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  • Articles: DFG German National Licenses  (3)
  • 1995-1999  (2)
  • 1980-1984  (1)
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  • Articles: DFG German National Licenses  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    A precise potentiometric method for determination of algal activity in an open CO2 system (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The activity of the green alga Scenedesmus obliquus was studied in simplified nutrient solutions (20 mol m−3 NaNO3, 20 mol m−3 NH4C1, 20 mol m−3 NH4NO3, and 20 mol m−3 NaCl, respectively) at 25 °C. The experiments were performed under welldefined incident photon density fluxes ranging from 10 to 200 μmol m2 s−1, Light-dependent changes in pH and alkalinity (A) were followed by means of a potentiometric method using a glass electrode. In the experiments, carbon dioxide with known partial pressure was bubbled through the algal suspension, and during dark periods ul intervals of 1 h, the solution was allowed to equilibrate with the gas phase. This technique was applied to calculate equilibrium values of pH and alkalinity at regular intervals during a 12-h period. Results obtained in NaNO3, solution show a linear increase in A with time, at each level of illumination studied. After an initial drop, A also increases in NH4NO3, solution in a similar way to that in NaNO3 solution. The change in A with time was also found to increase linearly with the photon density flux studied and no saturation level could be defined. In experiments in NaCl solution, no changes in A were registered while measurements in NH4Cl solution showed a decrease in A with time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11587621
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Imaging in chronic achilles tendinopathy: a comparison of ultrasonography, magnetic resonance imaging and surgical findings in 27 histologically verified cases (1996)
    Springer
    Skeletal radiology 25 (1996), S. 615-620 
    Details
    ISSN: 1432-2161
    Keywords: Key words Magnetic resonance imaging ; Ultrasonography ; Achilles tendon ; Tendinosis ; Partial rupture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To compare information gained by ultrasonography and magnetic resonance imaging (MRI) in chronic achilles tendinopathy with regard to the nature and severity of the lesion. Design. Imaging of both achilles tendons with ultrasonography and MRI was performed prior to unilateral surgery. Operative findings and histological biopsies together served as a reference. Patients. Twenty-seven patients (22 men, 5 women; mean age 44 years; 21 athletes) suffering from chronic achilles tendinopathy participated in the study. Eighteen patients had unilateral and 9 had bilateral symptoms. Results and conclusions. Surgical findings included 4 partial ruptures, 21 degenerative lesions and 2 macroscopically normal cases. Microscopy revealed tendinosis (degeneration) in all tendon biopsies, including cases with a partial rupture, but only slight changes in the paratendinous tissues (paratenon). Ultrasonography was positive in 21 of 26 and MRI in 26 of 27 cases. Severe intratendinous abnormalities and a sagittal tendon diameter 〉10 mm suggested a partial rupture. In tendons with a false negative result histopathological changes were mild and a tendency towards a better clinical outcome was noted in the sonographic cases. Assessment of the paratenon was unreliable with both methods. Ultrasonography and MRI give similar information and may have their greatest potential as prognostic instruments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050146
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Complexation of Gold(III)-Chloride at the Surface of Hematite (1998)
    Springer
    Aquatic geochemistry 4 (1998), S. 215-231 
    Details
    ISSN: 1573-1421
    Keywords: Gold ; hematite surface ; surface complexation ; adsorption ; potentiometric titration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The acid/base properties of the hematite/water interface and surfacecomplexation with gold has been studied by potentiometric titrations in thefour component system H+ – ≡FeOH –AuCl 4 - – Cl-. Equilibrium measurementswere performed in NaCl media at 298.2 K. In the evaluation of equilibriummodel from experimental data the constant capacitance model was applied. Theacid/base properties were investigated in 0.1 M NaCl in the range 2.6 ≤pH ≤ 7.4. The resulting intrinsic constants for protonation anddeprotonation of hydroxyl groups at the surface were logβ 1,1,0,0(int) s = 7.10 ± 0.06 andlog β -1,1,0,0(int) s = - 7.80 ±0.06. The density of proton active surface sites was 2.85nm-2 and the specific capacitance 2.5 C V-1 m-2. In the investigation of surface complexation of gold, thepotentiometric titrations were performed in the range 2.0 ≤ pH ≤ 10.2.Titration data was supplemented with analysis of Au in the aqueous phase byatomic absorbance spectrometry. The equilibrium model proposed consists ofthe following monodentate surface complexes: ≡FeOHAuCl3(log β 0,1,1,-1 s = 1.45 ± 0.03),≡FeOHAuCl2OH (logβ -1,1,1,-2 s = -3.89 ± 0.02), ≡FeOHAu(OH)3 (logβ -3,1,1,-4 s = -21.94 ± 0.05). Aslightly better fit could be obtained by assuming formation of a bidentatecomplex with the composition(≡FeO)2Au(OH)H2O. However, based onstructural arguments this complex was rejected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009622915376
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    Paper (German National Licenses)
    Fulltext
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