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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic force microscopy: General principles and application to longitudinal recording media (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1169-1183 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper discusses the principles of magnetic force microscopy (MFM) and its application to magnetic recording studies. We use the ac detection method which senses the force gradient acting on a small magnetic tip due to fields emanating from the domain structure in the sample. Tip fabrication procedures are described for two types of magnetic tips: etched tungsten wires with a sputter-deposited magnetic coating and etched nickel wires. The etched nickel wires are shown to have an apex radius on the order of 30 nm and a taper half-angle of approximately 3°. Lorentz-mode transmission electron microscopy of the nickel tips reveals that the final 20 μm is essentially single domain with magnetization approximately parallel with the tip axis. Images of written bit transitions are presented for several types of magnetic media, including CoPtCr, CoSm, and CoCr thin films, as well as γ-Fe2O3 particulate media. In general, the written magnetization patterns are seen with high contrast and with resolution better than 100 nm. A number of magnetic recording applications are discussed, including the investigation of overwrite behavior and the writing characteristics in CoSm media at high data density. Computer calculations were performed to simulate the MFM response to written magnetic transitions. By including the extended geometry of the tip, the nonparallel orientation of the cantilever, and the finite width of the magnetic transitions, good agreement with experiment was obtained. The model calculations correctly predict the experimentally observed change in image contrast that occurs as a function of tip orientation. Computer calculations showing the dependence of resolution on tip geometry are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346713
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic force microscopy of thin Permalloy films (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 318-320 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have imaged naturally occurring domains in soft magnetic films using the force microscope. Classic closure structures were seen in both sputtered and plated Permalloy films. These structures were compared to optical Kerr micrographs of the same films, with generally good correspondence. The force microscope had sufficient sensitivity and resolution to observe magnetic details such as ripple structure and a Bloch line. Clear evidence of tip-induced wall motion was seen when the tip-to-sample separation was less than about 100 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101898
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  • 3
    Electronic Resource
    Electronic Resource
    Force microscopy of magnetization patterns in longitudinal recording media (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1563-1565 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A force microscope with a magnetic tip has been used to examine magnetization patterns in a thin-film cobalt-alloy sample similar to that used in magnetic disk recording. Longitudinal magnetic bits were written on discrete tracks with a recording head flown over the surface of the sample. After minimal sample preparation, images were obtained showing strong magnetic contrast. Model calculations for the expected image contrast were found to be in excellent qualitative agreement with experimental results. By using a constant height imaging mode, enhanced contrast for fine detail was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99952
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  • 4
    Electronic Resource
    Electronic Resource
    Deposition and imaging of localized charge on insulator surfaces using a force microscope (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2717-2719 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A force microscope has been used in a new application to deposit and image localized surface charge on insulators. The lateral resolution for imaging surpasses that of currently available techniques. By applying voltage pulses to an etched nickel microscope tip, micron-sized regions of approximately 2×10−16 C were created on polymethylmethacrylate and single-crystal sapphire surfaces. After depositing the charge, high-contrast images of the charged region were obtained as contours of constant force gradient. The contrast was observed to decay over approximately 1 h, providing evidence for surface charge mobility. The minimum detectable surface charge was estimated to be on the order of 100 electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100162
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  • 5
    Electronic Resource
    Electronic Resource
    Force microscope using a fiber-optic displacement sensor (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2337-2340 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A force microscope is described which uses a fiber-optic interferometer as the cantilever displacement sensor. Low thermal drift and reduced susceptibility to laser frequency variation are achieved due to the small (several micrometer) size of the interferometer cavity. A sensitivity of 1.7×10−4 A(ring)/(Hz)1/2 is observed for frequencies above 2 kHz. The drift rate of the sensor is on the order of 3 A(ring)/min. As an initial demonstration, laser-written magnetic domains in a thin film sample of TbFeCo were imaged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139958
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  • 6
    Electronic Resource
    Electronic Resource
    Expression of GABAB Receptors in Magnocellular Neurosecretory Cells of Male, Virgin Female and Lactating Rats (2005)
