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  • 1990-1994  (8)
  • 1970-1974
  • 1994  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance in melt-spun Cu87Co13 : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6546-6547 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results for the temperature and magnetic-field dependence of melt-spun Cu87Co13 are presented and discussed. The magnetoresistance of the as-spun sample exhibits superparamagnetic behavior with a magnetoresistance of 18% at 0.4 K and in a field of 80 kOe. The magnetic-field dependence of the magnetoresistance is approximately proportional to the Langevin function. The microstructure of the sample was investigated by transmission electron microscopy and it appears that the giant magnetoresistance is due to the presence of small Co precipitates with an approximate mean diameter of 12 A(ring) and a mean separation of 35 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356943
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  • 2
    Electronic Resource
    Electronic Resource
    Field dependence of nuclear magnetic resonance in molecular beam epitaxy grown Co(111)/Cu multilayers : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6504-6506 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An initial study of the field dependence of 59Co nuclear magnetic resonance (NMR) has been undertaken for two Co/Cu(111) multilayer films grown by molecular beam epitaxy. The multilayer structure of the films was nominally identical, [Co(15 A(ring))/Cu(7 A(ring))]×20, however by growing the multilayers with similar structures on different buffer layers, Cu(200 A(ring)) and Au(10 A(ring)), saturation magnetoresistances ΔR/R of 4% and 22%, respectively, were obtained. The NMR signal in ferromagnetic materials arises due to the enhancement effect from the electronic magnetization. This enhancement effect is therefore a function of the domain structure and any external magnetic field. By applying a simple model of how the NMR enhancement factor varies with applied field, in the absence of a domain structure, the anisotropy fields at the interfaces and in the bulk were determined separately at T=4.2 K. These were then compared with the coercive field obtained from magnetization measurements. Our results show that at low temperature the anisotropy field at the interfaces is approximately equal to the coercivity obtained from magnetization measurements (260 Oe), while in the bulk the anisotropy field was found to be ∼550 Oe for the low magnetoresistance sample with ΔR/R=4%, and ∼1230 Oe for the high magnetoresistance sample with ΔR/R=22%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358243
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  • 3
    Electronic Resource
    Electronic Resource
    MO polar Kerr studies of Co rich molecular beam epitaxy grown Au/Co multilayers : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6783-6785 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magneto-optical (MO) polar Kerr rotation and ellipticity (PKR and PKE, respectively) of Co rich Au(111)/Co(0001) multilayers grown by molecular beam epitaxy on GaAs(110) substrates are reported. The individual layer thicknesses, tAu and tCo were tAu/tCo=2.6/3.2, 1.0/1.5, and 0.65/0.8 nm. The samples displayed perpendicular magnetic anisotropy smaller than demagnetization energy. PKR and PKE were measured at photon energies between 1.5 and 5.2 eV. In the multilayer with tCo=1.5 nm, PKR at 3.1 eV reached a value of −0.34°, remarkably higher than that reported on Au rich multilayers. The spectra were compared with theory. A satisfactory agreement was obtained only for the sample with the largest bilayer thickness, tAu+tCo=5.8 nm. This indicates that when tAu and tCo are reduced to a few atomic monolayers the role of interfaces is increased. The effects of strain, defects, and atomic mixing at Au-Co interfaces become more important. Both the magnetic and optical properties are modified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356829
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of Au impurities at the interfaces on the magnetoresistance of MBE-grown Co/Cu multilayers : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7055-7057 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown Co/Cu multilayers by MBE using a shuttering arrangement wherein half of the sample receives an amount of Au impurities at each interface. Under these controlled conditions, the differences in measurements between each half is attributed only to the effect of the impurities. The samples were characterized by x-ray diffraction and RHEED. We have found that small fractions of a monolayer of Au deposited at the Co/Cu interface significantly decreased the GMR. These results are discussed in the light of current theories on the role of bulk and interface scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356724
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  • 5
    Electronic Resource
    Electronic Resource
    NarL-phosphate must bind to multiple upstream sites to activate transcription the narG promoter of Escherichia coli (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 14 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The stimulation of Fnr-dependent transcription from the narG promoter by NarL-phosphate is known to require a cis-acting sequence, the NarL box, located approximately 195 bp upstream from the transcription start site, and the interaction of integration host factor (IHF) with a binding site in the intervening region (positions −110 to −140) between the NarL box and the transcription start site. By gel retardation and DNase I protection studies, we have demonstrated that NarL-phosphate, produced by the reaction of purified NarL with acetyl phosphate, specifically binds to a fragment derived from the upstream region of the narG promoter. The fragment was protected by NarL-phosphate binding to two distinct regions. One was an extended sequence of approximately 40 bp surrounding the NarL box at −195; the second was located downstream from the IHF-binding region and included a sequence extending from positions −80 to −120. Alteration by site-directed mutagenesis of a putative inverted NarL box sequence identified within the downstream protected region in a plasmid containing a narG-lacZ fusion eliminated the NarL-phosphate-mediated stimulation of transcription. NarL-phosphate bound to the two regions independently from IHF binding and it bound to each site independently when the two sites were separated by cleavage of the promoter fragment. Stimulation of transcription from the narG promoter by NarL-phosphate appears to result from the formation of a folded protein-DNA structure created by the binding of NarL-phosphate to multiple sites on either side of an IHF-induced bend in the upstream region of the promoter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb01302.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of acute selective 5-HT1, 5-HT2, 5-HT3 receptor andα 2 adrenoceptor blockade on naloxone-induced antinociception (1994)
