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  • 1
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    Incorporation of Mg and Sr in calcite of cultured benthic foraminifera (Heterostegina depressa and Ammonia tepida) and seawater carbonate chemistry, 2010 (2010)
    PANGAEA
    In:  Supplement to: Raitzsch, Markus; Dueñas-Bohórquez, Adriana; Reichart, Gert-Jan; de Nooijer, Lennart Jan; Bickert, Torsten (2010): Incorporation of Mg and Sr in calcite of cultured benthic foraminifera: impact of calcium concentration and associated saturation state. Biogeosciences, 7(3), 869-881, https://doi.org/10.5194/bg-7-869-2010
    Details
    Publication Date: 2024-03-15
    Description: We investigated the effect of the calcium concentration in seawater and thereby the calcite saturation state (omega) on the magnesium and strontium incorporation into benthic foraminiferal calcite under laboratory conditions. For this purpose individuals of the shallow-water species Heterostegina depressa (precipitating high-Mg calcite, symbiont-bearing) and Ammonia tepida (low-Mg calcite, symbiont-barren) were cultured in media under a range of [Ca2+], but similar Mg/Ca ratios. Trace element/Ca ratios of newly formed calcite were analysed with Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and normalized to the seawater elemental composition using the equation DTE=(TE/Cacalcite)/(TE/Caseawater). The culturing study shows that DMg of A. tepida significantly decreases with increasing omega at a gradient of -4.3x10-5 per omega unit. The DSr value of A. tepida does not change with omega, suggesting that fossil Sr/Ca in this species may be a potential tool to reconstruct past variations in seawater Sr/Ca. Conversely, DMg of H. depressa shows only a minor decrease with increasing omega, while DSr increases considerably with omega at a gradient of 0.009 per omega unit. The different responses to seawater chemistry of the two species may be explained by a difference in the calcification pathway that is, at the same time, responsible for the variation in the total Mg incorporation between the two species. Since the Mg/Ca ratio in H. depressa is 50-100 times higher than that of A. tepida, it is suggested that the latter exhibits a mechanism that decreases the Mg/Ca ratio of the calcification fluid, while the high-Mg calcite forming species may not have this physiological tool. If the dependency of Mg incorporation on seawater [Ca2+] is also valid for deep-sea benthic foraminifera typically used for paleostudies, the higher Ca concentrations in the past may potentially bias temperature reconstructions to a considerable degree. For instance, 25 Myr ago Mg/Ca ratios in A. tepida would have been 0.2 mmol/mol lower than today, due to the 1.5 times higher [Ca2+] of seawater, which in turn would lead to a temperature underestimation of more than 2 °C.
    Keywords: Abundance estimate; Alkalinity, total; Alkalinity, total, standard deviation; Ammonia tepida; Ammonia tepida, incorporation, magnesium; Ammonia tepida, incorporation, magnesium, standard deviation; Ammonia tepida, incorporation, strontium; Ammonia tepida, incorporation, strontium, standard deviation; Ammonia tepida, magnesium/calcium ratio; Ammonia tepida, magnesium/calcium ratio, standard deviation; Ammonia tepida, strontium/calcium ratio; Ammonia tepida, strontium/calcium ratio, standard deviation; Aragonite saturation state; Benthos; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calcite saturation state, standard deviation; Calcium; Calcium, standard deviation; Calculated; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon dioxide, standard deviation; Chromista; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Experimental treatment; Foraminifera; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Geo-Las 200Q 193 nm Excimerlaser (Lambda Physik); Heterostegina depressa; Heterostegina depressa, incorporation, magnesium; Heterostegina depressa, incorporation, magnesium, standard deviation; Heterostegina depressa, incorporation, strontium; Heterostegina depressa, incorporation, strontium, standard deviation; Heterostegina depressa, magnesium/calcium ratio; Heterostegina depressa, magnesium/calcium ratio, standard deviation; Heterostegina depressa, strontium/calcium ratio; Heterostegina depressa, strontium/calcium ratio, standard deviation; Heterotrophic prokaryotes; Identification; Laboratory experiment; Laboratory strains; Magnesium/Calcium ratio; Magnesium/Calcium ratio, standard deviation; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Salinity; Single species; Strontium/Calcium ratio; Strontium/Calcium ratio, standard deviation; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 304 data points
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  • 2
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    Seawater carbonate chemistry and impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera (Ammonia tepida and Heterostegina depressa), 2011 (2011)
