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  • 1
    Publication Date: 2020-11-30
    Description: During the 1982–1984 bradyseismic crises in the Campi Flegrei area (Italy), the University of Wisconsin deployed a network of seismological stations to record local earthquakes. In order to analyse the potential of the recorded data in terms of tomographic imaging, a blind test was recently set up and carried out in the framework of a research project. A model representing a hypothetical 3D structure of the area containing the Campi Flegrei caldera was also set up, and a synthetic dataset of time arrivals was in turn computed. The synthetic dataset consists of several thousand P- and S-time arrivals, computed at about fourteen stations. The tomographic inversion was performed by four independent teams using different methods. The teams had no knowledge of either the input velocity model or the earthquake hypocenters used to create the synthetic dataset. The results obtained by the different groups were compared and analysed in light of the true model. This work provides a thorough analysis of the earthquake tomography potential of the dataset recording the seismic activity at Campi Flegrei in the 1982–1984 period. It shows that all the tested earthquake tomography methods provide reliable low-resolution images of the background velocity field of the Campi Flegrei area, but with some differences. However, none of them succeeds in detecting the hypothetical structure details (i.e. with a size smaller than about 1.5–2 km), such as a magmatic chamber 4 km deep and especially the smaller, isolated bodies, which represent possible magmatic chimneys and intrusions.
    Description: Published
    Description: Article ID 505286
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: N/A or not JCR
    Description: restricted
    Keywords: Campi Flegrei ; Tomography ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2020-02-11
    Description: We present the results of a tomographic study performed in the framework of the 3F-Corinth project. The aim of this work is to better understand the rifting process by imaging the crustal structure of the western Gulf of Corinth. Forty-nine stations were deployed for a period of six months, allowing us to monitor the microseismicity. Delayed P and S first-arrival times have been simultaneously inverted for both hypocenter locations and 3-D velocity distributions. We use an improved linearized tomography method based on an accurate finite-difference travel-time computation to invert the data set. The obtained Vp and Vs models confirm the presence of a two-layer vertical structure characterized by a sharp velocity gradient lying at 5–7 km depth, which may be interpreted as a lithological contrast. The shallower part of the crust (down to 5 km depth) is controlled by the N-S extension and lacks seismicity. The deeper part (7–13 km depth) matches the seismogenic zone and is characterized by faster and more heterogeneous anomalies. In this zone, the background seismicity reveals a low-angle active surface dipping about 20° toward the north and striking WNW-ESE. The position of this active structure is consistent with both high Vp/Vs and low Vp.Vs anomalies identified at 8–12 km depth and suggesting a highly fracturated and fluid-saturated zone. Both the geometry of the active structure beneath the gulf and the presence of fluids at 8–12 km depth are in accordance with a low-angle detachment model for the western part of the Gulf of Corinth.
    Description: Published
    Description: 431–453
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 2 (1991), S. 202-204 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A fibre optic biosensor involving immobilized bioluminescence enzymes associated with a glass fibre bundle has been designed. The firefly luciferase fromPhotinus pyralis, as well as the bacterial luciferase-oxidoreductase system from eitherVibrio fischeri orVibrio harveyi, have been immobilized on preactivated polyamide membranes. First, the validity of the approach is demonstrated by performing the microdetermination of adenosine triphosphate (ATP) and sodium dehydrogenase (NADH) in a batch system. The detection limits are equal to 0.1nm for ATP and 0.3nm for NADH. With the NADH-based system, the extension of the biosensor potential to other analytes (ethanol, sorbitol and oxaloacetate) has been achieved using suitable dehydrogenases co-immobilized with the bacterial system. Second, the fibre optic biosensor is associated with a specially designed flow cell for the continuous-flow bioluminescent assay of NADH over the range 2 pmol-1 nmol with an r.s.d. of 3.4% at 0.1 nmol. Finally, a multifunction biosensor for the determination of either ATP or NADH using a single bioluminescence-based fibre optic probe is described. This was made possible by co-immobilizing the firefly luciferase with the bacterial system on the same preactivated polyamide membrane.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1996), S. 125-130 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Hydroxyapatite reinforced with monocrystalline Al2O3 platelets was densified by hot pressing. The effect of volume fraction and size of platelets on the microstructure, strength and toughness was investigated. It was demonstrated that no phase degradation occured during thermal treatments. A better homogeneity of composite mixtures was achieved when large platelets had been used. In return, the incorporation of small platelets appeared more favourable to increase the mechanical characteristics although limiting effect induced by microstructural defects. The flexural strength can reach 140 MPa with an associated fracture toughness of 2.5 MPa % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaOaaaeaaca% qGTbaaleqaaaaa!36F8!