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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 277 (1999), S. 340-346 
    ISSN: 1435-1536
    Keywords: Key words Chirality ; Clay organocomplexes ; Intercalation ; Nanophase reactors ; Binary liquid mixtures ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Chiral phenylethyl alkylammonium montmorillonites were prepared by ion exchange of Na montmorillonite (from Wyoming). The structure of chiral montmorillonite organocomplexes was studied in the dry state by X-ray diffraction, IR spectroscopy and 13C cross-polarized MAS NMR and after swelling by X-ray diffraction. The phenylethylammonium ions are intercalated in montmorillonite in a monolayer structure, while higher derivatives containing alkyl chains with lengths of n c=10−16 take up a bilayer orientation. The hydrophobized clay mineral is readily dispersed in organic solvents, for example in ethanol, toluene and their binary mixtures. Due to selective adsorption, the liquids penetrate into the interlamellar space under significant interlayer expansion producing a great variety of alkyl chain orientations within the interlamellar space, depending on the length of alkyl chains and on the mixture composition. Such interlamellar spaces are possible chiral nanoreactors with adjustable volume and may be prospectively utilized for shape-selective catalytic reactions and the production of enantiomers.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 322 (1968), S. 999-1004 
    ISSN: 1435-2451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In Akutversuchen bei Hunden wurde die Vena cordis magna proximal ligiert und distal davon mittels eines in die Aorta eingepflanzten Katheters arterialisiert. Der Einfluß der so erzeugten Coronarflowumkehr auf die Folgen der Ligatur des Ramus descendens anterior der Coronararterie wurde studiert. Bei 3 von 23 Experimenten verhinderte die Coronarflowumkehr ein Kammerflimmern. Dieser nur beschränkte Schutzeffekt wird durch die Beobachtung erklärt, daß mehr als 80% des der Vene zugeführten arteriellen Blutes durch venöse Kollateralen aus dem Descendensgebiet abgeleitet werden.
    Notes: Summary In acute experiments on dogs the great cardiac vein was ligated proximally. The distal protion was then arterialized by way of an indwelling catheter in the aorta. The effects of the thus produced reversal of the coronary flow on the sequelae to the ligature of the ramus descendens anterior of the coronary artery, were then studied. In 3 out of 23 experiments the reversal of the coronary flow prevented ventricular fibrillation. The only very limited protective function is explained by the observation that more than 80% of the arterial blood which enters the vein is drained away through the venous collaterals in the region of the descending branch.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 50 (1900), S. 65-71 
    ISSN: 1434-4726
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 57 (1903), S. 188-192 
    ISSN: 1434-4726
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 70 (1907), S. 213-218 
    ISSN: 1434-4726
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 70 (1907), S. 219-221 
    ISSN: 1434-4726
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Basic research in cardiology 83 (1988), S. 223-228 
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrogenative ring opening of methylcyclobutane and methylcyclopentane was studied over silica-supported Pt and Pd catalysts by kinetic and infrared (IR) spectroscopic measurements. First, the temperature (473-673 K) and hydrogen pressure (3.3-73.2 kPa) dependences of the ring-opening reactions were determined. The reaction rates were determined over the initial and the working catalysts for both compounds. According to the type of product formation vs. hydrogen pressure dependence curves either dissociative or associative adsorption was suggested for methylcyclobutane and methylcyclopentane. The geometry of adsorbed intermediates was proposed on the basis of the regioselectivity of ring opening. The regioselectivity data show close to statistical ring opening for both compounds, which indicate flat-lying adsorbed intermediates. The structure of adsorbed intermediates was also studied by transmission IR spectroscopy. The H-D exchange reactions between the surface hydroxyl groups and adsorbed species in most cases confirmed the type of adsorption suggested by kinetic measurements.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Heteropoly acid catalyzed adamantylation of aromatic compounds (toluene, anisole, fluoro- and bromobenzene) was studied. The catalysts applied were various dodecaheteropoly acids of Keggin- type (Hn[XM12O40]; n=3, 4; X=Si, P; M=Mo, W) and some of their derivatives (Cs2.5H0.5[PW12O40] and heat-treated H4[SiMo12O40]/SiO2). The reaction in each case took place in excellent yield, however, the selectivity strongly depended on the experimental conditions applied. The para-isomer was shown to be formed under kinetic control, whereas para to meta isomerization occurred in the presence of acids with high acid strength (H0≤ -13) during longer reaction time. As a rule, strong acidity dependence was observed for the regioselectivity: the Mo- containing acids yield the para-substituted isomers with high selectivity, whereas the W-containing catalysts result in high meta/para ratios. In addition, using halobenzenes as reactants the formation of adamantane was observed as a product of reductive side reaction. This transformation was found to be significant in the presence of Mo-containing acids due to the redox character of these compounds.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Research in experimental medicine 185 (1985), S. 121-129 
    ISSN: 1433-8580
    Keywords: Brain ischemia ; EEG frequency analysis ; Brain surface oxygen tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Complete cerebral ischemia was carried out in 19 dogs by repeated occlusion of the large neck arteries. The interruption of cerebral blood flow (CBF) was controlled with the electric silence recorded on EEG and the rapid fall of brain surface oxygen tension (bspO2). A critical flow was determined in each experiment by release of clamping of one artery (left carotid artery), which seemed effective not only to stop the decrease of bspO2 but also to ensure the reappearance of EEG waves. This crucial value of carotid artery flow (CAF) was 49 ml/min and 38 ml/min after the first and second occlusions, respectively. The EEG changes during different phases of experiments were stored on magnetic tape and analyzed by computer. The distribution of the analyzed power spectrum of EEG provides a special characterization of brain function. Strict correlations are found between the actual blood flow and the changes of EEG and bspO2. Either alteration of the recorded two parameters can accurately reflect the possibility of brain recovery during and after short-lasting ischemia.
    Type of Medium: Electronic Resource
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