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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 40 (2000), S. 858-862 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Gehirnperfusion ; Glukoseverbrauch ; Rezeptoren ; SPECT ; PET ; Keywords Regional cerebral blood flow ; Glucose metabolism ; Receptors ; Positron-emission tomography ; Single photon emission computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Positron-emission tomography (PET) and single photon emission computed tomography (SPECT) can be used to visualize and quantify cerebral perfusion, glucose consumption, neurotransmission, and amino acid uptake. These techniques are clearly superior to conventional structural imaging techniques for several indications. This contributioin describes the clinical role of PET and SPECT in clinical neurology.
    Notes: Zusammenfassung Mit den nuklearmedizinischen Computertomographien PET und SPECT lassen sich zerebrale Perfusion, Glukoseverbrauch, Neurotransmission und Aminosäureaufnahme untersuchen. Der vorliegende Artikel beschreibt den gegenwärtigen klinischen Stellenwert dieser Verfahren in der Neuromedizin, die hinsichtlich einer Reihe von Indikationen konventioneller strukturgebender Bildgebung überlegen sind.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 11 (1997), S. 513-521 
    ISSN: 1432-198X
    Keywords: Key words: Endothelin ; Urine ; Receptors ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Endothelin (ET) is a peptide with profound vasoconstrictive potential. First isolated from porcine endothelial cell supernatant, it is produced also by smooth muscle, epithelial and circulating cells. Besides vasoconstriction, a wide spectrum of biological activities of ET (via activation of membrane receptors) has been described. These include regulation of other hormones and neurotransmitters, cellular growth and proliferation, bronchoconstriction, and, in the kidney, natriuresis and water diuresis. ET exerts its effects mainly in an autocrine and paracrine fashion. A high concentration of ET is found in urine, compared with plasma originating mainly from the kidney itself. In this review we focus on the role of urinary excretion of ET in children. ET excretion was determined under different physiological and pathological conditions. In premature infants and newborns, the daily excretion of ET (corrected for body surface) was higher than in older children; it was constant, and comparable to the values in healthy adults after the age of 2 years. Renal ET excretion correlated positively with urine flow in both healthy and sick children. Conditions with tubular and/or collecting duct cell damage, such as severe hypoxia, hemolytic-uremic syndrome, renal transplantation, diabetes mellitus, chronic renal failure, and contrast media cytotoxicity were characterized by elevated urinary excretion of ET. In conclusion, the renal excretion of ET is influenced by several factors, probably reflecting the intrarenal ET production. ET has a low specificity with regard to renal injury.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0630
    Keywords: 72.20.Jv ; 29.40.Pe ; 85.60.Dw
    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 photoelectric response of p-n Si photodiodes under pulsed laser illumination (half width 10 ns) at 532 nm was studied as a function of dose which was varied over 6 orders of magnitude. The photocurrent transients are dominated by a plateau-like feature due to the build up of space charge at the intensities used. Increasing bias voltage increases the height of the plateau and decreases its length. In the low-dose range the length of the transient increases linearly with dose and the collected charge (integrated current) reaches a constant value. At high doses (above 10−5 J/pulse · cm2 or 2.7×1013 quanta/pulse · cm2) considerable charge loss (decrease in quantum yields) is accompanied by a less than proportional increase of the transient lifetime. From model calculations the dose and voltage dependence of the quantum yield of charge collection is shown to be the result of competition between current flow and first and higher order recombination. The model calculations are consistent with experimental results. Rate constants have been obtained by fitting.
    Type of Medium: Electronic Resource
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