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  • 1
    ISSN: 1432-0819
    Keywords: Key words Stromboli ; Neostromboli ; Orthocumulates ; Monzonites ; Magma chamber processes ; Geothermobarometry ; Flank collapse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We describe texture, mineralogy and whole-rock composition of cognate monzonite sub-volcanic clasts within debris flow deposits related to the 5000 years catastrophic phreatomagmatic eruption probably linked to the Sciara del Fuoco sector collapse. The debris flows are at the top of accretionary lapilli-rich ash deposits overlying potassic (KS, shoshonites) lavas of the Neostromboli period. The monzonites are inferred to be crystallized in situ, at low P, at the side walls and/or roof margins of a shallow magma chamber and to be cogenetic with the KS Neostromboli extrusives. They can be considered "ideal orthocumulates" since they approximately retain a bulk liquid composition and possibly represent "slowly cooled equivalents" of their KS shoshonite host rock. The "closure temperature" of final solidification of the monzonite lithic suite was estimated through ternary-feldspar geothermobarometry, plagioclase–K-feldspar and K-feldspar–biotite equilibria and is in the range of 750–790  °C with a maximum –logfO2 around 15.1–15.3. The estimated pressure of crystallization is 〈0.5 kbar. Potassic lavas and dikes, previously emplaced during the Neostromboli period, also resemble the monzonites in both major trace elements and mineral chemistry. The cogenetic relationship between KS Neostromboli extrusives and the monzonite host-rock magma from which the sub-volcanic clasts were derived is clear evidence that a shallow magma chamber existed between the caldera collapse of the Vancori period and the Sciara del Fuoco sector collapse (i.e. between 13 000 and 5000 years). The monzonite clasts were derived from crystallization at very shallow depth (ca. 1 km) and strongly support the hypothesis of violent decompression of the shallow magmatic plumbing system during the Sciara del Fuoco sector collapse. Climax of the regressive landslide event, with maximum disruption of the chamber walls, took place during emplacement of the debris flows, i.e. during the late stage of the Neostromboli phreatomagmatic eruption.
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  • 2
    ISSN: 1573-904X
    Keywords: iontophoresis ; transdermal delivery ; calcitonin ; reservoir ; peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of the work was to study iontophoretic transdermal administration of salmon calcitonin (sCt) in rabbits, with particular attention to drug reservoir composition. A dry sCt disc, to be dissolved on the application site, was used for preparing the reservoir for transdermal iontophoresis. As a reference drug reservoir, a pad wetted with drug solution was used. Methods. Experiments were done in rabbits depositing 100 IU of salmon calcitonin on skin and applying anodal iontophoresis. Serum calcium concentration was measured during iontophoresis, passive diffusion and after i.v. administration. Parameters such as pH value and reservoir type were examined. Results. Transdermal iontophoresis of sCt elicited a decrease in the serum calcium level, whereas, in the absence of electric current, no significant fall was measured. Using the reservoir prepared from drug solution, anodal iontophoresis at pH 4.2 was more effective than at pH 7.4, probably due to higher sCt net positive charge. Using the reservoir prepared from dry disc, similar kinetics and extent of drug effect were observed at both pH values. The reservoir prepared from solid drug deposit concentrated sCt next to the skin. Conclusions. Anodal iontophoresis for transdermal calcitonin administration shows therapeutical applicability. The type of reservoir is an important parameter affecting sCt transdermal iontophoresis.
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  • 3
    ISSN: 1573-904X
    Keywords: transdermal ; iontophoresis ; prodrug ; DHEA ; skin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of this work was to synthesize ionized dehydroepiandrosterone (DHEA) prodrugs with higher water solubility, useful for iontophoretic transdermal application. Methods. The synthesized derivatives were characterized and tested for sensitivity to chemical and enzymatic hydrolysis. Solid state and solution stability was also determined. Transdermal iontophoretic anodal transport in vitro was studied using excised rabbit skin. Results. Two DHEA ionized prodrugs were synthesized: PRO1, a primary amine derivative, and PRO2, a quaternary ammonium salt. The two derivatives possess higher water solubility and lower octanol/saline partition coefficients than DHEA. Prodrugs were sensitive to enzymatic hydrolysis; in particular the primary amine was hydrolyzed faster than the quaternary salt by esterase from porcine liver in vitro. Transdermal flux of the two prodrugs was slightly higher than the parent drug. In the case of passive diffusion, only DHEA was found in the receptor compartment, indicating the complete breakdown of the prodrug in the skin. Current application gave higher drug flux and a significant amount of prodrug was found in the receptor. Conclusions. The use of ionized prodrugs of DHEA can increase the flux attainable during transdermal anodal iontophoresis by up to 7 times, but they are useful for passive transport as well.
