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ABSTRACT: We propose a polarization demultiplexing method for coherent optical PDM-OFDM based on Stokes space, without inserting training symbols. The proposed approach performs well for different modulation formats of OFDM subcarrier, and shows comparable performances with that of conventional methods, but with a fast convergence speed and reduced overhead. The OFDM signal in the time domain cannot satisfy the conditions of SS-PDM accurately. Therefore, we first digitally convert the received OFDM signals to the frequency domain using fast Fourier transform (FFT). Each subcarrier of the OFDM signal has a much lower speed and narrower bandwidth, the polarization effects that it experiences can be treated as flat. Consequently, we can apply the polarization demultiplexing in Stokes space (SS-PDM) on per subcarrier basis. We verify this method in experiment by transmitting 66.6-Gb/s PDM-OFDM signal with 4QAM subcarrier modulation over 5440km SSMF and 133.3-Gb/s PDM-OFDM signal with 16QAM subcarrier modulation over 960km SSMF respectively. We also compare the results with those of training symbols. Finally, we analyze of the convergence speed of this method.
Optics Express 02/2013; 21(3):3885-3890. · 3.59 Impact Factor
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ABSTRACT: In quantum information processing, knowledge of the noise in the system is
crucial for high-precision manipulation and tomography of coherent quantum
operations. Existing strategies for identifying this noise require the use of
additional quantum devices or control pulses. We present a noise-identification
method directly based on the system's non-Markovian response of an ensemble
measurement to the noise. The noise spectrum is identified by reversing the
response relationship in the frequency domain. For illustration, the method is
applied to superconducting charge qubits, but it is equally applicable to any
type of qubits. We find that the identification strategy recovers the
well-known Fermi's golden rule under the lowest-order perturbation
approximation, which corresponds to the Markovian limit when the measurement
time is much longer than the noise correlation time. Beyond such approximation,
it is possible to further improve the precision at the so-called optimal point
by incorporating the transient response data in the non-Markovian regime. This
method is verified with experimental data from coherent oscillations in a
superconducting charge qubit.
11/2012;
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ABSTRACT: The red-eared slider turtle (Trachemys scripta elegans) exhibits well-developed natural anoxia tolerance that depends on multiple biochemical adaptations, including anoxia-induced hypometabolism. We hypothesized that signaling by the p53 protein could aid in the establishing the hypometabolic state by arresting the cell cycle, protecting against DNA damage as well as altering pathways of energy metabolism. Immunoblotting was used to evaluate the regulation and post-transcriptional modifications of p53 in liver and skeletal muscle of red-eared slider turtles subjected to 5 h or 20 h of anoxic submergence. Tissue specific regulation of p53 was observed with liver showing a more rapid activation of p53 in response to anoxia as well as differential expression of seven serine phosphorylation and two lysine acetylation sites when compared with skeletal muscle. Protein expression of MDM2, a major p53 inhibitor, was also examined but did not change during anoxia. Reverse-transcriptase PCR was used to assess transcript levels of selected p53 target genes (14-3-3σ, Gadd45α and Pgm) and one microRNA (miR-34a); results showed down-regulation of Pgm and up-regulation of the other three. These findings show an activation of p53 in response to anoxia exposure and suggest an important role for the p53 stress response pathway in regulating natural anoxia tolerance and hypometabolism in a vertebrate facultative anaerobe.
Gene 11/2012; · 2.34 Impact Factor
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ABSTRACT: We propose to synthesize arbitrary nonclassical motional states in
optomechanical systems by using sideband excitations, which is an extensively
used method in experiments, e.g., ground state cooling of the mechanical
resonator in optomechanical systems. We first demonstrate how the Hamiltonian
of the optomechanical systems can be reduced to that of trapped ions in the
strong single-photon coupling regime when the photon blockade occurs, and then
show a method to achieve target states. We further analyze the effect of the
photon leakage on the fidelity of the expected state due to small
anharmonicity. Moreover, we also discuss the experimental feasibility and
provide operational parameters using the current technology.
09/2012;
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ABSTRACT: Quantum input-output response analysis is a useful method for modeling the
dynamics of complex quantum networks, such as those for communication or
quantum control via cascade connections. Non-Markovian effects have not yet
been studied in such networks. Here we extend the Markovian input-output
network formalism developed in optical systems to non-Markovian cascaded
networks which can be used, e.g., to analyze the input-output response of
mesoscopic quantum networks. We use this formalism to explore the behavior of
superconducting qubit networks, where we examine the effect of finite cavity
bandwidths. We also discuss its application to open- and closed-loop control
networks, and show how these networks create effective Hamiltonians for the
controlled system.
