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  • 1
    Monograph non-lending collection
    Monograph non-lending collection
    [München] : [Piloty & Loehle]
    Call number: H G 6430
    Type of Medium: Monograph non-lending collection
    Pages: S. 24-127, 10 Bl. : Ill.
    Location: Pendulum room
    Branch Library: GFZ Library
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A two layer perceptron with backpropagation of error is used for quantitative analysis in ICP-AES. The network was trained by emission spectra of two interfering lines of Cd and As and the concentrations of both elements were subsequently estimated from mixture spectra. The spectra of the Cd and As lines were also used to perform multiple linear regression (MLR) via the calculation of the pseudoinverse S+ of the sensitivity matrix S. In the present paper it is shown that there exist close relations between the operation of the perceptron and the MLR procedure. These are most clearly apparent in the correlation between the weights of the backpropagation network and the elements of the pseudoinverse. Using MLR, the confidence intervals over the predictions are exploited to correct for the optical device of the wavelength shift.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 31-36 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode array detection ; UV library search ; Pharmaceutical compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for spectral library search based on the dependences of absorbance on the modifier contents in binary mobile phases was developed. The normalisation of spectra by absolute and relative maximum and with respect to the area was tested. The correlation coefficient and the Euclidian distance were used to compare the spectra. The new method of library search allows interpolation of spectra at every composition of eluent in the model range. The range is bracketted by the upper and lower content of modifier in the eluent. In this range five reference spectra were recorded. For validation 34 spectra of pharmaceutical substances in water/methanol and water/acetonitrile mixtures were recorded. In the best case 97 % of spectra were identified correctly. The main problems encountered are that very similar substances e.g. dexa- and betamethasone, have similar spectra as well as similar spectral dependences on the composition of the mobile phase.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Jahn-Teller Effect and Crystal Structure Distortion of the Copper Fluoroperovskites NaCuF3 and RbCuF3The crystal structures of triclinic NaCuF3 (a = 539.1, b = 555.2, c = 792.8 pm, α = 90.66, β = 92.05, γ = 86.95°; P1, Z = 4) and of tetragonal RbCuF3, isotypic with KCuF3, (a = 602.3, c = 791.2 pm; I4/mcm, Z = 4), were determined by x-ray methods and refined to wR = 0.038 (2113 reflections) resp. 0.039 (257 reflections). The structures derive from orthorhombic (GdFeO)3 and cubic perovskite type, resp., by Jahn-Teller distortion. The CuF64- octahedra, differently elongated in the two compounds (average NaCuF3: Cu—F = 188.9/197.3/225.6(2) pm; RbCuF3: 188.3/197.8/237.6(3) pm), show the same pattern of antiferrodistortive ordering, but there are bent bridges Cu—F—Cu = 144.2…148.0(1)° in NaCuF3. Structural relations to the prototypes mentioned and to comparably Jahn-Teller distorted copper fluoro compounds are discussed.
    Notes: Die Kristallstrukturen des triklinen NaCuF3 (a = 539,1, b = 555,2, c = 792,8 pm, α = 90,66, β = 92,05, γ = 86,95°; P1, Z = 4) und des tetragonalen, mit KCuF3 isotypen RbCuF3 (a = 602,3, c = 791,2 pm; I4/mcm, Z = 4) wurden röntgenographisch bestimmt und auf wR = 0,038 (2113 Reflexe) bzw. 0,039 (257 Reflexe) verfeinert. Die Strukturen leiten sich vom orthorhombischen (GdFeO3-) bzw. kubischen Perowskit-Typ durch Jahn-Teller-Verzerrung ab. Die in beiden Verbindungen unterschiedlich gestreckten CuF64--Oktaeder (Mittelwert NaCuF3: Cu—F = 188,9/197,3/225,6(2) pm; RbCuF3: 188,3/197,8/237,6(3) pm) sind nach demselben Muster antiferrodistortiv geordnet, jedoch unter Winkelung Cu—F—Cu = 144,2…148,0(1)° in NaCuF3. Strukturelle Beziehungen zu den genannten Prototypen und zu vergleichbar Jahn-Teller-verzerrten Kupfer-Fluorverbindungen werden diskutiert.