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Search Results: 1 - 10 of 89026 matches for " I. Shimizu "
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Impurities Effect on Carbonate Reactive Crystallization for the Wastewater
Y. Shimizu,I. Hirasawa
ISRN Chemical Engineering , 2013, DOI: 10.1155/2013/984163
Abstract:
Plastic behaviour and forming limit during biaxial compressions of magnesium alloy AZ31 at room temperature
Shimizu I.,Tada N.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100616001
Abstract: The plastic behaviour and compressive fracture of AZ31 magnesium alloy were examined at room temperature. The uniaxial compression tests and biaxial compression tests along linear and nonlinear strain paths were carried out until fracture using a unique biaxial compression testing machine developed by author. The results revealed the evolution of plastic anisotropy in biaxial compressions, that is the strain path dependency of work hardening. The adaptability of several forming limit criteria to the compressive fracture of AZ31 alloy was discussed. It was found that the uniform estimation of compressive forming limits by uniaxial and biaxial compressions was difficult by Freudenthal criterion and Oyane criterion. The result of Tresca energy criterion suggested that the criterion based on shear stress has possibility to predict the compressive forming limits at room temperature of AZ31 alloy.
Impurities Effect on Carbonate Reactive Crystallization for the Wastewater
Y. Shimizu,I. Hirasawa
ISRN Chemical Engineering , 2013, DOI: 10.1155/2013/984163
Abstract: Reactive crystallization designed to separate nickel or copper ion from effluents has been advanced for applying to actual industrial wastewater containing impurities. In the primary reaction of this method, metal sulfate solution reacts with sodium carbonate solution in a semibatch crystallizer. In the present study, during the process of nickel or copper ions incorporation, inhibitory effect on seed growth of impurities, like cobalt, manganese, zinc, and borate and phosphate ions, was investigated. Through the 8-hour reactive crystallization, obtained particles’ characters and metals removal efficient were examined. Considering analyses data on metal component ratio in produced crystals, metal ions initial uptake rate was found to be different by the kind of seeds and impurities. And the centrifugation was performed against obtained crystals aimed for examining target metal purity improvement. The results indicated that copper components can incorporate and remove other metal ions easily. In addition, when the anions are used as impurities, depending on the kind of anions, the effect of damaging the surface of seeds or producing many fine particles has been confirmed. 1. Introduction Metal ions in the wastewater have often been treated by coagulation and precipitation methods [1]. In this treatment, however, a large amount of sludge is produced and metal substances are disposed without recycling. Meanwhile, wastewater treatment technologies based on environmental crystallization have an advantage in collecting metal ions as solid crystals. For example, studies about metal ion separation and precipitation methods with the use of a fluidized bed reactor have been preceded [2–4]. Some metal ions were shown to be taken efficiently on seeds such as quartz-sands at an optimum pH. And in our recent report [5], in a study using semibatch crystallizer, we suggested that metal ions were recovered on seeds regularly and continuously at only particular seed inputs. Actually, in the industrial effluent, many kinds of metal ions are contained typically. Metal ions uptake mechanism somewhat relates to the adsorption or coprecipitation process. Some have found the order of metal ions adsorption strength to some base seeds [6–8], and others have examined the pH range at which metal ions can be selectively separated efficiently with the use of difference of solubility products in the process of co-precipitation [9, 10]. Thereby, in this paper, on the basis of nickel or copper ions crystallization in the regulated solution, seeds growth inhibition mechanisms by the
Phase structure of $Z_2$ gauge theories for frustrated antiferromagnets in two dimensions
K. Nakane,A. Shimizu,I. Ichinose
Physics , 2009, DOI: 10.1103/PhysRevB.80.224425
Abstract: In this paper, we study phase structure of $Z_2$ lattice gauge theories that appear as an effective field theory describing low-energy properties of frustrated antiferromagnets in two dimensions. Spin operators are expressed in terms of Schwinger bosons, and an emergent U(1) gauge symmetry reduces to a $Z_2$ gauge symmetry as a result of condensation of a bilinear operator of the Schwinger boson describing a short-range spiral order. We investigated the phase structure of the gauge theories by means of the Monte-Carlo simulations, and found that there exist three phases, phase with a long-range spiral order, a dimer state, and a spin liquid with deconfined spinons. Detailed phase structure and properties of phase transitions depend on details of the models.
