60 research outputs found
Optimizing Substrate-Mediated Plasmon Coupling toward High-Performance Plasmonic Nanowire Waveguides
Seeking better plasmonic waveguides is of critical importance for minimizing photonic circuits into the nanometer scale. We have made a theoretical study of the properties of surface plasmon polaritons in a metallic nanowire over substrate (NWOS) configuration. The dielectric substrate breaks the symmetry of the system and mediates the coupling of different primary wire plasmons. The lowest order hybridized mode can be used for subwavelength plasmonic waveguiding for NWOS with thin wire, for a low-permittivity substrate, and in the shorter wavelength region. For NWOS with a high-permittivity substrate, leaky radiation into the substrate raises the propagation losses so that the propagation distance is shorter in the longer wavelength region. By simply adding a high-permittivity layer onto the low-permittivity substrate, we show that leaky radiation can be blocked and high-performance plasmonic waveguiding can be extended to the near-infrared region. Importantly, the NWOS configuration is compatible with current silicon technologies and can be designed into various deep subwavelength active devices such as electro-optical or all-optical modulators
Quantum Yield of Single Surface Plasmons Generated by a Quantum Dot Coupled with a Silver Nanowire
The interactions between surface
plasmons (SPs) in metal nanostructures and excitons in quantum emitters
(QEs) lead to many interesting phenomena and potential applications
that are strongly dependent on the quantum yield of SPs. The difficulty
in distinguishing all the possible exciton recombination channels
hinders the experimental determination of SP quantum yield. Here,
we experimentally measured for the first time the quantum yield of
single SPs generated by the exciton–plasmon coupling in a
system composed of a single quantum dot and a silver nanowire (NW).
By utilizing the SP guiding property of the NW, the decay rates of
all the exciton recombination channels, i.e., direct free space radiation
channel, SP generation channel, and nonradiative damping channel,
are quantitatively obtained. It is determined that the optimum emitter-NW
coupling distance for the largest SP quantum yield is about 10 nm,
resulting from the different distance-dependent decay rates of the
three channels. These results are important for manipulating the coupling
between plasmonic nanostructures and QEs and developing on-chip quantum
plasmonic devices for potential nanophotonic and quantum information
applications
Low Frequency Vibration Assisted Catalytic Aquathermolysis of Heavy Crude Oil
Low frequency vibration was applied to assist the catalytic
aquathermolysis
reaction of heavy oil for the first time. The optimum vibration parameters
were first optimized by orthogonal experiments: vibration acceleration
is 3 m·s<sup>–2</sup>, vibration time is 90 min, and vibration
frequency is 20 Hz, and the efficient consequences of the parameters
are as follows: vibration acceleration > vibration time > vibration
frequency. Under the optimum vibration parameters, heavy oil viscosity
could be reduced by 88.2% after reaction, and the viscosity bounce
rate of treated oil is 4.9%. To evaluate the vibration’s performance,
the structure and group compositions of the oil before and after reaction
were characterized by modern chemical analysis techniques, such as
column chromatography, elemental analysis, gas chromatography, and
Fourier transform infrared spectrometery. It is found that vibration
cannot initiate new reactions in the process of catalytic aquathermolysis,
but it can promote the original reactions and deepen the reaction
degree such as dealcoholization reaction, hydrogenation reaction,
ring-opening reaction, and alkyl side chain removal reaction, etc.
Compared to catalytic aquathermolysis reaction, vibration assisted
catalytic aquathermolysis can further decrease the average molecular
weight of heavy oil, increase the saturate and aromatic contents,
decrease the resin and asphaltene contents, improve the ratio of <i>N</i><sub>H</sub>/<i>N</i><sub>C</sub>, and decrease
the heteroatoms content of heavy oil. Vibration plays more important
role in the in situ catalytic aquathermolysis reactions due to the
fact that vibration could aid to reduce the adsorption of catalyst
and help the catalysts contact with heavy oil sufficiently in the
porous media. The preliminary results proved that the vibration assisted
in situ catalytic aquathermolysis technique is feasible and it has
some practical value
Resolving Single Plasmons Generated by Multiquantum-Emitters on a Silver Nanowire
Surface plasmons, the collective
oscillations of electrons at metal
surface, provide the ability to enhance the weak interaction between
individual quantum emitters and photons for quantum information applications.
