Abstract We report the growth of bulk β-Ga 2 O 3 crystals based on crystal pulling from a melt using a cold container without employing a precious-metal crucible. Our approach, named oxide crystal ...growth from cold crucible (OCCC), is a fusion between the skull-melting and Czochralski methods. The absence of an expensive precious-metal crucible makes this a cost-effective crystal growth method, which is a critical factor in the semiconductor industry. An original construction 0.4–0.5 MHz SiC MOSFET transistor generator with power up to 35 kW was used to successfully grow bulk β-Ga 2 O 3 crystals with diameters up to 46 mm. Also, an original diameter control system by generator frequency change was applied. In this preliminary study, the full width at half maximum of the X-ray rocking curve from the obtained β-Ga 2 O 3 crystals with diameters ≤ 46 mm was comparable to those of β-Ga 2 O 3 produced by edge-defined film fed growth. Moreover, as expected, the purity of the obtained crystals was high because only raw material-derived impurities were detected, and contamination from the process, such as insulation and noble metals, was below the detection limit. Our results indicate that the OCCC technique can be used to produce high-purity bulk β-Ga 2 O 3 single crystalline substrate.
The phenomenon that the transformation texture near the initial texture reproduces after the phase transformation cycle such as ferrite (α, body-centered cubic)→austenite (γ, face-centered cubic)→α ...is called a texture memory. In this study, the texture change in a 0.1% C–1% Mn hot-rolled steel sheet during the α→γ→α transformation cycle was studied via neutron diffraction and the transformation texture prediction based on a variant selection rule that we call the double Kurdjumov–Sachs (K–S) relation. The texture change observed by neutron diffraction, which clearly showed the texture memory, could be quantitatively reproduced by the proposed variant selection rule adopted into the calculation method based on the spherical harmonics expansion of orientation distribution functions. Therefore, it is most likely that the texture memory in steel is caused by the preferential selection of those K–S variants that reduce the interfacial energy between a precipitate and two adjoining parent phase grains at the same time, which we call the double K–S relation.
Transcription by the nuclear factor of activated T cells (NFAT) is regulated by the frequency of Ca2+ oscillation. However, why and how Ca2+ oscillation regulates NFAT activity remain elusive. NFAT ...is dephosphorylated by Ca2+‐dependent phosphatase calcineurin and translocates from the cytoplasm to the nucleus to initiate transcription. We analyzed the kinetics of dephosphorylation and translocation of NFAT. We show that Ca2+‐dependent dephosphoryl ation proceeds rapidly, while the rephosphorylation and nuclear transport of NFAT proceed slowly. Therefore, after brief Ca2+ stimulation, dephosphoryl ated NFAT has a lifetime of several minutes in the cytoplasm. Thus, Ca2+ oscillation induces a build‐up of dephosphorylated NFAT in the cytoplasm, allowing effective nuclear translocation, provided that the oscillation interval is shorter than the lifetime of dephos phorylated NFAT. We also show that Ca2+ oscillation is more cost‐effective in inducing the translocation of NFAT than continuous Ca2+ signaling. Thus, the lifetime of dephosphorylated NFAT functions as a working memory of Ca2+ signals and enables the control of NFAT nuclear translocation by the frequency of Ca2+ oscillation at a reduced cost of Ca2+ signaling.
Abstract
A mechanism is proposed that can predict the textures as well as the influence of austenite grain size on martensite starting temperature in steels. The anisotropic elastic energy by shape ...change of martensite changes depending upon variants in neighbour austenite grains, whereas it does not in immediate parent grains in which martensite grows. A mechanism based on this behaviour of elastic energy can explain not only the texture formation of martensite but also the well-known austenite grain size dependence of Ms, particularly the abrupt drop of about 30K in the grain size range below 20 μm.
We have developed a vegetation monitoring lidar called a laser-induced fluorescence spectrum (LIFS) lidar which is able to get the living status of plants by observing their fluorescence remotely. ...The features of its operation are; daytime observations possible even outdoors, mobility and self-sufficiency, capability of mapping plant living information, and a user-friendly operation by unifying the controls of different equipment of the lidar using software. These features make observations by our LIFS lidar possible at any time and any place. In forest observations, we could depict three-dimensional structures of fluorescence spectrums. We also discuss in this work the possibility of monitoring other plant physiological information such as the concentration of chlorophyll and photosynthesis secondary metabolites in this work.
Due to their excellent thermoelectric (TE) performance, skutterudite materials have been selected by many laboratories and companies for development of TE modules to recover power from waste heat at ...high temperatures (300°C to 600°C). After years of effort, we have developed reliable
n
- and
p
-type skutterudite materials showing maximum figure of merit (
ZT
) of 1.0 at 550°C and 0.75 at 450°C, respectively. In this work, we systematically investigated the performance of a module made using these two kinds of skutterudite. We demonstrate ∼7.2% conversion efficiency for temperature of 600°C at the hot side of the module and 50°C at the cold side, and show that the module had excellent stability in the high-temperature environment. Further improving the TE performance of our skutterudites, the conversion efficiency reached ∼8.5% under the same condition.
A database containing spectrum and cross-section of the fluorescence of substances has been made. In test of forest environment monitoring by our Laser-Induced Fluorescence Spectrum (LIFS) lidar, the ...database showed that the origin substance of the aerosol observed by the lidar was cedar pollen, and the concentration was calculated using the cross-section. In the urban atmosphere monitoring, three substances stored in the database were proposed to be the origins of the aerosol. Based on these experiments, we discuss the usefulness of the fluorescence database in lidar observations.
Filled skutterudite is a promising material for thermoelectric power generation because its ZT value is relatively high. However, mass production of high-performance thermoelectric materials remains ...a challenge. This study focused on the sintering process of thermoelectric materials. Large-diameter
n
-type (Yb or La, Ca, Al, Ga, In)
0.8
(Co, Fe)
4
Sb
12
skutterudite sintering bodies with a small thickness were successfully produced by the spark plasma sintering (SPS) method. When direct current flows through the thermoelectric sintering body during the SPS pulse, the Peltier effect causes a temperature difference within the sintering body. To eliminate the Peltier effect, an electrical insulating material was inserted between the punch (electrode) and the sintering body. In this way, an
n
-type La-filled skutterudite sample with a diameter of 200 mm, thickness of 21 mm, and weight of 5 kg was successfully produced. The thermoelectric properties and microstructures of the sample were almost the same throughout the whole sintering body, and the dimensionless figure of merit reached 1.0 at 773 K.
A model to quantitatively predict ferrite (α) textures in hot-rolled steel sheets has been developed. In this model, the crystal plasticity model, called "Grain Interaction model (GIA)", and the ...transformation texture model, called "Double K-S relation (DKS)", are linked together. The deformed austenite (γ) texture is predicted by GIA with taking not only the standard {111} slip system but also non-octahedral slip systems into account. Then the transformed a texture is calculated by DKS, in which a nucleated α prefers to have orientation relationship near the Kurdjumov-Sachs relation with both of two neighboring γ grains. For validation, single pass hot-rolling tests on a C-Si-Mn steel were carried out. The comparison between the predicted and the experimental textures shows that the linked model (GIA & DKS) can lead to a remarkable reproduction of the texture of hot-rolled steel sheets.
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