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Progress in biocompatibility and tissue engineering would today be inconceivable without the aid of in vitro techniques. Endothelial cell cultures represent a valuable tool not just in haemocompatibility testing, but also in the concept of designing hybrid organs. In the past endothelial cells (EC) have frequently been used in cytotoxicity testing of materials, especially polymers, used in blood-contacting implants, as well as for investigating seeding technologies for vascular prostheses. At present the exponential development both in theory and practice of cell and molecular biology of the endothelium offers great promise in the biomaterial field. Up until now this EC research field has mostly been non-biomaterial orientated. Nevertheless, the relevance for biomaterial research is apparent. Four aspects will be concisely reviewed under the headings inflammation, with special reference to cell adhesion molecules (CAMs) and cytokines, angiogenesis, focusing on the healing response, signal transduction, presenting examples from cytokine- and metal ion-induced up-regulation of genes coding for CAMs, and, finally, endothelial functionality, with emphasis on the principal characteristics of the physiological endothelial phenotype. Finally, the application of these fields to three foci of biomaterial research will be discussed, emphasizing the role of EC culture techniques in controlling the host response to biomaterials (microvascular EC), controlling EC functionality (promoting positive effects and down-regulating negative effects), and tissue engineering (integration of EC into hybrid organs/biosensors). The need for more co-culture and three-dimensional models will be stressed and data from the authors’ laboratory presented to illustrate these principles. © 1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Deleterious effects of dental alloys, especially those of dental amalgams, have become an important issue in current discussions on biomaterials. Cytotoxicity and further related risks of amalgams are discussed in a controversial way in the literature without leading to a final conclusion. There is still a need for basic clinical and pre-clinical research, especially with respect to the wide distribution of dental amalgams. Standardized methods of cytotoxicity testing have been established by the ISO. It was the aim of the present study to detect and compare possible cytotoxic effects of dental amalgams and alternative non-amalgam alloys in vitro. According to the ISO standards, direct contact tests and extract dilution tests were performed using the cell lines HeLa and L-929 as well as primary isolated human fibroblasts, a relevant cell type of the human gingiva. For direct contact tests the samples were fixed on thermanox discs. Zn and Ni-chloride in defined molar concentrations were used as positive controls in the extract dilution tests, while copper was the positive control in the direct contact tests. The tested amalgam was a Non-Gamma-2 amalgam. For extract dilution tests sixteen extraction dilutions were performed. The different cell types were incubated with the extracts in 96-well microtitre plates. MTT-testing was performed to evaluate the effects on cellular metabolism. The BrdU labelling index was determined with the help of EIA methods to analyse the effects of the extracts on the cellular proliferation at DNA synthesis level. The morphological status of the cells seeded on the materials (direct contact test) were studied with the help of light microscopy. No cytotoxic effects of formerly extracted dental amalgam was found, although fresh amalgam elicited a significant cytotoxic effect, in general the non-amalgams have to be regarded as non cytotoxic. The negative control and the non-amalgams elicited no measurable cytotoxicity in the indirect contact assays, independent of the number of extraction dilutions. This applied to all cell types studied. The tested amalgam also gave a significant cytotoxic effect in the MTT-assays, while in addition a significant reduction of BrdU incorporation after incubation with the extracts of the first dilution series, compared to the silicone control was found. The effects were reduced after an incubation with the extracts of the higher dilution series. It is suggested by the presented results that amalgams might have cytotoxic effects, especially when being freshly applied. The cytotoxic effects were no longer detectable after extraction procedures. Nevertheless, a negative effect around such amalgams must be considered. The insights provided by the present studies might be helpful for a rational choice of dental materials.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The past two decades have witnessed a revolution in our understanding of chemical processes in living organisms. This is mainly a result of the massive advances in the fields of cell and molecular biology. These techniques are highly relevant to the biomaterials sector, as they offer the scientist the possibility to better understand the mechanisms involved in the interactions between cells and a material surface—a prerequisite for the rational development of medical devices with optimal biocompatibility. The purpose of the present article is to explain the rationale of the cell and molecular biological approach to biomaterial research and to present typical examples from the authors’ laboratory, as well as from the literature, to illustrate its application. Important aspects of interfacial biology, including the underlying biological mechanisms and methodology, are presented. Of the latter the combination of morphological techniques with methods of cell and molecular biology as well as molecular genetics (so-called “combinative techniques”) are particularly useful. The applicability of this approach is illustrated from a study on the pathomechanisms of metal ion-induced inflammation. In addition, the approach is essential to the development of targeted intervention strategies, as for example in the luminal surface modification of vascular prostheses to permit endothelial cell seeding.