Optimizing effective phase modulation in coupled double quantum well Mach–Zehnder modulators

We report optimal phase modulation based on enhanced electro–optic effects in a Mach–Zehnder（MZ） modulator constructed by AlGaAs/GaAs coupled double quantum well（CDQW） waveguides with optical gain. The net change of refractive indexes between two arms of the CDQW MZ modulator is derived by both the electronic polarization method and the normal-surface method. The numerical results show that very large refractive index change over 10^（-1） can be obtained, making the phase modulation in the CDQW MZ modulator very highly efficient. It is desirable and important that a very small voltage-length product for π phase shift, V_π× L_0= 0.0226 V · mm, is obtained by optimizing bias electric field and CDQW structural parameters, which is about seven times smaller than that in single quantum-well MZ modulators.These properties open an avenue for CDQW nanostructures in device applications such as electro–optical switches and phase modulators.

Effect of microenvironment modulation on stem cell therapy for spinal cord injury pain

Spinal cord injury （SCI） currently ranks second after mental retarda- tion among neurological disorders in terms of cost to society. Pain is a debilitating consequence of SCI related to the nature of the lesion, neurological structures damaged, and secondary pathophysiological changes of surviving tissues （Yezierski, 2005; D＇Angelo et al., 2013）.

Controlling the motion of solitons in BEC by a weakly periodic potential

By developing multiple-scale method combined with Wentzel-Kramer-Brillouin expansion, this paper analytically studies the modulating effect of weakly periodic potential on the dynamical properties of the Dose-Einstein condensates （BEC） trapped in harmonic magnetic traps. A black-grey soliton transition is observed in the BEC trapped in harmonic magnetic potential, due to the weakly periodic potential modulating effect. Meanwhile, it finds that with the slight increase of the weakly periodic potential strength, the velocity of the soliton decreases, while its width firstly decreases then increases, a minimum exists there. These results show that the amplitude, velocity, and width of matter solitons can be effectively managed by means of a weakly periodic potential

Signal modulating noise effect in bistable stochastic resonance systems and its analog simulation

The effect of signal modulating noise in bistable stochastic resonance systems was studied theoretically and experimentally. A mathematical analysis was made on the bistable stochastic resonance model with small system parameters. An analogue circuit was designed to perform the effect. The effect of signal modulating noise was shown in the analog simulation experiment. The analog experiment was conducted for two sinusoidal signals with different frequencies. The results show that there are a sinusoidal component corresponding to the input sinusoidal signal and a noise component presented as a Wiener process corresponding to the input white noise in the system output. By properly selecting system parameters, the effect of signal modulating noise can be manifested in the system output.

Effect of Phase Modulation on Electromagnetically Induced Grating in a Five-Level M-Type Atomic System

We theoretically investigate the phenomena of electromagnetically induced grating in an M-type five-level atomic system. It is found that a weak field can be effectively diffracted into high-order directions using a standing wave coupling field, and different depths of the phase modulation can disperse the diffraction light into different orders. When the phase modulation depth is approximated to the orders of π, 2π and 3π, the first-, second- and third-order diffraction intensity reach the maximum, respectively. Thus we can take advantage of the phase modulation to control the probe light dispersing into the required high orders.

Phenotypic Modulation of Mesangial Cells in Diabetic Rats and Effect of Tujian Mixture (菟箭合剂) on It

Objective: To explore whether there is phenotypic modulation of mesangial cells in streptozotocin (STZ) induced diabetic rats and study the effect of Tujian Mixture (TJM) on it. Methods: SD rats were divided into the normal control group , the unilateral nephrectomized control group , the STZ induced diabetes mellitus with unilateral nephrectomy model group , the Valsartan treated group (VT group, n=8) and the TJM treated group , rats in the latter two groups were modeled as in the DM group and treated with Valsartan (20 mg/kg·d) and TJM (20g/kg·d) respectively for 12 weeks. The expression of α-smooth muscle actin (α-SMA) and transforming growth factor-β 1 (TGF-β 1) in rats’ glomeruli were observed by immunohistochemistry assay, and the ratio of α-SMA and TGF-β 1 positive area/total glomerule tuft area (SMA/GT and TGF/GT) were analyzed using computer-assisted image analysis software. Results: In the NC and the QC groups, only trace of α-SMA positive staining was found. But there was prominant α-SMA positive staining in glomeruli of the DM group, with SMA/GT and TGF/GT increased significantly , and marked increase of 24 hrs proteinuria excretion ( P<0 01). As compared with the DM group, the three indexes were all significantly lower in the VT and ZY groups , and the lowering of proteinuria was more significant in the ZY group than that in the VT group (P<0 01). Conclusion: The expression of α-SMA in glomeruli in STZ induced diabetic rats with unilateral nephrectomy is pronounced, indicating that phenotypic modulation of mesangial cells involvement in the pathogenesis of diabetic nephropathy. TJM and Valsartan can reduce 24 hrs proteinuria excretion, inhibit the phenotypic modulation of mesangial cells and the expression of TGF-β 1 in glomeruli of diabetic rats, and the effect of TJM is more potent than that of Valsartan in lowering urinary protein excretion..

