We show here that the carrier mobility in the novel sp-sp(2) hybridization planar 6,6,12-graphyne sheet should be even larger than that in the graphene sheet. Both graphyne and graphene exhibit a Dirac cone structure near the Fermi surface. However, due to the sp-sp(2) hybridization forming the triple bonds in graphyne, the electron-phonon scattering is reduced compared with that of graphene. The carrier mobility is calculated at the first-principles level by using the Boltzmann transport equation coupled with the deformation potential theory. The intrinsic mobility of the 6,6,12-graphyne is 4.29 × 10(5) cm(2) V(-1) s(-1) for holes and 5.41 × 10(5) cm(2) V(-1) s(-1) for electrons at room temperature, which is found to be larger than that of graphene (∼ 3 × 10(5) cm(2) V(-1) s(-1)).
The signaling network of innate immunity in Drosophila is constructed by multiple evolutionarily conserved pathways, including the Toll-or Imd-regulated NF-κB and JNK pathways. The p38 MAPK pathway is evolutionarily conserved in stress responses, but its role in Drosophila host defense is not fully understood. Here we show that the p38 pathway also participates in Drosophila host defense. In comparison with wild-type flies, the sensitivity to microbial infection was slightly higher in the p38a mutant, significantly higher in the p38b mutant, but unchanged in the p38c mutant. The p38b; p38a double-mutant flies were hypersensitive to septic injury. The immunodeficiency of p38b;p38a mutant flies was also demonstrated by hindgut melanization and larvae stage lethality that were induced by microbes naturally presented in fly food. A canonical MAP3K-MKK cascade was found to mediate p38 activation in response to infection in flies. However, neither Toll nor Imd was required for microbe-induced p38 activation. We found that p38-activated heat-shock factor and suppressed JNK collectively contributed to host defense against infection. Together, our data demonstrate that the p38 pathway-mediated stress response contribute to Drosophila host defense against microbial infection.
Control of doping is crucial for
enhancing the thermoelectric efficiency
of a material. However, doping of organic semiconductors often reduces
their mobilities, making it challenging to improve the thermoelectric
performance. Targeting on this problem, we propose a simple model
to quantitatively obtain the optimal doping level and the peak value
of thermoelectric figure of merit (zT) from the intrinsic carrier
mobility, the lattice thermal conductivity, and the effective density
of states. The model reveals that high intrinsic mobility and low
lattice thermal conductivity give rise to a low optimal doping level
and a high maximum zT. To demonstrate how the model works, we investigate,
from first-principles calculations, the thermoelectric properties
of a novel class of excellent hole transport organic materials, 2,7-dialkyl[1]benzothieno[3,2-b][1]benzothiophene
derivatives (C
n
-BTBTs). The first-principles
calculations show that BTBTs exhibit high mobilities, extremely low
thermal conductivities (∼0.2 W m–1 K–1), and large Seebeck coefficients (∼0.3 mV
K–1), making them ideal candidates for thermoelectric
applications. Moreover, the maximum zT predicted from the simple model
agrees with that observed from the first-principles calculations.
This study has provided new insights to guide the search for organic
thermoelectric materials and their optimization.
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