\[\sqrt {\text{m}} \] compared to 137 MPa and 1.2 MPa % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaOaaaeaaca% qGTbaaleqaaaaa!36F8!\[\sqrt {\text{m}} \] for dense monolithic HAP. The observation of crack propagation allowed us to point out the mechanisms responsible of this toughening. Crack deflection on disk faces should be considered as the initiating phenomenon leading to platelet debonding, crack bridging or branching. Crack deflection and branching may also result in the formation of unbroken ligaments of material which bridge the crack.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 10 (1999), S. 533-540 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Fracture toughness of Al2O3 platelet-reinforced hydroxyapatite (HAP) ceramics was investigated using the Vickers' indentation technique. The geometrical anisotropy of alumina platelets induces an anisotropic toughening. The efficiency of reinforcing mechanisms remains maximum for a crack propagating with an angular deviation inferior to 30° around the direction perpendicular to alumina disc faces. This is assumed to result from a crack deflection mechanism which induces a favorable contribution of mode II failure. A small effect of hydroxyapatite grain size becomes noticeable in the direction parallel to alumina disc faces. The toughening depends on the size and volume content of alumina platelets. Large size platelets provoke a spontaneous microcracking of the HAP matrix which is detrimental to the mechanical reliability, whereas small platelets lead to a strong toughening. The results relate to the intensity of thermoelastic residual stresses within the matrix around alumina inclusions. © 1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 26 (1991), S. 457-464 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In order to characterize heavyweight carboxymethylcellulose (C.M.C) by 13C NMR it is necessary to hydrolysis them. This paper proposes and compares three different ways of degradation: acidic hydrolysis, sonication and enzymatic degradation. Acidic hydrolysis leads to poor results due to a strong alteration of the sample. Sonication gives quite good results but the enzymatic degradation is the most efficient method for degrading C.M.C under good conditions. After hydrolysis, the sample was analysed by 13C NMR and HPLC to obtain structural information such as substitution degree, preferential substitution sites and regularity of the substitution along the polymeric chain.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 31P MAS NMR of adsorbed trimethylphosphine (TMP) has been used to characterize the surface acid properties of γ-alumina and chlorinated γ-alumina. Combined with thermodesorption of TMP, NMR has allowed the determination of the strength distribution of Brønsted and Lewis acid sites on these samples. γ-alumina chlorination with 1,2-dichloropropane at 500°C first increases the numbers of ``strong'' Lewis and ``strong'' Brønsted acid sites, second decreases the number of ``weak'' Lewis acid sites. The ``strong'' sites are the ones TMP is desorbed from above 200°C and the ``weak'' sites up to 200°C.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 9
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    In:  The 24th International Symposium of the Society of Core Analysts (Halifax, Nova Scotia, Canada 2010)
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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  • 10
    Publication Date: 2018
    Description: 〈span〉〈div〉Summary〈/div〉We present a joint analysis of newly acquired gravity and teleseismic data in the North Tanzanian Divergence, where the lithospheric break-up is at its earliest stage. The impact of a mantle upwelling in more mature branches of the East African Rift has been extensively studied at a lithospheric scale. However, few studies have been completed that relate the deep-seated mantle anomaly detected in broad regional seismic tomography with the surface deformation observed in the thick Archaean Pan-African suture zone located in North Tanzania. Our joint inversion closes the gap between local and regional geophysical studies, providing velocity and density structures from the surface down to ca. 250 km depth with new details. Our results support the idea of a broad mantle upwelling rising up to the lithosphere and creating a thermal modification along its path. However, our study clearly presents an increasing amplitude of the associated anomaly both in velocity and density above 200 km depth, which cannot be solely explained by a temperature rise. We infer from our images the combined impact of melt (2-3%), composition and hydration that accompany the modification of a thick heterogenous cratonic lithosphere are a response to the hot mantle rising. The detailed images we obtained in density and velocity assert that Archaean and Proterozoic units interact with the mantle upwelling to restrict the lithosphere modifications within the Magadi-Natron-Manyara rift arm. The composition and hydration variations associated with those units equilibrate the thermal erosion of the craton root and allow for its stability between 100 and 200 km depth. Above 80 km depth, the crustal part is strongly affected by intruding bodies (melt and gas) which produces large negative anomalies in both velocity and density beneath the main magmatic centers. In addition to the global impact of a superplume, the velocity and density anomaly pattern suggests a 3D distribution of the crust and mantle lithospheric stretching, which is likely to be controlled by inherited fabrics and enhanced by lateral compositional and hydration variations at the Tanzanian craton-orogenic belt boundary.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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