Calculation of strongly-coupled rotational bands in terms of the tilted axis cranking model
S. -I. Ohtsubo,Y. R. Shimizu
Physics , 2002, DOI: 10.1016/S0375-9474(02)01356-8
Abstract: Recently observed strongly-coupled rotational bands associated with the $\nu [505]{11/2}^-$ quasiparticle state are studied by means of a microscopic tilted axis cranking (TAC) model. The results of calculation for the routhians and the $B(M1)/B(E2)$ ratios are investigated in the light of other existing models, i.e. the strong-coupling model and the conventional cranking model. It is demonstrated that only the TAC model can successfully reproduce these two observables at the same time. The reason of the success is clarified by making connections between these models.
DFT Calculations on the Effect of Solvation on the Tautomeric Reactions for Wobble Gua-Thy and Canonical Gua-Cyt Base-Pairs  [PDF]
Kazuya Nomura, Ryota Hoshino, Eisuke Shimizu, Yasuhiro Hoshiba, Victor I. Danilov, Noriyuki Kurita
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.43A059
Abstract:

To elucidate the reaction mechanism from wobble Guanine-Thymine (wG-T) to tautomeric G-T base-pairs, we investigate its transition state (TS) by density functional theory (DFT) calculations, in vacuum and in water approximated by continuum solvation model. From the comparison of these results, we attempt to elucidate the effect of solvation on the tautomeric reaction for wG-T. In addition, the same DFT calculations are performed for the canonical G-C base-pair, in order to reveal the difference in the activation energy for the reactions involving wG-T and G-C. The obtained TS structures between wG-T and G*-T/G-T* (asterisk is an enol-form of base) are almost the same in vacuum and in water. However, the activation energy is 16.6 and 19.1 kcal/mol in vacuum and in water, respectively, indicating that the effect of solvation enlarges the energy barrier for the reactions from wG-T to G-T*/G*-T. The activation energy for the tautomeric reaction from G-C to G*-C* is also evaluated to be 15.8 and 12.9 kcal/mol in vacuum and in water, respectively. Therefore, it is expected that the tautomeric reaction from wG-T to G*-T/G-T* can occur in vacuum with a similar probability as that from G-C to G*-C*. We furthermore investigate the TS structure for wG-BrU to reveal the effect of the BrU introduction into wG-T. The activation energy is 14.5 and 16.7 kcal/mol in vacuum and in water, respectively. Accordingly, the BrU introduction is found to increase the probability of the tautomeric reaction producing the enol-form G* and T* bases. Because G* prefers to bind to T rather than to C, and T* to G not A, our calculated results reveal that the spontaneous mutation from C to T or from A to G bases is accelerated by the introduction of wG-BrU base-pair.

DFT Study on Reaction Mechanism of DNA Base Pair with Hydroxyl Radical  [PDF]
Eisuke Shimizu, Ryota Hoshino, Kazuya Nomura, Victor I. Danilov, Noriyuki Kurita
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.43A062
Abstract:

In order to elucidate the indirect effect by radiation on DNA base pairs, we investigate the mechanism for the attacking reaction of a hydroxyl radical (·OH-radical) to the G-C and A-T base pairs, by the density functional theory (DFT) calculations. The effect of solvation on the mechanism is also revealed by performing the same DFT calculations under the continuum solvation approximation. We find the stable structures for the dehydrogenated G-C and A-T base pairs, in which the hydrogen atom of NH2 group of G or A base is abstracted by the ·OH-radical. The solvation around the base pairs stabilizes the dehydrogenated structures significantly, indicating the acceleration of the attacking reaction by ·OH-radical to the base pairs in water. Therefore, we conclude that the hydrogen atom of the NH2 group of G or A base in the G-C and A-T base pairs is the most preferably abstracted by the ·OH-radical in living cells.