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 17 (2005), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: GABA is one of the key neurotransmitters that regulate the firing activity of neurones in the supraoptic (SON) and paraventricular (PVN) nuclei. In the present study, we used immunohistochemical techniques to study the distribution and subcellular localisation of metabotropic GABAB receptors in magnocellular neurones in the SON and PVN. Robust GABAB receptor immunoreactivity (GABABR; both subunit 1 and subunit 2 of the heterodimer), was observed in the SON and PVN. At the light microcope level, GABABR immonoreactivity displayed a clustered pattern localised both intracytoplasmically and at the plasma membrane. Densitometry analysis indicated that GABABR immunoreactivity was significantly more intense in vasopressin cells than in oxytocin cells, both in male, virgin female and lactating rats, and was denser in males than in virgin females. Light and electron microscope studies indicated that cytoplasmic GABABR was localised in various organelles, including the Golgi, early endosomes and lysosomes, suggesting the cycling of the receptor within the endocytic and trafficking pathways. Some smaller clusters at the level of the cell plasma membrane were apposed to glutamic acid decarboxylase 67 immunoreactive boutons, and appeared to be colocalised with gephyrin, a constituent protein of the postsynaptic density at inhibitory synapses. The presence of GABABR immunoreactivity at synaptic and extrasynaptic sites was supported by electron microscopy. These results provide anatomical evidence for the expression of postsynaptic GABAB receptors in magnocellular neurosecretory cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.2005.01324.x
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  • 7
    Electronic Resource
    Electronic Resource
    Activation of Postsynaptic GABAB Receptors Modulate the Firing Activity of Supraoptic Oxytocin and Vasopressin Neurones: Role of Calcium Channels (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 16 (2004), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Oxytocin and vasopressin release from neurohypophysial terminals is closely related to the firing activity of magnocellular neurones in the supraoptic (SON) and paraventricular nuclei. It is well established that activation of GABAA receptors potently inhibits the activity of SON neurones and, thus, hormone release. However, whether postsynaptic GABAB receptors are expressed in magnocellular neurones, and the role they play in controlling their firing activity, is still controversial. In the present work, we combined immunohistochemical and electrophysiological techniques to determine whether activation of GABAB receptors in identified oxytocin and vasopressin neurones modulates their firing activity. Patch-clamp recordings from SON neurones were obtained either in the slice preparation or from acutely dissociated neurones. Activation of GABAB receptors with the selective agonist baclofen (10 µm) inhibited voltage-gated Ca2+ currents, reduced the duration of individual action potentials, as well as the magnitude of the hyperpolarizing after-potential. SON firing activity was reduced by baclofen, and effect that was accompanied by a small membrane hyperpolarization. The inhibition of firing discharge persisted in the presence of synaptic blockade media, and was also observed in acutely dissociated SON neurones. Finally, GABAB-mediated modulation of firing activity was largely blocked by the Ca2+ channel blocker Co2+ (2 mm). In general, baclofen modulatory actions were significantly larger, or observed more predominantly, in vasopressin neurones. In summary, these results support the expression of functional postsynaptic GABAB receptors in SON neurones, activation of which efficiently modulates neuronal excitability, in a Ca2+- and cell-type dependent manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0953-8194.2004.01148.x
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  • 8
    Electronic Resource
    Electronic Resource
    Correlation between serum and urinary calcium levels and psychopathology in patients with affective disorders (1996)
    Springer
    Journal of neural transmission 103 (1996), S. 509-513 
    Details
    ISSN: 1435-1463
    Keywords: Calcium metabolism ; MMPI ; psychopathology ; autonomic nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To examine whether serum and urinary calcium levels were related to the psychopathology index (i.e. average score in clinically relevant scales of Minnesota Multiphasic Personality Inventory), 24 women aged 35.6 ± 2.5 years and 20 men aged 34.3 ± 2.1 years, suffering from affective disorders, were studied. A non-parametric bivariate correlation analysis revealed a negative correlation between PI and serum calcium (r=−0.256, p 〈 0.01), while urinary calcium levels correlated positively with PI (r=0.236, p 〈 0.02). A positive correlation occurred between serum and urinary calcium (r=0.968, p 〈 0.0001). When the data were analyzed by categorical classification of patients with normal or abnormal PI scores, serum calcium levels were smaller, and urinary calcium levels higher, in patients with abnormal PI (p 〈 0.01). The results support to the concept that alterations of calcium homeostasis occur in psychopathology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276424
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  • 9
    Electronic Resource
    Electronic Resource
    Peripheral autonomic regulation of gonadotropin secretion in pubertal rats. Inhibition of post-castration rise of gonadotropins during wallerian degeneration after sympathetic superior cervical ganglionectomy (1994)
    Springer
    Journal of neural transmission 96 (1994), S. 41-50 
    Details
    ISSN: 1435-1463
    Keywords: Superior cervical ganglion ; gonadotropins ; puberty ; wallerian degeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Shortly after superior cervical ganglionectomy (SCGx) peripheral sympathetic nerve terminals in the median eminence degenerate, the neurotransmitter is released, and a transient period of increased postsynaptic ensues. The present experiments were undertaken to examine, in the anterograde degeneration paradigm after SCGx, the participation of peripheral sympathetic nerves in feedback regulation of gonadotropin release in pubertal rats. Groups of 18 days old or 26 days old rats of both sexes were subjected to castration or its sham-operation, and 4 h later to SCGx or sham-SCGx. Twenty-four h later, the rats were decapitated and serum luteinizing hormone (LH) and folliclestimulating hormone (FSH) levels were measured by RIA. In 19 days old male rats, the post-castration increase of circulating LH, but not of FSH, was prevented by the wallerian degeneration of sympathetic nerves after acute SCGx. At the 27th day of life, acute SCGx prevented FSH, but not LH, post-orchidectomy rise. In female rats, SCGx blunted the oophorectomy-induced increase of gonadotropin levels at both examined ages. SCGx brought about a significant decrease of serum LH levels in 19 days old, sham-castrated female rats. At the 19th day of life, acute SCGx decreased serum LH and FSH in neonatally orchidectomized rats, but not in neonatally androgenized female rats. The data are in favor of a negative influence of peripheral sympathetic neurons on gonadotropin release in prepubertal rats, predominantly in female rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01277927
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