08/2012;
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ABSTRACT: The wood frog (Rana sylvatica) is one of only a few vertebrate species that can survive extensive freezing of its body fluids during the winter. The mechanisms of natural freeze tolerance include metabolic rate depression to conserve energy and the implementation of cryoprotective strategies, especially the synthesis of huge amounts of glucose as a cryoprotectant. Liver is the main source of glucose production/export (and other cryoprotective actions) and plays a central role in freezing survival of the whole animal. Freezing is a multi-component stress that includes anoxia/ischemia due to the cessation of blood flow and dehydration of cells caused by ice accumulation in extracellular spaces. To help endure these stresses, cells need to suppress and reprioritize ATP-expensive cell functions. One of these is cell growth and proliferation, and we hypothesized that cell cycle arrest would be key to freezing survival. The present study examines the responses by key cell cycle components to freezing, anoxia and dehydration stresses in wood frog liver. Immunoblotting was used to investigate protein expression of Cdc 2, Cdks (2, 4, 6), and cyclins (A, B1, D1, E) as well as the phosphorylation states of Cdks (Thr14/Tyr15), the phosphatases Cdc25a (Ser76) and Cdc25c (Ser216) and the CIP/KIP Cdk inhibitors p21 (Thr145) and p27 (Thr187). Responses to 24 h freezing, 24 h anoxia and 40% dehydration as well as recovery from these stresses were analyzed. The results showed very similar responses by cell cycle components to anoxia or dehydration and were consistent with cell cycle suppression under stress and reversal during recovery. Freezing showed elements of cell cycle suppression, including reduced protein levels of Cdks and cyclins A and B1, but also showed unique responses by cyclin D1, Cdc25 phosphatases and p21/p27. These may be linked with alternative actions by these proteins that contribute to cryoprotection; e.g., an alternative action of cyclin D1 as a transcription factor may contribute to the upregulation of glucose-6-phosphatase, a key enzyme needed for the export of glucose cryoprotectant.
Cell cycle (Georgetown, Tex.) 05/2012; 11(9):1727-42. · 5.36 Impact Factor
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ABSTRACT: A simple, highly sensitive, and selective multiple microRNA (miRNA) detection method based on the graphene oxide (GO) fluorescence quenching and isothermal strand-displacement polymerase reaction (ISDPR) was proposed. The capability to discriminate ssDNA and double-stranded nucleic acid structure coupled with the extraordinary fluorescence quenching of GO on multiple organic dye allows the proposed strategy to simultaneously and selectively detect several miRNA labeled with different dyes in the same solution, while the ISDPR amplification endows the detection method with high sensitivity. The strong interaction between ssDNA and GO led to the fluorescent ssDNA probe exhibiting minimal background fluorescence. Upon the recognition of specific target miRNA, an ISDPR was triggered to produce numerous massive specific DNA-miRNA duplex helixes, and a strong emission was observed due to the weak interaction between the DNA-miRNA duplex helix and GO. A miRNA biosensor down to 2.1 fM with a linear range of 4 orders of magnitude was obtained. Furthermore, the large planar surface of GO allows simultaneous quenching of several DNA probes with different dyes and produces a multiple biosensing platform with high sensitivity and selectivity, which has promising application in profiling the pattern of miRNA expression and biomedical research.
Analytical Chemistry 04/2012; 84(10):4587-93. · 5.86 Impact Factor
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ABSTRACT: Code division multiple access (CDMA) is a spread-spectrum technology, in
which a code is used to spread the spectral content of information to achieve
larger network capacity. It has been widely used in classical communication and
wireless networks. Here, we extend CDMA to the quantum case, where many pairs
of nodes can transmit quantum information through a shared channel. This can be
achieved by chaotic encoding of quantum information to spread its spectral
content and by chaos synchronization, to separate different sender-receiver
pairs. The proposed method is robust to low-frequency noise, and achieves
faithful transmission with fidelities of up to 0.99.
04/2012;
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ABSTRACT: Cross-priming amplification (CPA) for Acidovorax citrulli detection was evaluated in this study. The sensitivity of CPA assay for pure bacterial culture was 3.7 × 10(3) CFU/ml. Bacteria on naturally infected watermelon seeds were detected using CPA assay, suggesting this method is suitable for A. citrulli on-site detection from watermelon seeds.