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  • 4
    ISSN: 1573-904X
    Keywords: iontophoresis ; acyclovir ; electroosmosis ; electrorepulsion ; transdermal delivery ; nude mouse skin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Iontophoresis was employed for enhancing the transdermal delivery of acyclovir through nude mouse skin in vitro, with the aim of understanding the mechanisms responsible for drug transport, in order to properly set the conditions of therapeutical application. Methods. Experiments were done in horizontal diffusion cells, using as donor a saturated solution of acyclovir at two different pH values (3.0 and 7.4). Different electrical conditions (current density and polarity) were employed. Results. At pH 3.0, acyclovir anodal transport was due to electrorepulsion, since acyclovir was 20% in the protonated form. In acyclovir anodal iontophoresis at pH 7.4 the main mechanism involved was electroosmosis, since the drug was substantially unionized and the negative charge of the skin at this pH caused the electroosmotic flow to be from anode to cathode. In the case of cathodal iontophoresis at pH 3.0, acyclovir transport was enhanced approx. seven times, due to the presence of an electroosmotic contribution caused by the reversal of the charge of the skin. At pH 7.4 during cathodal iontophoresis acyclovir transport was not enhanced because the electroosmotic flow was in the opposite direction, compared to drug electric transport, i.e. anode to cathode. The increased skin permeability caused by current application was demonstrated to be less important than electrorepulsion and electroosmosis. Conclusions. Anodal iontophoresis shows potential applicability for enhancing acyclovir transport to the skin, considering that both electric transport and electroosmosis can be used by appropriately setting the pH of the donor.
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  • 5
    ISSN: 1573-904X
    Keywords: nasal powder ; powder properties ; nasal powder delivery ; insufflation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Delivery of nasal powders of granulated β-cyclodextrin by insufflation was studied in order to find the relationship between powder properties and delivery behavior. Methods. Three nasal powder formulations, prepared by granulating β-cyclodextrin with different binders, were delivered from a powder insufflation device, in which the dose to be emitted was loaded in a gelatin capsule. The delivery sequence of powder was recorded and characterized using an image analysis program. Results. Particle size was the main parameter affecting nasal powder delivery, both as to the amount of dose sprayed and the aspect of cloud produced. Between 50–150 µm of particle size a substantial change in delivery behavior of powders was observed. Powder of around 100 µm in size showed useful insufflation characteristics for nasal delivery. Bioavailability of nasal formulations of progesterone/β-cyclodextrin powders was discussed in term of delivery behavior. Conclusions. The formulation approaches for improving nasal delivery of powders require the use of size optimized carriers. Insufflation of powders over 50 µm can favour the particle deposition by impaction, whereas for powders below 50 µm, deposition by sedimentation is moved. β-cyclodextrin is a suitable carrier for achieving high systemic availability following nasal administration of powder formulations.
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  • 6
    ISSN: 1573-0778
    Keywords: hepatocyte ; isolation ; membrane junctions ; electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A transmission E/M, scanning E/M and freeze fracture ultrastructural study has been performed on the rat hepatocyte in the course of isolation from the liver parenchyma. The cell submicroscopic aspect indicates a good morpho-functional preservation from the liver perfusion to the final stages of cell isolation. The freeze fracture membrane analysis evidentiates the constant presence of gap junctions and tight junctions, characterized by particular structural alterations, probably due to progressive functional uncoupling. The persistence of these cell differentiations until complete cell isolation may be considered a further morphological expression of the maintenance of the differentiated stage of the hepatocyte. Fragments of membranes from adjacent cells, still adherent to isolated hepatocyte surfaces, can also be occasionally detected by freeze-fracture techniques.
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  • 7
    ISSN: 0263-6484
    Keywords: Nuclear inositol lipids ; inositol-specific phospholipase C ; glucocorticoids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The possibility that inositol lipid metabolism is related to nuclear events accompanying steroid hormone action has been investigated by comparing lipid phosphorylation and breakdown in normal rat liver nuclei and in hypo- and hypercortisolemic conditions. Lipid phosphorylation in vitro showed the presence of diacylglycerol (DAG)-, phosphatidylinositol (PI)- and phosphatidylinositol-4-phosphate (PIP)-kinase activity, with differences between total tissue homogenates and isolated nuclei, relevant to the treatment in vivo. Administration of hydrocortisone (HC) produced a marked decrease in the phosphorylated nuclear products without influencing the homogenate kinase activity. Under conditions which were optimal for the kinase activities, nuclear PIP-kinase was strongly increased in presence of a high blood level of HC whereas PI-kinase activity was reduced. From these observations it appears that the observed differences were due to specific modulation of kinase activities rather than to changes in the availability of substrates.The phosphoinositide-specific phospholipase C (PLC) activity was also investigated. In the presence of a high HC blood level, the phosphodiesteratic cleavage of PIP strongly increased, while that of phosphatidylinositol bisphosphate (PIP2) was similar in normal and hypercortisolemic conditions. Nuclear phosphoinositide hydrolysis was affected by PLC, β and γ isoforms, which were equally represented in all the conditions investigated, indicating that the observed changes of activity were due to a modulation rather than to a change in the amount of enzyme.These results suggest that inositol lipid metabolism plays a role in the nuclear modifications accompanying steroid hormone induction of transcriptional activity.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2007-10-08
    Description: Thermal and porosimetric properties of different lithotypes of pietra ollare' (magnesite-bearing talc-shists, chlorite-schists, tremolite-bearing chlorite-schists and serpentine-schists) from the Italian Central Alps (Valchiavenna and Valmalenco) have been investigated. Some cross-correlations are established among the main mineral--petrographic and textural features, thermal behaviour and historical utilization of these lithotypes for the production of stoves and cooking pots during the Middle Ages. All the analysed samples show (1) low total open porosity (0.73-2.85%) with meso- and micropores prevailing over macropores; (2) regular linear expansion up to c. 700 {degrees}C, good thermal stability up to 1200 {degrees}C and negligible weight loss (〈 1%) to c. 500 {degrees}C; (3) high thermal expansion (5.57 x 10-6 {degrees}C-1 〈 {alpha}25-100 {degrees}C 〈 8.89 x 10-6 {degrees}C-1). The results indicate that, under the thermal conditions typical of the traditional medieval open fire system' (T [≤] 600 {degrees}C), the Italian pietra ollare' from the Central Alps was an excellent fire-resistant geomaterial, which did not undergo any significant transformation as a result of thermal shocks.
