Stoichiometric

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Guihua Liu - One of the best experts on this subject based on the ideXlab platform.

  • growth rate protein rna ratio and Stoichiometric homeostasis of submerged macrophytes under eutrophication stress
    Knowledge and Management of Aquatic Ecosystems, 2016
    Co-Authors: Wei Xing, Han Liu, Qingshan Shi, Guihua Liu
    Abstract:

    Growth rate hypothesis (GRH) and Stoichiometric homeostasis of photoautotrophs have always been questioned. However, little is known about GRH and Stoichiometric homeostasis of aquatic plants, especially submerged macrophytes. Therefore, we aim to test the GRH and explore Stoichiometric homeostasis of four freshwater submerged macrophytes under eutrophication stress. At the single species level and the multi-species level, N:P ratios of Potamogeton maackianus , Myriophyllum spicatum , Vallisneria natans and Ceratophyllum demersum had no consistent trends with growth rates. However, protein:RNA ratios of P. maackianus , M. spicatum and V. natans all correlated negatively with growth rates, demonstrating GRH can apply to freshwater submerged macrophytes, even though they are threatening by eutrophication stress. Protein:RNA ratios positively correlated with N:P ratios in culture media and tissues in submerged macrophytes except in P. maackianus (30d), suggesting effects of varying N:P ratios in culture media on protein:RNA ratios are basically in concert with tissue N:P ratios under short-time eutrophication stress. Stoichiometric homeostasis coefficients (H N:P ) indicated submerged macrophytes have weak homeostasis. Stoichiometric homeostasis of V . natans was stronger than those of P. maackianus , M. spicatum and C. demersum . The differences in GRH and homeostasis of the four submerged macrophytes may be due to species traits.

  • multielement stoichiometry of submerged macrophytes across yunnan plateau lakes china
    Scientific Reports, 2015
    Co-Authors: Wei Xing, Qiao Shi, Beibei Hao, Han Liu, Zhixiu Wang, Guihua Liu
    Abstract:

    Stoichiometric homeostasis of element composition is one of the central concepts of ecological stoichiometry. We analyzed concentrations of macroelements (C, N, P, Ca, K, Mg, S), microelements (Cu, Fe, Mn, Mo, Ni, Zn) and beneficial elements (Na, Se, Si) in submerged macrophytes, water and sediments across 20 Yunnan plateau lakes. We predicted that tissue element composition in submerged macrophytes is affected by lake trophic level and taxonomy, and submerged macrophytes have weak Stoichiometric homeostasis for all above 16 elements. Canonical discriminant analyses successfully discriminated among trophic level groups and taxa groups. Of all the elements, C, N, P and S most effectively discriminated among trophic level groups across 20 lakes, revealing lake trophic level mostly affect tissue macroelement composition in submerged macrophytes; while Ca, K and Se most effectively discriminated among submerged macrophytes taxa groups, suggesting taxonomy mostly affect compositions of macroelements and beneficial elements in submerged macrophytes. In addition, the Stoichiometric homeostatic coefficient of 1/HCa:C for all five taxa of submerged macrophytes were less than zero, suggesting submerged macrophytes in Yunnan plateau lakes have strong Ca Stoichiometric homeostasis. Our findings, not only broaden the knowledge of multielement Stoichiometric homeostasis, but also help to choose most appropriate lake management strategy.

Kenji Kitamura - One of the best experts on this subject based on the ideXlab platform.

  • quasi phase matched optical parametric oscillation with periodically poled Stoichiometric litao 3
    Optics Letters, 2000
    Co-Authors: Takaaki Hatanaka, Yasunori Furukawa, Koichiro Nakamura, Tetsuo Taniuchi, Hiromasa Ito, Kenji Kitamura
    Abstract:

    We have demonstrated, for the first time to our knowledge, periodic poling of a 2-mm-thick near-Stoichiometric LiTaO3 substrate and its operation in a nanosecond optical parametric oscillator. Because the coercive field of Stoichiometric LiTaO3 is ∼2 kV/mm, which is approximately one tenth that of the conventional congruent field, periodic poling of thicker Stoichiometric substrates was successfully performed by means of an electric-field poling process at room temperature. The performance of a parametric oscillator with a 1-mm-thick sample was compared with that of the oscillator with the periodically poled congruent oscillator. The Stoichiometric device exhibited better performance.