The generation of single plasmons by coupling silver nanowire with
single quantum emitters opens the prospects of using quantum optical
techniques to control single surface plasmons and designing novel
quantum plasmonic devices. However, the real applications will deal
with multiple plasmons generated from multiple quantum emitters. Here
we report the first experimental demonstration of resolving single
plasmons generated by a pair of quantum dots (QDs) on a silver nanowire
waveguide. The accurate positions of the two QDs with separation ranging
from micrometers to 200 nm within the diffraction limit are determined
by using super-resolution imaging method. The efficiency of plasmon
generation due to the exciton–plasmon coupling is obtained
for each QD. Our research takes a crucial step toward the experimental
study of coupled systems of multiple quantum emitters and plasmonic
waveguides and would shed new light on the study of light-matter interactions
for potential quantum optics and quantum information applications
Plasmon-Assisted Selective and Super-Resolving Excitation of Individual Quantum Emitters on a Metal Nanowire
Hybrid systems composed of multiple quantum emitters coupled with
plasmonic waveguides are promising building blocks for future integrated
quantum nanophotonic circuits. The techniques that can super-resolve
and selectively excite contiguous quantum emitters in a diffraction-limited
area are of great importance for studying the plasmon-mediated interaction
between quantum emitters and manipulating the single plasmon generation
and propagation in plasmonic circuits. Here we show that multiple
quantum dots coupled with a silver nanowire can be controllably excited
by tuning the interference field of surface plasmons on the nanowire.
Because of the period of the interference pattern is much smaller
than the diffraction limit, we demonstrate the selective excitation
of two quantum dots separated by a distance as short as 100 nm. We
also numerically demonstrate a new kind of super-resolution imaging
method that combines the tunable surface plasmon interference pattern
on the NW with the structured illumination microscopy technique. Our
work provides a novel high-resolution optical excitation and imaging
method for the coupled systems of multiple quantum emitters and plasmonic
waveguides, which adds a new tool for studying and manipulating single
quantum emitters and single plasmons for quantum plasmonic circuitry
applications
Midgut transcriptomal response of the rice leaffolder, <i>Cnaphalocrocis medinalis</i> (Guenée) to Cry1C toxin
<div><p><i>Cnaphalocrocis medinalis</i> (Guenée) is one of the important insect pests in rice field. Bt agents were recommended in the <i>C</i>. <i>medinalis</i> control and Bt rice is bred as a tactic to control this insect. However, the tolerance or resistance of insect to Bt protein is a main threat to the application of Bt protein. In order to investigate the response of <i>C</i>. <i>medinalis</i> transcriptome in defending a Cry1C toxin, high-through RNA-sequencing was carried in the <i>C</i>. <i>medinalis</i> larvae treated with and without Cry1C toxin. A total of 35,586 high-quality unigenes was annotated in the transcriptome of <i>C</i>. <i>medinalis</i> midgut. The comparative analysis identified 6,966 differently expressed unigenes (DEGs) between the two treatments. GO analysis showed that these genes involved in proteolysis and extracellular region. Among these DEGs, carboxylesterase, glutathione S-transferase and P450 were differently expressed in the treated <i>C</i>. <i>medinalis</i> midgut. Furthermore, trypsin, chymotrypsin, and carboxypeptidase were identified in DEGs, and most of them up-regulated. In addition, thirteen ABC transporters were downregulated and three upregulated in Cry1C-treated <i>C</i>. <i>medinalis</i> midgut. Based on the pathway analysis, antigen processing and presentation pathway, and chronic myeloid leukemia pathway were significant in <i>C</i>. <i>medinalis</i> treated with Cry1C toxin. These results indicated that serine protease, detoxification enzymes and ABC transporter, antigen processing and presentation pathway, and chronic myeloid leukemia pathway may involved in the response of <i>C</i>. <i>medinalis</i> to Cry1C toxin. This study provides a transcriptomal foundation for the identification and functional characterization of genes involved in the toxicity of Bt Cry protein against <i>C</i>. <i>medinalis</i>, and provides potential clues to the studies on the tolerance or resistance of an agriculturally important insect pest <i>C</i>. <i>medinalis</i> to Cry1C toxin.</p></div
ABC transporters differently expressed in <i>Cnaphalocrocis medinalis</i> larvae treated with Cry1C toxin.
<p>ABC transporters differently expressed in <i>Cnaphalocrocis medinalis</i> larvae treated with Cry1C toxin.</p
Trypsin genes of <i>Cnaphalocrocis medinalis</i> midgut in response to the ingestion of Cry1C toxin.
<p>Trypsin genes of <i>Cnaphalocrocis medinalis</i> midgut in response to the ingestion of Cry1C toxin.</p
Differentially expressed unigenes (DEGs) in the midgut of <i>Cnaphalocrocis medinalis</i> larvae fed with Cry1C toxin.
<p>(A) Number of DEGs. (B) Volcano plot to show the fold change and error rates. The non-DEGs are indicated by black dots, the DEGs up-regulated are indicated by red dots, and the DEGs down-regulated are indicated by blue dots.</p
TRs and <i>hrs</i> analysis.
<p><b>(A)</b> Alignment of the part of <i>hrs</i> in the CnmeGV genome. Palindromes within the repeats are indicated by arrows on the alignment. <b>(B)</b> Predicted secondary structure of the Tr51. <b>(C)</b> The repetitive sequence in coding regions of Tr6, CAG is repeating unit.</p
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