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Search Results: 1 - 10 of 455 matches for " Furukawa "
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Interactive Visualization System of Taylor Vortex Flow Using Stokes' Stream Function  [PDF]
Hiroyuki Furukawa
World Journal of Mechanics (WJM) , 2012, DOI: 10.4236/wjm.2012.24023
Abstract: Taylor vortex flow between two concentric rotating cylinders with finite axial length includes various patterns of laminar and turbulent flows, and its behavior has attracted great interests. When mode bifurcation occurs, quantitative parameters such as the volume-averaged energy change rapidly. It is important to visualize the behaviors of vortices. In this study, a three-dimensional visualization system with respect to time is devised. This system can change the viewpoint of flow visualization, and we can observe the track of a vortex from any point. The volume-averaged energy is projected to the track of the center of a vortex. The proposed system can help to investigate the relationship between the mode bifurcation process and the volume-averaged energy.
Asymmetric Local Government Consolidations with Heterogeneous Local Public Goods  [PDF]
Akiyoshi Furukawa
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.44041
Abstract:

This paper analyzes the consolidation of asymmetric local governments. When a small district merges into a larger one, the consolidating government can provide a higher level of public services. Normally, residents in large districts favor consolidation while residents in small district oppose it. This paper shows a condition in which desirable consolidation is realized. The result is that only when fixed costs exist within which the public good is produced after consolidation and the commuting cost is very low, is consolidation realized. In an alternate case, consolidation does not occur although it is desirable.

Study on Non-Uniqueness of Taylor Vortex Flow Changing Inner Cylinder Acceleration Time  [PDF]
Hiroyuki Furukawa, Tomohito Suzuki
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.88023
Abstract: In concentrically rotating double cylinders consisting of a stationary outer cylinder a rotating inner cylinder, Taylor vortex flow appears. Taylor vortex flow occurs in journal bearings, various fluid machineries, containers for chemical reaction, and other rotating components. Therefore, the analysis of the flow structure of Taylor vortex flow is highly effective for its control. The main parameters that determine the modes of Taylor vortex flow of a finite length are the aspect ratio, Reynolds number Re. Aspect ratio is defined as the ratio of the cylinder length to the gap length between cylinders, and Re is determined on the basis of the angular speed of the inner cylinder. Aspect ratio was set to be 4.0, and Re to be values in the range from 100 to 1000 at intervals of 100. Thus far, a large number of studies on Taylor vortex flow have been carried out; however, the effects of the differences in initial conditions have not yet been sufficiently clarified. In this study, we changed the acceleration time of the inner cylinder in a numerical analysis, and examined the resulting changes in the mode formation and bifurcation processes. The acceleration time was changed from 1.0 s to 10.0 s. As a result, a difference was observed in the final mode depending on the difference in the acceleration time. From this finding, non-uniqueness, which is a major characteristic of Taylor vortex flow, was confirmed. However, no regularities regarding the difference in mode formation were found and the tendency of the mode formation process was not specified. Moreover, the processes of developing the vortex resulting in different final modes were monitored over time by visual observation. Similar flow behaviors were initially observed after the start of the calculation. Then, a bifurcation point, at which the flow changed to a mode depending on the acceleration time observed, and finally the flow became steady. In addition, there was also a difference in the time taken for the well-developed flow to reach the steady state. Both EFD (Experimental Fluid Dynamics) and CFD (Computational Fluid Dynamics) results show good agreement qualitatively.
