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Search Results: 1 - 10 of 1099 matches for " Nobuhiro Tamura "
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Difference in Structural Relaxation Times of Inner Surface and Inner Bulk Region of Silica Glass Arc Tube  [PDF]
Takuya Honma, Nobuhiro Tamura, Kazuya Saito, Edson Sekiya
New Journal of Glass and Ceramics (NJGC) , 2013, DOI: 10.4236/njgc.2013.31008
Abstract: The fictive temperature and structural relaxation of a silica glass arc tube were investigated to elucidate the origin of cracking in the arc tubes used in high-intensity discharge lamps for vacuum ultraviolet light sources. The structural relaxation time near the inner surface was decreased much more than that in the inner bulk region, resulting in a large difference in the fictive temperature between these two areas at high-intensity discharge lamp operating temperatures. This difference should induce strain in the silica glass network. On the basis of our results, we suggest ways to avoid cracking and extend the lifetime of high-intensity discharge lamps.
Platelet Dynamics in the Sinusoid of the Liver after Ischemia- Reperfusion
Takafumi Tamura,Tadashi Kondo,Kiyoshi Fukunaga,Nobuhiro Ohkohchi
Journal of Gastroenterology and Hepatology Research , 2012, DOI: 10.6051/ j.issn.2224-3992.2012.01.102
Abstract: Hepatic ischemia-reperfusion (I/R) activates Kupffer cells (KCs),which produce various inflammatory cytokines, causing adhesionof neutrophils to sinusoidal endothelium and microcirculatorydisturbance. These phenomena are well known as mechanisms ofhepatic I/R injury. Recently, in the early period of I/R, i.e., within120 min after reperfusion, it was proved that accumulation of plateletsto sinusoid is strongly associated with mechanism of the I/R.In this editorial, we describe the mechanism of I/R injury focusingon platelets and KCs in the early period of I/R. We successfullyobserved the dynamics of platelets and KCs in the hepatic sinusoidtime dependently using an intravital microscopy (IVM) system inrat. Platelets were isolated from the whole blood of syngeneic ratsand labeled with rhodamine-6G. KCs were labeled using the liposomeentrapment method. The observations revealed that plateletsattached to KCs and sinusoidal endothelial cells (SECs) duringthe early period of I/R. The number of platelets adhering to bothKCs and SECs increased in proportion to the duration of reperfusion.These interactions may be causally related to the downstreameffects of I/R and are important to characterize. The existence ofplatelets as well as KCs is indispensable for the I/R injury.
Heterogeneity and Colonial Governance  [PDF]
Nobuhiro Mizuno
Theoretical Economics Letters (TEL) , 2015, DOI: 10.4236/tel.2015.52032
Abstract: Some existing studies argue that indirect colonial rule adversely affects postcolonial development. To analyze the situation under which a colonial power adopts indirect rule to govern a colony, we analyze a delegation model wherein the colonial power decides whether to delegate policy choice to an agent who has an information advantage but has different policy preferences from that of the colonial power. The colonial power decides whether to delegate policy choice in multiple districts, and can acquire information by paying a cost in each district. We show that colonial powers are prone to adopt indirect rule when the heterogeneity among districts is high. The results are a possible explanation for why colonial powers utilized indirect rule in Africa, a region with high levels of ethnic diversity.
