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  • Electronic Resource  (17)
  • 1995-1999  (15)
  • 1965-1969  (2)
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  • Electronic Resource  (17)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 361 (1998), S. 601-602 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photoelectron spectroscopy on pyrolytic carbon films revealed a main part of carbon atoms in graphitic planes and a smaller part of functional groups with oxygen bonded to carbon atoms. Oxygen totalled a share of 10 at% and more of the carbon coating. The films with a turbostratic structure consist of nearly parallel oriented atomic layers of hexagonal rings with dimensions in the nanometer scale, which is well known from HREM investigations. The oxygen atoms are proposed to saturate the numerous dangling bonds around these individual atomic planes. The oxygen atoms form double bonds or bridges between carbon atoms.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Human temporal lobe epilepsy is characterized by strong synaptic reorganization that leads to abnormal recurrent excitatory synaptic connections among hippocampal neurons. In addition, electrophysiological studies show that synaptic activity of the main afferent input to the hippocampus, the perforant path, is prolonged and amplified by changes in postsynaptic glutamate receptors. The current view is that these morphological and physiological abnormalities contribute significantly to the hyperexcitability seen in the hippocampus of temporal lobe epilepsy. Recently, it was found that presynaptic inhibitory metabotropic glutamate receptors are an important negative feedback mechanism that controls synaptic release of glutamate in the hippocampus. In this study, we assessed the functionality of this feedback system by investigating the metabotropic glutamate receptor mediated depression of excitatory synaptic transmission in surgically removed hippocampi from patients with marked synaptic reorganization (Ammon's horn sclerosis group) and from patients without detectable reorganization (lesion group). We report here that this control of synaptic transmission is lost in hippocampi from the Ammon's horn sclerosis group whereas this control is preserved in hippocampi from the lesion group. The data presented here suggest that the loss of feedback inhibition mediated by metabotropic glutamate receptors could be a further, previously not recognized, mechanism in the pathophysiology of temporal lobe epilepsy.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The death of buzzards (Buteo buteo) found in fodder and sugar beet fields treated with granular carbofuran was investigated. To determine if there was a causal relationship between carbofuran treatment and bird mortality, earthworms of a specific fodder beet field as well as the crop contents of dead buzzards were analyzed for carbofuran contamination. Earthworms of the fodder beet field contained carbofuran concentrations up to 3.2 mg/kg, while remains of earthworms and carbofuran were detected in all buzzard crop contents. The carbofuran concentrations found in the earthworms as well as in the crops of the buzzards corroborate the suspicion that the buzzards found on fodder and sugar beet fields treated with granular carbofuran had died of secondary poisoning with carbofuran via contaminated earthworms.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 30 (1996), S. 373-378 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The 96-h toxicity of four organophosphates (thiometon, disulfoton, malathion, and demeton-S-methyl, the oxygen analogue of thiometon) in the freshwater bivalve mollusc Dreissena polymorpha was tested using different nominal concentrations ranging between 6 and 50 mg/L. No mortalities were observed in mussels exposed to malathion and demeton-S-methyl (26 mg/L and 6 mg/L, respectively), and at the lowest concentrations of thiometon and disulfoton (6 and 10 mg/L, respectively). At higher thiometon and disulfoton concentrations, mortalities occurred. At the highest concentrations of 50 mg thiometon/L and 30 mg disulfoton/L, mussel mortalities of 88 and 93%, respectively, were determined. Organophosphate concentrations of up to a factor 10 times higher than in the ambient water were found in exposed mussels, irrespective of whether they were alive or dead. The search for organophosphate metabolites via GC/MS analysis of mussel tissue extracts was negative, suggesting lacking or low oxidative activation of the insecticides used. The mollusc is highly resistant to toxic effects of organophosphate insecticides and their biological active oxygen analogues.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 30 (1996), S. 373-378 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The 96-h toxicity of four organophosphates (thiometon, disulfoton, malathion, and demeton-S-methyl, the oxygen analogue of thiometon) in the freshwater bivalve mollusc Dreissena polymorpha was tested using different nominal concentrations ranging between 6 and 50 mg/L. No mortalities were observed in mussels exposed to malathion and demeton-S-methyl (26 mg/L and 6 mg/L, respectively), and at the lowest concentrations of thiometon and disulfoton (6 and 10 mg/L, respectively). At higher thiometon and disulfoton concentrations, mortalities occurred. At the highest concentrations of 50 mg thiometon/L and 30 mg disulfoton/L, mussel mortalities of 88 and 93%, respectively, were determined. Organophosphate concentrations of up to a factor 10 times higher than in the ambient water were found in exposed mussels, irrespective of whether they were alive or dead. The search for organophosphate metabolites via GC/MS analysis of mussel tissue extracts was negative, suggesting lacking or low oxidative activation of the insecticides used. The mollusc is highly resistant to toxic effects of organophosphate insecticides and their biological active oxygen analogues.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 11 (1965), S. 323-333 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Anhand von über 140 Mikrosondenanalysen von Mineralien der „klassischen Vorkommen” wird in dieser Arbeit versucht die Mischkristallfelder im Dreieckdiagramm der natütlichen Eisen-Kobalt-Nickel-Skutterudite zu ermitteln. Dabei zeigte sick einmal eine wesentlich größere Streuung der Skutteruditanalysen, als dies aus den Analysenangaben und den experimentell bestimmten Mischkristallfeldern der bisherigen Literatur zu vermuten war. Weiterhin konnte ein außergewohnliches Schwanken des Metall-Arsenverhaltnisses zwischen etwa 1:1,9 bis 1: 3,3 bei dieser Mineralart festgestellt werden. Es zeigte sich, daß die niederen Metall-Arsenverhältnisse bevorzugt an die Eisen-Skutterudite, die mittleren mehr an die Kobalt-Skutterudite bzw. an die Kobalt-Nickel-Skutterudite und die höheren bevorzugt an die eigentlichen Nickel- Skutterudite gebunden sind. Während bei den Eisen-Skutteruditen aufgrund der rein mikroskopischen Bestimmung die Möglichkeit eineir Fehldiagnose nicht völlig ausgeschlossen werden kann, erscheint der Nachweis eines fast reinen Nickel- Skutterudites dem Verfasser als gesichert. Das kristallchemisch interessante Problem, wie these großen Stöchiometrie-schwankungen in ein und derselben Struktur ohne wesentliehe Änderungelr auftreten können, versucht der Verfasser durch eine vorwiegend metallische Bindung in einem Legierungstyp zu erklären.
