170 research outputs found
A generalized Caroli formula for transmission coefficient with lead-lead coupling
We present a generalized transmission coefficient formula for the
lead-junction-lead system, in which interaction between the leads has been
taken into account. Based on it the Caroli formula could be easily recovered
and a transmission coefficient formula for interface problem in the ballistic
system can be obtained. The condition of validity for the formula is carefully
explored. We mainly focus on heat transport. However, the corresponding
electrical transport could be similarly dealt with. Also, an illustrative
example is given to clarify the precise meaning of the quantities used in the
formula, such as the concept of the reduced interacting matrix in different
situations. In addition, an explicit transmission coefficient formula for a
general one-dimensional interface setup is obtained based on the derived
interface formula.Comment: 6 pages, 1 figur
Transient behavior of full counting statistics in thermal transport
The generating function of energy counting statistics is derived for phononic
junction systems. It is expressed in terms of the contour-ordered self-energy
of the lead with shifted arguments, , where
is the usual contour-ordered self-energy of the left
lead. The cumulants of the energy transferred in a given time from the
lead to the center is obtained by taking derivatives. A transient result of the
first four cumulants of a graphene junction is presented. It is found that
measurements cause the energy to flow into the lead.Comment: 4 pages, 2 figure
Role of the on-site pinning potential in establishing quasi-steady-state conditions of heat transport in finite quantum systems
We study the transport of energy in a finite linear harmonic chain by solving
the Heisenberg equation of motion, as well as by using nonequilibrium Green's
functions to verify our results. The initial state of the system consists of
two separate and finite linear chains that are in their respective equilibriums
at different temperatures. The chains are then abruptly attached to form a
composite chain. The time evolution of the current from just after switch-on to
the transient regime and then to later times is determined numerically. We
expect the current to approach a steady-state value at later times.
Surprisingly, this is possible only if a nonzero quadratic on-site pinning
potential is applied to each particle in the chain. If there is no on-site
potential a recurrent phenomenon appears when the time scale is longer than the
traveling time of sound to make a round trip from the midpoint to a chain edge
and then back. Analytic expressions for the transient and steady-state currents
are derived to further elucidate the role of the on-site potential.Comment: version accepted for publication in PR
Molecular characterization of a mosaic locus in the genome of 'Candidatus Liberibacter asiaticus'
<p>Abstract</p> <p>Background</p> <p>Huanglongbing (HLB) is a highly destructive disease of citrus production worldwide. '<it>Candidatus </it>Liberibacter asiaticus', an unculturable alpha proteobacterium, is a putative pathogen of HLB. Information about the biology and strain diversity of '<it>Ca</it>. L. asiaticus' is currently limited, inhibiting the scope of HLB research and control.</p> <p>Results</p> <p>A genomic region (CLIBASIA_05640 to CLIBASIA_05650) of '<it>Ca</it>. L. asiaticus' showing hyper-sequence variation or locus mosaicism was identified and investigated using 262 bacterial strains (188 from China and 74 from Florida). Based on the characteristic electrophoretic profiles of PCR amplicons generated by a specific primer set, eight electrophoretic types (E-types) were identified, six E-types (A, B, C, D, E, and F) in China and four E-types (A, C, G, and H) in Florida. The '<it>Ca</it>. L. asiaticus' strains from China consisted predominately of E-type A (71.3%) and E-type B (19.7%). In contrast, the '<it>Ca</it>. L. asiaticus' strains from Florida was predominated by E-type G (82.4%). Diversity of '<it>Ca</it>. L. asiaticus' in China was also evidenced. Strains from the high altitude Yunnan Province consisted of five E-types with E-type B being the majority (62.8%), whereas strains from the low altitude coastal Guangdong Province consisted of only two E-types with E-type A as the majority (97.0%). Sequence analyses revealed that variation of DNA amplicons was due to insertion/deletion events at CLIBASIA_05650 and the downstream intergenic region.</p> <p>Conclusions</p> <p>This study demonstrated the genomic mosaicism of '<it>Ca</it>. L. asiaticus' resulted from active DNA insertion/deletion activities. Analyses of strain variation depicted the significant inter- and intra-continent diversity of '<it>Ca</it>. L. asiaticus'.</p
Isolation of Mycobacterium tuberculosis complex (MTBC) from dairy cows in China
Eleven thousand five hundred and eighty non-blood samples from dairy cows were subjected to mycobacterium culture and genotyping. As a result, a total of 142 isolates of Mycobacterium tuberculosis complex (MBTC) were identified. Among them, 65 were Mycobacterium tuberculosis, while 77 Mycobacterium bovis. The genotype of M. tuberculosis strains was mainly Beijing family. In addition, the isolation rates of MTBC were 33.89% for lung lymph nodes, 2.81% for nasal swabs, and 3.95% for pharyngeal swabs from cattle positive to tuberculin skin test, respectively. This evidence implied that M. tuberculosis infection in cattle is a new risk to public health and should be paid more attention.Key words: Mycobacterium tuberculosis complex, cows, tuberculosis, zoonosis
Recommended from our members
Machine learning-guided co-optimization of fitness and diversity facilitates combinatorial library design in enzyme engineering
The effective design of combinatorial libraries to balance fitness and diversity facilitates the engineering of useful enzyme functions, particularly those that are poorly characterized or unknown in biology. We introduce MODIFY, a machine learning (ML) algorithm that learns from natural protein sequences to infer evolutionarily plausible mutations and predict enzyme fitness. MODIFY co-optimizes predicted fitness and sequence diversity of starting libraries, prioritizing high-fitness variants while ensuring broad sequence coverage. In silico evaluation shows that MODIFY outperforms state-of-the-art unsupervised methods in zero-shot fitness prediction and enables ML-guided directed evolution with enhanced efficiency. Using MODIFY, we engineer generalist biocatalysts derived from a thermostable cytochrome c to achieve enantioselective C-B and C-Si bond formation via a new-to-nature carbene transfer mechanism, leading to biocatalysts six mutations away from previously developed enzymes while exhibiting superior or comparable activities. These results demonstrate MODIFY's potential in solving challenging enzyme engineering problems beyond the reach of classic directed evolution
- …