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The increasing number of patients requiring prosthetic substitution of segments of the vascular system strongly supports the need to optimize a relevant, standardized testing panel for new materials designed for synthetic vascular prostheses. The ISO gives the standard requirements for testing biomaterials provided for implantation. Our primary interest was the establishment of a reliable in vitro panel as a useful and relevant screening system for vascular implant devices to evaluate blood/device interactions under flow conditions. The aim of the present study was to evaluate influences of different flow conditions on blood cell–biomaterial interactions with special emphasis on the interactions of human granulocytes (PMN) and polymeric surfaces. PMN were isolated and vital cells were quantified by flow cytometrical analysis directly before, as well as immediately after the experiments. The viscosity of the final cellular suspension was analysed by using a computerized cone-plate rheometer. As reference materials we used FEP-teflon, PVC-DEHD, PU, PP and PE. Dacron and ePTFE synthetic vascular protheses were tested in a comparative way to those references. The adhesion processes were observed over a period of 40 minutes under arterial (shear stress 0.74 Pa) and venous (shear stress 0.16 Pa) flow conditions in a parallel plate flow chamber system under highly standardized conditions and laminar flow. The cells were observed with the help of inverse light microscopy. Cell behaviour was recorded and analysed in both analogue (video) and digital (imaging system) modes. Samples of the cell suspensions were obtained at regular time intervals and analysed by enzyme linked immuno sorbent assay (ELISA) to quantify LTB4 release. Irrespective of the material, approximately 3 to 4 times more PMN adhered to the biomaterial surfaces under venous flow conditions compared to the arterial. Shear intensity did not influence the running order of biomaterials with respect to cell numbers. This response in descending order at the end of the experiments was as follows: PU, PVC-DEHD, PP, PE and ePTFE. The biochemical analyses indicate that in the system used only a weak effect on LTB4 release induced by the different materials could be determined. A significant effect caused by flow conditions was not observed. Further experiments, both static as well as dynamic, must be performed for multiple, relevant parameters of haemocompatibility, for potential biomaterials as well as those currently in use in vascular prostheses.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Zur Erhöhung der Selektivität katalytischer Methoden kann das zu bestimmende Metallion extrahiert und anschließend katalytisch in nichtwäßrigem Medium bestimmt werden. Diese Möglichkeit wird an Hand der Bestimmung von Kupfer demonstriert. Als Indikatorreaktion diente die Cu-katalysierte, durch Pyridin aktivierte Oxydation von Sulfanilsäure durch Wasserstoffperoxid. Kupfer wird als ein Gemischt-Ligand-Komplex mit Pyridin und Salizylat in Chloroform extrahiert, den Extrakt gibt man direkt zu den in Äthanol gelösten Reagenzien. Unter günstigsten Bedingungen konnte Cu(II) in einem Konzentrationsbereich von 3–60 ng/ml bestimmt werden. Der Variationskoeffizient betrug für 30 ng Cu/ml 11,2%. Der Einfluß verschiedener Fremdionen wurde untersucht und die Selektivität des extraktionskatalymetrischen Verfahrens mit einer katalytischen Bestimmung ohne Extraktion verglichen.
    Notes: Summary The selectivity of catalytic methods can be increased if the metal ion to be determined is extracted and then determined catalytically in non-aqueous medium. This possibility is demonstrated for the example of copper determination based on its catalytic effect on the oxidation of sulphanilic acid by hydrogen peroxide, activated with pyridine. Copper is extracted as a mixed pyridine salicylate complex, with chloroform, and the extract is added directly to the solution of all reagents in ethanol. By selection of the most suitable conditions copper can be determined in the range 3–60 ng/ml. The coefficient of variation of the method was 11.2% for 30 ng of Cu(II)/ml. The influence of various metal ions was compared for the catalytic determination with and without extraction.
    Type of Medium: Electronic Resource
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