  • Stoichiometric litao3 single crystal growth by double crucible czochralski method using automatic powder supply system
    Journal of Crystal Growth, 1999
    Co-Authors: Yasunori Furukawa, Kenji Kitamura, Eisuke Suzuki, Kazuo Niwa
    Abstract:

    Stoichiometric LiNbO 3 single crystals 40 mm in diameter and 50–100 mm in length were grown by the Czochralski method using a double crucible and automatic powder supply system. The crystals were grown from a Li-rich melt (Li 2 O 58–60 mol%) in the inner crucible, and the Stoichiometric LiNbO 3 powder was supplied smoothly and continuously to the outer melt. From the lattice parameter and Curie temperature measurements, the chemical composition through the grown crystal was found to be close to the Stoichiometric composition. The as-grown crystals were of single domain except at the periphery. From a comparison of the transmittance between Stoichiometric and congruent LiNbO 3 single crystals, the absorption edge wavelength of the Stoichiometric crystal was found to be 10 nm shorter than the congruent crystal. From these results, it is expected that this double crucible Czochralski method can be effectively applied to control crystal stoichiometry during growth and to produce uniformly doped single crystals of various oxide compositions.

  • Stoichiometric mg linbo 3 as an effective material for nonlinear optics
    Optics Letters, 1998
    Co-Authors: Yasunori Furukawa, Shunji Takekawa, Kazuo Niwa, Kenji Kitamura, Hideki Hatano
    Abstract:

    Photorefractive damage, optical absorption, photoconductivities, and photogalvanic currents of Stoichiometric LiNbO(3) single crystals with different Mg doping levels have been investigated. Nominally pure Stoichiometric LiNbO(3) shows lower photorefractive damage resistance than congruent crystal; however, Stoichiometric crystals doped with MgO of more than 1.8 mol. % exhibit no measurable photorefractive damage at 532 nm to intensities of as much as 8 MW/cm(2) . This remarkable damage resistance can be attributed not only to increased photoconductivity but also to decreased photogalvanic current. Stoichiometric Mg:LiNbO(3) also demonstrates the shortest absorption edge, 302 nm, and a single-domain nature with low scattering losses.

  • crystal growth and low coercive field 180 domain switching characteristics of Stoichiometric litao3
    Applied Physics Letters, 1998
    Co-Authors: Kenji Kitamura, Yasunori Furukawa, Kazuo Niwa, Venkatraman Gopalan, T E Mitchell
    Abstract:

    We grew LiTaO3 single crystals with a composition close to stoichiometry by using a double crucible Czochralski method. The switching field required for 180° ferroelectric domain reversal and the internal fields originating from nonStoichiometric point defects were compared for the Stoichiometric and conventional commercially available crystals. The switching fields for the domain reversal in the Stoichiometric crystal with a Curie temperature of 685 °C was 1.7 kV/mm. This is about one thirteenth of the switching field required for the conventional LiTaO3  crystals with a Curie temperature near 600 °C. The internal field in the Stoichiometric crystal drastically decreased to 0.1 kV/mm.

Yasunori Furukawa - One of the best experts on this subject based on the ideXlab platform.

  • quasi phase matched optical parametric oscillation with periodically poled Stoichiometric litao 3
    Optics Letters, 2000
    Co-Authors: Takaaki Hatanaka, Yasunori Furukawa, Koichiro Nakamura, Tetsuo Taniuchi, Hiromasa Ito, Kenji Kitamura
    Abstract:

    We have demonstrated, for the first time to our knowledge, periodic poling of a 2-mm-thick near-Stoichiometric LiTaO3 substrate and its operation in a nanosecond optical parametric oscillator. Because the coercive field of Stoichiometric LiTaO3 is ∼2 kV/mm, which is approximately one tenth that of the conventional congruent field, periodic poling of thicker Stoichiometric substrates was successfully performed by means of an electric-field poling process at room temperature. The performance of a parametric oscillator with a 1-mm-thick sample was compared with that of the oscillator with the periodically poled congruent oscillator. The Stoichiometric device exhibited better performance.

