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  • 1
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  This study presents an investigation of the adhesion properties of a chromium-gold-titanium layer system, which is used in the LIGA process to create moveable microstructures. The main purpose has been the improvement of the process parameters to increase yield reliability. Three mechanisms affecting the adhesion have been identified. As a consequence of humidity adsorbed H2O reacts with Al2O3 to AlO(OH) (aluminum meta hydrates), which does not bond to the sputtered chromium layer. Thus the hydrate must be removed by cleaning the surface with Ar+-ions. Tight layers without pores could be realized by optimization pressure and temperature during sputtering of chromium and gold. Thus, diffusion of chromium or penetration of etchants into the gold layer as well as impact or diffusion of titanium into the gold layer could be prevented. In addition, a copper layer was introduced as a further intermediate layer by electroforming to improve the formation of stable nickel alloys at the interface between the sputtered gold and the electroplated nickel. These measures resulted in an improvement of the adhesion, so that full functional acceleration sensors were produced with a high yield.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Microsystem technologies 2 (1996), S. 63-70 
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract The performance and lifetime of micro electro mechanical systems (MEMS) is strongly affected by friction and wear. We therefore analysed the friction and wear characteristics of microstructures produced by the LIGA-process. The measurements were carried out in a special designed microtribometer, which is capable to work inside a scanning electron microscope (SEM), and hence offering the possibility of a high resolution in-situ observation of the microscopic tribological mechanism during operation of the system. The material combinations investigated were chosen in order to represent the most important tribological junctions occurring in the ‘micro-motor’ and ‘micro-turbine’ currently produced by the LIGA-technique. We studied the tribological properties of nickel-nickel micro components (LIGA-side-wall/LIGA-sidewall and LIGA-bottom side/LIGA-top side), as well as nickel micro components (bottom side)-Al2O3-ceramic substrates (contact between rotor-base). The results indicate a strong influence of the relative humidity level (RHL) on the friction and wear properties of the metal/ceramic as well as of the metal/metal contacts appearing in the LIGA-MEMS, showing the lowest level of friction and wear at high RHL-values. We also found out that the friction and wear parameters were highly influenced by the applied surface pressure. Changing the surface pressure results in the formation of different kinds of wear debris accumulating or smearing out in the wear track. The metal oxides produced hereby in the wear track can lower adhesion and thus reduce the friction of the system.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Microsystem technologies 2 (1996), S. 63-70 
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  The performance and lifetime of micro electro mechanical systems (MEMS) is strongly affected by friction and wear. We therefore analysed the friction and wear characteristics of microstructures produced by the LIGA- process. The measurements were carried out in a special designed microtribometer, which is capable to work inside a scanning electron microscope (SEM), and hence offering the possibility of a high resolution in-situ observation of the microscopic tribological mechanism during operation of the system. The material combinations investigated were chosen in order to represent the most important tribological junctions occurring in the ‘micro-motor’ and ‘micro-turbine’ currently produced by the LIGA-technique. We studied the tribological properties of nickel–nickel micro components (LIGA-sidewall/LIGA-sidewall and LIGA-bottom side/LIGA -top side), as well as nickel micro components (bottom side)– Al2O3-ceramic substrates (contact between rotor-base). The results indicate a strong influence of the relative humidity level (RHL) on the friction and wear properties of the metal/ceramic as well as of the metal/metal contacts appearing in the LIGA-MEMS, showing the lowest level of friction and wear at high RHL-values. We also found out that the friction and wear parameters were highly influenced by the applied surface pressure. Changing the surface pressure results in the formation of different kinds of wear debris accumulating or smearing out in the wear track. The metal oxides produced hereby in the wear track can lower adhesion and thus reduce the friction of the system.