    PANGAEA
    In:  Supplement to: Dueñas-Bohórquez, Adriana; Raitzsch, Markus; de Nooijer, Lennart Jan; Reichart, Gert-Jan (2011): Independent impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera. Marine Micropaleontology, 81(3-4), 122-130, https://doi.org/10.1016/j.marmicro.2011.08.002
    Details
    Publication Date: 2024-03-15
    Description: Laboratory culture experiments were conducted to determine effects of seawater carbonate ion concentration ([CO32-]), and thereby calcite saturation state, on Mg and Sr incorporation into calcite of two species of shallow-water benthic foraminifera: Ammonia tepida and Heterostegina depressa. Impact on Mg and Sr incorporation by increased seawater [CO32-] and thereby higher calcite saturation state, is absent in either species. Comparison to results from a similar culturing experiment, in which calcite saturation state was varied as a function of [Ca2+], reveals that saturation state affects incorporation of Mg and Sr through calcium- rather than carbonate availability. The similarity in response by both species is surprising since the average Mg/Ca ratio is ~ 70 times higher in H. depressa than in A. tepida. Furthermore, these results suggest that the ions involved in biomineralization (i.e. Ca2+ and DIC) are processed by separate cellular transport mechanisms. The similar response of Mg and Sr incorporation in this study suggests that only differences in the Ca2+ transport mechanism affect divalent cation partitioning.
    Keywords: Alkalinity, total; Alkalinity, total, standard deviation; Ammonia tepida; Ammonia tepida, chambers added; Ammonia tepida, chambers added per individual; Ammonia tepida, magnesium/calcium ratio; Ammonia tepida, magnesium/calcium ratio, standard deviation; Ammonia tepida, strontium/calcium ratio; Ammonia tepida, strontium/calcium ratio, standard deviation; Aragonite saturation state; Benthos; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcification/Dissolution; Calcite saturation state; Calcite saturation state, standard deviation; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbonate ion; Carbonate ion, standard deviation; Carbonate system computation flag; Carbon dioxide; Chromista; Coast and continental shelf; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Foraminifera; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Heterostegina depressa; Heterostegina depressa, magnesium/calcium ratio; Heterostegina depressa, magnesium/calcium ratio, standard deviation; Heterostegina depressa, strontium/calcium ratio; Heterostegina depressa, strontium/calcium ratio, standard deviation; Heterotrophic prokaryotes; Identification; Laboratory experiment; Measured; Mortality/Survival; North Atlantic; Number of specimens; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; pH, standard deviation; Replicates; Rows of chambers added; Rows of chambers added per individual; Salinity; Salinity, standard deviation; Single species; Species; Temperate; Temperature, standard deviation; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 282 data points
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of refilling effects on deep-level transient spectroscopy measurements in Se-doped AlxGa1−xAs (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 525-530 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep-level transient spectroscopy (DLTS) and constant-capacitance DLTS (CC-DLTS) techniques have been used to investigate selenium-related DX centers in AlGaAs alloys. The value of the thermal activation energy obtained by both techniques was the same (0.21 eV); however, experimental curves show some important differences. While CC-DLTS curves show only one peak, which reveals that there exists only one DX center in Se-doped AlGaAs, in DLTS curves it is possible to resolve up to two peaks lying at a lower temperature than the one observed by CC-DLTS. This disagreement may be due to the fact that DLTS measurements are strongly affected by refilling effects which occur in the edge zone of the space-charge region during capacitance transients performed at constant voltage. These effects accelerate the capacitance transients and can lead to too high thermal-emission rates. In contrast, these effects do not affect CC-DLTS curves, because in constant-capacitance voltage transients the edge of the space-charge region remains unchanged and refilling effects do not take place. These effects are rather important on DX levels because they exhibit thermally activated capture cross sections and very low ionization factors at the experimental temperatures and, therefore, capture processes are slow and their time constants can be similar to those of the emission processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351883
