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  • 1
    Publication Date: 2018-02-15
    Type: paper
    Format: application/pdf
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  • 2
    Publication Date: 2018-02-15
    Type: paper
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  • 3
    Publication Date: 2007-10-08
    Description: Basement inliers of high-grade metamorphic rocks within the eastern Colombian Andes record a Grenvillian history. Among them, the Garzon Complex and the Dibulla, Bucaramanga and Jojoncito gneisses were studied using different geochronological methods to produce better correlations in the context of the reconstruction of the Grenville belt and of the supercontinent of Rodinia. The dynamic evolution of all of these units includes a final collisional event with exhumation of high-grade rocks. Such a tectonic history bears strong similarities with the Grenville Province in Canada and seems to confirm that these domains took part in the aggregation of Rodinia. Mesoproterozoic U-Pb zircon ages indicate heritage from magmatic protoliths, and the Sm-Nd model ages, as well as the {varepsilon}Nd values, suggest derivation from an evolved continental domain, such as the Amazonian craton, with some mixing with juvenile Neoproterozoic material. When these continental fragments are correlated with similar terrains in Mexico and the Central Andes, a large crustal fragment is implied; very probably it made up the southern portion of the Grenville belt within Rodinia, which was disrupted when Laurentia separated from Gondwana forming the Iapetus Ocean, leaving behind cratonic fragments that were later accreted to the South American Platform.
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  • 4
    Publication Date: 2007-11-19
    Description: The Inner MongoliaDaxinganling Orogenic Belt (IMDOB), located between the North China and South Mongolia Blocks, consists of several ENEWSW- to NESW-trending zones including dismembered ophiolite blocks, metamorphic rocks and granitoids. Although numerous studies have been carried out on this belt, its tectonic evolution has been a subject of controversy, chiefly because of the lack of reliable geochronological data. Based on a synthesis of newly published geochronological data and our unpublished data for the IMDOB, we define two oceanic basins: Ondor Sum and Hegenshan. The former, probably the main one, was initiated during the Ordovician (〉467 Ma) period, whereas the latter, representing a back-arc basin, opened on a pre-Permian basement at, or earlier than, Early Permian times (c. 295 Ma). These two oceanic basins were separated by a magmatic arc (SunidBaolidao), and were probably closed simultaneously when the final orogenesis of the IMDOB occurred during the Triassic period (240220 Ma). Importantly, the Triassic timing of the final orogenesis of the IMDOB due north of the North China Craton is essentially coeval with that of the QinlingDabieSuLu orogenic belt on the southern margin of the North China Craton. It is inferred that this two-sided subductioncollision scenario in the Triassic may have contributed to the Mesozoic lithospheric thinning event of the North China Craton, although the details are unclear.
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  • 5
    ISSN: 1573-899X
    Keywords: Local blood flow ; cortical layers ; vibrissal stimulation ; comparative analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The present work reports studies of the quantitative spatial and temporal characteristics of changes in local blood flow in different layers of the somatosensory cortex of rats during adequate mechanical stimulation of the vibrissae. Studies were performed using 34 Wistar rats. Skull trepanning was performed under urethane (1 g/kg) anesthesia. Television-guided microscopy was used to introduce a set of three platinum electrodes (100 μm in diameter, with tip diameters of 30–40 μm) into the somatosensory cortex projection zone of the vibrissae. The first and third electrodes were positioned in cortical layers I–III and IV–VI and the central electrode was used to generate hydrogen within the tissue. Electrode positions were confirmed histologically after experiments. Animals were placed on artificial ventilation and one or all vibrissae were stimulated at a frequency of 3 Hz for 60 sec, with interstimulus intervals of 3 min. Changes in the local blood flow were measured during stimulation and for 1 min afterwards, using the hydrogen clearance method, and brain tissue impedance was also measured. There was a small (up to 5–7%) reduction in blood flow in the first seconds of stimulation, which was followed 15–25 sec later by an increase and subsequent return to initial when stimulation stopped. The increases in blood flow during stimulation of all vibrissae were by 24.2±6.7% (n=36) in layers IV–VI and 24.5±5.6% (n=34) in layers I–III; increases in response to stimulation of single vibrissae were by 19.4±7.4% (n=28) and 17.8±6.4% (n=28) respectively. The dynamics of impedance changes corresponded to those of blood flow changes. Thus, heterogeneity was found in changes of local brain blood flow in different layers of the somatosensory cortex during increases in cortical functional activity.
