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  • 1990-1994  (11)
  • 1960-1964
  • 1994  (5)
  • 1993  (4)
  • 1992  (2)
  • 1
    Electronic Resource
    Electronic Resource
    A Comparison of Two Alternatively Spliced Forms of a Metabotropic Glutamate Receptor Coupled to Phosphoinositide Turnover (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 61 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A comparison of the pharmacological and physiological properties of the metabotropic glutamate 1α and 1β receptors (mGluR1α and mGluR1β) expressed in baby hamster kidney (BHK 570) cells was performed. The mGluR1β receptor is an alternatively spliced form of mGluR1α with a modified carboxy terminus. Immunoblots of membranes from the two cell lines probed with receptor-specific antipeptide antibodies showed that mGluRIa migrated with an Mr= 154, 000, whereas mGluR1β migrated with an Mr= 96, 000. Immunofluorescence imaging of receptors expressed in BHK 570 cells revealed that the mGluR1α receptor was localized to patches along the plasmalemma and on intracellular membranes surrounding the nucleus, whereas mGluR1β was distributed diffusely throughout the cell. Agonist activation of the mGluR1α and the mGluR1β receptors stimulated phosphoinositide hydrolysis. At both receptors, glutamate, quisqualate, and ibotenate were full agonists, whereas trans-(+)-1-aminocyclopentane-1, 3-dicarboxylate appeared to act as a partial agonist. The stimulation of phosphoinositide hydrolysis by mGluR1α showed pertussis toxin-sensitive and insensitive components, whereas the mGluR1β response displayed only the toxin-insensitive component. The mGluR1α and mGluR1β receptors also increased intracellular calcium levels by inducing release from intracellular stores. These results indicate that the different carboxy terminal sequences of the two receptors directly influences G protein coupling and subcellular deposition of the receptor polypeptides and suggest that the two receptors may subserve different roles in the nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03540.x
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  • 2
    Electronic Resource
    Electronic Resource
    Far-infrared spectroscopy of the supreconductor YBa2Cu4O8 (1992)
    Springer
    The European physical journal 86 (1992), S. 329-335 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The frequencies of allB 1u (z) phonon modes predicted by a group-theoretical analysis were measured and found to agree well with recent lattice dynamical calculations for this compound. We report also the determination of two superconducting gap values in YBa2Cu4O8 through phonon self-energy effects in the normal and superconducting conducting state. The gap-to-T c ratios obtained from an analysis of these effects are 2Δ 1/kT c ≦2.5 and 5.8≦2Δ 2/kT c ≦9.2. This coincides with previous results of both phononic and electronic Raman scattering where values of 2.1 and 6.3 were found. We further find anomalous softenings of two phonon modes ∼40 Kabove T c , which correlate with an observed deviation from the linear temperature dependence of the average plasma frequency ν p (T).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323725
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  • 3
    Electronic Resource
    Electronic Resource
    Superconducting gap in Pr x Y1−x Ba2Cu4O8 and YBa2−y Sr y Cu4O8 probed by infrared phonon self-energies (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 113-116 
    Details
    ISSN: 1572-9605
    Keywords: High-temperature superconductivity ; superconducting gap ; phonons ; reflectivity spectra ; alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We report a reflectivity study of thez-polarized TO-phonons of Pr x Y1−x Ba2Cu4O8 and YBa2−y Sr y Cu4O8 alloys in the temperature range 10–300 K. Anomalies of the frequency and linewidth of the plane-oxygen vibration atω∼300 cm−1 due to the opening of the superconducting gap are found to occur upon crossing the superconducting transition temperatureT c . Phonon self-energy effects are strongly dependent onT c , providing evidence for a relative shift of the gap with respect to the energy of phonon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00730379
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  • 4
    Electronic Resource
    Electronic Resource
    Raman studies of nonlinear phenomena in fullerene crystallites (1993)
    Springer
    Applied physics 57 (1993), S. 299-302 
    Details
    ISSN: 1432-0630