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  • 9
    Publication Date: 1997-09-23
    Description: We describe texture, mineralogy and whole-rock composition of cognate monzonite sub-volcanic clasts within debris flow deposits related to the 5000 years catastrophic phreatomagmatic eruption probably linked to the Sciara del Fuoco sector collapse. The debris flows are at the top of accretionary lapilli-rich ash deposits overlying potassic (KS, shoshonites) lavas of the Neostromboli period. The monzonites are inferred to be crystallized in situ , at low P, at the side walls and/or roof margins of a shallow magma chamber and to be cogenetic with the KS Neostromboli extrusives. They can be considered "ideal orthocumulates" since they approximately retain a bulk liquid composition and possibly represent "slowly cooled equivalents" of their KS shoshonite host rock. The "closure temperature" of final solidification of the monzonite lithic suite was estimated through ternary-feldspar geothermobarometry, plagioclase–K-feldspar and K-feldspar–biotite equilibria and is in the range of 750–790  °C with a maximum –logfO_2 around 15.1–15.3. The estimated pressure of crystallization is 〈0.5 kbar. Potassic lavas and dikes, previously emplaced during the Neostromboli period, also resemble the monzonites in both major trace elements and mineral chemistry. The cogenetic relationship between KS Neostromboli extrusives and the monzonite host-rock magma from which the sub-volcanic clasts were derived is clear evidence that a shallow magma chamber existed between the caldera collapse of the Vancori period and the Sciara del Fuoco sector collapse (i.e. between 13 000 and 5000 years). The monzonite clasts were derived from crystallization at very shallow depth (ca. 1 km) and strongly support the hypothesis of violent decompression of the shallow magmatic plumbing system during the Sciara del Fuoco sector collapse. Climax of the regressive landslide event, with maximum disruption of the chamber walls, took place during emplacement of the debris flows, i.e. during the late stage of the Neostromboli phreatomagmatic eruption. ©1997 Springer-Verlag Berlin Heidelberg
    Print ISSN: 0258-8900
    Electronic ISSN: 1432-0819
    Topics: Geosciences
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  • 10
    Publication Date: 2020-02-01
    Description: Many buildings of the historic centre of Urbino (Marche, Central Italy), included in the UNESCO World Heritage List, are characterized by portals consisting of sedimentary rocks such as limestones or sandstones. In order to identify the possible quarries of provenance of sandstones used for architecture, we addressed our research to the Sant'Ippolito area (20 km ESE of Urbino), where historical stonemasons have been extensively documented since the 14th century. Few traces of ancient exploitation indicate some extraction sites. All the investigated rocks (both from monumental portals of Urbino and geological outcrops) consist of fine to medium grainsize sandstones with a variable content of bioclasts. Two different groups were recognized (using the petrographic Q-F-R classification diagram): (i) lithic arenites belonging to the Colombacci Formation; and (ii) feldspathic lithic arenites referable to the Tripoli Unit. In particular, petrographic data indicate that the sandstones used in the historical buildings of Urbino, come from the arenitic lithofacies of the Messinian p.p. Colombacci Formation of the Sant'Ippolito area. In addition, comparative geochemical studies of whole rock major and trace elements point out three outcrops, of the above formation, as possible sites of ancient extraction. Sandstones of the Tripoli Unit and the Marnoso-Arenacea Formation, widespread in the study area and near Urbino respectively, are ruled out as source rocks, based on both petrographic and geochemical data. Anomalously high values of some heavy elements such as Pb, Zn and As, recognized in some of the portals, likely derive from a combination of various anthropogenic sources of pollution close to the investigated monuments, such as domestic heating and emissions from road traffic in the past. From a mechanical point of view, the uniaxial compressive strength tests, carried out on a representative number of selected samples of the Colombacci Formation lithic arenites, yelded low values and high variability. Other investigated physical parameters also indicate that the stones used for the portals did not represent a good choice as building material. This implies that the stonemasons of Sant'Ippolito chose local raw materials for their availability, aesthetic qualities and good workability, rather than structural properties.
    Print ISSN: 2038-1719
    Electronic ISSN: 2038-1727
    Topics: Geosciences
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