  • the correlation of mgo doped near Stoichiometric linbo3 composition to the defect structure
    Journal of Crystal Growth, 2000
    Co-Authors: Yasunori Furukawa, Y. Yajima, K Kitamura, Shunji Takekawa, Kazuo Niwa, Nobuo Iyi, I Mnushkina, P Guggenheim, J M Martin
    Abstract:

    Abstract Undoped and MgO-doped LiNbO 3 single crystals with near-Stoichiometric compositions were grown from K 2 O-doped melts and Li-rich melts by two different growth techniques. Near-Stoichiometric LiNbO 3 single crystals, having large [Li]/[Nb] ratios of 0.988–0.993, showed smaller threshold concentrations of MgO than congruent crystals for the behavior of Curie temperature, OH absorption band and optical damage properties. We discuss the ideal defect structure models, and find that the Li-site vacancy model is consistent with the experimental results for MgO-doped near-Stoichiometric LiNbO 3 single crystals.

  • Stoichiometric litao3 single crystal growth by double crucible czochralski method using automatic powder supply system
    Journal of Crystal Growth, 1999
    Co-Authors: Yasunori Furukawa, Kenji Kitamura, Eisuke Suzuki, Kazuo Niwa
    Abstract:

    Stoichiometric LiNbO 3 single crystals 40 mm in diameter and 50–100 mm in length were grown by the Czochralski method using a double crucible and automatic powder supply system. The crystals were grown from a Li-rich melt (Li 2 O 58–60 mol%) in the inner crucible, and the Stoichiometric LiNbO 3 powder was supplied smoothly and continuously to the outer melt. From the lattice parameter and Curie temperature measurements, the chemical composition through the grown crystal was found to be close to the Stoichiometric composition. The as-grown crystals were of single domain except at the periphery. From a comparison of the transmittance between Stoichiometric and congruent LiNbO 3 single crystals, the absorption edge wavelength of the Stoichiometric crystal was found to be 10 nm shorter than the congruent crystal. From these results, it is expected that this double crucible Czochralski method can be effectively applied to control crystal stoichiometry during growth and to produce uniformly doped single crystals of various oxide compositions.

  • Stoichiometric mg linbo 3 as an effective material for nonlinear optics
    Optics Letters, 1998
    Co-Authors: Yasunori Furukawa, Shunji Takekawa, Kazuo Niwa, Kenji Kitamura, Hideki Hatano
    Abstract:

    Photorefractive damage, optical absorption, photoconductivities, and photogalvanic currents of Stoichiometric LiNbO(3) single crystals with different Mg doping levels have been investigated. Nominally pure Stoichiometric LiNbO(3) shows lower photorefractive damage resistance than congruent crystal; however, Stoichiometric crystals doped with MgO of more than 1.8 mol. % exhibit no measurable photorefractive damage at 532 nm to intensities of as much as 8 MW/cm(2) . This remarkable damage resistance can be attributed not only to increased photoconductivity but also to decreased photogalvanic current. Stoichiometric Mg:LiNbO(3) also demonstrates the shortest absorption edge, 302 nm, and a single-domain nature with low scattering losses.

  • crystal growth and low coercive field 180 domain switching characteristics of Stoichiometric litao3
    Applied Physics Letters, 1998
    Co-Authors: Kenji Kitamura, Yasunori Furukawa, Kazuo Niwa, Venkatraman Gopalan, T E Mitchell
    Abstract:

    We grew LiTaO3 single crystals with a composition close to stoichiometry by using a double crucible Czochralski method. The switching field required for 180° ferroelectric domain reversal and the internal fields originating from nonStoichiometric point defects were compared for the Stoichiometric and conventional commercially available crystals. The switching fields for the domain reversal in the Stoichiometric crystal with a Curie temperature of 685 °C was 1.7 kV/mm. This is about one thirteenth of the switching field required for the conventional LiTaO3  crystals with a Curie temperature near 600 °C. The internal field in the Stoichiometric crystal drastically decreased to 0.1 kV/mm.

Wei Xing - One of the best experts on this subject based on the ideXlab platform.