    Keywords: 33.00 ; 35.00 ; 78.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The resonant Raman scattering of C60 crystallites is monitored as a function of excitation intensity at 514.5 nm. At low intensities, a strong line at 1468 cm−1 is observed. No feature at 1459 cm−1 is observable. With increasing intensities, the 1468 cm−1 line shifts continuously and reversibly to lower frequencies. The mode softening is nonlinearly dependent on the input intensity and is accompanied by a nonlinear increase in the Raman intensity. The spectral changes are discussed in terms of a nonlinear reduction in force constant and increase in bond polarisability as a result of an increased intermolecular delocalisation of the π-electron cloud. The nonlinear changes are associated with the nonlinear luminescence and photoconductive response observed in fullerenes and are contrasted to the irreversible phototransformation recently discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332280
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  • 5
    Electronic Resource
    Electronic Resource
    Cerebrospinal fluid flow and production in patients with normal pressure hydrocephalus studied by MRI (1994)
    Springer
    Neuroradiology 36 (1994), S. 210-215 
    Details
    ISSN: 1432-1920
    Keywords: Cerebrospinal fluid flow ; Cerebrospinal fluid production ; Magnetic resonance imaging ; Normal pressure hydrocephalus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An interleaved velocity-sensitised fast low-angle shot pulse sequence was used to study cerebrospinal fluid (CSF) flow in the cerebral aqueduct, and supratentorial CSF production in 9 patients with normal pressure hydrocephalus (NPH) and 9 healthy volunteers. The peak aqueduct CSF flow, both caudal and rostral, was significantly increased in patients with NPH. No significant difference in the supratentorial CSF production rate was found between patients (mean 0.60+/−0.59 ml/min) and healthy volunteers (mean 0.68+/−0.31 ml/min). Our method may be useful for investigation and monitoring of patients with NPH before and after ventriculoperitoneal shunt operations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588133
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  • 6
    Electronic Resource
    Electronic Resource
    Assessment of CSF dynamics and venous flow in the superior sagittal sinus by MRI in idiopathic intracranial hypertension: a preliminary study (1994)
    Springer
    Neuroradiology 36 (1994), S. 350-354 
    Details
    ISSN: 1432-1920
    Keywords: MRI ; CSF flow ; CSF production ; Blood flow, superior sagittal sinus ; Pseudotumour cerebri ; Benign intracranial hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A velocity-sensitive magnetic resonance imaging (MRI) phase-mapping method was used for noninvasive study of cerebrospinal fluid (CSF) flow in the cerebral aqueduct, for indirect calculation of supra-tentorial CSF production, and for measurement of blood flow in the superoor sagittal sinus (SSS). We examined 12 patients with idiopathic intracranial hypertension (HH; pseudotumour cerebri), and 10 healthy volunteers. The peak caudal and rostal CSF flow in the aqueduct during the cardiac cycle did not differ significantly between the patients and the volunteers. A significant correlation was found between the CSF volume flow amplitude and the resistance to cerebrospinal fluid out-flow in the patients (p〈0.05). The calculated mean supratentorial CSF production rate was 0.79 ml/min in the patients and 0.70 ml/min in the controls, but this difference was not statistically significant. However, the MRI measurements suggested CSF hypersecretion in three patients, whereas increased transependymal passage of CSF could have been the cause of negative calculated CSF production rates in two others. A tendency towards lower mean blood flow in the SSS (mean 345 ml/min) in the patients than in the controls (mean 457 ml/min) was found, and in two patients showed very low values. We showed that MRI phase-mapping may be used to study the relative importance of the pathophysiological factors thought to play a role in the development of IIH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612116
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  • 7
    Electronic Resource
    Electronic Resource
    Pulsatile brain movement and associated hydrodynamics studied by magnetic resonance phase imaging (1992)
    Springer
    Neuroradiology 34 (1992), S. 370-380 
    Details