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of the DX centers in AlGaAs:Si by admittance spectroscopy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4300-4305 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work we have applied the admittance spectroscopy technique to characterize the DX centers in AlxGa1−xAs alloys doped with silicon. Our experimental results reveal the existence of two DX centers related to silicon in AlxGa1−xAs alloys, named DX-I and DX-II centers, with thermal activation energies of 0.370 and 0.415 eV, respectively. These values are lower than those obtained by other authors using capacitance techniques. To explain this disagreement it should be noticed that capacitance techniques can be affected by the nonexponential behavior of the thermal emission transients of the DX centers in AlxGa1−xAs alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348403
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  • 5
    Electronic Resource
    Electronic Resource
    Particle distribution study for low-volume fraction magnetostrictive composites (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2433-2439 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental results for [1–3] magnetostrictive composites containing a 20% volume-fraction of Terfenol-D coarse particles ((very-much-greater-than)1 μm) suspended in a nonmetallic binder. Results from magnetostrictive strain and magnetoelastic measurements are provided for particle distributions that differ in particle size and range of size distribution. Particle size and packing density are shown to effect strain response and are attributed to demagnetization and loading (prestress) effects. Both a decreasing and increasing ΔE effect are measured for low and high fields, respectively, and found to be independent of particle distribution. The response of an optimized bimodal distribution increases packing density and produces 15% larger magnetostrictive strains than the other widely dispersed (polydispersed) (〈106, 〈212, and 〈300 μm) and narrowly dispersed (monodispersed) (〈45, 98, and 275 μm) distributions at comparable magnetic field levels. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1389518
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  • 6
    Electronic Resource
    Electronic Resource
    Electrical characterization of He-ion implantation-induced deep levels in p+n InP junctions (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4855-4860 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical characterization of He-ion implantation-induced deep levels existing in fully implanted p+n InP junctions isolated by He bombardment is reported in this work. An electron trap located at 0.19 eV below the conduction band and a hole trap located at 0.13 eV above the valence band were detected by deep-level transient spectroscopy (DLTS). Several emission characteristics of these traps were extracted from the correlation between DLTS and the capacitance–voltage transient technique. The experimental determination of trap capture properties was also carried out. In particular, the capture kinetics was found to exhibit a strong temperature dependence for both centers. Two experimental methods—direct recording of capture transients and analysis of DLTS peaks—were used to estimate the capture parameters. Finally, some tentative arguments are proposed in order to correlate the results obtained from the thermal emission and capture measurements. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371452
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical characterization of electron cyclotron resonance deposited silicon nitride dual layer for enhanced Al/SiNx:H/InP metal–insulator–semiconductor structures fabrication (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6924-6930 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a study of metal–insulator–semiconductor (MIS) structures on InP. The interfacial state density and deep levels existing in MIS structures were measured by deep level transient spectroscopy (DLTS) technique. The electrical insulator properties were measured by current–voltage techniques. MIS structures were fabricated on InP substrates by direct deposition of silicon nitride (SiNx:H) thin films by electron cyclotron resonance chemical vapor deposition. In this work, we show that interfacial state density can be diminished, without degrading electrical insulator properties, by fabricating MIS structures based on a dual layer insulator with different compositions and with different thickness. The effect of rapid thermal annealing treatment has been analyzed in detail in these samples. Interface state densities as low as 3×1011 cm−2 eV−1 were measured by DLTS in some structures. Conductance transients caused by disorder-induced gap states have been observed and analyzed providing some information about interface width. Finally, deep levels induced in the substrate have been investigated. Three deep levels at energies of 0.19, 0.24, and 0.45 eV measured from the conduction band have been found, and their dependence on the rapid thermal annealing process has been analyzed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371774