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  • 4
    ISSN: 1432-0789
    Keywords: Key words Arbuscular mycorrhiza ; Legume-rhizobia symbiosis ; 15N natural abundance ; Phaseolus vulgaris ; Rhizobium spp. ; Glomus spp. ; Inoculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The interactions between Phaseolus vulgaris, Rhizobium spp. strains nodulating P. vulgaris, and arbuscular mycorrhizal (AM) fungi were assessed under greenhouse conditions in a nonsterilized Typic Haplustalf soil from Cauca, Colombia. Our results indicate a specific involvement of AM fungal species in nitrogen acquisition by the legume plants from symbiotic nitrogen fixation and from soil. A significant specific influence of inoculation with Glomus spp. on the 15N/14N ratio in plant shoots was dependent on the inoculated rhizobial strain, but AM fungal inoculation had no significant effect on shoot dry weight or nodule occupancy in the two different rhizobial strain treatments. The results imply that in low P soils the effects of an improved mycorrhizal symbiosis may include improved symbiotic N2 fixation efficiency and/or improved soil N uptake.
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  • 5
    ISSN: 0022-4731
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 85 (1996), S. 525-535 
    ISSN: 1437-3262
    Keywords: Clay mineralogy ; Mid-Atlantic Reykjanes Ridge ; Quaternary sediments ; Source areas ; Deep-water circulation ; Iceland-Scotland Overflow Water (ISOW) ; Ice-rafted sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses. The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary. Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from the volcanogenous Icelandic shelf and reflects the influence of Iceland-Scotland Overflow Water (ISOW). Stratigraphic variability in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts of illite, chlorite, and kaolinite characterize ice-rafted sediments of the “Heinrich layers”. In these sediments smectite crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order, similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18–16 ka), indicating a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase in fine-grained quartz (〈2µm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated at around 10 ka, where a strong increase in smectite of low crystallographic order is detected.
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  • 7
    ISSN: 0016-7835
    Keywords: Key words Clay mineralogy ; Mid-Atlantic Reykjanes Ridge ; Quaternary sediments ; Source areas ; Deep-water circulation ; Iceland ; Scotland Overflow Water (ISOW) ; Ice-rafted sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses. The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary. Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from the volcanogenous Icelandic shelf and reflects the influence of Iceland–Scotland Overflow Water (ISOW). Stratigraphic variability in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts of illite, chlorite, and kaolinite characterize ice-rafted sediments of the "Heinrich layers". In these sediments smectite crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order, similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18–16 ka), indicating a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase in fine-grained quartz (〈2 μm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated at around 10 ka, where a strong increase in smectite of low crystallographic order is detected.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 24 (1968), S. 498-499 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Fünfzehn erwachsene weibliche Ratten wurden ein Jahr nach erfolgter Hypophysektomie mit HCG und PMS behandelt. Trotz der extrem langen Involutionsperiode reagierten die völlig atrophierten Ovarien unmittelbar auf die parenteral applizierten Hormonpräparate. Jedoch nur das FSH- plus ICSH-Aktivitäten enthaltende PMS (Serumgonadotropin) induzierte ein deutliches Follikelwachstum. Ovulationen konnten nicht nachgewiesen werden, wohl infolge der acyclischen Applikationsform der Substanzen.
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  • 9
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Nach einer einjährigen Involutionsperiode im Anschluss an die Hypophysektomie gelang es mit Hilfe eines PMS-Präparates bereits nach 24tägiger Applikationsdauer, die völlig atrophierten Testes zu annähernd normalen Gewichten mit vollständiger Spermatogenese zu restaurieren. Im Gegensatz hierzu war ein HCG-Präparat, das keine messbaren FSH-Potenzen aufwies, praktisch nur in der Lage, die Leydigschen Zwischenzellen selektiv zu stimulieren. Diese Ergebnisse deuten an, dass bei Ratten die Hodenfunktion trotz maximaler Atrophie wieder völlig hergestellt werden kann, sofern ein Präparat eingesetzt wird, das sowohl ausreichende ICSH- als auch FSH-Potenzen enthält.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 25 (1969), S. 533-534 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Die normalerweise der Hypophysorchidektomie juveniler Ratten folgende Prostataatrophie wurde durch Behandlung mit Progesteron und Prolaktin verhindert. Direkte hypophysäre Einflüsse auf die Prostata werden diskutiert.
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