| 1. |
- Ablikim, M., et al.
(author)
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Measurements of (XcJ)-> K+K-K+K- decays
- 2006
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 642:3, s. 197-202
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Journal article (peer-reviewed)abstract
- Using 14M psi(2S) events taken with the BESII detector, chi(cJ) -> 2(K+K-) decays are studied. For the four-kaon final state, the branching fractions are B(chi(c0,1,2) ->.2(K+K-)) = (3.48 +/- 0.23 +/- 0.47) x 10(-3), (0.70 +/- 0.13 +/- 0.10) x 10(-3), and (2.17 +/- 0.20 +/- 0.31) x 10(-3). For the phi K+K- final state, the branching fractions, which are measured for the first time, are B(chi(c0,1,2) -> phi K+K-) = (1.03 +/- 0.22 +/- 0.15) x 10(-3), (0.46 +/- 0.16 +/- 0.06) x 10(-3), and (1.67 +/- 0.26 +/- 0.24) x 10(-4). For the phi phi final state, B(chi(c0,2) -> phi phi) = (0.94 +/- 0.21 +/- 0.13) x 10(-3) and (1.70 +/- 0.30 +/- 0.25) x 10(-3).
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| 2. |
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| 3. |
- Chen, H., et al.
(author)
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The distribution of grating-coupled field of quantum well infrared photodetector using FDTD method
- 2007
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In: Infrared Materials, Devices, and Applications. - : SPIE - International Society for Optical Engineering. - 9780819470102 ; , s. 68351E-
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Conference paper (peer-reviewed)abstract
- For most commonly used GaAs/AlGaAs n-type quantum well infrared photodetectors (QWIPs), the normal incident absorption is not possible because of the transition rule. The optical grating is required to achieve high absorption quantum efficiencies. When some gratings are patterned on the metal plate, the polarization direction can be changed greatly because of the diffraction effect. Finite difference time domain (FDTD) method has been used to investigate the effect of a reflection metal grating on the couple efficiency previously. However, the authors only take one metal grating and apply periodic boundary condition along the grating direction due to the computation limit. For a real QWIP system, such simulation is crude. In this work we consider a real GaAs/AlGaAs QWIP with a wavelength response around 15um and use FDTD method to investigate the effect of a reflection metal grating on the electric field pattern and the couple efficiency. The simulating results show that the electric field pattern is not periodic for every metal grating in a real QWIP system. We have also studied the influence of the substrate thickness and the grating period on the electric field pattern and the couple efficiency. These results offer a guideline for the design of QWIP.
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| 4. |
- Zhe, XW, et al.
(author)
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Pulse wave velocity is associated with metabolic syndrome components in CAPD patients
- 2008
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In: American journal of nephrology. - : S. Karger AG. - 1421-9670 .- 0250-8095. ; 28:4, s. 641-646
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Journal article (peer-reviewed)abstract
- <i>Background:</i> Overall, the proportion of deaths due to cardiovascular disease (CVD) reached 40–50% in dialysis patients. Pulse wave velocity (PWV) reflects arterial stiffness and may provide an integrated index of vascular status and CVD risk. Individual components of the metabolic syndrome (MetS) are well-established cardiovascular risk factors. Thus we conducted a cross-sectional study in continuous ambulatory peritoneal dialysis (CAPD) patients to explore the association of MetS components with PWV. <i>Methods:</i> Prevalent CAPD patients (n = 148, 63 M/85 F) were categorized according to the number of traits of the MetS into one of three groups (No MetS, Risk of MetS, MetS). Due to the effect of peritoneal dialysis (PD), waist circumference was not assessed. Aortic stiffness was assessed by carotid-femoral PWV (C-F PWV). <i>Results:</i> Patients’ MetS trait numbers were positively associated with C-F PWV (r = 0.301, p < 0.01), pulse pressure (r = 0.256, p < 0.01), systolic blood pressure (r = 0.233, p < 0.01), and serum albumin (r = 0.205, p < 0.05). In a multivariate regression analysis, PWV was independently determined by age (p < 0.01) and MetS score (p = 0.01). Adjusted R<sup>2</sup> of the model was 0.24. <i>Conclusion:</i> MetS traits were closely associated with an increased C-F PWV, even after adjustment for confounders. This suggests that commonly recognized MetS criteria are useful also when predicting CVD in CAPD patients.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Wu, Yanrui, et al.
(author)
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Light coupling for single-mode photonic crystal waveguides
- 2006
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In: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 35:1, s. 93-98
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Journal article (peer-reviewed)abstract
- We use a transfer-matrix method (TMM) to investigate light coupling into and out of single-end single-mode photonic crystal waveguides. Without multi-reflection complexity, we give clearly the unambiguous quantitative determination of the coupling efficiency of external light into guided mode and the transition among guided modes. It is shown that the waveguide with a line defect along Gamma J direction exhibits a much better coupling efficiency than that with a line-defect orientation along Gamma M direction.
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| 9. |
- Zeng, Yong, et al.
