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  • Quantum optics, physics of lasers, nonlinear optics, classical optics  (2)
  • Depth of thaw  (1)
  • Photosynthesis  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Environmental effects on CO2 efflux from riparian tundra in the northern foothills of the Brooks Range, Alaska, USA (1992)
    Springer
    Oecologia 92 (1992), S. 568-577 
    Details
    ISSN: 1432-1939
    Keywords: Arctic tundra ; Depth of thaw ; Ecosystem carbon exchange ; Permafrost ; Soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Carbon dioxide efflux and soil microenvironmental factors were measured diurnally in Carex aquatilus-and Eriophorum angustifolium-dominated riparian tundra communities to determine the relative importance of soil environmental factors controlling ecosystem carbon dioxide exchange with the atmosphere. Measurements were made weekly between 18 June and 24 July 1990. Diurnal patterns in carbon dioxide efflux were best explained by changes in soil temperature, while seasonal changes in efflux were correlated with changes in depth to water table, depth to frozen soil and soil moisture. Carbon dioxide efflux rates were lowest early in the growing season when high water tables and low soil temperatures limited microbial and root activity. Individual rainfall events that raised the water table were found to strongly reduce carbon dioxide efflux. As the growing season progressed, rainfall was low and depth to water table and soil temperatures increased. In response, carbon dioxide efflux increased strongly, attaining rates late in the season of approximately 10 g CO2 m−2 day−1. These rates are as high as maxima recorded for other arctic sites. A mathematical model is developed which demonstrates that soil temperature and depth to water table may be used as efficient predictors of ecosystem CO2 efflux in this habitat. In parallel with the field measurements of CO2 efflux, microbial respiration was studied in the laboratory as a function of temperature and water content. Estimates of microbial respiration per square meter under field conditions were made by adjusting for potential respiring soil volume as water table changed and using measured soil temperatures. The results indicate that the effect of these factors on microbial respiration may explain a large part of the diurnal and seasonal variation observed in CO2 efflux. As in coastal tundra sites, environmental changes that alter water table depth in riparian tundra communities will have large effects on ecosystem CO2 efflux and carbon balance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317851
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Factors influencing carbon fixation and water use by mediterranean sclerophyll shrubs during summer drought (1990)
    Springer
    Oecologia 82 (1990), S. 381-393 
    Details
    ISSN: 1432-1939
    Keywords: Photosynthesis ; Stomata ; Model ; Rootshoot interaction ; Sclerophyllous plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mediterranean sclerophyll shrubs respond to seasonal drought by adjusting the amount of leaf area exposed and by reducing gas exchange via stomatal closure mechanisms. The degree to which each of these modifications can influence plant carbon and water balances under typical mediterranean-type climate conditions is examined. Leaf area changes are assessed in the context of a canopy structure and light microclimate model. Shifts in physiological response are examined with a mechanistically-based model of C3 leaf gas exchange that simulates progressive reduction of maximum photosynthesis and transpiration rates and increasingly strong midday stomatal closure over the course of drought. The results demonstrate that midday stomatal closure may effectively contribute to drought avoidance, increase water use efficiency, and strongly alter physiological efficiency in the conversion of intercepted light energy to photoproducts. Physiological adjustments lead to larger reductions in water use than occur when comparing leaf area index 3.5 to 1.5, extremes found for natural stands of sclerophyll shrubs in the California chaparral. Reductions in leaf area have the strongest effect on resource capture and use during non-water-stressed periods and the least effect under extreme drought conditions, while shifts in physiological response lead to large savings of water and efficient water use under extreme stress. An important model parameter termed GFAC (proportionality factor expressing the relation of conductance [g] to net photosynthesis rate) is utilized, which changes in response to the integrated water stress experimence of shrubs and alters the degree to which stomata may open for a given rate of carbon fixation. We attempt to interpret this parameter in terms of physiological mechanisms known to modify control of leaf gas exchange during drought. The analysis helps visualize means by which canopy gas exchange behavior may be coupled to physiological changes occurring in the root environment during soil drying.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317487
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  • 3
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    Ultralow-dissipation micro-oscillator for quantum optomechanics (2012)
    American Physical Society (APS)
    Details
    Publication Date: 2012-11-27
    Description: Author(s): E. Serra, A. Borrielli, F. S. Cataliotti, F. Marin, F. Marino, A. Pontin, G. A. Prodi, and M. Bonaldi Generating nonclassical states of light by optomechanical coupling depends critically on the mechanical and optical properties of micro-oscillators and on the minimization of thermal noise. We present an oscillating micromirror with a mechanical quality factor Q =2.6×10 6 at cryogenic temperature and ... [Phys. Rev. A 86, 051801] Published Mon Nov 26, 2012
    Keywords: Quantum optics, physics of lasers, nonlinear optics, classical optics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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  • 4
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    Frequency-noise cancellation in optomechanical systems for ponderomotive squeezing (2014)
    American Physical Society (APS)
    Details
    Publication Date: 2014-03-08
    Description: Author(s): A. Pontin, C. Biancofiore, E. Serra, A. Borrielli, F. S. Cataliotti, F. Marino, G. A. Prodi, M. Bonaldi, F. Marin, and D. Vitali Ponderomotive squeezing of the output light of an optical cavity has been recently observed in the megahertz range in two different cavity optomechanical devices. Quadrature squeezing becomes particularly useful at lower spectral frequencies, for example, in gravitational wave interferometers, despi... [Phys. Rev. A 89, 033810] Published Fri Mar 07, 2014
    Keywords: Quantum optics, physics of lasers, nonlinear optics, classical optics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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