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Yamaji, Daisuke,Kang, Keunsoo,Robinson, Gertraud W.,Hennighausen, Lothar Oxford University Press 2013 Nucleic acids research Vol.41 No.3
<P>The transcription factors Signal Transducer and Activator of Transcription (STAT) 5A/B mediate prolactin-induced mammary development during pregnancy. However, it is not clear how the different processes, expansion and maturation of alveolar precursor cells and the differential induction of milk protein genes are regulated on a molecular level. We have used mouse genetics and genome-wide analyses to determine how altering concentrations of STAT5A and STAT5B impacts mammary epithelial development during pregnancy and the regulation of target genes. The presence of only a single <I>Stat5a</I> or <I>Stat5b</I> allele was sufficient for the establishment of histologically undifferentiated alveolar units and two alleles permitted the execution of a differentiation program similar to that found with all four alleles. While one copy of <I>Stat5</I> induced limited expression of target genes, two copies activated a lactation-like gene signature. Using ChIP-seq analyses on intact tissue under physiological conditions, we found that highly expressed and regulated genes were bound by STAT5 in their promoter proximal regions, whereas upstream binding had minor biological consequences. Remarkably, 80% of the genes bound by STAT5 <I>in vivo </I>were not under STAT5 control. RNA polymerase II intensity was directly proportional to STAT5 concentration only on STAT5 regulated genes providing mechanistic insight by which STAT5 activates mammary specific genes.</P>
Yamaji, Minoru,Hakoda, Yuuma,Horimoto, Ami,Okamoto, Hideki Korean Society of Photoscience 2014 Rapid communication in photoscience Vol.3 No.4
Novel diphenylphenanthrenes (DPPs) were prepared by a photocyclization method, and the substituent effects of the phenyl groups on the photophysical properties of the phenanthrene chromophore were investigated based on measurements of fluorescence yields, lifetimes, and transient absorption. Fluorescence activities in DPPs are increased by introducing phenyl rings that can enhance the transition moment along the short axis of the phenanthrene skeleton. Intersystem crossing from the fluorescent states to the triplet manifolds is shown to be operative through the triplet-triplet absorption spectra obtained by laser photolysis techniques.
Toru Yamaji,Hideto Tada,Koji Fukushima,Msafumi Kobune,Tetsuo Yazawa 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Bismuth lanthanum titanate (BLT) films with compositions of (1-x)Bi3.25La0.75Ti3O12 + xBi2O3, where x = 0.28 . 0.36, were successfully deposited on Pt(111)/SiO2/Si(100) substrates by rf-magnetron sputtering using a powder target. All the BLT films were confirmed to have a single-phase bismuth-layer perovskite structure without the presence of a secondary phase. The x = 0.28 and 0.30 BLT films exhibited rounded grain morphologies with an average grain size of approximately 320 nm. On the other hand, BLT films with excess Bi2O3 of x 0.32 had significantly enhanced grain growth, exhibiting oval grain morphologies with an average grain size of approximately 500 nm × 200 nm. From the results for the J . E characteristics, the x = 0.30 BLT films showed the highest electrical insulation. The x = 0.30 BLT film also showed the best hysteresis loop shape with a remanent polarization of 2Pr = 31 μC/cm2 and a coercive field of 2Ec = 170 kV/cm. Measurements of the fatigue characteristics showed that all the samples exhibited nearly fatigue-free behavior that resisted degradation even after 1 × 1010 cycles.C
Kubo Yoshihiro,Yamaji Akifumi 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.3
FEMAXI-ATF is being developed for fuel performance modeling of SiC cladded UO2 fuel with focuses on modeling pellet-cladding mechanical interactions (PCMI). The code considers probability distributions of mechanical strengths of monolithic SiC (mSiC) and SiC fiber reinforced SiC matrix composite (SiC/SiC), while it models pseudo-ductility of SiC/SiC and propagation of cladding failures across the wall thickness direction in deterministic manner without explicitly modeling cracks based on finite element method in one-dimensional geometry. Some hypothetical BWR power ramp conditions were used to test sensitivities of different model parameters on the analyzed PCMI behavior. The results showed that propagation of the cladding failure could be modeled by appropriately reducing modulus of elasticities of the failed wall element, so that the mechanical load of the failed element could be re-distributed to other intact elements. The probability threshold for determination of the wall element failure did not have large influence on the predicted power at failure when the threshold was varied between 25 % and 75 %. The current study is still limited with respect to mechanistic modeling of SiC failure as it only models the propagation of the cladding wall element failure across the homogeneous continuum wall without considering generations and propagations of cracks.
Degradation of SOFC Cell/Stack Performance in Relation to Materials Deterioration
Yokokawa, Harumi,Horita, Teruhisa,Yamaji, Katsuhiko,Kishimoto, Haruo,Brito, M.E. The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.1
The characteristic features of solid oxide fuel cells are reviewed from the viewpoint of the thermodynamic variables to be developed inside cells/stacks particularly in terms of gradients of chemical potential, electrical potential and temperature and corresponding flows of air, fuel, electricity and heat. Examples of abrupt destruction of SOFC systems were collected from failures in controlling their steady flows, while continuous degradation was caused by materials behaviors under gradients of chemical potentials during a long operation. The local equilibrium approximation has been adopted in NEDO project on the durability/reliability of SOFC stacks/systems; this makes it possible to examine the thermodynamic stability/reactivity as well as mass transfer under the thermodynamic variable gradients. Major results of the NEDO project are described with a focus on degradation/deterioration of electrolyte and electrode materials.
Materials Chemical Point of View for Durability Issues in Solid Oxide Fuel Cells
Yokokawa, Harumi,Horita, Teruhisa,Yamaji, Katsuhiko,Kishimoto, Haruo,Brito, M.E. The Korean Ceramic Society 2010 한국세라믹학회지 Vol.47 No.1
Degradation in Solid Oxide Fuel Cell performance can be ascribed to the following fundamental processes from the materials chemical point of view; that is, diffusion in solids and reaction with gaseous impurities. For SOFC materials, diffusion in solids is usually slow in operation temperatures $800\sim1000^{\circ}C$. Even at $800^{\circ}C$, however, a few processes are rapid enough to lead to some degradations; namely, Sr diffusion in doped ceria, cation diffusion in cathode materials, diffusion related with metal corrosion, and sintering of nickel anodes. For gaseous impurities, chromium containing vapors are important to know how the chemical stability of cathode materials is related with degradation of performance. For LSM as the most stable cathode among the perovskite-type cathodes, electrochemical reduction reaction of $CrO_3$(g) at the electrochemically active sites is crucial, whereas the rest of the cathodes have the $SrCrO_4$ formation at the point where cathodes meet with the gases, leading to rather complicated processes to the degradations, depending on the amount and distribution of reacted Cr component. These features can be easily generalized to other impurities in air or to the reaction of nickel anodes with gaseous impurities in anode atmosphere.