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  • 1
    Language: English
    In: Angewandte Chemie International Edition, 10 May 2010, Vol.49(21), pp.3567-3567
    Description: Harvard University Press 2009. 192 pp., hardcover € 27.95.—ISBN 978‐0674035669
    Keywords: Popular Science Book
    ISSN: 1433-7851
    ISSN: Angewandte Chemie International Edition
    E-ISSN: 1521-3773
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  • 2
    In: PLoS ONE, 2015, Vol.10(11)
    Description: We have analyzed monthly hydrological, meteorological and water quality data from three irrigation and drinking water reservoirs in the lower Jordan River basin and estimated the atmospheric emission rates of CO 2 . The data were collected between 2006 and 2013 and show that the reservoirs, which differ in size and age, were net sources of CO 2 . The estimated surface fluxes were comparable in magnitude to those reported for hydroelectric reservoirs in the tropical and sub-tropical zones. Highest emission rates were observed for a newly established reservoir, which was initially filled during the sampling period. In the two older reservoirs, CO 2 partial pressures and fluxes were significantly decreasing during the observation period, which could be related to simultaneously occurring temporal trends in water residence time and chemical composition of the water. The results indicate a strong influence of water and reservoir management (e.g. water consumption) on CO 2 emission rates, which is affected by the increasing anthropogenic pressure on the limited water resources in the study area. The low wind speed and relatively high pH favored chemical enhancement of the CO 2 gas exchange at the reservoir surfaces, which caused on average a four-fold enhancement of the fluxes. A sensitivity analysis indicates that the uncertainty of the estimated fluxes is, besides pH, mainly affected by the poorly resolved wind speed and resulting uncertainty of the chemical enhancement factor.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: Limnology and Oceanography, Jan, 2010, Vol.55(1), p.354(11)
    Description: Turbulence was measured in situ within shoals of juvenile perch Perca fluviatilis with a self-contained autonomous microstructure profiler near an artificial reef in Lake Constance, Germany. Depth-averaged dissipation rates of turbulent kinetic energy (TKE) correlated with the density of shoaling fish, providing evidence for fish-induced turbulence in a large and stratified lake. The observed range and the depth-averaged values of TKE dissipation rates associated with fish-generated turbulence were comparable with magnitudes of turbulence typically caused by internal waves or wind forcing. Enhanced turbulence within fish shoals could only be observed during periods of low background turbulence and high fish abundance. The observed rates of dissipation of TKE are about two orders of magnitude smaller than production rates of TKE estimated from empirical models on the basis of observed fish size and swimming speed.
    Keywords: Sand Bars -- Natural History ; Fish Populations -- Distribution ; Turbulence -- Measurement ; Population Density -- Measurement
    ISSN: 0024-3590
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Science (New York, N.Y.), 02 December 2005, Vol.310(5753), pp.1427-9
    Keywords: Conservation of Natural Resources ; Fishes
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 5
    Language: English
    In: Applied Physics Letters, 10 October 2011, Vol.99(15)
    Description: Theoretical investigations of the switch-on behavior of semiconductor quantum dot based nanocavity laser devices are presented. From a microscopic treatment of the carrier-carrier and carrier-photon interaction, we find a fast switch-on of the laser device that is enabled by ultrafast carrier dynamics and heavily damped relaxation oscillations. We show that the timescales of the dynamics within the continuum states and the quantum dot states are strongly coupled and investigate the time dependence of the non-equilibrium scattering rates in detail.
    Keywords: Lasers, Optics, And Optoelectronics
    ISSN: 0003-6951
    E-ISSN: 1077-3118
    Source: © 2011 American Institute of Physics (AIP)〈img src=http://exlibris-pub.s3.amazonaws.com/AIP_edited.gif style="vertical-align:middle;margin-left:7px"〉
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  • 6
    Language: English
    In: Applied Physics Letters, 04 July 2011, Vol.99(1)
    Description: Theoretical investigations for the realization of population inversion of semiconductor quantum dot ground-state transitions by means of adiabatic passage with chirped optical pulses are presented. While the inversion due to Rabi oscillations depends sensitively on the resonance condition, the pulse area, as well as on the absence of carrier scattering and dephasing, we find that adiabatic passage is surprisingly insensitive to the excitation conditions and carrier scattering effects. Quantum kinetic models for the interaction of quantum-dot carriers with longitudinal optical phonons are used to describe carrier scattering and dephasing in the corresponding simulations and allow to quantify the conditions to simultaneously invert an ensamble of quantum dots.