Molecular and Cellular Probes 04/2012; 26(4):175-6. · 2.08 Impact Factor
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ABSTRACT: When a micro cantilever with a nano-scale tip is manipulated on a substrate
with atomic-scale roughness, the periodic lateral frictional force and
stochastic fluctuations may induce stick-slip motion of the cantilever tip,
which greatly decreases the precision of the nano manipulation. This unwanted
motion cannot be reduced by open-loop control especially when there exist
parameter uncertainties in the system model, and thus needs to introduce
feedback control. However, real-time feedback cannot be realized by the
existing virtual reality virtual feedback techniques based on the position
sensing capacity of the atomic force microscopy (AFM). To solve this problem,
we propose a new method to design real-time feedback control based on the force
sensing approach to compensate for the disturbances and thus reduce the
stick-slip motion of the cantilever tip. Theoretical analysis and numerical
simulations show that the controlled motion of the cantilever tip tracks the
desired trajectory with much higher precision. Further investigation shows that
our proposal is robust under various parameter uncertainties. Our study opens
up new perspectives of real-time nano manipulation.
04/2012;
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ABSTRACT: This study is to investigate the effect of ferulic acid on learning and memory impairments of vascular dementia (VD) rats and its mechanism of action. VD rats model was replicated by permanent bilateral common carotid artery occlusion (2VO). The learning and memory capability of VD rats was evaluated by Morris water maze. The activity of acetylcholinesterase (AChE) and superoxide dismutase (SOD) and the content of glutamic acid (Glu) and malondialdehyde (MDA) in hippocampus of VD rats' brain were determined, separately. The results showed that ferulic acid could alleviate learning and memory deficits of VD rats significantly. Ferulic acid was found to inhibit the activity of AChE and increased the activity of SOD in rat hippocampus. In addition, ferulic acid could also decrease the content of Glu and MDA in rat hippocampus. These results suggested that ferulic acid could alleviate VD rats' learning and memory deficits, which might be due to antioxidation, the improvement of cholinergic system in brain, or the inhibitory of nerve injury by excitatory amino acids.
Yao xue xue bao = Acta pharmaceutica Sinica 02/2012; 47(2):256-60.
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ABSTRACT: The spontaneous emission characteristics of green- and red-emitting InGaN quantum wells (QWs) on ternary InGaN substrate are analyzed, and the radiative recombination rates for the QWs grown on ternary substrate were compared with those of InGaN QWs on GaN templates. For green- and red-emitting InGaN QWs on In0.15Ga0.85N substrate, the spontaneous emission rates were found as ∼2.5-3.2 times of the conventional approach. The enhancement in spontaneous emission rate can be achieved by employing higher In-content InGaN ternary substrate, which is also accompanied by a reduction in emission wavelength blue-shift from the carrier screening effect. The use of InGaN substrate is expected to result in the ability for growing InGaN QWs with enhanced spontaneous emission rates, as well as reduced compressive strain, applicable for green- and red-emitting light-emitting diodes.
Journal of Applied Physics 12/2011; 110(11):113110-113110-5. · 2.17 Impact Factor
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ABSTRACT: This paper focuses on the near real-time implementation of end-to-end 3DTV System. It is specially designed for the generation of high-quality disparity map and depth-image-based rendering (DIBR) on the graphics processing unit (GPU) through CUDA (Compute Unified Device Architecture) API. We propose our novel methods including a kind of stereo matching with adaptive windows and an asymmetric edge adaptive filter (AEAF) for industrial application. These algorithms are structured in a way that exposes as much data parallelism as possible and the power of shared memory and data parallel programming in GPU is exploited. We evaluate our proposed methods and implementation based on the benchmark Middlebury and the experiment results show that our method is suitable for application on the trade-off among accuracy and execution speed. Running on an NVIDIA Quadro FX4800 graphics card, for each 480x375 stereo images with 60 disparity levels, the proposed system reaches about 146ms for stereo matching and reaches the speed of DIBR 5.7ms for rendering 1 view or 14ms for rendering 8 views.
Image and Graphics (ICIG), 2011 Sixth International Conference on; 09/2011
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ABSTRACT: We have measured and analyzed the photoluminescence spectra from InGaN/GaN multiple quantum wells. Emission peaks due to recombination of the photogenerated carriers occupying localized states and extended states within quantum wells have been identified through temperature-dependent photoluminescence. Fast and slow decays have been attributed to recombination of carriers in extended states and localized states, respectively, based on time-resolved pump-probe differential photoluminescence.
