Stem cells do not all respond the same way, but the mechanisms underlying this heterogeneity are not well understood. Here, we found that expression of Hes1 and its downstream genes oscillate in mouse embryonic stem (ES) cells. Those expressing low and high levels of Hes1 tended to differentiate into neural and mesodermal cells, respectively. Furthermore, inactivation of Hes1 facilitated neural differentiation more uniformly at earlier time. Thus, Hes1-null ES cells display less heterogeneity in both the differentiation timing and fate choice, suggesting that the cyclic gene Hes1 contributes to heterogeneous responses of ES cells even under the same environmental conditions. Supplemental material is available at http://www.genesdev.org.
Understanding changes in excited state properties under the influence of an external stimulus, such as pressure or temperature, is important in the context of optimizing molecular components for a number of applications including sensors and imaging reagents. Herein, we use UV/Vis absorption, fluorescence and excitation spectroscopies and fluorescence lifetime measurements supported by calculations to probe the effect of hydrostatic pressure on the excited state characteristics of a conformationally-divergent mechanochromic compound PTZ-DBPHZ (containing two phenothiazine moieties attached to a dibenzo[a,j]phenazine core) in toluene and methylcyclohexane. We demonstrate that hydrostatic pressure can be used to manipulate the equilibria between excited state conformers. This work provides new perspectives for mechanoresponsive materials and as an attractive alternative to conventional ratiometric sensors.[a] Prof.
Yttrium oxide (Y 2 O 3 ) coatings have been prepared by axial suspension plasma spraying with fine powders. It is clarified that the coatings have high hardness, low porosity, high erosion resistance against CF 4 -containing plasma and retention of smooth eroded surface. This suggests that the axial suspension plasma spraying of Y 2 O 3 is applicable to fabricating equipment for electronic devices, such as dry etching. Surface morphologies of the slurry coatings with splats are similar to conventional plasmasprayed Y 2 O 3 coatings, identified from microstructural analysis. Dense coating structures with no lamellar boundaries have been seen, which is apparently different from the conventional coatings. It has also been found that crystal structure of the suspension coatings mainly composed of metastable monoclinic phase, whereas the powders and the conventional plasma spray coatings have stable cubic phase. Mechanism of coating formation by plasma spraying with fine powder slurries is discussed based on the results.
MoB/CoCr, a novel cermet material for thermal spraying, with high durability in molten alloys has been developed to utilize for aluminum die-casting parts, and for hot continuous dipping rolls in Zn and Al-Zn plating lines. The durability of the MoB/CoCr coatings prepared by high velocity oxy-fuel (HVOF) spraying has been investigated using a molten-metal immersion tester. The tests revealed that the MoB/ CoCr coating has much higher durability without dissolution in the molten Al-45wt.%Zn alloy. Little change of crystal structure, mainly composed of double borides of CoMoB and CoMo 2 B 2 , is observed after the immersion test, suggesting that the double borides have much higher durability. Using undercoat is effective to reduce the influence of large difference in thermal expansion between the MoB/ CoCr topcoat and substrate of stainless steel of AISI 316L, widely used for the hot continuous dipping rolls. Optimized thickness combinations of topcoat and undercoat are necessary to obtain intrinsic performance of low reactive MoB/CoCr against the molten Al-45wt.%Zn alloy.
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