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Brain motion ; Brain volume ; Arterial expansion ; Pulsation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Brain tissue movements were studied in axial, sagittal and coronal planes in 15 healthy volunteers, using a gated spin echo MRI sequence. All movements had characteristics different from those of perfusion and diffusion. The highest velocities occurred during systole in the basal ganglia (maximum 1.0 mm/s) and brain stem (maximum 1.5 mm/s). The movements were directed caudally, medially and posteriorly in the basal ganglia, and caudally-anteriorly in the pons. Caudad and anterior motion increased towards the foramen magnum and towards the midline. The resultant movement occurred in a funnelshaped fashion as if the brain were pulled by the spinal cord. This may be explained by venting of brain and cerebrospinal fluid (CSF) through the tentorial notch and foramen magnum. The intracranial volume is assumed to be always constant by the Monro-Kellie doctrine. The intracranial dynamics can be viewed as an interplay between the spatial requirements of four main components: arterial blood, capillary blood (brain volume), venous blood and CSF. These components could be characterized, and the expansion of the arteries and the brain differentiated, by applying the Monro-Kellie doctrine to every moment of the cardiac cycle. The arterial expansion causes a remoulding of the brain that enables its piston-like action. The arterial expansion creates the prerequisites for the expansion of the brain by venting CSF to the spinal canal. The expansion of the brain is, in turn, responsible for compression of the ventricular system and hence for the intraventricular flow of CSF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00596493
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  • 8
    Electronic Resource
    Electronic Resource
    Quantification of portal venous blood flow during fasting and after a standardized meal — a MRI phase-mapping study (1993)
    Springer
    European radiology 3 (1993), S. 242-247 
    Details
    ISSN: 1432-1084
    Keywords: Magnetic resonance imaging (MRI) ; Flow-quantification ; Portal vein ; Standardized meal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Portal venous blood flow was measured with a double-oblique phase-sensitive magnetic resonance imaging (MRI) flow measurement technique in six healthy volunteers after 7 h of fasting. A standard liquid meal with an energy content of 4200 kJ, containing equal parts of carbohydrate, protein and fat was given to the volunteers while in the scanner. Flow measurements were performed 5, 15 and 30 min after intake of the meal. The average portal vein blood flow was 0.88 ± 0.17 l · min−1 during fasting. After intake of the standard meal, flow increased by 30,67 and 111% after 5, 15 and 30 min, respectively. This study shows that a non-invasive MRI technique can be used for volume flow determinations in the portal vein and that physiological changes in flow can be quantified. The technique may be of clinical value in evaluation of patients with abdominal angina as well as patients with portal hypertension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425902
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  • 9
    Electronic Resource
    Electronic Resource
    A molecular beam fourier transform microwave spectrometer developed for analytical purposes (1994)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 349 (1994), S. 272-276 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A pulsed molecular beam Fourier transform microwave spectrometer especially designed for the quantitative analysis of polar pollutants in air is presented. This very fast method has a sensitivity in the ppm range and can be applied to a wide variety of substances. Details of the apparatus and the results of some performance tests are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323202
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  • 10
    Electronic Resource
    Electronic Resource
    Above-T c anomalies of the infrared-active phonons in RBa2Cu4O8 (R=Dy, Ho) and Y2Ba4Cu7O15−δ superconductors (1993)
    Springer
    The European physical journal 92 (1993), S. 9-15 
    Details
    ISSN: 1434-6036
    Keywords: 74.25.Gz ; 74.25.Kc ; 78.30.Er
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report a far-infrared reflectivity study of DyBa2Cu4O8, HoBa2Cu4O8 and Y2Ba4Cu7O15−δ superconductors in the temperature range 10–300 K. The assignment of thez-polarized infrared-acitve vibrations of the rare-earth-ion (R) was verified by the substitution ofR. Since the structure of the Y2Ba4Cu7O15−δ compound inz-direction is an ordered sequence of YBa2Cu3O7−δ and YBa2Cu4O8 blocks, the phonon spectrum of Y2Ba4Cu7O15−δ is a superposition of their respective phonon modes. The temperature dependence of the infrared-active phonons in RBa2Cu4O8 and Y2Ba4Cu7O15−δ was analyzed. A narrowing of the plane-oxygen phonon upon sample cooling was found to occur atT c , as it was reported for single-chain YBa2Cu3O7 materials; however a pronounced frequency softening of this mode for both RBa2Cu4O8 and Y2Ba4Cu7O15−δ was found to start well aboveT c , suggesting the interaction of infrared-active phonons with an excitation gap similar to that observed in spin-dependent measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01309161
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