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Prolongation Structure Analysis of a Coupled Dispersionless System
Souleymanou Abbagari, **, Bouetou Bouetou Thomas, Kuetche Kamgang Victor, Mouna Ferdinand, Timoleon Crepin Kofane
Chin. Phys. Lett. 2011, 28 (2):
020204
.
DOI: 10.1088/0256-307X/28/2/020204
We address the problem of integrability of a coupled dispersionless system recently introduced by Zhaqilao, Zhao and Li [Chin. Phys. B 18 (2009) 1780] which physically describes the propagation of electromagnetic fields within an optical nonlinear medium, but also arrives in the physical description of a charged object dynamics in an external magnetic field. Following the prolongation structure analysis developed by Wahlquist and Estabrook, we derive a more general form of Lax pairs of the previous coupled dispersionless system and its concrete non-Abelian Lie algebra resorting to a hidden symmetry. Also, we construct the Bäcklund transformation of the system using the Riccati form of the linear eigenvalue problem.
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Effects of Dzyaloshinskii–Moriya Interaction on Optimal Dense Coding Using a Two-Qubit Heisenberg XXZ Chain with and without External Magnetic Field
CAI Jiang-Tao, ABLIZ Ahmad**, BAI Yan-Kui, JIN Guang-Sheng
Chin. Phys. Lett. 2011, 28 (2):
020307
.
DOI: 10.1088/0256-307X/28/2/020307
We investigate the effects of different components of the Dzyaloshinskii–Moriya (DM) anisotropic antisymmetric interaction on optimal dense coding with a two-qubit Heisenberg XXZ chain in the presence and in the absence of external magnetic fields. The anisotropic coupling parameter Δ, isotropic coupling parameter J, and the DM interaction parameters are found to be effective for optimal dense coding, while the magnetic field turns out to be destructive. Moreover, the results show that the case of antiferromagnetic (AFM) is more ideal for optimal dense coding than the case of ferromagnetic (FM) in general. In the case of AFM, by comparison of the two cases with the same fixed x− and z−component parameters of DM interaction (Dx and Dz), the appropriate model for optimal dense coding is indicated for the different value intervals of Δ. Comparison of the effects of Dz and Dx on optimal dense coding is made and their dominant regions are clarified.
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QCT Calculations of Reactions of F+LiH→LiF+H and F+LiD→LiF+D: Product Polarization and Isotope Effects
WANG Tao, YUE Xian-Fang
Chin. Phys. Lett. 2011, 28 (2):
023101
.
DOI: 10.1088/0256-307X/28/2/023101
Using the quasi-classical trajectory (QCT) method, the product polarization at the collision energy of 46 kcal/mol is investigated for the reactions of F+LiH (v=0, j=0)→LiF+H and F+LiD (v=0, j=0)→LiF+D on the 2A' ground state potential energy surface (PES)[J. Chem. Phys. 106(1997)1013). The distribution of P(θr), which represents the K and J' correlation, the dihedral angle distribution of K−K'-J' P(φr), the angular distribution P(θr,φr) and the four PDDCSs[(2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt), (2π/σ)(dσ21−/dωt)] are presented and discussed. In addition, isotope effects are investigated. The results indicate that at the collision energy of 46 kcal/mol, with isotopic mass substitution, the orientation degree of LiF perpendicular to the scattering degree becomes stronger while the polarization degree of LiF perpendicular to K keeps almost changeless. In addition, the angular distribution of LiF strongly prefers forward scattering.
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Efficient Spherical Wavefront Correction near the Focus for the 0.89PW/29.0fs Ti:Sapphire Laser Beam
REN Zhi-Jun, LIANG Xiao-Yan**, YU Liang-Hong, LU Xiao-Ming, LENG Yu-Xin, LI Ru-Xin**, XU Zhi-Zhan**
Chin. Phys. Lett. 2011, 28 (2):
024201
.
DOI: 10.1088/0256-307X/28/2/024201
We demonstrate a new loop system of the spherical wavefront (SW) correction near the beam focus to effectively improve the focusability of 0.89 PW/29.0 fs Ti:sapphire chirped pulse amplification laser. After wavefront correction, the Strehl ratio is improved to reach 0.91, and the focal spot size using the f/4 off−axis parabola is reduced to 6.34×6.94 μm2 (corresponding to 1.63×1.78 times diffraction limitation). With full peak power of 0.89 PW, the peak intensity of 2.59×1021 W/cm2 is obtained. The experimental results show that the SW correction scheme near the beam focus is comparatively simple, economic and high-efficient.