  • growth rate protein rna ratio and Stoichiometric homeostasis of submerged macrophytes under eutrophication stress
    Knowledge and Management of Aquatic Ecosystems, 2016
    Co-Authors: Wei Xing, Han Liu, Qingshan Shi, Guihua Liu
    Abstract:

    Growth rate hypothesis (GRH) and Stoichiometric homeostasis of photoautotrophs have always been questioned. However, little is known about GRH and Stoichiometric homeostasis of aquatic plants, especially submerged macrophytes. Therefore, we aim to test the GRH and explore Stoichiometric homeostasis of four freshwater submerged macrophytes under eutrophication stress. At the single species level and the multi-species level, N:P ratios of Potamogeton maackianus , Myriophyllum spicatum , Vallisneria natans and Ceratophyllum demersum had no consistent trends with growth rates. However, protein:RNA ratios of P. maackianus , M. spicatum and V. natans all correlated negatively with growth rates, demonstrating GRH can apply to freshwater submerged macrophytes, even though they are threatening by eutrophication stress. Protein:RNA ratios positively correlated with N:P ratios in culture media and tissues in submerged macrophytes except in P. maackianus (30d), suggesting effects of varying N:P ratios in culture media on protein:RNA ratios are basically in concert with tissue N:P ratios under short-time eutrophication stress. Stoichiometric homeostasis coefficients (H N:P ) indicated submerged macrophytes have weak homeostasis. Stoichiometric homeostasis of V . natans was stronger than those of P. maackianus , M. spicatum and C. demersum . The differences in GRH and homeostasis of the four submerged macrophytes may be due to species traits.

  • multielement stoichiometry of submerged macrophytes across yunnan plateau lakes china
    Scientific Reports, 2015
    Co-Authors: Wei Xing, Qiao Shi, Beibei Hao, Han Liu, Zhixiu Wang, Guihua Liu
    Abstract:

    Stoichiometric homeostasis of element composition is one of the central concepts of ecological stoichiometry. We analyzed concentrations of macroelements (C, N, P, Ca, K, Mg, S), microelements (Cu, Fe, Mn, Mo, Ni, Zn) and beneficial elements (Na, Se, Si) in submerged macrophytes, water and sediments across 20 Yunnan plateau lakes. We predicted that tissue element composition in submerged macrophytes is affected by lake trophic level and taxonomy, and submerged macrophytes have weak Stoichiometric homeostasis for all above 16 elements. Canonical discriminant analyses successfully discriminated among trophic level groups and taxa groups. Of all the elements, C, N, P and S most effectively discriminated among trophic level groups across 20 lakes, revealing lake trophic level mostly affect tissue macroelement composition in submerged macrophytes; while Ca, K and Se most effectively discriminated among submerged macrophytes taxa groups, suggesting taxonomy mostly affect compositions of macroelements and beneficial elements in submerged macrophytes. In addition, the Stoichiometric homeostatic coefficient of 1/HCa:C for all five taxa of submerged macrophytes were less than zero, suggesting submerged macrophytes in Yunnan plateau lakes have strong Ca Stoichiometric homeostasis. Our findings, not only broaden the knowledge of multielement Stoichiometric homeostasis, but also help to choose most appropriate lake management strategy.

Reinhold H Dauskardt - One of the best experts on this subject based on the ideXlab platform.

  • fracture properties of hydrogenated amorphous silicon carbide thin films
    Acta Materialia, 2012
    Co-Authors: Yusuke Matsuda, Sean W King, J Bielefeld, J Xu, Reinhold H Dauskardt
    Abstract:

    Abstract The cohesive fracture properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin films in moist environments are reported. Films with Stoichiometric compositions (C/Si ≈ 1) exhibited a decreasing cohesive fracture energy with decreasing film density similar to other silica-based hybrid organic–inorganic films. However, lower density a-SiC:H films with non-Stoichiometric compositions (C/Si ≈ 5) exhibited much higher cohesive fracture energy than the films with higher density Stoichiometric compositions. One of the non-Stoichiometric films exhibited fracture energy (∼9.5 J m −2 ) greater than that of dense silica glasses. The increased fracture energy was due to crack-tip plasticity, as demonstrated by significant pileup formation during nanoindentation and a fracture energy dependence on film thickness. The a-SiC:H films also exhibited a very low sensitivity to moisture-assisted cracking compared with other silica-based hybrid films. A new atomistic fracture model is presented to describe the observed moisture-assisted cracking in terms of the limited Si O Si suboxide bond formation that occurs in the films.