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  • 6
    ISSN: 1573-899X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-8264
    Keywords: growth ; Indian mustard ; lead uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of different concentrations of lead nitrate (10−5 to 10−3 M) on root, hypocotyl, and shoot growth of Indian mustard (Brassica juncea L. var. megarrhiza), and the uptake and accumulation of Pb2+ by its roots, hypocotyls, and shoots were investigated. Lead had no significant inhibitory effect on the root growth at concentrations of 10−5 to 10−4 M during the entire treatment, while at 10−3 M, Pb slightly inhibited the root and shoot growth. B. juncea has ability to take up Pb from solutions and accumulate it in its roots, and transport and concentrate it. The Pb contents in the parts of plants treated with 10−3 M Pb were greater than those of untreated plants, by factors of 230 in the roots, 170 in the hypocotyls, and 3 in the shoots.
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  • 8
    ISSN: 1741-2765
    Keywords: Composites ; joining ; impact ; perforation ; energy absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A previous study on impact response of composite laminates concluded that impact perforation was the most important damage stage in composite laminates subjected to impact loading, since impact characteristics (peak force, contact duration and absorbed energy) and mechanical properties degradation of composite laminates reached critical points once perforation took place. It was also found that thickness had a greater influence on impact perforation resistance than did in-plane dimensions. However, as the composite laminates became very thick, the manufacturing cost for obtaining high-quality composite laminates increased. In an effort to meet design requirements and reduce manufacturing costs, assembled composite plates, which were organized by assembling multiple thin composite laminates, were considered as alternatives for thick single-laminate composite plates. Various joining techniques including mechanical riveting, adhesive bonding and stitch joining, and their combinations, were used in assembling two- and three-laminate plates. Experimental results revealed that adhesive bonding outperformed other joining techniques. Although good bonding resulted in higher joining (bending) stiffness and subsequently higher perforation thresholds, increasing the laminate thickness or the number of laminates was found to be more efficient in raising perforation threshold than in improving the joining stiffness. The assembled three-laminate plates were found to have higher perforation thresholds than their thick single-laminate counterpart.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 29 (1989), S. 115-120 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thin glass/epoxy plates fabricated from 3M prepreg tape were subjected to low-velocity impact. Delamination in the impacted composite plates was measured by edge replication and was identified as the major damage mode. The effects of fiber orientation, thickness, and lamination on the delamination resistance were investigated. Experimental results verified three previous findings: (1) a linear relationship holds between delamination area and impact energy, (2) the mismatch of bending stiffness between adjacent laminae can be correlated with the delamination area on the interface, and (3) the behavior of a thin composite plate under low-velocity impact is very similar to that caused by global bending. In addition, based on the calculation of impact energy per unit delamination area, the dynamic fracture energy and the energy of dissipation in the thin glass/epoxy plates can be examined.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 36 (1996), S. 142-147 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This study investigates the repair of a glass/vinylester composite material with damage caused by impact loading and bending. The repair technique is based on the “standard procedures” established in a previous study. In addition to the damage due to bending, the repair of composite plates with straight cutting-line damage is also investigated due to its similarity to the bending fracture and good repeatability for evaluation. It is found that two glass reinforcing patches of plain weave—that is, (0, 90)2—on each side of the specimen can restore the original load-bearing capability of the composite material of concern. The investigation of the cutting-line damage can also be viewed as a study of bond-line angles for composite joining. It is concluded that a bond-line angle greater than 60° can restore the undamaged composite strength. In maintaining a large bond-line angle as well as a large bonding surface, various bond-line configurations are presented. Results from the five joints of V, W, WW, U, and UU shapes further verify this conclusion.
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