Applied Physics Letters 08/2011; 99(8):081104-081104-3. · 3.84 Impact Factor
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ABSTRACT: Double-metallic Au/Ag layers deposited on top of InGaN/GaN quantum wells (QWs) are used to tune the Purcell peak enhancement of the radiative recombination rate for nitride light-emitting diodes. By modifying the Au/Ag thicknesses, the Purcell factor can be widely tuned between the surface plasmon frequencies of Au/GaN and Ag/GaN. Photoluminescence studies demonstrated the concept of the Purcell factor tuning by using the double-metallic Au/Ag layers.
Applied Physics Letters 05/2011; · 3.84 Impact Factor
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ABSTRACT: The timing and optical laser phase of individual bands in multi-band OFDM are correlated. We significantly reduce the OFDM overhead through using FFT window synchronization for channel estimation and sharing pilot subcarriers for phase estimation.
Optical Fiber Communication Conference and Exposition (OFC/NFOEC), 2011 and the National Fiber Optic Engineers Conference; 04/2011
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ABSTRACT: We have investigated terahertz (THz) generation from InGaN/GaN multiple quantum wells (QWs). For the laser pump power of 400 mW at 391 nm, the highest THz output power is nearly 1 μW. Assuming that the output power quadratically scales up with the interaction length, such an output power corresponds to a normalized output power of 1.7nW/nm<sup>2</sup>. The normalized output power measured on the InGaN/GaN multiple quantum-well structures correspond to probably one of the highest values ever reported among all different semiconductor and nonlinear materials. Following our measurements of the output spectrum, power, and polarization angle as functions of average pump intensity, incident angle, and pump polarization angle, respectively, we have attributed the mechanism for the THz generation from the InGaN/GaN QWs to the radiation of the dipoles, following the generation of the spatially separated electrons and holes under the strong built-in electric fields inherently present in the nitride-based quantum-well structures.
IEEE Journal of Selected Topics in Quantum Electronics 03/2011; · 3.78 Impact Factor
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ABSTRACT: In the control of classical mechanical systems, the feedback has been
successfully applied to the production of the desired nonlinear dynamics.
However, how much this can be done is still an open problem in quantum
mechanical systems. This paper proposes a scheme of generating strong nonlinear
quantum effects via the recently developed coherent feedback techniques, which
can be shown to outperform the measurement-based quantum feedback scheme that
can only generate pseudo-nonlinear quantum effects. Such advancement is
demonstrated by two application examples in quantum optics on chip. In the
first example, we show that the nonlinear Kerr effect can be generated and
amplified to be comparable with the linear effect in a transmission line
resonator (TLR). In the second example, we show that by tuning the gains of the
quantum amplifiers in a TLR coherent feedback network, non-Gaussian "light"
(microwave field) can be generated and manipulated via the nonlinear effects
which exhibits fully quantum sub-Poisson photoncount statistics and photon
antibunching phenomenon. The scheme opens promising applications in
demonstrating strong nonlinear quantum optics on chip, which is extremely weak
and inflexible in traditional quantum optical devices.
02/2011;
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ABSTRACT: We propose a strategy to suppress decoherence of a solid-state qubit coupled
to non-Markovian noises by attaching the qubit to a chaotic setup with the
broad power distribution in particular in the high-frequency domain. Different
from the existing decoherence control methods such as the usual dynamics
decoupling control, high-frequency components of our control are generated by
the chaotic setup driven by a low-frequency field, and the generation of
complex optimized control pulses is not necessary. We apply the scheme to
superconducting quantum circuits and find that various noises in a wide
frequency domain, including low-frequency $1/f$, high-frequency Ohmic,
sub-Ohmic, and super-Ohmic noises, can be efficiently suppressed by coupling
the qubits to a Duffing oscillator as the chaotic setup. Significantly, the
decoherence time of the qubit is prolonged approximately $100$ times in
magnitude.
01/2011;
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ABSTRACT: To suppress decoherence of solid-state qubits which are coupled to the
non-Markovian noises, we propose a strategy to couple the qubit with a chaotic
device, of which the broad power distribution in the high-frequency domain can
be used to freeze the noises just like the dynamical decoupling control (DDC)
method. Compared with the DDC, high-frequency components can be generated by
the chaotic device even driven by a low-frequency field and we do not need to
optimize the control fields to generate complex control pulses. As an
application to superconducting circuits, we find that various noises in a wide
frequency domain, including low-frequency $1/f$, high-frequency Ohmic,
sub-Ohmic, and super-Ohmic noises, can be efficiently suppressed by coupling
the qubit to a Duffing oscillator, and the decoherence rate of the qubit is
efficiently decreased for about 100 times in magnitude.
01/2011;