Kerr effect and Kerr constant enhancement in vertically aligned deformed helix ferroelectric liquid crystals

In this article,we review recently achieved Kerr effect progress in novel liquid crystal（LC） material：vertically aligned deformed helix ferroelectric liquid crystal（VADHFLC）.With an increasing applied electric field,the induced inplane birefringence of LCs shows quadratic nonlinearity.The theoretical calculations and experimental details are illustrated.With an enhanced Kerr constant to 130 nm/V2,this VADHFLC cell can achieve a 2π modulation by a small efficient electric field with a fast response around 100 μs and thus can be employed in both display and photonics devices.

Influence of Structure Parameters on Performance of the Thermoelectric Module

A numerical model of thermoelectric module （TEM） is created by academic analysis,and the impacts of the resistance ratio and thermoelement size on the output power and thermoelectric efficiency of the TEM are analyzed by the MATLAB numerical calculation.The numerical model is validated by the ANSYS thermal,electrical,and structural coupling simulation.The effects of the variable physical property parameters and contact effect on the output power and thermoelectric efficiency are evaluated,and the concept of aspect ratio optimal domain is proposed,which provides a new design approach for the TEM.

Modulating effects of survivin antisense oligonucleotide on changes of apoptosis and cell cycle of human hepatocellular carcinoma cell line SMMC-7721

To investigate the modulating effects of survivn antisense oligonucletode (ASODN) on the cell cycle and apoptosis of human hepatocellular carcinoma (HCC) cell line SMMC-7721 and explore its mechanism.Methods Survivin ASODN was transfected into SMMC-7721 cells mediated by DOTAP liposomal reagent.Electron microscopy,flow cytometry and RT-PCR were used to detect the changes in cell ultrastructure,apoptosis,cell cycle and the expression of cyclinB1 mRNA,respectively.Results After transfection of survivin ASODN,the expression of cyclinB1 mRNA in the cells significantly increased and increase in G2-M arrest and apoptosis appeared.Meanwhile,the cell ultrastructure had apoptotic changes such as chromatin condensation and apoptotic body formation.Conclusion Survivin ASODN can induce the expression of cyclinB1 that may result in G2-M arrest.Consequently,apoptosis is triggered.Survivin ASODN transfection might be an improtant new treatment for HCC.14 refs,2 figs,1 tab.

Simple Raman scattering sensor integrated with a metallic planar optical waveguide: effective modulation via minor structural adjustment

We report experimental realization of Raman spectra enhancement of copper phthalocyanine, using an on-chip metallic planar waveguide of the sub-millimeter scale. The oscillating ultrahigh order modes excited by the direct coupling method yield high optical intensity at resonance, which is different from the conventional strategy to create localized ＂hot spots.＂ The observed excitation efficiency of the Raman signal is significantly enhanced,owing to the high Q factor of the resonant cavity. Furthermore, effective modulation of the Raman intensity is available by adjusting the polymethyl methacrylate（PMMA） thickness in the guiding layer, i.e., by tuning the light–matter interaction length. A large modulation depth is verified through the fact that 10 times variation in the enhancement factor is observed in the experiment as the PMMA thickness varies from 7 to 23 μm.

Investigation of Eccentric PM on High-frequency Vibration in FSCW PM Machine Considering Force Modulation Effect

This study investigates the negative influence of an eccentric permanent-magnet(PM)design on high-frequency electromagnetic vibration in fractional-slot concentrated-winding(FSCW)PM machines.First,an analytical expression for the sideband current harmonics was derived using the double Fourier series expansion method.Then,the characteristics of the flux-density harmonics are studied from the perspective of the space-time distribution and initial phase relationship.The influence of the eccentric PM design on high-frequency electromagnetic and concentrated forces was studied based on the electromagnetic force modulation effect.Consequently,an eccentric PM design is not conducive to reducing the 2pth-order high-frequency electromagnetic forces.Finally,two FSCW PM machines with conventional and eccentric PM designs are manufactured and tested to verify the theoretical analysis.The results show that the eccentric PM design worsens high-frequency vibrations.