Identification of Toxoplasma gondii antigens involved in the IgM AND IgG indirect hemagglutination tests for the diagnosis of toxoplasmosis
YAMAMOTO, Y.I.;HUBER, V.;HOSHINO-SHIMIZU, S.;
Revista do Instituto de Medicina Tropical de S?o Paulo , 1997, DOI: 10.1590/S0036-46651997000300005
Abstract: crude toxoplasma gondii antigens represent raw material used to prepare reagents to be employed in different serologic tests for the diagnosis of toxoplasmosis, including the igm and igg indirect hemagglutination (igg-ha and igm-ha) tests. so far, the actual antigenic molecules of the parasite involved in the interaction with agglutinating anti-t. gondii antibodies in these tests are unknown. the absorption process of serum samples from toxoplasmosis patients with the igg-ha reagent (g-toxo-ha) demonstrated that red cells from this reagent were coated with t. gondii antigens with mr of 39, 35, 30, 27, 22 and 14 kda. the immune-absorption process with the igm-ha reagent (m-toxo-ha), in turn, provided antibody eluates which recognized antigenic bands of the parasite corresponding to mr of 54, 35 and 30 kda, implying that these antigens are coating red cells from this reagent. the identification of most relevant antigens for each type of ha reagent seems to be useful for the inspection of the raw antigenic material, as well as of reagent batches routinely produced. moreover the present findings can be used to modify these reagents in order to improve the performance of ha tests for the diagnosis of toxoplasmosis
Identification of Toxoplasma gondii antigens involved in the IgM AND IgG indirect hemagglutination tests for the diagnosis of toxoplasmosis
YAMAMOTO Y.I.,HUBER V.,HOSHINO-SHIMIZU S.
Revista do Instituto de Medicina Tropical de S?o Paulo , 1997,
Abstract: Crude Toxoplasma gondii antigens represent raw material used to prepare reagents to be employed in different serologic tests for the diagnosis of toxoplasmosis, including the IgM and IgG indirect hemagglutination (IgG-HA and IgM-HA) tests. So far, the actual antigenic molecules of the parasite involved in the interaction with agglutinating anti-T. gondii antibodies in these tests are unknown. The absorption process of serum samples from toxoplasmosis patients with the IgG-HA reagent (G-toxo-HA) demonstrated that red cells from this reagent were coated with T. gondii antigens with Mr of 39, 35, 30, 27, 22 and 14 kDa. The immune-absorption process with the IgM-HA reagent (M-toxo-HA), in turn, provided antibody eluates which recognized antigenic bands of the parasite corresponding to Mr of 54, 35 and 30 kDa, implying that these antigens are coating red cells from this reagent. The identification of most relevant antigens for each type of HA reagent seems to be useful for the inspection of the raw antigenic material, as well as of reagent batches routinely produced. Moreover the present findings can be used to modify these reagents in order to improve the performance of HA tests for the diagnosis of toxoplasmosis
Numerical modeling of Asian dust emission and transport with adjoint inversion using LIDAR network observations
K. Yumimoto,I. Uno,N. Sugimoto,A. Shimizu
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: A four-dimensional variational (4D-Var) data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4) is applied to a heavy dust event which occurred between 20 March and 4 April 2007 over eastern Asia. The vertical profiles of the dust extinction coefficients derived from NIES LIDAR observation network are directly assimilated. We conduct two experiments to evaluate impacts of selections of observation sites: Experiment A uses five Japanese observation sites located only downwind of dust source regions; the other Experiment B uses these sites together with two other sites near source regions (China and Korea). Validations using various observation data (e.g., PM10 concentration, MODIS AOT, OMI Aerosol Index, and the dust extinction coefficient derived by space-based LIDAR NASA/CALIPSO) are demonstrated. The modeled dust extinction coefficients are improved considerably through the assimilation. Assimilation results of Experiment A are consistent with those of Experiment B, indicating that observations of Experiment A can capture the dust event correctly and include sufficient information for dust emission inversion. Time series of dust AOT calculated by modeled and LIDAR dust extinction coefficients show good agreement. At Seoul, Matsue, and Toyama, assimilation reduces the root mean square errors of dust AOT by 31–32%. Vertical profiles of the dust layer observed by CALIPSO are also compared with assimilation results. The dense dust layer was trapped between θ=280–300 K and elevated higher toward the north; the model reproduces those characteristics well. The modeled dust AOT along the orbit paths agrees well with the CALIPSO dust AOT, OMI AI, and the coarse mode AOT retrieved from MODIS; especially the modeled dust AOT and the MODIS coarse mode AOT are consistent quantitatively. Assimilation results increase dust emissions over the Gobi Desert and Mongolia considerably; especially between 29 and 30 March, emission flux is increased by about 2–3 times. The heavy dust event is caused by the heavy dust uplift flux over the Gobi Desert and Mongolia during those days. We obtain the total optimized dust emissions of 57.9 Tg (Experiment A; 57.8% larger than before assimilation) and 56.3 Tg (Experiment B; 53.4% larger).
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