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31.
Electronic properties of graphene nanoribbon doped by boron/nitrogen pair: a first-principles study
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By using the first-principles calculations, the electronic properties of graphene nanoribbon (GNR) doped by boron/nitrogen (B/N) bonded pair are investigated. It is found that B/N bonded pair tends to be doped at the edges of GNR and B/N pair doping in GNR is easier to carry out than single B doping and unbonded B/N co-doping in GNR. The electronic structure of GNR doped by B/N pair is very sensitive to doping site besides the ribbon width and chirality. Moreover, B/N pair doping can selectively adjust the energy gap of armchair GNR and can induce the semimetal-semiconductor transmission for zigzag GNR. This fact may lead to a possible method for energy band engineering of GNRs and benefit the design of graphene electronic device. 相似文献
32.
Chongtao Ge Liming OuYang Qingbao Ding Ling Ou 《Applied biochemistry and biotechnology》2009,159(1):168-177
The genes encoding purine nucleoside phosphorylase (PNPase), uridine phosphorylase (UPase), and thymidine phosphorylase (TPase)
from Escherichia coli K12 were cloned respectively into expression vector pET-11a or pET-28a. The recombinant plasmids were transformed into the
host strain E. coli BL21(DE3) to construct four co-expression recombinant strains. Two of them had double recombinant plasmids (DUD and DAD)
and the other two had tandem recombinant plasmid (TDU and TDA) in them. Under the repression of antibiotic, recombinant plasmids
stably existed in host strains. Enzymes were abundantly expressed after induction with IPTG and large amount of target proteins
were expressed in soluble form analyzed with SDS-PAGE. Compared with the host strain, enzyme activity of the recombinant strains
had been notably improved. In the transglycosylation reaction, yield of 2,6-diaminopurine-2’-deoxyriboside (DAPdR) from 2,6-diaminopurine
(DAP) and thymidine reached 40.2% and 51.8% catalyzed by DAD and TDA respectively; yield of 2,6-diaminopurine riboside (DAPR)
from DAP and uridine reached 88.2% and 58.0% catalyzed by TDU and DUD respectively. 相似文献
33.
Influence of the ordered structure of short-chain polymer molecule all-trans-β-carotene on Raman scattering cross section in liquid
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We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures.The results demonstrated that the Raman scattering cross section(RSCS) of short-chain polymer all-trans-β-carotene is extremely high in liquid.Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions.Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure.All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties,which lead to large RSCS in the solvent with large density and low concentration at low temperature. 相似文献
34.
This paper quantificationally probes into time-varying migration processes of moving neutralization boundary (MNB) on immobilized pH gradient (IPG) strip in ammonia-rehydration buffers. The time-varying migration processes are determined by both time-varying dissociation equilibria of ammonia and position-varying pH environments formed by immobilized carrier ampholytes (CAs) on the IPG strip. Thus, the local dissociation equilibria of ammonia and the position-varying pH are introduced into the recursion equation of position of MNB migrations. The theoretical position-time curves and the velocity-time curves of MNB migrations obtained by the recursion approach were satisfactorily validated by a series of images of boundary migrations from the IPG-MNB experiments by using rehydration buffers with different ammonia concentrations on pH 3-6 IPG strips. The results achieved herein have significant evidence to a quantificational understanding of the mechanism of MNB and IEF. 相似文献
35.
36.
Liang‐fei OuYang Qian Liu Heng Liang Yuhua Shi Junwei Shi Xiaoguang Yin 《Journal of separation science》2013,36(4):645-657
The 0‐1 model‐inverse method of nonequilibrium nonlinear chromatography was developed to simultaneously determine the isotherm parameters and the lumped mass transfer coefficients of the two‐component systems in RPLC. By comparing the simulated elution curves with experimental curves with regard to profiles and areas, the suitable isotherm parameters and the lumped mass transfer coefficients were obtained with the 0‐1 model‐inverse method. With a solute cell unit width of cm, the average errors of the peak areas were 0.178% for one component and ?0.40% for two components, and the numerical diffusions of the 0‐1 model for the contribution to band broadening may be negligible. In addition, the results showed that the lumped mass transfer coefficients decrease as the solute concentration increases. The 0‐1 model‐inverse method has not only the advantages of high calculation speed (less than 10 min for one‐component systems or approximately 3 h for two‐component systems using an ordinary computer) and high accuracy in simultaneously obtaining thermodynamic parameters and kinetic parameters of two‐component systems, but this method also possesses the potential to optimally design and control the time‐variant preparative chromatographic system due to the thermodynamic state recursion and the Lagrangian‐Eulerian presentation of the 0‐1 model. 相似文献
37.
介绍了低温温度计标定装置中的热沉问题;建立了数学模型;找出了计算与热沉接触电引线长度的方法;并给出了实例计算。为解决低温装置中的热沉问题提供了理论依据。 相似文献
38.
Using the first-principles study, we calculate the electronic band structure of metallic carbon nanotubes (MCNTs) with B/N co-doping. We show the formation energies which suggest that the B/N co-doping configuration is the energetically stable structure. We find that the electronic structure properties depend on the doping concentration of MCNTs, as well as the doping position. Energy gap opens rapidly when the symmetry breaking of MCNTs happens. These unconventional doping effects could be used to design novel nanoelectronic devices. 相似文献