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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Lectin-binding studies were performed at the ultrastructural level to characterize glycoconjugate patterns on membrane systems in pancreatic acinar cells of the rat. Five lectins reacting with different sugar moieties were applied to ultrathin frozen sections: concanavalin A (ConA): glucose, mannose; wheat-germ agglutinin (WGA): N-acetylglucosamine, sialic acid; Ricinus communis agglutinin I (RCA I): galactose; Ulex europaeus agglutinin I (UEA I): l-fucose; soybean agglutinin (SBA): N-acetylgalactosamine). Binding sites of lectins were visualized either by direct conjugation to colloidal gold or by the use of a three-step procedure involving additional immune reactions. The rough endoplasmic reticulum and the nuclear envelope of acinar cells was selectively labelled for ConA. The membranes of the Golgi apparatus bound all lectins applied with an increasing intensity proceeding from the cis-to the trans-Golgi area for SBA, UEA I and WGA. In contrast RCA I selectively labelled the trans-Golgi cisternae. The membranes of condensing vacuoles and zymogen granules were labelled for all lectins used although the density of the label differed between the lectins. In contrast the content of zymogen granules failed to bind SBA and WGA. Lysosomal bodies (membranes and content) revealed binding sites for all lectins used. The plasma membranes were heavily labelled by all lectins except for SBA which showed only a weak binding to the lateral and the apical plasma membrane. These results are in accordance to current biochemical knowledge of the successive steps in the glycosylation of membrane proteins. It could be demonstrated, that the cryo-section technique is suitable for the fine structural localisation of surface glycoconjugates of plasma membranes and internal membranes in pancreatic acinar cells using plant lectins.
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  • 2
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss various possibilities to improve the sensitivity of parity and time reversal asymmetry measurements in gamma decaying nuclei. We compare the best known parity violating case180mHf to a similar isotope178mHf. Although the parity violation may not be as large, the 178 isomer is better suited to eliminate experimental systematic problems. We introduce a new detector to enhance the sensitivity of such measurements. Our first experiments indicate applicability of these detectors to P symmetry tests.
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of pH values suffers from two sources of error. One is the method of calibration of glass electrode cells. Multiple point calibration with linear regression is highly recommended instead of the usual bracketing procedure in cases where a precision of Δ pH〈±0.02 is required. Advantages of this method are discussed, particularly regarding the contribution of the liquid junction potentials to the cell emf. The second uncertainty is caused by batch to batch variations of Standard Reference Materials and their respective standard pH(S), actual values of which are part of the data set of microprocessor-controlled pH meters. Differential potentiometry is proposed as the method of choice to avoid these differences. It results in pH(S) independent of a particular material. Experimental data of the restandardization of pH reference materials are also presented.
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  • 4
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Stripping voltammetry peaks of an iron solochrome violet complex are shown to be strongly effected by anions present in the sample solution. Chloride and sulphate exhibit different dependencies of the peak height as a function of concentration. They have to be taken into account if the results of iron determinations are to be precise as well as accurate (i.e. the same as those obtained by an independent method). Graphite furnace atomic absorption spectrometry, after extraction of the acetylacetone complex, has been used here for comparison purposes.
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  • 5
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract pH Measurements were carried out by means of cells containing Pt/hydrogen and glass electrodes, both equipped with the same type of ground glass sleeve junction carefully selected with respect to the leak rate. The cells were calibrated with the same set of standard buffers using multiple point calibration with linear regression. The slopes of the regression lines were compared with the theoretical (Nernst) slope of the E versus pH function and yielded the electromotive efficiency of the two cells. The accuracy of the measurements was obtained from the residual liquid junction potential errors.
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  • 6
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Anodic (cathodic) stripping voltammetry at the mercury film electrode as well as adsorptive stripping voltammetry at the hanging mercury drop electrode are applied in order to determine trace amounts of heavy and transition metals in alkaline and alkaline-earth metal salts. The procedures used are slightly modified versions of procedures known in sea water analysis. Examples of application include high purity potassium and sodium salts for optical purposes, etching solutions for silicon wafer production and sodium salts for the dialysis technique.
