3,114 research outputs found
Electron self-energy and effective mass in a single heterostructure
In this paper, we investigate the electron self-energy and effective mass in
a single heterostructure using Green-function method. Numerical calculations of
the electron self-energy and effective mass for GaAs/AlAs heterostructure are
performed. The results show that the self energy (effective mass) of electron,
which incorporate the energy of electron coupling to interface-optical phonons
and half three-dimension LO phonons, monotonically increase(decrease) from that
of interface polaron to that of 3D bulk polaron with the increase of the
distance between the position of the electron and interface.Comment: 10 pages, 2 figure
http://zoobank.org/urn:lsid:zoobank.org:pub:AABD9D82-919C-4A22-96FC-3C4EFBE18846
www.mapress.com/zootaxa
One-step implementation of multi-qubit conditional phase gating with nitrogen-vacancy centers coupled to a high-Q silica microsphere cavity
The diamond nitrogen-vacancy (NV) center is an excellent candidate for
quantum information processing, whereas entangling separate NV centers is still
of great experimental challenge. We propose an one-step conditional phase flip
with three NV centers coupled to a whispering-gallery mode cavity by virtue of
the Raman transition and smart qubit encoding. As decoherence is much
suppressed, our scheme could work for more qubits. The experimental feasibility
is justified.Comment: 3 pages, 2 figures, Accepted by Appl. Phys. Let
Genome replication engineering assisted continuous evolution (GREACE) to improve microbial tolerance for biofuels production
BACKGROUND: Microbial production of biofuels requires robust cell growth and metabolism under tough conditions. Conventionally, such tolerance phenotypes were engineered through evolutionary engineering using the principle of “Mutagenesis followed-by Selection”. The iterative rounds of mutagenesis-selection and frequent manual interventions resulted in discontinuous and inefficient strain improvement processes. This work aimed to develop a more continuous and efficient evolutionary engineering method termed as “Genome Replication Engineering Assisted Continuous Evolution” (GREACE) using “Mutagenesis coupled-with Selection” as its core principle. RESULTS: The core design of GREACE is to introduce an in vivo continuous mutagenesis mechanism into microbial cells by introducing a group of genetically modified proofreading elements of the DNA polymerase complex to accelerate the evolution process under stressful conditions. The genotype stability and phenotype heritability can be stably maintained once the genetically modified proofreading element is removed, thus scarless mutants with desired phenotypes can be obtained. Kanamycin resistance of E. coli was rapidly improved to confirm the concept and feasibility of GREACE. Intrinsic mechanism analysis revealed that during the continuous evolution process, the accumulation of genetically modified proofreading elements with mutator activities endowed the host cells with enhanced adaptation advantages. We further showed that GREACE can also be applied to engineer n-butanol and acetate tolerances. In less than a month, an E. coli strain capable of growing under an n-butanol concentration of 1.25% was isolated. As for acetate tolerance, cell growth of the evolved E. coli strain increased by 8-fold under 0.1% of acetate. In addition, we discovered that adaptation to specific stresses prefers accumulation of genetically modified elements with specific mutator strengths. CONCLUSIONS: We developed a novel GREACE method using “Mutagenesis coupled-with Selection” as core principle. Successful isolation of E. coli strains with improved n-butanol and acetate tolerances demonstrated the potential of GREACE as a promising method for strain improvement in biofuels production
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