Pathological Roles of Wild-Type Cu, Zn-Superoxide Dismutase in Amyotrophic Lateral Sclerosis
Yoshiaki Furukawa
Neurology Research International , 2012, DOI: 10.1155/2012/323261
Abstract: Dominant mutations in a Cu, Zn-superoxide dismutase (SOD1) gene cause a familial form of amyotrophic lateral sclerosis (ALS). While it remains controversial how SOD1 mutations lead to onset and progression of the disease, many in vitro and in vivo studies have supported a gain-of-toxicity mechanism where pathogenic mutations contribute to destabilizing a native structure of SOD1 and thus facilitate misfolding and aggregation. Indeed, abnormal accumulation of SOD1-positive inclusions in spinal motor neurons is a pathological hallmark in SOD1-related familial ALS. Furthermore, similarities in clinical phenotypes and neuropathology of ALS cases with and without mutations in sod1 gene have implied a disease mechanism involving SOD1 common to all ALS cases. Although pathogenic roles of wild-type SOD1 in sporadic ALS remain controversial, recent developments of novel SOD1 antibodies have made it possible to characterize wild-type SOD1 under pathological conditions of ALS. Here, I have briefly reviewed recent progress on biochemical and immunohistochemical characterization of wild-type SOD1 in sporadic ALS cases and discussed possible involvement of wild-type SOD1 in a pathomechanism of ALS. 1. Introduction Amyotrophic lateral sclerosis (ALS) is a fatal paralytic disorder caused by degeneration of motor neurons in the brain and spinal cord. One tenth of the total ALS cases occur in familial forms (fALS), while the other is sporadic with no known genetic components (sALS) [1]. The clinical phenotypes between fALS and sALS are usually indistinguishable; therefore, the understanding of the genetic cause in fALS will be also relevant in sALS cases. In spite of tremendous numbers of clinical, pathological, and biochemical studies, however, we still have no cure for this devastating disease. In 1993, there was a milestone event in the studies on ALS; mutations in sod1 gene were identified to be associated with fALS [2, 3]. Together with the recent findings on the pathogenic mutations in c9orf72 gene [4, 5], the mutations in sod1 are now prevailed in fALS (~20% of total familial cases), and more than a hundred mutations in sod1 have been found to be associated with fALS (ALSoD: http://alsod.iop.kcl.ac.uk/). The sod1 gene encodes a protein, Cu, Zn-superoxide dismutase (SOD1), which catalyzes the detoxification of superoxide anion by dismutation into oxygen and hydrogen peroxide [6]. Retardation of such SOD1 activity with mutations had been initially expected to be pathogenic in fALS; however, knockout of sod1 gene in mice did not reproduce the ALS-like symptoms [7],
Biogeochemical consequences of macrofauna burrow ventilation?
Yoko Furukawa
Geochemical Transactions , 2001, DOI: 10.1186/1467-4866-2-83
Abstract: Burrowing infauna in aquatic sediments induce temporal fluctuation in concentrations of dissolved species (i.e., geochemical oscillation) through their metabolism and burrow ventilation activities. They periodically irrigate their burrows to replace metabolite-rich burrow water with fresh overlying water. The immediate vicinity of burrow walls is subject to periodic changes in the concentrations of oxygen, nutrients, and other pore water species.[1,2]Geochemical oscillation affects the courses of organic carbon (OC) diagenesis.[3] Field and laboratory studies suggest that OC remineralization rates are enhanced by the redox oscillation, even though the anoxic period in each oscillation cycle is typically much longer (~10–100X) than the oxic period for a given sediment microenvironment.[4,5] Temporally averaged redox conditions do not directly correlate to the rates and magnitudes of OC reactions.[3,6] A comprehensive understanding of OC diagenesis in aquatic sediments thus requires an adequate characterization of the temporal dynamics of redox and other geochemical parameters.Directly observed data for geochemical oscillation induced by infauna are not abundant. A few studies have measured temporal dynamics of geochemical variables in biologically reworked sediments using redox potential, Eh, and oxygen microprobes.[1,7,8] The number of such studies is small despite the importance of geochemical oscillation: this may be largely due to the technical difficulties in measuring the geochemical phenomena that are not only temporally variable but also are confined to small regions. For example, in shallow marine and estuarine sediments, O2 penetration in the vicinity of burrow walls is limited to a few millimeters,[9] and thus oscillation of redox and other related parameters may be restricted to the regions within a few millimeters of burrow walls. The temporal scale of oscillation at burrow walls depends on the burrow ventilation habits of infauna, and each oscillation c
O PCC e a gest?o dos presídios em S?o Paulo
Furukawa, Nagashi;
Novos Estudos - CEBRAP , 2008, DOI: 10.1590/S0101-33002008000100003
Abstract: in this interview, former secretary of public security of the state of s?o paulo nagashi furukawa discusses his administration and polices related to public security in brazil. the crisis caused by the attacks of the pcc (primeiro comando da capital) in 2006, its origins and consequences are among the main subjects of the interview.