The modulating effect of N coordination on single-atom catalysts researched by Pt-N_(x)-C model through both experimental study and DFT simulation

N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates from the coordinating structure between single metal site(M) and the doped nitrogen(N) in carbon matrix by forming M-N_(x)-C structure(1≤x≤4).The M-N4-C structure is widely considered to be the most stable and effective catalytic site.However,there is no in-depth research for the "x" modulation in Pt-Nx-C structure and the corresponding catalytic properties.Herein,atomically dispersed Pt on N-doped carbon(Pt-NC) with Pt-Nx-C structure(1≤x≤4),as a research model,is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction.Different carbonization temperatures are used to control N loss,and then modulate the N coordination of Pt-Nx-C structure.The Pt-NC has the predictable low half-wave potential(E_(1/2)) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81 V due to low Pt content.Remarkably,the Pt-NC shows a high onset potential(1.10 V vs RHE,determined for j=-0.1 mA cm^(2)) and a high current density of 5.2 mA cm^(-2),more positive and higher than that of Pt/C 20%(0.96 V) and 4.9 mA cm^(-2),respectively.As the structural characterization and DFT simulation confirmed,the reducing PtN coordination number induces low valence of Pt atoms and low free energy of oxygen reduction,which is responsible for the improved catalytic activity.Furthermore,the Pt-NC shows high mass activity(172 times higher than that of Pt/C 20%),better stability and methanol crossover resistance.

Magnets Shifting Design of Dual PM Excited Vernier Machine for High-torque Application

In this study,a novel dual permanent magnet excited vernier machine(DPMEVM)with magnets shifting in stator is proposed.Compared with the conventional permanent magnet synchronous machine(PMSM),the DPMEVM based on the bidirectional field modulation effect can operate in a wider torque range.However,the torque ripple of a conventional DPMEVM is high because of the superposition of the torque generated by the stator-side and rotor-side PMs.Consequently,a novel DPMEVM with magnets shifting is proposed to further reduce the torque ripple.First,the topologies and working principles of the baseline machine and proposed machines are introduced.Second,the torque-contribution harmonics are analyzed and calculated using the Maxwell tensor method.The calculation results reveal that the DPMEVM,benefiting from multiple working harmonics,can offer an enhanced torque capability compared to the PMSM.In addition,the torque ripple characteristics of the proposed machines are analyzed.It is verified that the torque ripple can be significantly reduced through magnets shifting.Third,the performances of the baseline machine and proposed machines are analyzed and compared in terms of flux density,open-circuit back-EMF,and torque characteristics.In addition,the proposed principle can be extended to machines with the same unit motor.Finally,a 120s-110p prototype machine is manufactured for validation.

Realizing high thermoelectric performance for p-type SiGe in medium temperature region via TaC compositing

SiGe is recognised as an excellent thermoelectric material with superior mechanical properties and thermal stability in regions with high temperatures.This study explores a novel strategy for coregulating thermoelectric transport parameters to achieve high thermoelectric properties of p-type SiGe in the mid-temperature region by incorporating nano-TaC into SiGe combined ball milling with spark plasma sintering.By optimizing the amount of TaC in the SiGe matrix,the power factors were significantly increased due to the modulation doping effect based on the work function matching of SiGe with TaC.Simultaneously,the ensemble effect of the nanostructure leads to a significant decrease in thermal conductivity.Thus,a high ZT of 1.06 was accomplished at 873 K,which is 64%higher than that of typical radioisotope thermoelectric generator.Our research offers a novel strategy for expanding and enhancing the thermoelectric properties of SiGe materials in the medium temperature range.

Conductivity modulation enhanced lateral IGBT with SiO_2 shielded layer anode by SIMOX technology on SOI substrate

A new lateral insulated-gate bipolar transistor（LIGBT） with a SiO_2 shielded layer anode on SOI substrate is proposed and discussed.Compared to the conventional LIGBT,the proposed device offers an enhanced conductivity modulation effect due to the SiO_2 shielded layer anode structure which can be formed by SIMOX technology.Simulation results show that,for the proposed LIGBT,during the conducting state,the electron-hole plasma concentrations in the n-drift region are several times larger than those of the conventional LIGBT;the conducting current is up to 37% larger than that of the conventional one.The enhanced conductivity modulation effect by SiO_2 shielded layer anode does not sacrifice other characteristics of the device,such as breakdown and switching,but is compatible with other optimized technologies.