Suzaku Observations of the Merging Cluster Abell 85: Temperature Map and Impact Direction
Nobuhiro Tanaka,Akihiro Furuzawa,Shigeru J. Miyoshi,Takayuki Tamura,Tadafumi Takata
Physics , 2010, DOI: 10.1093/pasj/62.3.743
Abstract: To investigate the present situation of the merging in the southern outer region of Abell 85, we carried out long (~100 ks) observations with Suzaku, and produced an X-ray hardness ratio map. We found a high hardness ratio peak in the east side of a subcluster located in the south of the cluster; an X-ray spectrum of the region including this peak indicates a high temperature of ~8.5 keV. This hot spot has not been reported so far. We consider that this hot spot is a postshock region produced by the infall of the subcluster from the southwest. By using the Rankine--Hugoniot jump conditions for shocks, the Mach number and the infall velocity of the subcluster are obtained as 1.5 +/- 0.2 and 1950^{+290}_{-280} km s^{-1}, respectively, in the case of merging with the subcluster from the southwest direction. By using the redshift difference between the A 85 and the subcluster obtained from optical observations, the angle between the line of sight and the direction of the motion of the subcluster is estimated to be 75^{+7}_{-8} degrees. We estimate the kinetic energy of the subcluster and the energy used for intracluster medium (ICM) heating to be ~10^{63} and \lesssim 8 \times 10^{60} erg, respectively. This shows that the deceleration of the subcluster by ICM heating has been negligibly small.
Fluoroquinolone resistance mechanisms in an Escherichia coli isolate, HUE1, without quinolone resistance-determining region mutations
Toyotaka Sato,Shin-ichi Yokota,Ikuo Uchida,Torahiko Okubo,Masaru Usui,Masahiro Kusumoto,Masato Akiba,Nobuhiro Fujii,Yutaka Tamura
Frontiers in Microbiology , 2013, DOI: 10.3389/fmicb.2013.00125
Abstract: Fluoroquinolone resistance can cause major clinical problems. Here, we investigated fluoroquinolone resistance mechanisms in a clinical Escherichia coli isolate, HUE1, which had no mutations quinolone resistance-determining regions (QRDRs) of DNA gyrase and topoisomerase IV. HUE1 demonstrated MICs that exceeded the breakpoints for ciprofloxacin, levofloxacin, and norfloxacin. HUE1 harbored oqxAB and qnrS1 on distinct plasmids. In addition, it exhibited lower intracellular ciprofloxacin concentrations and higher mRNA expression levels of efflux pumps and their global activators than did reference strains. The genes encoding AcrR (local AcrAB repressor) and MarR (MarA repressor) were disrupted by insertion of the transposon IS3-IS629 and a frameshift mutation, respectively. A series of mutants derived from HUE1 were obtained by plasmid curing and gene knockout using homologous recombination. Compared to the MICs of the parent strain HUE1, the fluoroquinolone MICs of these mutants indicated that qnrS1, oqxAB, acrAB, acrF, acrD, mdtK, mdfA, and tolC contributed to the reduced susceptibility to fluoroquinolone in HUE1. Therefore, fluoroquinolone resistance in HUE1 is caused by concomitant acquisition of QnrS1 and OqxAB and overexpression of AcrAB–TolC and other chromosome-encoded efflux pumps. Thus, we have demonstrated that QRDR mutations are not absolutely necessary for acquiring fluoroquinolone resistance in E. coli.
Discovery of an Outstanding Disk in the cD Galaxy of the Hydra A Cluster
Yutaka Fujita,Nobuhiro Okabe,Kosuke Sato,Takayuki Tamura,Satoki Matsushita,Hiroyuki Hirashita,Masanori Nakamura,Kyoko Matsushita,Kazuhiro Nakazawa,Motokazu Takizawa
Physics , 2013, DOI: 10.1093/pasj/65.6.L15
Abstract: The central cD galaxy of the Hydra A cluster has one of the most powerful active galactic nuclei (AGNs) in the nearby Universe (z <0.2). We report on the discovery of a dust lane in the cD galaxy using Subaru telescope. The i'-band image shows the existence of a dark band of the size of 3.6"x 0.7" (4 kpc x 0.8 kpc), which appears to be quite similar to the dust lane observed in Centaurus A. The morphology indicates that the cold disk that seen as the dust lane is almost edge-on and rotates around the AGN. Since the minor axis of the dust lane is nearly parallel to the radio jets emerging from the AGN, the disk is probably feeding its gas into the central black hole. From the absorption, we estimate the hydrogen column density of the lane is N_H=2.0 x 10^21 cm^-2, and the mass of the disk is ~8 x 10^7 M_sun. The column density is consistent with constraints obtained from Chandra X-ray observations. The age of the disk is >~ 4 x 10^7 yr. The position angle of the disk and the galaxy's photometric axis are misaligned, which may imply that the cold gas in the disk is brought via galaxy mergers. Our observations may indicate that the supply of cold gas by galaxy mergers is required for the most intensive feedback from AGNs.