Redox environment is an intracellular factor to operate distinct pathways for aggregation of Cu,Zn-superoxide dismutase in amyotrophic lateral sclerosis
Yoshiaki Furukawa
Frontiers in Cellular Neuroscience , 2013, DOI: 10.3389/fncel.2013.00240
Abstract: Dominant mutations in Cu,Zn-superoxide dismutase (SOD1) cause a familial form of amyotrophic lateral sclerosis (fALS). Misfolding and aggregation of mutant SOD1 proteins are a pathological hallmark of SOD1-related fALS cases; however, the molecular mechanism of SOD1 aggregation remains controversial. Here, I have used E. coli as a model organism and shown multiple distinct pathways of SOD1 aggregation that are dependent upon its thiol-disulfide status. Overexpression of fALS-mutant SOD1s in the cytoplasm of E. coli BL21 and SHuffleTM, where redox environment is reducing and oxidizing, respectively, resulted in the formation of insoluble aggregates with notable differences; a disulfide bond of SOD1 was completely reduced in BL21 or abnormally formed between SOD1 molecules in SHuffleTM. Depending upon intracellular redox environment, therefore, mutant SOD1 is considered to misfold/aggregate through distinct pathways, which would be relevant in description of the pathological heterogeneity of SOD1-related fALS cases.
Magnetoresistance of the Double-Exchange Model in Infinite Dimension
Nobuo Furukawa
Physics , 1995, DOI: 10.1143/JPSJ.64.2734
Abstract: Double-exchange model in infinite dimension is studied as the strong Hund's coupling limit $J\to\infty$ of the Kondo lattice model. Several quantities such as Green's function and the d.c.\ conductivity are calculated in analytical forms. Magnetoresistance in lightly doped (La,Sr)MnO$_3$ is reproduced very well.
Temperature Dependence of the Conductivity in (La,Sr)MnO$_3$
Nobuo Furukawa
Physics , 1995, DOI: 10.1143/JPSJ.64.3164
Abstract: Using the Kondo lattice model with classical spins in infinite dimension, conductivity in the perovskite-type $3d$ transition-metal oxide (La,Sr)MnO$_3$ is theoretically studied. Green's functions as well as spontaneous magnetization are obtained exactly on the Bethe lattice as a function of temperature. Conductivity is calculated from the Kubo formula. Below the Curie temperature, resistivity as a function of magnetization is in a good agreement with the experimental data. Anomalous behaviour in the temperature dependence of the optical conductivity observed in (La,Sr)MnO$_3$ is also explained.
Magnetic Transition Temperature of (La,Sr)MnO$_3$
Nobuo Furukawa
Physics , 1995, DOI: 10.1143/JPSJ.64.2754
Abstract: Using the Kondo lattice model with classical spins in infinite dimension, magnetic phase transition in the perovskite-type $3d$ transition-metal oxide (La,Sr)MnO$_3$ is theoretically studied. On the Bethe lattice, the self-consistency equations are solved exactly. Curie temperatures at the region of double-exchange ferromagnetism $0.1 < x < 0.25$ as well as the Neel temperature at $x=0$ are well reproduced quantitatively. Pressure effect on the Curie temperature is also discussed.
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