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  • Springer  (115)
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  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different acid compositions (HNO3, H2O2, HF and HClO4) and low pressure microwave digestion were applied to the microwave assisted dissolution of ancient peats. The digests were evaluated with respect to the decomposition of the inorganic and organic fraction of peats and to an optimised determination of Pb by differential pulse anodic stripping voltammetry (DPASV). Addition of hydrofluoric acid was necessary to achieve a complete dissolution of the resistant inorganic phase of the peat and to obtain the total Pb concentration. Addition of perchloric acid decreased the concentration of dissolved organic carbon significantly, enabling reliable voltammetric signals for Pb determinations with satisfying peak shape, baseline, sensitivity, and precision. The limit of detection for Pb in peats was 1 ng/mL in the acid digest, equivalent to 0.2 μg/g in solid peat. This allowed the determination of low, pre-industrial concentrations of Pb in peat bogs from various locations (Europe and SE Asia). A chelation column used to isolate the metals from the complex matrix to further improve the detection limits failed to provide good recoveries for the peats and plants.
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  • 2
    ISSN: 1432-1041
    Keywords: Key words Nisoldipine ; Hypertension; Ca antagonist ; pharmacokinetics ; pharmacodynamics ; PK/PD modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Nisoldipine, a calcium antagonist of the dihydropyridine class, has been used in the treatment of hypertension and angina pectoris. A new controlled-release dosage form (nisoldipine coat-core, NCC) has been developed to allow once daily dosing. In addition to a formal food interaction study as requested by regulatory authorities for controlled-release dosage forms, a subsequent study was conducted to determine the clinical relevance of the changes in nisoldipine plasma concentration vs time profiles seen in the food effect study. Methods: After a placebo run-in phase of 6 days, 12 hypertensive patients started treatment with 20 mg NCC once daily (days 0–3, 5–6, 8–9). On days 4, 7 and 10 the NCC was substituted for 5, 10 and 20 mg nisoldipine solution, respectively, in order to obtain nisoldipine plasma concentration vs time profiles comparable to the ones resulting from the concomitant intake of food and NCC. Simultaneous measurements of blood pressure (BP) and nisoldipine concentration were performed on days 3, 4, 7 and 10. Results: The relationship between nisoldipine plasma concentrations and percentage reduction in BP [diastolic (DBP) and systolic (SBP), supine and standing] could be described by an Emax model. The mean maximum reduction (Emax) relative to baseline was about 36.4% and 37.7% (DBP, supine and standing) and 27.9% and 29.2% (SBP, supine and standing), respectively. The interindividual variability (% CV) in Emax was low, ranging from 17.6% to 28.8%. The mean nisoldipine plasma concentration corresponding to 50% of the maximum effect (EC50) ranged between 0.99 and 2.62 μg · l–1 with a pronounced interindividual variability (% CV) of 89.5–108.8%. Mean Cmax values after administration of the 30 and 40 mg NCC together with food were 4.5 and 7.5 μg · l–1, respectively. Based on the concentration-effect relationship established in the present study, the effect achieved with a concentration of 7.5 μg · l–1 will be about 77% of Emax for DBP and about 88% of Emax for SBP, respectively. Conclusion: At the time of maximum plasma concentration the additional decrease in BP relative to baseline due to the food effect will be about 7–15% for DBP and 3–9% for SBP. After administration of the 10␣mg solution with a mean Cmax of 8.7 μg · l–1, only headache and flush with mild severity have been reported as adverse events. These maximum concentrations are comparable to Cmax values seen after intake of 40 mg NCC with food. With regard to heart rate (HR) there were distinct differences between the two formulations: Following administration of 5, 10 and 20 mg nisoldipine solution, there were dose-dependent increases in HR by a maximum of 4, 12 and 16 beats · min−1, respectively, whereas the HR profile for the NCC was similar to that seen under placebo treatment.
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  • 3
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using pre- and post-embedding procedures, neuron-specific enolase and calcitonin were localized in rat thyroid parafollicular cells by light and electron microscopy. Peroxidase-antiperoxidase (PAP), biotin-avidin (ABC) and protein A — colloidal gold techniques were used. In paraffin sections neuron-specific enolase was demonstrated in all calcitonin-storing parafollicular cells in rats aging 1 to 180 days. The post-embedding procedure failed to detect neuron-specific enolase in ultrathin sections, but the enzyme could be demonstrated using a preembedding procedure. Neuron-specific enolase was localized exclusively within the cytosol of parafollicular cells, while calcitonin was localized within secretory granules applying either post- or pre-embedding incubation techniques.
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  • 4
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hypercalcemia was induced in rats by the administration of A.T.10. We then determined the levels of total and ionized calcium and calcitonin in the serum, as well as performed ultrastructural observations and histochemical investigations of the calcitonin and neuron-specific enolase immunoreactivities in the stimulated parafollicular cells. The main aim of the study was to apply histochemical procedures to determine the immunoreactions of calcitonin gene-related peptide (CGRP), somatostatin and secretory protein-I in stimulated parafollicular cells. Immunoreactions of CGRP and calcitonin decreased strikingly in A.T.10-treated animals, whereas no visible changes were noted in somatostatin immunoreactivity. In the case of secretory protein-I, an insignificant increase of its immunoreactivity was observed in the treated animals. The cytophysiological significance of these results is discussed.