The effect of conductor loss on half-wave voltage and modulation bandwidth of electro-optic modulators

In this paper, we theoretically deduce the expressions of half-wave voltage and 3-dB modulation bandwidth in which conductor loss is taken into account. The results suggest that it will affect the theoretical values of half-wave voltage and bandwidth as well as the optimized electrode's dimension whether considering the conductor loss or not. As an example, we present a Mach-Zehnder (MZ) type polymer waveguide amplitude modulator. The half-wave voltage increases by 1 V and the 3-dB bandwidth decreases by 30% when the conductor loss is taken into account. Besides, the effects of impedance mismatching and velocity mismatching between microwave and light wave on the half-wave voltage, and 3-dB bandwidth are discussed.

Coordinating Zirconium Nodes in Metal-Organic Framework with Trifluoroacetic Acid for Enhanced Lewis Acid Catalysis

Regulating Lewis acid sites with well-defined electronic state and steric environment is still challenging for achieving high catalytic efficiency.Here we show coordinating zirconium nodes in the typical metal-organic framework known as MOF-545 with the monocarboxylate modulators including trifluoroacetic acid(TFA)or benzoic acid(BA)over meso-tetra(4-carboxyphenyl)-porphine(H_(2)TCPP),denoted as MOF-545-TFA or MOF-545-BA.Impressively,MOF-545-TFA shows the significantly enhanced performance for the catalytic ring-opening reaction of various epoxides with alcohols and good recyclability at 40°C in respect with MOF-545-BA and ZrO_(2).This mainly originates from the stronger Lewis acidity and more active zirconium sites induced by the electron-withdrawing TFA,resulting in the increased ability for activation of epoxides.This modulation approach is promising for enlarging the toolbox to extend the MOFs-based Lewis acid catalysis.

An Integrated-Plasmonic Chip of Bragg Reflection and Mach-Zehnder Interference Based on Metal-Insulator-Metal Waveguide

In this paper,a Bragg reflector is proposed by placing periodic metallic gratings in the center of a metal-insulator-metal(MIM)waveguide.According to the effective refractive index modulation caused by different waveguide widths in a period,a reflection channel with a large bandwidth is firstly achieved.Besides,the Mach-Zehnder interference(MZI)effect arises by shifting the gratings away from the waveguide center.Owing to different optical paths with unequal indices on both sides of the grating,a narrow MZI band gap will be obtained.It is interesting to find out that the Bragg reflector and Mach-Zehnder interferometer are immune to each other,and their wavelengths can be manipulated by the period and the grating length,respectively.Additionally,we can obtain three MZI channels and one Bragg reflection channel by integrating three different gratings into a large period.The performances are investigated by finite-difference time-domain(FDTD)simulations.In the index range of 1.33–1.36,the maximum sensitivity for the structure is as high as 1500 nm/RIU,and it is believed that this proposed structure can find widely applications in the chip-scale optical communication and sensing areas.

Modulation effect in adjacent dual metal single atom catalysts for electrochemical nitrogen reduction reaction

Nitrogen reduction reaction (NRR) is a clean mode of energy conversion and the development of highly efficient NRR electrocatalysts under ambient conditions for industrial application is still a big challenge. Metal-nitrogen-carbon (M-N-C) has emerged as a class of single atom catalyst due to the unique geometric structure, high catalytic activity, and clear selectivity. Herein, we designed a series of dual metal single atom catalysts containing adjacent M-N-C dual active centers (MN_(4)/M'N_(4)-C) as NRR electrocatalysts to uncover the structure-activity relationship. By evaluating structural stability, catalytic activity, and selectivity using density functional theory (DFT) calculations, 5 catalysts, such as CrN_(4)/M'N_(4)-C (M’ = Cr, Mn, Fe, Cu and Zn), were determined to exhibit the best NRR catalytic performance with the limiting potential ranging from -0.64 V to -0.62 V. The CrN_(4) center acted as the main catalytic site and the adjacent M'N_(4) center could enhance the NRR catalytic activity by modulation effect based on the analysis of the electronic properties including the charge density difference, partial density of states (PDOS), and Bader charge variation. This study offers useful insights on understanding the structure-activity relationship of dual metal single atom catalysts for electrochemical NRR.

elliptically birefringent fibers modulation instability ellipticity angle

Previous studies on modulation instabilities（MIs） in birefringent optical fibers focus on the ordinary linearly and circularly ones. This paper reports an analysis of MIs in the general elliptically birefringent fibers with the emphasis on investigating the effects of ellipticity angle（0？ ≤θ≤ 90？）. Both symmetric and antisymmetric CW states are considered. In the anomalous dispersion regime, for the symmetric（antisymmetric） CW states, we show that MI gain increases dramatically（reduces first and then enhances greatly） as the increment of θ. In the normal dispersion regime, for the both CW states, the distinctive feature is that the gain of the MI bands reduces first, vanishes at θ = 45？,reappears across this ellipticity angle, and quickly increases after then.