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Diode-End-Pumped Tm:Ho:GdVO4 Microchip Laser at Room Temperature
YAO Bao-Quan**, CHEN Fang, WANG Qiang, WU Chun-Ting, LI Gang, ZHANG Chao-Hui, WANG Yue-Zhu, JU You-Lun
Chin. Phys. Lett. 2011, 28 (2):
024210
.
DOI: 10.1088/0256-307X/28/2/024210
Room-temperature Tm:Ho:GdVO4 microchip laser operated around 2 μm is demonstrated for the first time to our knowledge. At a heat sink temperature of 283 K, maximum output power of 29.7 mW is obtained by using a 0.25−mm-long crystal at an absorbed pump power of 912 mW, corresponding to a slope efficiency of 5.0%. At the temperature to 283 K, a single-longitudinal-mode laser as much as 8mW at 2048.5 nm is achieved. The M2 factor is measured to be 1.4.
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Influence of Turbulent Atmosphere on Polarization Properties of Stochastic Electromagnetic Pulsed Beams
DING Chao-Liang**, ZHAO Zhi-Guo, LI Xiao-Feng, PAN Liu-Zhan***, YUAN Xiao
Chin. Phys. Lett. 2011, 28 (2):
024214
.
DOI: 10.1088/0256-307X/28/2/024214
Using the coherence theory of non-stationary fields and the characterization of stochastic electromagnetic pulsed beams, the analytical expression for the spectral degree of polarization of stochastic electromagnetic Gaussian Schell-model pulsed (GSMP) beams in turbulent atmosphere is derived and is used to study the polarization properties of stochastic electromagnetic GSMP beams propagating through turbulent atmosphere. The results of numerical calculation are given to illustrate the dependence of spectral degree of polarization on the pulse frequency, refraction index structure constant and spatial correlation length. It is shown that, compared with free-space case, in turbulent atmosphere propagation there are two positions at which the on-axis spectral degree of polarization P is equal to zero. The position change depends on the pulse frequency, refraction index structure constant and spatial correlation length.
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Micro-acting Force in Boundary Layer in Low-Permeability Porous Media
FENG Yu-Liang, ZHANG Yuan, JI Bing-Yu, MU Wen-Zhi
Chin. Phys. Lett. 2011, 28 (2):
024703
.
DOI: 10.1088/0256-307X/28/2/024703
There are lots of reasons to restrict a low-permeability oil layer to enhance the recovery factor. Based on the research results of non-Darcy flow, microflow of water drive and micro-acting force in low permeability porous media are studied by establishing the expression of fluid viscosity factor. Numerical calculation shows that under the condition of L/S interaction, the radial velocity distribution near the solid wall changes obviously, and the curve form changes from convex to concave. The tinier the capillary radius is, the stronger the L/S interaction is. The larger the n value is, more obviously the flowing velocity decreases. The results will help people to deal with improving recovery factor of low permeability reservoir, and understanding the fluid flow behavior in blood capillary.
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Clarification on Polarity of Bipolar Electric Field Solitary Structures in Space Plasmas with Satellite Observation
M. N. S. Qureshi, **, SHI Jian-Kui, Klaus Torkar, LIU Zhen-Xing
Chin. Phys. Lett. 2011, 28 (2):
025204
.
DOI: 10.1088/0256-307X/28/2/025204
The bipolar electric field solitary (EFS) structures observed frequently in space plasmas by satellites have two different polarities, first positive electric field peak then negative (i.e., positive/negative) and first negative then positive peak (i.e., negative/positive). We provide the physical explanation on the polarity of observed bipolar EFS structures with an electrostatic ion fluid model. The results show that if initial electric field E0>0, the polarity of the bipolar EFS structure will be positive/negative; and if E0 <0, the polarity of the bipolar EFS structure will be negative/positive. However, for a fixed polarity of the EFS, either positive/negative or negative/positive, if the satellite is located at the positive side of the EFS, the observed polarity should be positive/negative, if the satellite is located at the negative side of the EFS, the observed polarity should be negative/positive. Therefore, we provide a method to clarify the natural polarity of the EFS with observed polarity by satellites. Our results are significant to understand the physical process in space plasma with the satellite observation.
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Effect of Pressure on Thermal Stability and Decomposition of KDP Crystal
DING Jian-Xu, WANG Tao, WANG Sheng-Lai**, CUI De-Liang**, MU Xiao-Ming, XU Xin-Guang
Chin. Phys. Lett. 2011, 28 (2):
026402
.