    Keywords: Lasers, Optics, And Optoelectronics
    ISSN: 0003-6951
    E-ISSN: 1077-3118
    Source: © 2011 American Institute of Physics (AIP)〈img src=http://exlibris-pub.s3.amazonaws.com/AIP_edited.gif style="vertical-align:middle;margin-left:7px"〉
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  • 7
    Language: English
    In: Limnology and Oceanography, March, 2011, Vol.56(2), p.695(12)
    Description: Temporal variability of vertical zooplankton distributions is analyzed on timescales from minutes to days based on 7 months of acoustic backscatter strength data in Lake Constance. A comparison with net samples reveals that most of the observed variability in volume backscatter strength is associated with variations in the abundance of large Daphnia. Diel vertical migration (DVM) of zooplankton was a persistent feature throughout the entire period of observation, while amplitude, daily migration timing, and migration speed varied with season. This active motion of zooplankton was affected by internal waves on a broad range of timescales. In spring, the maximum depth of DVM follows variations in isothermal depths associated with long-wavelength, basin-scale internal waves. Propagating, short-wavelength, internal waves with comparable amplitudes affect vertical zooplankton distributions on timescales of minutes. Spectral analyses of zooplankton abundance, temperature, and current velocity reveal close correspondence of spectral peaks and slopes, indicating that up to timescales of several days, the only temporal scale at which biological processes dominate over passive transport is associated with DVM. Whereas horizontal transport dominates at long periods, vertical transport occurs only at short timescales. doi:10.4319/lo.2011.56.2.0695
    Keywords: Freshwater Zooplankton -- Distribution ; Migratory Animals -- Research ; Plankton Populations -- Research ; Internal Waves -- Environmental Aspects
    ISSN: 0024-3590
    Source: Cengage Learning, Inc.
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  • 8
    In: Limnology and Oceanography, May 2014, Vol.59(3), pp.724-732
    Description: The potential contribution of swimming zooplankton to the vertical mixing of stratified waters has been the topic of an ongoing scientific debate. Current estimates, which are primarily based on scale analyses and numerical simulations, range from negligible effects to significant contributions that are comparable in magnitude to physical driving forces, such as wind and tides. Here, we analyzed laboratory observations of fluid mixing that are caused by vertically migrating zooplankton () in a density‐stratified water column. Mixing rates were quantified at the scale of individual organisms in terms of the dissipation rates of small‐scale spatial variance of tracer concentration measured by laser‐induced fluorescence. At the bulk scale, we analyzed temporal changes in the mean density stratification. Organism and bulk scale observations were used to estimate apparent diffusion coefficients in trails of individuals and organism groups. Mean diffusivities of 0.8–5.1 × 10 m s, which were averaged over trail volumes of 1.5–13 × 10 m, are on the same order of magnitude as the molecular diffusivity of salt. A comparable diffusivity (1.1 × 10 m s) was estimated on the bulk scale, and the initial density stratification, although frequently passed by migrating , was preserved over the 5 d experimental period. The present results agree with scaling arguments and suggest the negligible enhancement of vertical transport in comparison with the turbulent mixing that is typically observed in oceans and lakes.
    Keywords: Oceanography;
    ISSN: 0024-3590
    E-ISSN: 1939-5590
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  • 9
    Language: English
    In: Physical Review B, 4/2015, Vol.91(15)
    Keywords: Physics;
    ISSN: 1098-0121
    E-ISSN: 1550-235X
    Source: American Physical Society (APS) (via CrossRef)
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  • 10
    Language: English
    In: Physical Review B, 1/2015, Vol.91(4)
    Description: We present a time-domain model for the simulation of light-matter interaction in semiconductors in arbitrary geometries and across a wide range of excitation conditions. The electromagnetic field is treated classically using the finite-difference time-domain method. The polarization and occupation numbers of the semiconductor material are described using the semiconductor Bloch equations including many-body effects in the screened Hartree-Fock approximation. Spontaneous emission noise is introduced using stochastic driving terms. As an application of the model, we present simulations of the dynamics of a nanowire laser including optical pumping, seeding by spontaneous emission and the selection of lasing modes. Comment: 7 pages, 6 figures
    Keywords: Physics - Optics ; Condensed Matter - Mesoscale And Nanoscale Physics;
    ISSN: 1098-0121
    E-ISSN: 1550-235X
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