RESUMO
We present a combination of first-principles calculations and the Boltzmann transport theory to understand the carrier transport and thermoelectric performance of mixed halide perovskite alloys CsPb(I1-xBrx)3 with different Br compositions. Our computational results correlate the conduction band splitting in CsPb(I1-xBrx)3 to the significant anisotropy in their carrier transport properties, such as effective masses and deformation potential constants. Such band splitting originates from the symmetry-broken crystal structures of CsPb(I1-xBrx)3 polymorphs: with residue stresses/strains in asymmetric CsPb(I1-xBrx)3, nondegenerate orbitals reconstruct the conduction band and reduce the Pb-halide antibonding character along certain directions. While the Seebeck coefficient (S) and the relaxation time-normalized electrical conductivity (σ/τ) show weak directional anisotropy, the carrier relaxation time (τ) is highly direction-dependent. The reconstruction of the conduction band finally leads to significantly anisotropic and enhanced thermoelectric power factors (PF = S2σ) in CsPb(I1-xBrx)3 compared to those in pure CsPbI3 and CsPbBr3, showing anomalous nonlinear alloy behavior. A delicate balance between S2σ and combined measurement of the carrier effective mass and deformation potential constant, m*EDP, is confirmed. The lattice thermal conductivities of CsPb(I1-xBrx)3 are significantly suppressed compared to those of their pure counterparts due to strong mass disordering and strain fields upon halogen substitution. As a result, symmetry breaking in CsPb(I1-xBrx)3 leads to anisotropy in carrier transport, high PF, and scattered phonon transport (ultralow thermal conductivity), concurrently contributing to their promising thermoelectric figures of merit (ZT) up to 1.7 at room temperature. The principles behind the asymmetry-induced factors would serve as new design concepts to tailor the thermoelectric properties of alloys, mixtures, superlattices, and low-dimensional materials.
RESUMO
Non-aqueous Li-CO2 batteries reported in literature have almost exclusively relied upon glyme-based electrolytes, leading to a hypothesis that they are uniquely active for CO2 discharge. Here, we study the effect of electrolyte composition on CO2 activity to examine whether this is the case. The results indicate that TEGDME-based electrolytes containing moderate concentrations of Li+ salts (roughly within the range of 0.7-2 M examined herein) are most conducive to CO2 activation, especially compared to dimethyl sulfoxide and propylene carbonate-based electrolytes. Through electrochemical, spectroscopic, and computational methods, we determine that glymes have lower desolvation energies for Li+ compared to other solvent candidates, whereas high salt concentrations increase the local density of Li+ surrounding CO2 and reduction intermediates. These attributes collectively increase the availability of Li+, crossing a threshold necessary to support CO2 activation. Discharge voltage and reaction rates are also sensitive to the alkali cation identity, further invoking its key role in enabling or suppressing reactivity.
RESUMO
Avian leukosis virus subgroup K (ALV-K) is an emerging ALV tumor virus of chickens. We developed a SYBR green-based real-time polymerase chain reaction (PCR) assay for the rapid and economical detection of ALV-K in chicken flocks. The assay was specific for ALV-K and did not cross-react with other ALV subgroup or avian influenza virus, Newcastle disease virus, or Marek's Disease virus. The method was 100 times more sensitive than conventional PCR and 10 times more sensitive than the enzyme-linked immunosorbent assay (ELISA) for the P27 antigen. The assay was also more sensitive than conventional PCR in tests of 86 clinical plasma samples. DF-1 tissue culture cells infected with 1 TCID50 ALV-K particle were identified as negative using ELISA but tested positive with the real-time PCR method. The viral loads in organs and tissues in infected chickens were highest in kidney, lungs, and glandular stomach, and these results matched ELISA findings.