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  • 5
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract To establish an electrochemical HPLC detection system which is suitable for the voltammetric characterisation of unknown contaminants and food components at working potentials lower than –1 V, a modified flow-through cell for the use of a hanging mercury drop electrode (HMDE) is described. The introduction of silanised glass capillaries and a new flow-channel design provide a high HMDE lifetime, which is recommended in HPLC detection. As test system the herbicides diquat, paraquat and difenzoquat and ethylviologen as internal standard were measured using differential pulse voltammetry (DPV) detection to improve selectivity. Spiked water samples were analysed with voltammetric and UV-detection and results agreed well.
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  • 6
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Although feline salivary glands have been used in investigations on secretion and microlithiasis and both processes involve calcium, nothing is known about its distribution in these glands. Therefore we have demonstrated the presence of calcium by a histochemical technique using glyoxal bis(2-hydroxyanil) and a biochemical technique using dry ashing. The histochemical technique stained serous acinar cells weakly and rarely found mucous acinar cells strongly in the parotid gland, mucous acinar cells moderately to strongly and serous acinar cells weakly in the sublingual gland, and central and demilunar acinar cells moderately to strongly in the submandibular gland. The biochemical technique revealed less calcium in the parotid than in the submandibular and sublingual glands. Both techniques revealed a decrease of calcium in submandibular and sublingual glands following parasympathetic stimulation. The histochemical distribution of calcium, which corresponds to that of acinar secretory glycoprotein, and the loss of calcium following parasympathetic stimulation, which causes release of secretory granules, indicate the presence of calcium in secretory granules. The concentration of calcium in the different types of acinar cell corresponds to the acidity of the secretory glycoprotein and suggests that calcium is present as a cationic shield to allow the condensation of polyionic glycoprotein in secretory granules.
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  • 7
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method of deducing airborne particle size distributions from the deposition on a collector is described. The method basically consists in collecting submicron-sized particles on whisker filters for subsequent electron-microscopic examination. The empirical size distributions on the collectors can be approximated by log-normal functions. Moreover, it has been found that the variation in particle distribution across a four-stage whisker filter can be interpreted on the basis of a simple model of the collection process. The effective absorption coefficient derived from this modeling is used to correct the empirical data for the effect of a selective collection characteristic.
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  • 8
    ISSN: 1432-1041
    Keywords: Pharmacokinetics ; Caucasians ; Repirinast ; Antiallergic drug ; single dose ; oral administration ; metabolite ; BAY w 8199
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of BAY w 8199, the active metabolite of the prodrug repirinast (BAY u 2372), has been investigated after oral administration of 150, 300 and 450 mg repirinast to twelve healthy male Caucasians. Plasma BAY w 8199 concentrations were very variable between subjects. The mean peak level (geom. mean; 1s-range) was 0.14 (0.08–0.25), 0.19 (0.13–0.29) and 0.24 (0.14–0.42) mg/l after the 150, 300 and 450 mg doses, respectively. Peak levels were reached 0.5–2.5 h after drug intake. Terminal half-lives were calculated as 5.9 h (150 mg), 8.0 h (300 mg) and 9.8 h (450 mg). The dose proportionality of the plasma profiles of BAY w 8199 and of its excretion in urine was demonstrated by testing several parameters. About 7.4% of each dose (calculated as BAY w 8199) was excreted in urine over 36 h. The renal clearance of about 27 l/h suggests that BAY w 8199 is excreted by tubular secretion in addition to glomerular filtration.
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  • 9
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Contents Starting from a model of a g.o. silicon-iron sheet with ideal goss-texture and an in-plane misoriented grain in the center the magnetization, the structure of the inner field and of the flux density in dependence on the external applied field are shown so that the deterioration of the flux guidance caused by such misoriented grains becomes visible.
    Notes: Übersicht Ausgehend von einem Modell eines kornorientierten Silizium-Eisenbleches mit idealer Goss-Textur und einem in der Blechebene fehlorientierten Korn im Zentrum werden die Magnetisierung, die Struktur des inneren Feldes und die Flußdichte berechnet. Die Struktur des inneren Feldes und der Flußdichte wird in Abhängigkeit vom aussteuernden Feld dargestellt, so daß die Verschlechterung der Flußführung durch derartig fehlorientierte Körner sichtbar wird.
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  • 10
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Contents From a survey of the important stray-field sources of a grain oriented M-shaped silicon-iron sheet follows that only the stray field at the air gap can give a remarkable contribution to the stray-field coupling. The influence of this air-gap stray fields on the magnetization structure and the magnetization reversal of a neighbouring sheet is investigated. From the shielding effect of the neighbouring sheet in dependence on the excitation in an applied field some statements concerning the influence of the stray-field coupling on the energy loss and the efficiency of the complete transformer core consisting of several sheets are derived and some proposals for the improvement of the efficiency during voltage transformation are given.
    Notes: Übersicht Aus einem vergleichenden Überblick über die wesentlichen Streufeldquellen eines M-Schnitt-Bleches aus kornorientiertem Silizium-Eisen folgt, daß nur das Luftspaltfeld einen merklichen Anteil zur Streufeldkopplung liefern kann. Der Einfluß dieses Luftspalt-Streufeldes auf die Magnetisierungsstruktur und den Ummagnetisierungsvorgang in einer benachbarten Blechlage wird untersucht. Aus einer Diskussion der abschirmenden Wirkung des benachbarten Bleches in Abhängigkeit von der Aussteuerung folgen Aussagen über den Einfluß der Streufeldkopplung auf die Energieverluste und den Wirkungsgrad des kompletten Transformatorkernes aus mehreren Blechlagen und Vorschläge zur Verbesserung des Wirkungsgrades bei der Spannungswandlung.
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