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  • 1
    ISSN: 1434-601X
    Keywords: 21.65.+f ; 21.10.Dr ; 12.40.Aa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We evaluate form factors for the scattering ofσ, ω andπ mesons from nucleons described by the MIT bag model. These form factors are then written covariantly and used for nuclear matter in the Hartree-Fock approximation to theσω model of quantum hadrodynamics with pions. For fixed parameters (meson couplings and masses) the inclusion of these form factors results in more binding at a higher saturation density. After refitting the parameters to reproduce the empirical saturation properties, the result is very close to that without form factors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 27.70.+q ; 21.60.Cs ; 21.30.+y
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Excited states in the nucleus150Tb have been investigated up to spin 39ħ and 13 MeV excitation energy using the130Te(27Al, 7n) reaction and the EUROGAM array. The theoretical interpretation of the observed states has been performed in the framework of the deformed independent particle model. The analysis of the decay out of the yrast superdeformed band indicates that normal-deformed states with spins between 24ħ and 28ħ are fed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Norcamphor (1) was anodically oxidized at Pb/PbO2 anodes in 1 M · H2SO4, MeCN/H2O (V/V = 1/1). 3-Oxocyclopentaneacetic acid (3) and oxabicyclo[3.3.0]octan-3-one (4) were obtained with material yields up to 76% and 42%, respectively. The effects of electrode materials, current densities and concentrations were studied. A possible anodic oxidation mechanism was proposed.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 1432-1440
    Keywords: Organic osmolytes ; Rat kidney ; Diabetes insipidus ; Diabetes mellitus ; Hormone treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four organic small molecules belonging to the chemical groups of trimethylamines (betaine and glycerophosphorylcholine) and polyols (sorbitol and inositol) have been shown to act as organic osmolytes in the kidney. When measured along the corticopapillary axis, each exhibits a specific distribution pattern, indicating a specific localization and function. Studying their behaviour under vasopressin treatment in diabetes insipidus rats and after insulin treatment in diabetes mellitus rats confirmed this conclusion: AVP led to a steady increase of sorbitol and glycerophosphorylcholine over 7 days with no effect on inositol levels. Insulin treatment of diabetic rats, on the other hand, decreased sorbitol with a concomitant increase in glycerophosphorylcholine, again without any effect on tubular inositol concentrations. From this and in vitro studies it can be concluded that both hormones act by indirect mechanisms which alter interstitial osmolality. This in turn leads to a change in tubular osmolyte synthesis, uptake and release rates. In addition, the concentrations of the respective precursors glucose and choline influence the formation rates of sorbitol and betaine.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 69 (1991), S. 184-184 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 6
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Bromide ions (typicallyc=1 mM) are oxidized in acetonitrile electrolytes at platinum anodes in two steps, well separated by about 300 mV, leading to tribromoanions1 and to bromine2, respectively. These basic electrochemical reactions interfere quite differently with pyrrole3, typicallyc=0.1-0.01 M, added to the system.1 oxidizes3 to bromopyrroles, indicated by an amplification of the limiting current density of the first wave by a factor of three. No polypyrrole is deposited. In the course of the second wave,2 oxidizes3 to the radical cation4. The rate determining step in the formation of polypyrrole is a dimerization of4 moieties, and the strong electrostatic shielding effect via complexation of1 with4 leads to a catalytic enhancement of the polymerization rate by more than a factor of 10 with respect to conventional systems. Regeneration of1 in the course of these processes gives a large current amplification in the second wave. The overall reaction leads to polypyrrole, which forms an electrode coating. The material has improved properties, for example electronic conductivities above 100 S cm−1. The current efficiency is nearly 100%, but only if the convection is weak. This ‘negative stirring effect’ is discussed in detail.
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  • 7
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A screening of twenty aqueous electrolytes for a film-forming electropolymerization of pyrrole with Al was performed. Electrodeposition of well adhering homogeneous polypyrrole layers on aluminium is possible from aqueous electrolytes containing 0.1–0.8M oxalic acid. Pretreatment of the metal by polishing (PD) or by anodic (galvanostatic) activation (GA) is an essential step. In all cases, the Al2O3 surface layer with pores, usually filled with electrolyte, is transformed to a Al2O3 layer with polypyrrole filled pores. The PPy-layers on Al allow an easy cathodic coating with metals like copper. The hydrogenoxalate doped layers exhibit the ususal redox capacity,y=0.3. The sandwich structure Al/Al2O3/PPy represents a condenser with an unusual composite dielectric with the electronically conducting ‘plates’ Al and PPy. According to our impedance measurements, the PPyin the pores is a high resistivity material due to overoxidation in the course of electropolymerization at high local current densities. The composite, Al2O3/overoxidized PPy, exhibits an unusually high permittivity, in the order of 103.
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  • 8
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Composite PPy/WO3 materials were synthesized anodically under various conditions. The cyclovoltammetric switching curves are very close to the blank polypyrrole. The redox behaviour of the filler is only detected through electrochromism, leading to a yellow grey colour at +0.4 V vs SCE and to a green surface at −0.6 V. For overoxidation of the composite, a degree of overoxidation Y = 5 is found, the same as for the matrix alone. Photoelectrochemical response is due to the conducting polymer at negative potentials and even at 0 V vs SCE. A strong effect at positive potentials is due to the WO3 pigment. From this, a flat band potential of +0.15 V vs SCE is determined for aqueous 0.1 m LiClO4. Some non-electrochemical properties are also reported. Surface roughness increases with increasing WO3 concentration, but for thicker layers, from MeCN, it decreases. SEM micrographs reveal homogeneous distribution of WO3. Large secondary particles are observed in NBu4BF4 electrolyte. True and nominal thicknesses differ by up to a factor 1.65 due to the porous structure and this explains differences between densities measured by the flotation and the jump method. X-ray diffraction analysis exhibits unchanged WO3-lines, but no PPy-lines due to the amorphous character. The conductivity of the composite from MeCN is much lower than expected by the volume filling of the WO3.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 23 (1993), S. 781-789 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The anodic codeposition of WO3 and polypyrrole at constant current densities was studied. The powdery solid was dispersed in the electrolyte (0.1m pyrrole, 0.1m LiClO4) under strong convection at c L = 0.01–30 g dm−3. Water or wet acetonitrile were employed as solvents. Various modes of convection were developed. The resulting WO3 Concentrations in the PPy/WO3 composites were up to c C = 53 wt%. c C was found to increase with increasing convection intensity and with decreasing current density. Quantitative evaluation leads to a relationship c C = K log c E/c E.0, where K is a constant,and c E.0 is a threshold concentration. This equation was derived from a model assuming a Temkin type adsorption of the impinging particles and their field enhanced final incorporation into the polypyrrole matrix K is proportional to j −1. The new model complements the older theory of Guglielmi originally developed for systems with metal matrices, and it also holds for these very well known composites. The homogeneous distribution of WO3 in PPy is demonstrated by the linear increase of the WO3 mass with the thickness of the composite in combination with SEM techniques.
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  • 10
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 0163-8998
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Type of Medium: Electronic Resource
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