SummaryHeme activator protein (HAP), also known as nuclear factor Y or CCAAT binding factor (HAP/NF-Y/CBF), has important functions in regulating plant growth, development and stress responses. The expression of rice HAP gene (OsHAP2E) was induced by probenazole (PBZ), a chemical inducer of disease resistance. To characterize the gene, the chimeric gene (OsHAP2E::GUS) engineered to carry the structural gene encoding b-glucuronidase (GUS) driven by the promoter from OsHAP2E was introduced into rice. The transgenic lines of OsHAP2Ein::GUS with the intron showed high GUS activity in the wounds and surrounding tissues. When treated by salicylic acid (SA), isonicotinic acid (INA), abscisic acid (ABA) and hydrogen peroxide (H 2 O 2 ), the lines showed GUS activity exclusively in vascular tissues and mesophyll cells. This activity was enhanced after inoculation with Magnaporthe oryzae or Xanthomonas oryzae pv. oryzae. The OsHAP2E expression level was also induced after inoculation of rice with M. oryzae and X. oryzae pv. oryzae and after treatment with SA, INA, ABA and H 2 O 2, respectively. We further produced transgenic rice overexpressing OsHAP2E. These lines conferred resistance to M. oryzae or X. oryzae pv. oryzae and to salinity and drought. Furthermore, they showed a higher photosynthetic rate and an increased number of tillers. Microarray analysis showed up-regulation of defence-related genes. These results suggest that this gene could contribute to conferring biotic and abiotic resistances and increasing photosynthesis and tiller numbers.
A Si-based
superlattice is one of the promising thermoelectric films for realizing
a stand-alone single-chip power supply. Unlike a p-type superlattice
(SL) achieving a higher power factor due to strain-induced high hole
mobility, in the n-type SL, the strain can degrade the power factor
due to lifting conduction band degeneracy. Here, we propose epitaxial
Si-rich SiGe/Si SLs with ultrathin Ge segregation interface layers.
The ultrathin interface layers are designed to be sufficiently strained,
not to give strain to the above Si layers. Therein, a drastic
thermal conductivity reduction occurs by larger phonon scattering
at the interfaces with the large atomic size difference between Si
layers and Ge segregation layers, while unstrained Si layers preserve
a high conduction band degeneracy leading to a high Seebeck coefficient.
As a result, the n-type Si0.7Ge0.3/Si SL with
controlled interfaces achieves a higher power factor of ∼25
μW cm–1 K–2 in the in-plane
direction at room temperature, which is superior to ever reported
SiGe-based films: SiGe-based SLs and SiGe films. The Si0.7Ge0.3/Si SL with controlled interfaces also exhibits a
low thermal conductivity of ∼2.5 W m–1 K–1 in the cross-plane direction, which is ∼5
times lower than the reported value in a conventional Si0.7Ge0.3/Si SL. These results demonstrate that strain and
atomic differences controlled by ultrathin layers can bring a breakthrough
for realizing high-performance light-element-based thermoelectric
films.
Critical thicknesses (t
c) of Ge-rich strained Si1-xGex layers grown on various Ge substrates are precisely determined experimentally, and t
c is revealed to strongly depend on the substrate conditions. We find that t
c of Si1-xGex on Ge-on-Si(111) is much lower than that on the Ge(111) substrate for x > 0.75 while, for x < 0.75, t
c becomes equivalent between both substrates, origins of which can be discussed in terms of dislocation nucleation and surface ridge formation. This study provides critical design parameters for strained SiGe(111) based devices, such as high-mobility channels and spintronic devices on a Si platform.
This study presents the material design of Si1−xGex epitaxial films/Si for thin film thermoelectric generators (TFTEGs) by investigating their thermoelectric properties. The thermoelectric films composed of group-IV elements are advantageous due to their compatibility with the Si process. We fabricated Si1−xGex epitaxial films with various controlled x values and strains using various growth methods. Ge epitaxial films without strains exhibited the highest thermoelectric power factor (∼47 μW cm−1 K−2) among various strain-controlled Si1−xGex (x ≠ 1) epitaxial films, which is higher at room temperature than SiGe alloy-based bulks ever reported. On the other hand, strained Si1−xGex epitaxial films showed an ultralow thermal conductivity of ∼2 W m−1 K−1, which is close to the value for amorphous Si. In addition to strained SiGe films with the ultralow thermal conductivity, unstrained Ge films with a high thermoelectric power factor can also be used for future TFTEGs by applying a nanostructuring technique. A preliminary TFTEG of Ge epitaxial films was realized, which generated a maximum power of ∼0.10 μW cm−2 under a temperature difference of 20 K. This demonstrates that epitaxial films composed of group-IV semiconductors are promising materials for TFTEG applications.
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