DOI: 10.1088/0256-307X/28/2/026402
Effect of pressure on thermal behavior of KDP crystals is investigated by using the in-situ infrared reflective spectra. Compared with that under normal atmosphere, the onset temperature of decomposition under pressure of 1 MPa is improved to from 210 °C to 213 °C, suggesting that the thermal stability of KDP is enhanced. Under pressure of 2 MPa, the thermal stability is deteriorated and KDP begins to decompose at 183 °C. Under normal atmosphere KDP decomposes in route of translating to K4P2O7 firstly, and then to KPO3. Under pressures of 1 MPa and 2 MPa, KDP translates to KPO3 directly without any other polymeric intermediates.
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Polarization Mechanism of Oxygen Vacancy and Its Influence on Dielectric Properties in ZnO
WANG Li-Na, FANG Xiao-Yong**, HOU Zhi-Ling, LI Ya-Lin, WANG Kun, YUAN Jie, CAO Mao-Sheng**
Chin. Phys. Lett. 2011, 28 (2):
027101
.
DOI: 10.1088/0256-307X/28/2/027101
We report on the mechanism of the dielectric properties of oxygen vacancy in ZnO, using ab initio numerical simulations of oxygen vacancy on the band structure and dielectric properties, to develop photoelectric material applications. It is revealed that the appearance of oxygen vacancies leads to wider energy band gap, obvious blue shift and increase in the peak of dielectric function as compared to the intrinsic ZnO simulation. We explain these unusual phenomena and analyze the dielectric changes with the mechanism of polarization in the semiconductors. It is shown that the main mechanism of influencing dielectric properties is the electron displacement polarization. The result may be helpful for development of photoelectric materials.
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Properties of Si Doped Al0.4Ga0.6N Epilayers with Different AlGaN Window Layer Grown on High Quality AlN Buffer by MOCVD
YU Chen-Hui, LIU Cheng, HAN Xiang-Yun, KANG Wei, FANG Yan-Yan, DAI Jiang-Nan, WU Zhi-Hao, CHEN Chang-Qing**
Chin. Phys. Lett. 2011, 28 (2):
027301
.
DOI: 10.1088/0256-307X/28/2/027301
Si-doped Al0.4Ga0.6N (Si−Al0.4Ga0.6N) epilayers grown on an AlGaN window layer (WL) with different Al contents are prepared using a high−quality AlN buffer layer by metal-organic chemical vapor deposition. Surface morphology, crystalline quality and electric properties of these epilayers are investigated by using atomic force microscopy, x-ray diffraction, Raman scattering spectrum and Hall techniques. Results show that the surface morphology of these epilayers are mainly determined by the Si-doping level which, together with the effect of Al content of WL, also has an obvious impact on the electron concentrations. On the other hand, the insertion of AlGaN WL is helpful to the increase of Si doping level and conductivity of subsequently grown Si-Al0.4Ga0.6N epilayers. However, the insertion as well as the increase of Al content of WL result in increase of dislocation densities, compressive strain in Si−Al0.4Ga0.6N epilayers, and tilt of AlN subgrains at the top interface of the buffer layer. Further, the degradation of crystalline quality with the Al content of WL exerts a decisive influence on the conductivity of the Si−Al0.4Ga0.6N epilayers grown on WL with Al content of 0.6 through a dramatic decrease in electron mobility.
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Electronic Non-Resonant Tunneling through Diaminoacenes: A First-Principles Investigation
ZHENG Ji-Ming, HUANG Yao-Qing**, REN Zhao-Yu, YANG Hui-Jing, CAO Mao-Sheng**
Chin. Phys. Lett. 2011, 28 (2):
027302
.
DOI: 10.1088/0256-307X/28/2/027302
The electron transport through diaminoacenes sandwiched between two Au electrodes is simulated by using a first-principles analysis. The nonlinear current-voltage characteristic is observed. Effects of the ring number and positions of amine groups on equilibrium transport properties are found. For 1,4 series, the greater the number of the rings, the stronger the transmission spectrum near the Fermi energy. For 2,6 series, the larger the number of the rings, the weaker the transmission spectrum near the Fermi energy. This is helpful for understanding the recently reported results on conductance measurements using amines.