Anonymous Giving as a Vice: An Application of Image Motivation  [PDF]
Masaoki Tamura
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.24071
Abstract: While some donors boast about their giving, others give anonymously. A novel feature of this paper is that anonymity is endogenously controlled by donors themselves, not exogenously controlled by fundraisers. Is anonymous giving really a virtue, as is generally recognised? Paradoxically, this paper proves that anonymity is a vice for fundraisers even if it is what donors desire. If many altruists (a good type) switch from known to anonymous giving, it relatively lowers the group reputation of known donors and enhances that of non-donors. These effects dilute the incentive for other individuals to become known donors, if they have psychological “image motivation”. I suggest a practical method to control the expected number of anonymous donors: fundraisers remove the “check boxes” from their web sites.
Mechanical Properties of a Vacuum-Sintered Apatite Body for Use as Artificial Bone  [PDF]
Kenichi Tamura
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2015, DOI: 10.4236/jbnb.2015.61005
Abstract:

Regenerative artificial bone material and bone parts were fabricated using vacuum-sintered bodies of a “titanium medical apatite (TMA?)” that is formed by chemically connecting Ti oxide molecules to the reactive [Ca10 (PO4 )6 ] group of hydroxyapatite (HAp). Sintering at temperatures of 1273 - 1773 K caused this TMA sintered bodies to recrystallize and form a varying mix of α-TCP (tricalcium phosphate), β-TCP and Perovskite-CaTiO3 phases. The Perovskite crystals proved to be quite stable and hard, forming a uniform distribution of similarly sized fibers in all directions under vacuum sintering, but an irregular distribution and size when sintered in the presence of oxygen. Complete recrystallization was achieved by vacuum sintering at temperatures in excess of 1473 K. In particular, TMA vacuum-sintered bodies at 1573 K are given the maximum value; a Vickers hardness of 400, a bending strength of 43 MPa, a compressive strength of 270 MPa and a density of approximately 2300 kg/m3 was achieved that closely corresponds to that of compact bone or a tooth. As these TMA bodies could also be cut into various forms, they are considered a promising biomaterial for use as artificial bone in the regeneration of natural bone, or to provide reinforcement of bone junctions in dental and orthopedic surgery.

A Signaling Explanation for Political Parties and Advertisements  [PDF]
Tamura Masaoki
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.83018
Abstract: This study examines the signaling roles of political parties and political advertising. Although politicians’ types are unobservable during an election, their party affiliations and political advertisements are observable to the voters. Through these two political behaviors, politicians can reveal their hidden types to the public. We extend Snyder and Ting to a multi-period model with the possibility of reelection and examine the roles and relationships of political parties and advertisements. We show that political parties are not sufficient signals to reveal politicians’ types. Political advertisements work as a complementary signal to political parties. With political parties and advertisements, voters can elect their favored candidates adequately. Even if the advertisements are a waste of money, they contribute to voting for favored candidates.
On Otaki’s Keynesian Macroeconomic Model  [PDF]
Masaoki Tamura
Theoretical Economics Letters (TEL) , 2019, DOI: 10.4236/tel.2019.91010
Abstract:

“Otaki model” is an overlapping generations (OLG) model with fiat money and imperfect competition. It derives Keynesian implications such as involuntary unemployment, welfare-improving fiscal and monetary policy, and money non-neutrality. Though its structure can be applied to other models with productive implications, the Otaki model has not been fully understood by economists. One reason could be that in seminal works about the Otaki model, he implicitly changed the hidden assumptions, and hence, the implications of the model. By employing such assumptions, he aimed at dealing with multiplicity of equilibria in the OLG model. This paper points out the hidden assumptions and reinterprets the Otaki model from the viewpoint of multiple equilibria.

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