    Notes: Abstract This paper demonstrates with approximately 140 electron micro probe analyses of minerals from the „classic localities” the areas of solid solution in the ternary diagram of the natural iron-cobalt-nickel-skutterudites. The skutterudites analyses show a. much more scattered pattern over all the diagram than presumed by the analyses or by the experimental determined areas of solid solution in the recent literature. Furthermore, a fluctuation in the metalarsenic-ratio between 1:1.9 to 1:3.3 was ascertained for this mineral type. The iron-skutterudites favour the lower metal-arsenic-ratios, the cobalt-skutterudites and respectively the cobalt-nickel-skutterudites more the medium, and the nickel-skutterudites more the higher ratios. With solely microscopic determination of the iron-skutterudite mineral phase an error could be possible, whereas the determination of the nearly pure nickee-skutterudite (which is a new mineral phase) seems certain to the author. Finally, the author tries to explain the extreme fluctuation of stochiometry in the same structure to be caused by a chiefly metalic bond in an alloy type.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract SEM, EDS and GDOES investigations on ferrous ore and slag samples contribute to the local history of mining and metallurgy. Quantitative X-ray analysis confirms the ore to be limonite. The slag consists of fayalithe and incompletely reduced ore parts (iron scale). Additional calcium and charcoal inclusions were reactants of the bloomery process. The charcoal shows anatomical details of spruce (Picea abies (L.) Karst.). A multitude of typical trace elements was detected by GDOES both in ore and slag samples. The comparison of normalised GDOES signals for a series of constituents showed that the ore from the assumed deposit (Euba) was processed in the location (Sternmühlenthal), where the slag was discarded. The process was probably performed in the 17th century.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 361 (1998), S. 653-655 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Investigations on CVD boron nitride films on fibres by means of photoelectron and X-ray spectroscopy resulted in B/N ratios above the stoichiometric value 1 and oxygen contents up to 25 at%. Compared to the hydrolytic rate of the films an apparent dependence was found on the deposition rate and some evidence of the oxygen concentration. CVD fibre coatings exhibit a hexagonal turbostratic structure with extremely small atomic layer plane dimensions, which was proved by transmission electron microscopy. Corresponding to oxygen concentrations in pyrolytic carbon films with similar structure a model is proposed, where the small atomic layers with dimensions of some nanometers cause a relatively high oxygen concentration in the boron nitride films. The oxygen atoms saturate the dangling bonds. Moreover the B/N ratio extents the expected stoichiometric ratio due to the oxygen atoms at nitrogen sites.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 358 (1997), S. 105-107 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Crystalline strontium titanate layers were deposited on titanium anodes from Sr(OH)2 aqueous electrolyte solutions by a plasmachemical-electrochemical process of anodic spark deposition. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to study the properties of the polycrystalline material. Strontium titanate was deposited on the titanium anode surface as a ceramic layer from an aqueous electrolyte. The typical pore structure morphology of the anodic spark deposit (ASD) was characterized by SEM as well as fractures which provide an intimate contact between layer and substrate. XRD-study showed that the layers are composed of a mixture of SrTiO3 and TiO2.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 255-257 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Reinforcement effects in composites are widely influenced by fibre coatings. A detailed understanding of their microstructure and chemical composition is of great interest. Boron nitride films were deposited continuously on fibre rovings of various ceramics in CVD reactors of vertical as well as horizontal position. XPS depth profilings show that the film compositions are close to stoichiometric BN with carbon and oxygen impurities in the range of 10 at%. Cross-sections of separated fibres were investigated by HREM and TEM diffraction. All BN films are hexagonal turbostratic. The (002) layers with an increased distance (about 0.36 nm) showed a mean stacking sequence near to graphite and a characteristic orientation to the fibre in the interface region. We assume the gas flow type and hence the exchange rate of matter and energy determines the film structure in this region. With increasing film thickness the (002) layers fold randomly in all directions or form nanocrystals at elevated temperatures.
    Type of Medium: Electronic Resource
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