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Up-Conversion Photostimulated Luminescence of Mg2SnO4 for Optical Storage
ZHANG Jia-Chi**, QIN Qing-Song, YU Ming-Hui, SUN Jia-Yao, SHI Liu-Rong, MA Xin-Long
Chin. Phys. Lett. 2011, 28 (2):
027802
.
DOI: 10.1088/0256-307X/28/2/027802
We report the first observation of up-conversion photostimulated luminescence in non-doped Mg2SnO4. Stimulated by 980 nm infrared laser (reading) after ultraviolet irradiation (writing), the phosphor shows photostimulated emission band covering 470–550 nm, which is due to the recombination of F centers with holes. After ceasing ultraviolet irradiation, the storage intensity would rapidly decrease to 59% of its original storage intensity in 2.5 h and then would not degrade anymore. It is suggested that the Mg2SnO4 has potential applications for optical storage. Accordingly, the possible photostimulated luminescence mechanisms of Mg2SnO4 are proposed.
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Photoluminescence of Nominally Undoped Heavy n-Type ZnO Nanowires
TANG Hai-Ping, HE Hai-Ping**, LIU Chao, KWON Bong-Jun, YE Zhi-Zhen, LEE Soonil, PARK Ji-Yong***
Chin. Phys. Lett. 2011, 28 (2):
027803
.
DOI: 10.1088/0256-307X/28/2/027803
We report the identification of a donor band and the correlation between n-type conductivity and the green emission in ZnO nanowires. Temperature-dependent photoluminescence is used to investigate nominally undoped ZnO nanowires with high n-type conductivity. Within the whole temperature range, a dominant free-to-bound transition with a donor band of about 150 meV below the conduction band minimum is observed. The nanowires show very strong green emission, which is quenched with activation energy of about 220 meV. The correlation between the high n-type conductivity and the strong green emission is discussed in detail, and we suggest that they may have different origins.
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Nd-Doping Induced Lattice Distortion in TiO2 Nanoparticles
WANG Yue, WU Da-Jian, YANG Yue-Tao, LIU Xiao-Jun**
Chin. Phys. Lett. 2011, 28 (2):
027804
.
DOI: 10.1088/0256-307X/28/2/027804
Nd-doping effects are investigated in TiO2 nanoparticles with various annealing temperatures T from 70 °C to 1100 °C by means of x−ray diffraction (XRD) and Raman scattering spectroscopy. XRD results indicate that the sample shows a rutile phase at 1100 °C, which changes to anatase phase at 900 °C. With decreasing T down to 300 °C, a significant lattice shrink is found, that is, the lattice parameter c is significantly suppressed while the a value shows a gradual decrease. With further decrease of T, the c−value shows an unexpected increase while the a−value keeps a gradual decrease. Thus, a lattice distortion takes place with changing the annealing temperature. In Raman investigation, all the Raman modes for the anatase phase show hardening behaviors with decreasing T in the range 900–300 °C, and then the Eg and A1g modes show softening behaviors below 300 °C, suggesting the variation of the lattice distortion. The variation of the lattice distortion at different annealing temperatures is ascribed to different depositions of Nd ions on the surface of TiO2 nanoparticles.
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Synthesis of Red Phosphor CaZrO3:Eu3+ for White Light-Emitting Diodes
LI Xu, GUAN Li**, AN Jia-Yi, JIN Li-Tao, YANG Zhi-Ping, YANG Yan-Min, LI Pan-Lai, FU Guang-Sheng
Chin. Phys. Lett. 2011, 28 (2):
027805
.
DOI: 10.1088/0256-307X/28/2/027805
A red-emitting CaZrO3:Eu3+ phosphor has been prepared by solid state reaction and its luminescent properties are studied. The crystal structure is investigated by the x−ray diffraction. Through energy transitions of 5D0→7FJ (J=0, 1, 2, 3) in Eu3+ ions, the emission spectrum of the phosphor shows a series of narrow bands under near−ultraviolet light and the strongest peak locates at 613 nm. The emission intensity of Ca1-xZrO3:xEu3+ phosphor will reach the maximum as the molar concentration of Eu3+ is 5 mol%.
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Optical Characteristics of La-Doped ZnS Thin Films Prepared by Chemical Bath Deposition
XIE Hai-Qing, CHEN Yuan, HUANG Wei-Qing, HUANG Gui-Fang, PENG Ping, PENG Li, WANG Tai-Hong, ZENG Yun, **
Chin. Phys. Lett. 2011, 28 (2):
027806
.
