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  • 1
    Electronic Resource
    Electronic Resource
    Large Arrays of Escape-Suppressed Gamma-Ray Detectors (1994)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Nuclear and Particle Science 44 (1994), S. 561-607 
    Details
    ISSN: 0163-8998
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ns.44.120194.003021
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  • 2
    Electronic Resource
    Electronic Resource
    On the mystery of the golden angle in phyllotaxis (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Phyllotaxis, the arrangement of leaves around a stem, shows in the vast majority of cases a regularity in the divergence angle of subsequent leaves which divide the whole circle into regular fractions. These are in most cases rational fractions of two Fibonacci numbers in an alternating series, converging towards the irrational limit of the golden section, corresponding to the golden divergence angle of 137.5  . . . degrees. This peculiarity was a long-standing mystery. Here, it is related to the evolutionary pressure of optimal light capture for maximal photosynthetic activity. A model is established which relates minimal shadowing for the lower leaves to the divergence angle. Numerical results of this model agree well with semi-empirical data on the dependence of light capture from the divergence angle. The basic shadow function of the model is also related with the demand of minimal shadowing for the angular separation of leaves and obtain, using elementary number theory, as solution the golden section. Further numerical studies show that the rational approach to the golden section (Schimper–Braun series) is related to the leaf width and the number of leaves of the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01185.x
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  • 3
    Electronic Resource
    Electronic Resource
    Prevalence of fluconazole-resistant strains of Candida albicans in otherwise healthy outpatients (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of oral pathology & medicine 31 (2002), S. 0 
    Details
    ISSN: 1600-0714
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  In contrast to the immunosupressed patient population, the prevalence of fluconazole-resistant strains of Candida albicans among healthy individuals has not been extensively studied.Methods:  Candida species were cultured form 50 healthy outpatients with clinical signs of oral candidiasis. Following one week of the recommended fluconazole regimen, post-treatment cultures were obtained. Both pre- and post-treatment yeasts were identified and in vitro susceptibility testing was performed using the NCCLS M-27A method. Strains were further differentiated using established cDNA probes.Results:  Forty-four patients (88%) had positive C.albicans cultures prior to treatment. Antifungal susceptibility testing of these strains demonstrated no in vitro resistance to fluconazole. At post-treatment evaluation, eight patients (18%) had persistent signs of infection and 10 patients (23%) had positive Candida sp. cultures despite no clinical signs of infection. DNA analysis confirmed that the same C. albicans strain was present both in the pre-treatment and the post-treatment cultures.Conclusions:  Our results showed that the presence of fluconazole-resistant strains of C.albicans does not appear to be prevalent among healthy outpatients furthermore, in vitro antifungal susceptibility testing does not always predict successful therapy in these patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0714.2002.310207.x
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  • 4
    Electronic Resource
    Electronic Resource
    Electrodeposition of polypyrrole layers on aluminium from aqueous electrolytes (1990)
    Springer
    Journal of applied electrochemistry 20 (1990), S. 596-605 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01008869
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of anodically formed polypyrrole/tungsten trioxide composites (1993)
    Springer
    Journal of applied electrochemistry 23 (1993), S. 957-965 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266116
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  • 6
    Electronic Resource
    Electronic Resource
    Electrocatalytic deposition of polypyrrole in the presence of bromide (1992)
    Springer
    Journal of applied electrochemistry 22 (1992), S. 332-340 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01092685
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  • 7
    Electronic Resource
    Electronic Resource
    Anodic formation of polypyrrole/tungsten trioxide composites (1993)
    Springer
    Journal of applied electrochemistry 23 (1993), S. 781-789 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249950
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  • 8
    Electronic Resource
    Electronic Resource
    An alternative gamma tracking method using the Compton scattering probability (2003)
    Springer
    The European physical journal 20 (2003), S. 203-204 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. A new gamma tracking method, called probabilistic method and based on the Compton scattering probability of photons in a highly segmented Ge spectrometer, has been evaluated with the GEANT simulation code. This method has been used to calculate the performances of a 4 $\pi$ array composed of planar detectors as their crystal shape allows to realize identical segments of quasi-cubic shape. The tracking algorithm selects the full-absorption events by taking into account only the centre of gravity of the segments hit and the partial energies released in each of them. The results obtained, in terms of photopeak detection efficiency and peak-to-total ratio, are comparable to the ones deduced from the usual tracking methods. The probabilistic algorithm seems also to apply efficiently for other types of detectors as simulation calculations performed on a single stack of planar detector and a single segmented CLOVER detector give nearly the same reconstruction efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2002-10354-7
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  • 9
    Electronic Resource
    Electronic Resource
    Superdeformed nuclear matter in nuclei with $Z \ge 82$ : Magnetic properties and neutron shell gap (2003)
    Springer
    The European physical journal 20 (2003), S. 31-32 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We report the results of an experiment, realized with the EUROBALL IV spectrometer, in which superdeformed (SD) states have been populated in 197,198Pb nuclei. Crosstalk transitions between two signature partner SD bands in 197Pb have been observed with an established M1 character, giving access to the magnetic properties of the $\nu$ [752]5/2 intruder orbital. Six new SD bands have been identified in 197,198Pb. The results are interpreted in the framework of cranked Hartree-Fock calculations. A mixing between quasi-particle excitations and an octupole vibration is suggested in the two SD isotopes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epja/i2002-10314-3
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  • 10
    Electronic Resource
    Electronic Resource
    Regulation and localization of organic osmolytes in mammalian kidney (1990)
    Springer
    Journal of molecular medicine 68 (1990), S. 1091-1095 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01798058
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