Temporal Phosphorus Dynamics in Shallow Eutrophic Lake Suwa, Japan

It can be difficult to decrease the water phosphorus (P) concentration in eutrophic shallow lakes, even if the external P loading is reduced, owing to a high level of internal P loading to surface water from sediment. However, in shallow Lake Suwa, Japan, lake water P concentration has largely decreased in recent years owing to low levels of internal P loading, as well as declining external P loading. We measured water/sediment P and iron (Fe) concentrations and the P release rate from sediment in Lake Suwa, and then compared it with data from the 1970s. In the 1970s, the P concentration throughout the lake water was high during the hypoxic period. Recently, however, the P concentration has increased only in the hypolimnion during the hypoxic period. This suggests that internal P loading from sediment to surface water has largely been suppressed during the hypoxic period in recent years. This may be due to (i) stronger water stratification from global warming, (ii) a greater decrease in the P release rate from the sediment owing to a decline in sediment P concentration from the 1970s to 2020, and (iii) stronger formation of the Fe–P cycle in Lake Suwa recently, compared with that in the 1970s. Our results indicated the need to reduce both external P loading, and internal P loading from sediment to water, for effective water quality improvement in shallow lakes.Water 2024, 16, 1340.journal articl

Organic Phosphorus Substantially Contributes to Crop Plant Nutrition in Soils with Low Phosphorus Availability

To evaluate phosphorus (P) availability and the role of microorganisms in P dynamics in the barley rhizosphere, we constructed a rhizobox using two arable Andosols under different fertilization management regimens and cultivated barley (Hordeum vulgare L. cv. Minorimugi) for 5 weeks. The phosphatase-labile pool of organic phosphorus (Po) was assessed using a phosphataseaddition approach in combination with chemical extraction of Po from soils. A considerable amount of inorganic P (Pi) in the NaHCO3 fraction was taken up by barley roots in a soil with high Pi availability, whereas Po, primarily phytate-like P in the NaHCO3 fraction, was hydrolyzed and then taken up by barley roots in a soil with low Pi availability. No significant utilization of either NaOH-Pi or NaOH-Po was observed for both soils during the 5-week cultivation. In the soil with low Pi availability, elevated acid phosphomonoesterase and phosphodiesterase activities, and greater utilization of Po substrates by bacteria in the Biolog ECO plate, were observed in the rhizosphere when compared with those in the bulk soil. This suggested enhanced Po hydrolysis by increased phosphatase activities to meet the P demand, making the Po an important P source for barley in the soil.ArticleAgronomy, 11(5): 903, 2021journal articl

周波数可変多重検出電子スピン共鳴装置の開発とパイ共役系分子デバイスへの応用

学位記番号：理工博甲1

Rab11-like GTPase associates with and regulates the structure and function of the contractile vacuole system in \u3ci\u3eDictyostelium\u3c/i\u3e

Screening of a cDNA library revealed the existence of a Dictyostelium cDNA encoding a protein 80% identical at the amino acid level to mammalian Rab11. Subcellular fractionation and immunofluorescence studies revealed that DdRab11 was exclusively associated with the ATPase proton pump-rich contractile vacuole membrane system, consisting of a reticular network and bladder-like vacuoles. Video microscopy of cells expressing GFP-DdRab11 revealed that this Rab was associated with contractile vacuolar bladders undergoing formation, fusion and expulsion of water. The association of DdRab11 with contractile vacuole membranes was disrupted when cells were exposed to either hypo-osmotic conditions or an inhibitor of the ATPase proton pump. Cells that overexpressed a dominant negative form of DdRab11 were analyzed biochemically and microscopically to measure changes in the structure and function of the contractile vacuole system. Compared with wild-type cells, the dominant negative DdRab11-expressing cells contained a more extensive contractile vacuole network and abnormally enlarged contractile vacuole bladders, most likely the result of defects in membrane trafficking. In addition, the mutant cells enlarged, detached from surfaces and contained large vacuoles when exposed to water, suggesting a functional defect in osmotic regulation. No changes were observed in mutant cells in the rate of fluid phase internalization or release, suggesting the DdRab11-mediated membrane trafficking defects were not general in nature. Surprisingly, the rate of phagocytosis was increased in the dominant negative DdRab11-expressing cells when compared with control cells. Our results are consistent with a role for DdRab11 in regulating membrane traffic to maintain the normal morphology and function of the contractile vacuole