DOI: 10.1088/0256-307X/28/2/027806
Undoped and La-doped ZnS thin films are prepared by chemical bath deposition (CBD) process through the co-precipitation reaction of inorganic precursors zinc sulfate, thiosulfate ammonia and La2O3. Composition of the films is analyzed using an energy-dispersive x-ray spectroscopy (EDS). Absorption spectra and spectral transmittances of the films are measured using a double beam UV-VIS spectrophotometer (TU-1901). It is found that significant red shifts in absorption spectra and decrease in absorptivity are obtained with increasing lanthanum. Moreover, optical transmittance is increased as La is doped, with a transmittance of more than 80% for wavelength above 360 nm in La-doped ZnS thin films. Compared to pure ZnS, the band gap decreases and flat-band potential positively shifts to quasi-metal for the La-doped ZnS. These results indicate that La-doped ZnS thin films could be valuably adopted as transparent electrodes.
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Influence of N2 Flux on InN Film Deposition on Sapphire (0001) Substrates by ECR-PEMOCVD
ZHOU Zhi-Feng, QIN Fu-Wen, **, ZANG Hai-Rong, ZHANG Dong, CHEN Wei-Ji, ZHI An-Bo, LIU Xing-Long, YU Bo, JIANG Xin,
Chin. Phys. Lett. 2011, 28 (2):
028102
.
DOI: 10.1088/0256-307X/28/2/028102
Highly preferred InN films are deposited on sapphire (0001) substrates by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) without using a buffer layer. The structure, surface morphological and electrical characteristics of InN are investigated by in-situ reflection high energy electron diffraction, x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy and Hall effect measurement. The quality of the as-grown InN films is markedly improved at the optimized N2 flux of 100 sccm. The results show that the properties of the films are strongly dependent on N2 flux.
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Effect of Substrate Temperature on the Structural, Electrical and Optical Properties of Nanocrystalline Silicon Films in Hot-Filament Chemical Vapor Deposition
GUO Xiao-Song, ZHANG Shan-Shan, BAO Zhong, ZHANG Hong-Liang, CHEN Chang-Cheng, LIU Li-Xin, LIU Yan-Xia, XIE Er-Qing**
Chin. Phys. Lett. 2011, 28 (2):
028103
.
DOI: 10.1088/0256-307X/28/2/028103
Hydrogenated nanocrystalline silicon films are deposited onto glass substrates at different substrate temperatures (140–400 °C) by hot−filament chemical vapor deposition. The effect of substrate temperature on the structural properties are investigated. With an increasing substrate temperature, the Raman crystalline volume fraction increases, but decreases with a further increase. The maximum Raman crystalline volume fraction of the nanocrystalline silicon films is about 74% and also has the highest microstructural factor (R=0.89) at a substrate temperature of 250 °C. The deposition rate exhibits a contrary tendency to that of the crystalline volume fraction. The continuous transition of the film structures from columnar to agglomerated is observed at a substrate temperature of 300 °C. The optical band gaps of the grown thin films declines (from 1.89 to 1.53 eV) and dark electrical conductivity increases (from about 10−10 to about 10−6 S/cm) with the increasing substrate temperature.
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Photo-Crosslinking Induced Geometric Restriction Controls the Self-Assembly of Diphenylalanine Based Peptides
TIE Zuo-Xiu, QIN Meng**, ZOU Da-Wei, CAO Yi**, WANG Wei
Chin. Phys. Lett. 2011, 28 (2):
028702
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DOI: 10.1088/0256-307X/28/2/028702
The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π−π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive "smart" materials.
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Evolution of Interacting Viscous Dark Energy Model in Einstein Cosmology
CHEN Ju-Hua, **, ZHOU Sheng, WANG Yong-Jiu,
Chin. Phys. Lett. 2011, 28 (2):
029801
.
DOI: 10.1088/0256-307X/28/2/029801
We investigate the evolution of the viscous dark energy (DE) interacting with the dark matter (DM) in the Einstein cosmology model. By using the linearizing theory of the dynamical system, we find that, in our model, there exists a stable late time scaling solution which corresponds to the accelerating universe. We also find the unstable solution under some appropriate parameters. In order to alleviate the coincidence problem, some authors considered the effect of quantum correction due to the conform anomaly and the interacting dark energy with the dark matter. However, if we take into account the bulk viscosity of the cosmic fluid, the coincidence problem will be softened just like the interacting dark energy cosmology model. That is to say, both the non-perfect fluid model and the interacting the dark energy cosmic model can alleviate or soften the singularity of the universe.
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69 articles
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