magnetic properties.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6128-6130 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetization curves and hysteresis loops for field-oriented powders of Smn+1Co3n+5B2n (n=0, 1, and 3) and PrCo5 were measured at T=4.2 K and partly at 77 K, under a strong pulsed field up to 36 T. Magnetic measurements for Smn+1Co3n+1B2n (n=1, 2, and 3) compounds were also performed. Huge anisotropy fields of 120 T for SmCo4B and of 130 T for Sm2Co7B3 were obtained. The Sm sublattice anisotropy of SmCo4B was found to be larger than that of SmCo5. To explain this, the Sm f-electron state for n≥ (R18)2 of Smn+1Co3n+5B2n has been expected to change from that for n≤1. Huge coercivities of 8 T and 27.5 T were observed at T=4.2 K for SmCo4B and for Sm2Co7B3 respectively. Magnetization processes for field-oriented PrCo5 at T=4.2 K were found to be similar to those of Nd2Fe14B at T=4.2 K.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 16 (2002), S. 0 
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Long-term potentiation (LTP), a form of synaptic plasticity in the hippocampus, is a cellular model for the neural basis of learning and memory, but few studies have investigated the contribution of long-term depression (LTD), a counterpart of LTP. To address the possible relationship between hippocampal LTD and spatial performance, the spatial cognitive ability of a rat was assessed in a spontaneous alternation test and, thereafter, LTD in response to low-frequency burst stimulation (LFBS) was monitored in the dentate gyrus of the same rat under anaesthesia. To enhance a divergence in the ability for spatial performance, some of the animals received fimbria–fornix (FF) transection 14 days before the experiments. LTD was reliably induced by application of LFBS to the medial perforant path of intact rats, while no apparent LTD was elicited in rats with FF lesions. The behavioural parameters of spatial memory showed a significant correlation with the magnitude of LTD. We found no evidence that the cognitive ability correlated with other electrophysiological parameters, e.g. basal synaptic responses, stimulus intensity to produce half-maximal responses, paired-pulse facilitation or paired-pulse depression. These results suggest that the magnitude of LTD in the dentate gyrus serves as a reliable index of spatial cognitive ability, providing insights into the functional significance of hippocampal LTD.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 15 (2002), S. 0 
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Early in postnatal development, glutamatergic synapses contain primarily NMDA receptors and progressively acquire AMPA receptor function. To determine whether this transformation occurs in a process of regenerative synaptogenesis following axotomy, we investigated the recovery of AMPA and NMDA receptor-mediated neurotransmission after the transection of mossy fibres (MF) in organotypic hippocampal cultures. An NMDA component could already be elicited 1 day after the lesion and reached a saturated level after 3 days. Thereafter, an AMPA component appeared and slowly matured after 10 days. The preceding establishment of NMDA receptor function implies that immature MF synapses are functionally silent at least for the first several days of recovery. The appearance of AMPA receptor-mediated neurotransmission was unchanged in the presence of an NMDA-receptor antagonist or tetrodotoxin, which suggests that the AMPA receptor maturation is virtually independent of neuronal activity. Thus, the conversion of silent to functional synapses is not unique to synaptic plasticity or developmental processes but also occurs in recovery after brain damage, but its mechanism is likely to differ from NMDA receptor-dependent recruitment of AMPA receptors in synaptic plasticity.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Crystal Growth 65 (1983), S. 77-83 
    ISSN: 0022-0248
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Crystal Growth 79 (1986), S. 144-148 
    ISSN: 0022-0248
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 104-107 (1992), S. 1369-1370 
    ISSN: 0304-8853
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 35 (1983), S. 223-225 
    ISSN: 0304-8853
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 76-77 (1988), S. 499-503 
    ISSN: 0304-8853
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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