Rab11-like GTPase associates with and regulates the structure and function of the contractile vacuole system in \u3ci\u3eDictyostelium\u3c/i\u3e

Screening of a cDNA library revealed the existence of a Dictyostelium cDNA encoding a protein 80% identical at the amino acid level to mammalian Rab11. Subcellular fractionation and immunofluorescence studies revealed that DdRab11 was exclusively associated with the ATPase proton pump-rich contractile vacuole membrane system, consisting of a reticular network and bladder-like vacuoles. Video microscopy of cells expressing GFP-DdRab11 revealed that this Rab was associated with contractile vacuolar bladders undergoing formation, fusion and expulsion of water. The association of DdRab11 with contractile vacuole membranes was disrupted when cells were exposed to either hypo-osmotic conditions or an inhibitor of the ATPase proton pump. Cells that overexpressed a dominant negative form of DdRab11 were analyzed biochemically and microscopically to measure changes in the structure and function of the contractile vacuole system. Compared with wild-type cells, the dominant negative DdRab11-expressing cells contained a more extensive contractile vacuole network and abnormally enlarged contractile vacuole bladders, most likely the result of defects in membrane trafficking. In addition, the mutant cells enlarged, detached from surfaces and contained large vacuoles when exposed to water, suggesting a functional defect in osmotic regulation. No changes were observed in mutant cells in the rate of fluid phase internalization or release, suggesting the DdRab11-mediated membrane trafficking defects were not general in nature. Surprisingly, the rate of phagocytosis was increased in the dominant negative DdRab11-expressing cells when compared with control cells. Our results are consistent with a role for DdRab11 in regulating membrane traffic to maintain the normal morphology and function of the contractile vacuole

CHF enhancement of a large heated surface by a honeycomb porous plate and a gridded metal structure in a saturated pool boiling of nanofluid

The enhancement of the critical heat flux (CHF) in saturated pool boiling of water-based nanofluid (containing TiO2 nanoparticles) by the attachment of a honeycomb porous plate (HPP) and a gridded metal structure (GMS) on a horizontal heated surface have been investigated experimentally. The honeycomb porous plate attached to the heated surface enhances the liquid supply due to capillary action to the heated surface and the release of vapor through the vapor escape channel. The deposition of nanoparticles on the heated surface during the boiling of the nanofluid enhances the spread of liquid along the heated surface due to the capillary action. The preceding papers by the present authors revealed that the CHF could be significantly enhanced by 2.2 times that of water boiling by the attachment of the HPP on the heated surface with the nanoparticle deposition layer. According to the hydrodynamic theory by Lienhard et al. (1973), the installation of a gridded structure on the heated surface could also enhance the CHF because the number of the escaping vapor jets each of which allows the liquid flow to the heated surface near the CHF conditions increases with the increment in the number of grid. The present paper describes the results directed toward the further enhancement of the pool boiling CHF of nanofluid by the installation of the GMS onto the HPP on a large heated surface. The tested surface has a diameter of ϕ50 mm, which is 20 times the capillary length, λC(=σ/g(ρl-ρv). For plain surfaces being larger than 20 times the length λC, the CHF can be regarded as being equivalent to that of an infinite large surface. Based on the Lienhard model, grid size of the GMS is chosen so that the CHF of water boiling is increased most effectively. As a result, for simultaneous existence of three factors (the HPP, the GMS and deposition layer of nanoparticles), the CHF has been enhanced to 3.1 MW/m2, which is the higher than either of the HPP in water, the HPP in water-based nanofluid and the GMS in water. High-speed-movie visualization of water boiling revealed that the attachment of the gridded metal structure shortens the hovering period of the coalesced bubble compared to the plain surface. Shortened period causes the more frequent liquid supply to the heated surface. These results illustrate the potential for increasing the safety margin in the IVR (In-Vessel Retention) systems as a heat removal technology

Effective hadron masses and couplings in nuclear matter and incompressibility

The role of effective hadron masses and effective couplings in nuclear matter is studied using a generalized effective Lagrangian for sigma-omega model. A simple relation among the effective masses, the effective couplings and the incompressibility K is derived. Using the relation, it is found that the effective repulsive and the effective attractive forces are almost canceled to each other at the normal density. Inversely, if this cancellation is almost complete, K should be 250-350MeV.Comment: 13 pages of text, 16 figure