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  • 1990-1994  (8)
  • 1993  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Electron-spin polarization in photoemission from thin AlxGa1−xAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5189-5192 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The polarization of photoemitted electrons from thin AlxGa1−xAs layers grown by molecular-beam epitaxy has been studied as a function of Al concentration by varying x in steps of 0.05 from 0.0 to 0.15. As the fraction x is increased, the wavelength dependence of the polarization shifts toward shorter wavelengths, permitting wavelength tuning of the region of maximum polarization. A maximum electron polarization of 42%–43% is obtained for AlxGa1−xAs samples with x≥0.05 while the maximum polarization of GaAs (x=0) samples reaches 49%. To investigate the lower polarization of AlxGa1−xAs, additional samples have been studied, including a short-period superlattice (GaAs)7 - (AlAs)1 .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353744
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  • 2
    Electronic Resource
    Electronic Resource
    The role of cytotoxic macrophages in non-obese diabetic mice: cytotoxicity against murine mastocytoma and beta-cell lines (1993)
    Springer
    Diabetologia 36 (1993), S. 1252-1257 
    Details
    ISSN: 1432-0428
    Keywords: Non-obese diabetic mice ; macrophage ; Type 1 (insulin-dependent) diabetes mellitus ; cytokine ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cytotoxicity of macrophages from non-obese diabetic (NOD) mice against murine mastocytoma (P-815), and murine beta-cell lines having the NOD gene background (MIN6N-9a), were examined. Peritoneal exudate cells from 20-week-old mice showed higher cytotoxicity, measured as inhibition of thymidine uptake into P-815, than those from 12-week-old mice (p 〈0.01). In cyclophosphamide-injected mice, cytotoxicity of peritoneal exudate cells had increased at 8 days post-injection, at which time the mice were not diabetic. To confirm macrophage cytotoxicity against pancreatic cells and examine its cytolytic mechanism, the cytotoxicity of peritoneal exudate cells from cyclophosphamide-injected NOD mice against MIN6N-9a cells was measured by the chromium release assay. These peritoneal exudate cells showed higher cytotoxicity as compared to those of saline-injected mice (p 〈0.001). Macrophages were demonstrated to be the major component of peritoneal exudate cells (50%) by flowcytometric analyses. Cytotoxicity increased with macrophage enrichment by adhesion (p 〈0.01). Furthermore, a macrophage toxin, silica, completely blocked the cytotoxicity (p 〈0.001). Cytokines (interleukin 1 and tumour necrosis factor) and a nitric-oxide-producing vasodilator, sodium nitroprusside, were cytotoxic to MIN6N-9a cells but only sodium nitroprusside showed cytotoxicity when incubated for the same period as peritoneal exudate cells. Thus, macrophages play an important role in beta-cell destruction and soluble factors other than cytokines (e.g. nitric oxide) may be mediators of this early cytolytic process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400802
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Role of carbonic anhydrase in the supply of inorganic carbon to the giant clam—zooxanthellate symbiosis (1993)
    Springer
    Marine biology 115 (1993), S. 605-611 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanism whereby inorganic carbon (Ci) is acquired by the symbiotic association between the giant clam (Tridacna derasa) and zooxanthellae (Symbiodinium sp.) has been investigated. Ci in the haemolymph of the clam is in equilibrium with the surrounding sea water. The photosynthesis rate exhibited by the intact clam varies as a function of the Ci concentration in the clam haemolymph. The gill tissue contains high carbonic anhydrase activity which may be important in adjusting the Ci equilibrium between haemolymph and sea water. Zooxanthellae (Symbiodinium sp.) isolated from the clam mantle prefer CO2 to HCO 3 - as a source of inorganic carbon. The zooxanthellae have low levels of carbonic anhydrase on the external surface of the cell; however, mantle extracts display high carbonic anhydrase activity. Carbonic anhydrase is absent from the mantle of aposymbiotic clams (T. gigas), indicating that this enzyme may be essential to the symbiosis. The enzyme is probably associated with the zooxanthellae tubes in the mantle. The results indicate that carbonic anhydrase plays an important role in the supply of carbon dioxide within the clam symbiosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349368
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Spatial mesoscale patterns of West Pacific picophytoplankton as analyzed by flow cytometry: their contribution to subsurface chlorophyll maxima (1993)
    Springer
    Marine biology 115 (1993), S. 209-215 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vertical distributions of picophytoplankton (ppp) (〈2 μm) were studied by ship-board flow cytometry during two cruises in Western Pacific waters to Palau and to Australia in 1990. Weak red-fluorescing small “ppp”, supposed to be free-living prochlorophytes (Chisholm et al. 1988), were abundant in the area surveyed. These ppp, designated “the prochlorophytes”, were abundant in the surface waters (〉104 cells ml-1) at the northern region (27°03′N; 7°11′N) in November, whereas in December at the southern tropical stations (0°23.54′S; 9°20.30′S; 13°50.6′S), they formed subsurface maximum layers (〉105 cells ml-1) on a nitracline at a depth of 3.5 to 5.4% surface irradiation. Their fluorescence intensity increased with depth below 10% surface irradiation. The prochlorophytes at a depth of 1% surface irradiation had ten times higher fluorescence than those at the surface layer. The total fluorescence intensity of the prochlorophytes accounted for 32 to 63% of the sum of the total fluorescence intensity of all fluorescing phytoplankton detected at subsurface chlorophyll maxima in the tropical area. These results suggest that distribution of the prochlorophytes is greatly affected by nitracline and by light intensity and that their chlorophyll is a major contributor to the subsurface chlorophyll maximum in the pelagic West Pacific Ocean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346337