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 8
    ISSN: 1572-8943
    Keywords: alkaline earth hydroxide hydrate ; heat storage materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Entsprechend ihrer hohen spezifischen Schmelzenthalpie und dem Bereich der Schmelztemperaturen sind die Hydrate der Alkalierdmetallhydroxide Ba(OH)2·8H2O und Sr(OH)2·8H2O potentielle Umwandlungswärme-Speichersubstanzen. Die mittels DTA- und DSC-Methoden durchgeführten Untersuchungen des Schmelz- und Erstarrungsverhaltens von Sr(OH)2·8H2O und seinen Gemischen mit Ba(OH)2·8H2O in einem geschlossenen System und mit einer konstanten Makrozusammensetzung führen zu Feststellungen über die Schmelztemperatur und die spezifische Schmelzwärme in Abhängigkeit von der Konzentration. Eine theoretische Speicherdichte von 532 MJ/m3 konnte für das Gemische aus 80% Ba(OH)2·8H2O und 20% Sr(OH)2·8H2O und ein Wert von 655 MJ/m3 für Sr(OH)2·8H2O ermittelt werden. Die Kinetik der Rehydratation zu den Oktahydraten besitzt einen großen Einfluß auf die Speichertemperatur und die Speicherdichte.
    Notes: Abstract Owing to their high specific melting enthalpy and the range of the melting temperatures the alkaline-earth hydroxide hydrates Ba(OH)2·8H2O and Sr(OH)2·8H2O are promising latent heat storage materials. The investigations of the melting and solidification behaviour of Sr(OH)2·8H2O and its mixtures with Ba(OH)2·8H2O, which had been performed by means of DTA and DSC methods in the closed system with a constant gross composition lead to statements on the melting temperature and specific melting enthalpyvs. concentration. Theoretical storage densities of 532 MJ/m3 are obtained for the mixture of Ba(OH)2·8H2O and Sr(OH)2·8H2O (80/20) and a value of 655 MJ/m3 can be achieved for Sr(OH)2·8H2O. The kinetics of rehydration to the octahydrates has a great influence on the storage temperature and storage density.
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  • 9
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Beim thermischen Abbau der Magnesiumsulfathydrate MgSO4.nH2O (n=7; 6; 5; 4; 3; 2; 5/4; 1) unter quasiisothermen- und quasiisobaren Bedingungen werden bei p−0.1 MPa, in AbhÄngigkeit von den Wassergehalten, die Zwischenstufen MgSO4.3H2O; MgSO4.2H2O; MgSO4.H2O sowieΒ-MgSO4 beobachtet. Die erhaltene Monohydratphase ist strukturell mit Kieserit identisch. Der thermische Abbau der Magnesiumsulfathydrate wird wesentlich vom Wasserdampfpartialdruck beeinflu\t.
    Notes: Abstract In the course of thermal decomposition of the magnesium sulphate hydrates MgSO4.nH2O (n=7; 6; 5; 4; 3; 2; 5/4; 1) the intermediate steps MgSO4.3H2O, MgSO4.2H2O, MgSO4.H2O andΒ — MgSO4 are observed under quasi-isothermal and quasi-isobaric conditions atp ≅ 0.1 MPa dependent on the water contents. The structure of the obtained monohydrate phase is identical with that of kieserite. Thermal decomposition of the magnesium sulphate hydrates is essentially influenced by the water vapour partial pressure.
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  • 10
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung In einem abgeschlossenem System wurde unter dynamischen und quasiisothermen und quasiisobaren Bedingungen im Temperaturbereich zwischen 20°C und 300°C oder 600°C das Schmelz- und Zersetzungsverhalten der Doppelsalze MBrMgBr2·6H2O (mitM=K, NH4, Rb, Cs) untersucht. DTA-Heiz- und Kühlzyklen zeigen das Schmelzverhalten der Doppelsalze und geben gleichzeitig Auskunft über den Schmelzpunkt dieser Verbindungen. Die thermische Zersetzung der Doppelsalze unter quasiisothermen und quasiisobaren Bedingungen erfolgt ausgehend von der Schmelze (mit Ausnahme von RbBrMgBr2·6H2O) und unter vermindertem Druck ausgehend vom Feststoff. Ein Doppelsalz des Typs MBrMgBr2·2H2O wird als Zwischenprodukt gebildet. Das Endprodukt bei allen Zersetzungstypen sind basische Produkte mit unterschiedlichem Hydroxidoder Oxidgehalt.
    Notes: Abstract The melting and decomposition behaviour of the double salts MBr·MgBr2·6H2O (M=K, NH4, Rb, Cs) has been investigated in a closed system under dynamic and quasi-isothermal and quasi-isobaric conditions between 20°C and 300°C or 600°C, respectively. DTA heating and cooling cycles illustrate the melting behaviour of the double salts and give information on the melting point of these substances. The thermal decomposition of double salts under quasi-isothermal and quasi-isobaric conditions takes place in the melt (with the exception of RbBr·MgBr2·6H2O) and under reduced pressure in the solid phase. A double salt of the type MBr·MgBr2·6H2O is formed as a stable intermediate. The final product of all types of thermal decomposition are basic products with different hydroxide or oxide contents, respectively.
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