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  • 8
    Electronic Resource
    Electronic Resource
    Dopant level freeze-out and nonideal effects in 6H–SiC epilayer junctions (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 310-315 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results obtained from current–voltage (I–V) and capacitance–voltage techniques along with admittance spectroscopy have been qualitatively correlated to achieve a more comprehensive picture of dopant freeze-out and conduction mechanisms in a 6H–SiC n+p-type junction. Special attention was paid to the temperature range of 100–200 K. The dependence of the ideality factor, n, on the temperature was obtained experimentally from the I–V measurements. Two contributions have been considered in its evolution. At room temperature, n is very close to 2, indicating that recombination processes dominate the forward conduction mechanism. This result may be related to the SiC sample preparation process: structural defects may be present at the junction interface giving rise to interface states which act as recombination centers. At low temperatures (100–200 K), the Poole–Frenkel effect on the impurity level is the main effect responsible for the nonideal behavior of the junction. We have carried out a quantitative estimation of the n factor predicted by this effect incorporating partial ionization of the dopant. These calculations agree very well with the experimental values. At these temperatures the thermal excitation is low, the traps remain inactive, and their contribution to the conduction mechanisms is negligible. When the temperature increases, traps become thermally activated and then the recombination processes participate in the conduction mechanisms and they become dominant at room temperature. The admittance analysis allows numerical values of the aluminum emission rate to be obtained at different temperatures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360831
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  • 9
    Electronic Resource
    Electronic Resource
    Deep-level transient spectroscopy and electrical characterization of ion-implanted p-n junctions into undoped InP (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5325-5330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Current-voltage, small-signal measurements, and deep-level transient spectroscopy (DLTS) spectra of p-n junctions made by Mg implantation into undoped InP are described. The I-V characteristics show that the dominant conduction mechanism at forward bias is recombination in the space-charge zone, whereas a thermally activated tunneling mechanism involving a trap at 0.32 eV dominates at reverse bias. Five deep levels located in the upper-half of the band gap were detected in the junctions by DLTS measurements, three of which (at 0.6, 0.45, and 0.425 eV) were found to appear due to rapid thermal annealing. The origin of the other two levels, at 0.31 and 0.285 eV, can be ascribed to implantation damage. Admittance spectroscopy measurements showed the presence of three levels at 0.44, 0.415, and 0.30 eV, all in agreement with those found by DLTS. The DLTS measurements showed that the concentration of deep levels decreased after longer annealing times, and that the concentration of deep levels due to the implantation increased after additional P or Si implantations. This explains the influence of annealing time and additional implantations on the I-V characteristics of the junctions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359710
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  • 10
    Electronic Resource
    Electronic Resource
    Deep levels in p+-n junctions fabricated by rapid thermal annealing of Mg or Mg/P implanted InP (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3143-3150 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, we investigate the deep levels present in ion implanted and rapid thermal annealed (RTA) InP p+-n junctions. The samples were implanted with magnesium or coimplanted with magnesium and phosphorus. These levels were characterized using deep level transient spectroscopy (DLTS) and capacitance–voltage transient technique (CVTT). Seven majority deep levels located in the upper half of the band gap were detected in the junctions by using DLTS measurements, four of which (at 0.6, 0.45, 0.425, and 0.2 eV below the conduction band) result from RTA, while the origin of the other three levels (at 0.46, 0.25, and 0.27 eV below the conduction band) can be ascribed to implantation damage. An RTA-induced origin was assigned to a minority deep level at 1.33 eV above the valence band. From CVTT measurements, several characteristics of each trap were derived. Tentative assignments have been proposed for the physical nature of all deep levels. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364348
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