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Adaptation of solitary corals and their zooxanthellae to low light and UV radiation (1993)
    Springer
    Marine biology 117 (1993), S. 685-691 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adaptation of solitary corals, Fungia repanda and F. echinata, and their zooxanthellae to low light and ultraviolet light B (UV-B) was studied with respect to changes in their protein contents, photosynthetic pigment contents and the photosynthesis-irradiance (P-I) curves. The corals were collected from 1 to 50 m depths in the Republic of Belau (Paulau) in 1990 and 1991. The chlorophyll a content in a unit surface area of the coral did not change significantly with the depth of the habitat, whereas cellular chlorophyll a in the algae increased with the depth. Zooxanthellae density and protein content in a unit surface area of Fungia spp. decreased with the depth. Photosynthetic parameters normalized by a unit surface area of the Fungia spp., maximum gross photosynthetic rate (P gmax area-1) and dark respiration rate (R area-1), were negatively correlated with the depth, while initial slope of the P-I curve (α) did not show significant correlation with the depth. Compensation light intensity (Ic) decreased with the depth. In isolated zooxanthellae, P max chl a -1, and R chl a -1 decreased with the depth, while αchl a was constant. P gmax cell-1 and R cell-1 did not change significantly but αcell increased with the depth. Ic decreased with the depth as in the intact corals. Reduction of protein content in a unit area of the coral from deeper habitat implies decrease of host animal tissues. Reduction of Ic can be explained by decrease of R area-1, which may be due to the diminution of animal tissues. The photoadaptational response to low light intensity of intact Fungia spp. was found to be a combination of the photoadaptation of symbiotic algae and the decrease of host animal tissue. In order to study their adaptation to ultraviolet (UV) radiation, P-I curves of Fungia spp. and isolated zooxanthellae were analyzed before and after UV-B irradiation. 1 h UV-B irradiation showed no effect on the photosynthetic rate of the shallow water (1 m) corals, while it inhibited the photosynthesis of the deep water (30 m) corals and zooxanthellae isolated from both shallow and deep water corals. These results indicate that the host, Fungia spp., in shallow water have protective mechanism for intense UV-B in their habitat. These photoadaptational mechanisms seem to allow the Fungia spp. to have wide vertical distribution where light intensity spans more than two orders of magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349781
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Vanadium dioxide thin films prepared by chemical vapour deposition from vanadium(III) acetylacetonate (1993)
    Springer
    Journal of materials science 28 (1993), S. 5073-5078 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Vanadium dioxide thin films were prepared by an atmospheric-pressure chemical vapour deposition method. The raw material was vanadium(III) acetylacetonate. Polycrystalline thin films were obtained at a reaction temperature of 500°C. Slow post-deposition cooling of the deposits on a substrate of fused quartz or sapphire single crystal yields vanadium dioxide films which are not mixed with other phases, i.e. V3O7 or V4O9. Optical and electrical switching behaviours strongly depend on film thickness. At a film thickness of about 300 nm the transition temperature showed a minimum value of 44 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00361182
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  • 7
    Electronic Resource
    Electronic Resource
    Copper thin films prepared by chemical vapour deposition from copper dipivalylmethanate (1993)
    Springer
    Journal of materials science 28 (1993), S. 5540-5542 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Copper thin films were prepared by a low-temperature atmospheric-pressure chemical vapour deposition method. The raw material was copper dipivalylmethanate which is volatile and thermally stable. At a reaction temperature above 220°C, polycrystalline copper films can be obtained by hydrogen reduction of the raw material. The resistivity of the film was in the range 1.7–2.7 μΩ cm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367827
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  • 8
    Electronic Resource
    Electronic Resource
    Nickel thin films prepared by chemical vapour deposition from nickel acetylacetonate (1993)
    Springer
    Journal of materials science 28 (1993), S. 5345-5348 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Nickel thin films were prepared by a low-temperature atmospheric-pressure chemical vapour deposition method. The raw material was nickel acetylacetonate. At a reaction temperature above 250 °C, polycrystalline nickel films can be obtained by hydrogen reduction of the raw material. The resistivity (8.1–13.3 μΩ cm) of the film was close to that of bulk nickel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570088
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