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  • 2005-2009  (175)
  • 1985-1989  (65)
  • 1950-1954  (7)
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  • 1
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    Unknown
    Table 3: Reproductive viability of Hemichloris antarctica after cycles of cooling und warming (1988)
    PANGAEA
    In:  Supplement to: Meyer, M A; Huang, G-H; Morris, G J; Friedmann, E Imre (1988): 2.2 The effect of low temperatures on Antarctic endolithic green algae. Polarforschung, 58(2/3), 113-119, hdl:10013/epic.29606.d001
    Details
    Publication Date: 2023-07-10
    Description: Laboratory experiments show that undercooling to about -5°C occurs in colonized Beacon sandstones of the Ross Desert, Antarctica. High-frequency temperature oscillations between 5°C and -5°C or -10°C (which occur in nature on the rock surface) did not damage Hemichloris antarctica. In a cryomicroscope, H. antarctica appeared to be undamaged after slow or rapid cooling to -50°C. l4CO2 incorporation after freezing to -20°C was unaffected in H. antarctica or in Trebouxia sp. but slightly depressed in Stichococcus sp. (isolated from a less extreme Antarctic habitat). These results suggest that the freezing regime in the Antarctic desert is not injurious to endolithic algae. It is likely that the freezing-point depression inside the rock makes available liquid water for metabolic activity at subzero temperatures. Freezing may occur more frequently on the rock surface and contribute to the abiotic nature of the surface.
    Keywords: Age; Cycles; Range; Standard deviation; Viability
    Type: Dataset
    Format: text/tab-separated-values, 112 data points
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    DATA PANGAEA
  • 2
    Electronic Resource
    Electronic Resource
    Computer modeling of a liquid–liquid interface (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1067-1073 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics method and Lennard-Jones potential functions are employed to model liquid–liquid interfaces. The simulations are carried out in a range of temperature and pressure near the triple point. The investigated systems are symmetric and composed of two identical liquids L1 and L2. The interactions between the atoms of L1 and L2 are obtained from modified Lennard-Jones potential functions where extra parameters are introduced to reduce the miscibility between the two liquids. The interfacial tensions and the miscibilities are varied by using different parameters. The interfaces thus obtained are stable on the time scale of the simulation as shown by the density and pressure profiles. This is also confirmed by a geometrical analysis performed in order to characterize the fluctuations of the interfaces. The calculation of the diffusion coefficients shows clearly an anisotropy of the diffusion process in the interfacial region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455259
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  • 3
    Electronic Resource
    Electronic Resource
    Selective laser pyrolysis of metalorganics as a method of forming patterned thin-film superconductors (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1335-1337 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fine line superconductors of Y-Ba-Cu-O were formed on 〈100〉 SrTiO3 by the completely nonvacuum techniques of metalorganic deposition and selective laser pyrolysis. Lines 35 μm wide were written, using an Ar laser, in metal neodecanoates prior to pyrolysis. Regions of the metalorganics not exposed to laser pyrolysis were developed away using a xylene wash. Complete pyrolysis of the metal neodecanoates and rapid thermal annealing produced lines having superconducting onsets above 90 K and zero resistance at 69 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100454
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  • 4
    Electronic Resource
    Electronic Resource
    Plastic Deformation and the Meyer Constants of Metals (1952)
    [s.l.] : Nature Publishing Group
    Nature 169 (1952), S. 237-238 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It can be shown that if the true stress-strain curve of annealed metals can be represented by : * = g*x, (2) where x (for annealed cubic metals4 about 0-5) and g are constants of the metal, a the true stress and e the plastic elongation, then Hu must increase and n must decrease with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/169237a0
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  • 5
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    Unknown
    Do's and Don'ts in Pension Planning (1950)
    Saranac Lake, N.Y., etc. : Periodicals Archive Online (PAO)
    Management Review. 39:2 (1950:Feb.) 105 
    Details
    ISSN: 0025-1895
    Topics: Economics
    Notes: INSURANCE
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:7504-1950-039-02-000041
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  • 6
    Electronic Resource
    Electronic Resource
    Zooplankton communities in the Southern Weddell Sea (Antartica) (1988)
    Springer
    Polar biology 8 (1988), S. 225-233 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Standardized abundances of 40 frequently occurring macrozooplankton taxa collected by double-oblique bongo net hauls between the surface and 200 m depth were submitted to an agglomerative hierarchical cluster analysis, to characterize surface zooplankton communities in the southern and eastern Weddell Sea. The sensitivity of the analysis concerning reduction of the number of considered taxa (especially stages of species) was tested. Dominant taxa in the entire area over the whole period were copepods Metridia gerlachei and Calanoides acutus. Calanus propinquus, Appendicularia spp. and calyptopis-1 larvae of krill, Euphausia superba were abundant at 73°S/19°W. Euphausia crystallorophias and larval fish Pleuragramma antarcticum dominated at 77°S/40°W on the southern shelf. The cluster analysis revealed marked similarities between the southern shelf community and the January community further to the northeast. E. crystallorophias, and larval Pleuragramma antarcticum are thought to be transported in surface layers of the coastal current to the southwest. Oceanic species such as Thysanoessa sp. and E. superba are probably not transported in the same way. Possible mechanisms for the maintenance of the community structures are discussed. A simplified method of characterizing communities, based on analysis of euphausiids, is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00443454
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  • 7
    Electronic Resource
    Electronic Resource
    Carbon dioxide exchange of two ecodemes of Schistidium antarctici in Continental Antarctica (1989)