    Springer
    Psychopharmacology 113 (1994), S. 527-533 
    Details
    ISSN: 1432-2072
    Keywords: Naloxone-induced antinociception ; Serotonin receptor antagonists ; α2-Adrenoceptor antagonists ; Pain ; Opiate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Several studies have demonstrated a paradoxical form of antinociception induced by the repeated administration of opioid antagonists accompanied by exposure to a painful stimulus. The underlying mechanism of this naloxone-induced antinociception (NIA) is still unknown, but the results of several studies suggest that it is a non-opioid response. This study was designed to investigate serotonergic and noradrenergic involvement in NIA. Rats were treated daily with systemic injections of 5 mg/kg naloxone, followed by a 45-s hot plate test of nociception (temperature=51.5 ± 0.5°C). After rats reached plateau levels of NIA, they received a test trial in which they were treated with various doses of different selective 5-HT or α2 adrenoceptor antagonists in addition to naloxone before the hot plate test. Rats treated with 0.16, 0.32 and 0.63 mg/kg pirenperone or 2.5 mg/kg ritanserin showed significant reductions in paw lick latency with respect to rats treated with vehicle. In addition, high doses of yohimbine (7.5–10 mg/kg) also effectively reversed NIA. In contrast, NIA was not affected by acute blockade of 5-HT1 or 5-HT3 receptors by methiothepin or MDL 72222, respectively, or by the α2 adrenoceptor blocker idazoxan. None of the 5-HT or α2 adrenoceptor antagonists had any effect on the paw lick latencies of saline-treated rats. A possible role of 5-HT2 receptors in the antinociception induced by opioid receptor blockade is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245234
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  • 7
    Electronic Resource
    Electronic Resource
    Eversible abdominal vesicles and some observations of the male reproductive system of the spoon wing lacewing Palmipenna (Neuroptera: Nemopteridae) (1994)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 219 (1994), S. 47-58 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The anatomy and histology of the abdominal eversible vesicles and the male reproductive tract of the spoonwing lacewing Palmipenna (Neuroptera: Nemopteridae) have been examined. The eversible vesicles open as a pair of large bulbous sacs between tergites five and six, each folding into halves during retraction. They consist of highly pleated cuticle, beneath which are typical gland cells, each having a circular or oval end apparatus surrounded by closely packed microvilli. These communicate to the surface via cuticularized channels. In spite of considerable behavioral observations, male Palmipenna were never noted with everted vesicles. Even during mating trials, where females were presented to males in the field, the vesicles were never everted during the attempted copulation that ensued. Our observations indicate that mate attraction is mediated by the release of a female pheromone. The function of the eversible vesicles and their associated gland cells remains unknown, and their structure appears to be unique to the Nemopteridae. The reproductive tract is similar to that of other Neuroptera, consisting of a pair of five-lobed testes, a medium-to-large pair of seminal vesicles, and three pairs of accessory glands. The major accessory glands are surrounded by circular and longitudinal muscle, and are lined by an epithelium, the cells of which presumably secrete the amorphous rods of material always present in this pair of glands. The sperm in the seminal vesicles are elongate, with a pointed head and a 9 + 9 + 2 configuration in the flagellum. A single spermatophore, similar in shape to that described for other Neuroptera, was found occluding the bursa copulatrix of a teneral female. © 1994 Wiley-Liss, Inc.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052190107
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  • 8
    Electronic Resource
    Electronic Resource
    “Schizoid” personality in childhood: Auditory P300 and eye tracking responses at follow-up in adult life (1994)
    Springer
    Journal of autism and developmental disorders 24 (1994), S. 487-500 
    Details
    ISSN: 1573-3432
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract The auditory P300 response and smooth pursuit eye tracking were recorded from a group of 23 male adult subjects who had been diagnosed in childhood as having schizoid personality. No differences were found in these physiological measures between the study group, their matched controls of other child psychiatric patients, and a group of population controls. The essentially negative findings are discussed in the light of abnormalities of these psychophysiological responses previously found in schizophrenic patients, in some of their biological relatives, and in other groups of psychiatric patients, including autistic children and adults with a diagnosis of borderline and schizotypal personality disorder. Results suggest that “schizoid” children, despite their high scores on a measure of schizotypy, do not have schizophrenia spectrum disorder or that schizotypy is a heterogeneous condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172130
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