    Springer
    Polar biology 9 (1989), S. 415-422 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Schistidium antarctici is the commonest of five bryophytes known in the Windmill Islands area of Wilkes Land, Greater Antarctica. In moist habitats it forms closed carpets, but in dry sites it develops a short cushion growth form. Carbon dioxide exchange of both a mesic (Sm) and a xeric growth form (Sx) was investigated by means of an IRGA system in the field near Casey Station under natural light and simulated ambient or controlled temperature conditions in the plant chamber. The chlorophyll content in Sm was three times higher than in Sx. The light compensation point of Sm was lower than in Sx. The data for photosynthesis and dark respiration were computed by means of non-linear and linear regression analysis. Sm was more productive and had a wider temperature range of positive net photosynthesis than Sx under similar conditions. Dark respiration per gram of the whole moss sample was identical in both ecodemes. A decline of the photosynthesis curves at quantum flux densities above 500 μmol m-2 s-1 PAR indicated a photoinhibitory effect in Sm. Sx was even more sensitive to high irradiance levels. Photoinhibition was not apparent in laboratory measurements under artificial light. According to our field measurements the photoinhibitory effect increases with increasing temperature. Moisture loss was avoided during the experiments by water supply from the bottom and frequently spraying the moss samples with water. In the natural habitat the desiccating effect of solar radiation is important, as it quickly causes photosynthesis to cease. The moss will dry out sooner in a xeric habitat than in one which is continuously moist. Consequently, the mesic Schistidium might particularly be subjected to photoinhibition by bright sunshine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00443227
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  • 8
    Electronic Resource
    Electronic Resource
    Seasonal changes of ionic concentrations in the vacuolar sap of Chara vulgaris L. growing in a brackish water lake (1987)
    Springer
    Oecologia 74 (1987), S. 122-127 
    Details
    ISSN: 1432-1939
    Keywords: Chara vulgaris ; Ionic concentrations ; Salinity ; Osmotic potential ; Reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The composition of the vacuolar sap of Chara vulgaris growing in a brackish water lake was estimated weekly over 2 years (1984–1985). The ionic concentrations of the main cations Na+, K+, Ca2+, and Mg2+ and the anion Cl- varied depending on cell age, developmental state, and season. The average of all measurements (in mM) was Na+: 35, K+: 106, Ca2+: 7, Mg2+: 23, Cl-: 101, SO 2- 4 : 20, and PO 3- 4 : 5. At the onset of growth in May/June the ionic content was lower compared to the mean value for the year, steadily increasing until it reached its maximum above the annual mean in winter. During the period of fructification (sexual reproduction: formation of antheridia and oogonia), when up to 100 mM sucrose was accumulated in the vacuolar sap, ionic content was lowest. This resulted in a fairly constant osmotic potential throughout the year. Mg2+ and Ca2+ concentrations were correlated with the physiological age of the cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377355
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  • 9
    Electronic Resource
    Electronic Resource
    The gold content of some Archaean rocks and their possible relationship to epigenetic gold-quartz vein deposits (1985)
    Springer
    Mineralium deposita 20 (1985), S. 284-289 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Gold mineralization in Archaean granite-greenstone environments, especially gold-quartz veins, contributes considerably to the world's gold production. The formation of epigenetic gold mineralization in greenstone belts is generally explained by the metamorphic secretion theory. This theory is based on the assumption that the source of the gold may be komatiitic or tholeiitic lavas, pyritic chemical or clastic sediments and even granitic rocks from which, as a result of regional metamorphic overprinting, gold was extracted and concentrated in suitable structures. It has been shown that in proposed potential source rocks, gold is predominantly associated with sulfide minerals and thus relatively easily accessible to secretion and reconstitution processes. A large number of various rock types originating from granite-greenstone terranes of the Kaapvaal and the Rhodesian cratons were geochemically investigated, and the following ranges for gold determined: volcanic rocks (komatiitic and tholeiitic): 0.1–372 ppb granitic rocks of the basement: 0.3–7.8 ppb iron-rich chemical sediments: 1.0–667 ppb Statistical treatment of the data reveals that volcanic rocks as well as iron-rich chemical sediments are favorable sources for epigenetic gold mineralization formed by metamorphic secretion, while the granitic rocks make less suitable primary gold sources. This finding explains the close spatial relationship which is common between gold-quartz veins and greenstone belts. The conspicuous abundance of epigenetic gold mineralization in the Archaean, however, is attributed to the unique geologic and metamorphic history of the granite-greenstone terranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204288
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of aggregate size in cell cultures of Tagetes patula on thiophene production and cell growth (1989)
    Springer
    Applied microbiology and biotechnology 30 (1989), S. 18-25 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of the size of Tagetes patula (marigolds) cell aggregates on growth and thiophene production in MS-medium was studied. A heterogeneous aggregate suspension was aseptically divided into 7 fractions, each with a defined aggregate diameter range, with subsequent inoculation of the fractions into MS growth medium. Growth occurred in all aggregate fractions and thiophene production increased with increasing aggregate diameter starting at about 3 mm, an effect possibly due to an increasing lack of oxygen in the aggregate centre. Calculations of oxygen concentration profiles in the aggregates showed namely, that the critical aggregate diameter where the oxygen concentration in the aggregate centre becomes very low, is about 3 mm. Aggregates with a diameter exceeding 1.2 cm showed a decreased thiophene production, however, these aggregates were hollow. The thiophenes produced mainly consisted of 5-(4-hydroxy-1-butenyl)1-2,2′-bithienyl, which was excreted into the medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255991
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