(author)
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Complete band gaps in three-dimensional quantum dot photonic crystals
- 2006
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:11, s. 115325-
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Journal article (peer-reviewed)abstract
- Nonlocal investigations have been performed about exciton-photon couplings in three-dimensional quantum-dot (QD) photonic crystals and a complete photonic band gap has been found in the band structure of a diamond lattice. The width of such a band gap can be broadened by increasing the filling ratio of the QDs (increasing the QD radius or/and decreasing the lattice constant of the photonic crystal). By decomposing the diamond lattice into two interlacing face-centered-cubic (fcc) sublattices, we have found that by significantly modifying the QD radius in one fcc sublattice (the diamond lattice therefore changed to the zinc blende lattice), the band structure of the zinc blende lattice is in principle the sum of two individual fcc sublattices. However, a huge exciton-photon coupling is observed near the band gaps of the two individual fcc sublattices when the radii of the QDs in the two fcc sublattices approach each other, resulting in the complete band gaps of the diamond structure.
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| 10. |
- Zeng, Yong, et al.
(author)
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Dynamics of the damping oscillator formed by the collective generation of surface polaritons for extraordinary light transmission through subwavelength hole arrays in thin metal films
- 2007
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:12
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Journal article (peer-reviewed)abstract
- Light transmissions through a subwavelength hole array in a thin metal film are characterized by resonance peaks in the transmission spectrum. In this work we study the surface polaritons (SPs) in perforated thin metal films by analyzing the dynamic behavior of the Poynting vectors based on a full-vector finite-difference time-domain approach. It is shown that each resonance peak in the transmission spectrum is caused by a collective generation of SPs in the form of a dynamic damping oscillator which oscillates in space and time. The energy of the incident light is transported between the upper and the lower metal-air surfaces during the spatial oscillations largely through the air holes. This energy transport mechanism prevails even when the metal-film thickness becomes as thin as 100 nm, under which circumstance the wave functions of the SPs, localized separately on the two metal-air surfaces when the metal film is thick, begin to strongly overlap with each other. The lifetimes of the damping oscillators are different for different resonance peaks in the transmission spectrum and remain distinguishable by the order of their temporal development.
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| 11. |
- Zeng, Yong, et al.
(author)
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Effective dielectric constant of two-dimensional photonic crystals in optical bands
- 2006
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In: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 138:4, s. 205-210
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Journal article (peer-reviewed)abstract
- By using the Fourier expansion method, we have developed an approach to calculate the effective dielectric index of a two-dimensional photonic crystal. The approach is very general: it can take into account various Bravais lattice structure as well as arbitrary spatial variation of the dielectric index. It has been found that near a nondegenerate frequency w(n)(Gamma) at Gamma point, the transverse magnetic (TM) mode is ordinary, as it is independent of the propagation direction, whereas in general the transverse electric (TE) mode depends on the propagation direction, it is extraordinary. Therefore, a two-dimensional photonic crystal can always be described by an effective dielectric index for TM mode near the nondegenerate frequency w(n)(Gamma). However, the TE mode is much more complicated unless the lattice structure is highly symmetric. Moreover, a two-dimensional square photonic crystal has been identified as an effective birefringent crystal having two negative refractive indexes from the perspective of Snell's law.
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| 12. |
- Zeng, Y, et al.
(author)
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Exciton polaritons of nano-spherical-particle photonic crystals in compound lattices
- 2006
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In: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 49:3, s. 313-318
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Journal article (peer-reviewed)abstract
- Nonlocal investigations are presented for exciton-photon coupling in three-dimensional nano-spherical-particle photonic crystals in compound lattices for a tailored dielectric environment to optimize the optical properties of nano particles. The photonic band structure can be modified by tuning the nano particle size and the distance between two interlacing identical face-centered sub-lattices making up the photonic crystal lattice. A complete photonic band gap with a gap-midgap ratio as large as 40.82% has been found in the wurzite structure under the current investigation.
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| 13. |
- Zeng, Yong, et al.
(author)
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Extended plane-wave-based transfer-matrix approach to simulating dispersive photonic crystals
- 2006
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In: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 139:7, s. 328-333
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Journal article (peer-reviewed)abstract
- It has been difficult to compute the band structures and transmission spectra for photonic crystals (PCs) with dispersive components included in the periodic units. Here we show that by using an extended plane-wave-based transfer-matrix method, we are able to formulate the problem for computing optical properties of dispersive PCs, including magnetic and left-handed PCs. This approach is very general, since it can treat PCs with arbitrary Bravais lattice composed of materials with arbitrary dielectric permittivities and magnetic permeabilities. Combined with the supercell method, this method can further simulate defective PCs such as PC-based waveguides and microcavities.
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| 14. |
- Zeng, Yong, et al.
(author)
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Finite-difference time-domain simulations of exciton-polariton resonances in quantum-dot arrays
- 2008
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In: Optics Express. - 1094-4087. ; 16:7, s. 4507-4519
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Journal article (peer-reviewed)abstract
- The optical properties of nanosize quantum-dot (QD) arrays are found to vary significantly around the exciton resonance frequency of the QDs. In order to simulate the interactions between electromagnetic waves and QD arrays, a general auxiliary-differential-equation, finite-difference time-domain approach is introduced and utilized in this article. Using this numerical method, the exciton-polariton resonances of single-layer and double-layer GaAs QD arrays are studied. The optical properties of a single-layer QD array are found to be characterized by the Mie resonance of its constituent QDs, while a double-layer QD array is characterized by the quasi-dipole formed by two QDs positioned in each of the two layers.
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| 15. |
- Zeng, Yong, et al.
(author)
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Highly efficient generation of entangled photon pair by spontaneous parametric downconversion in defective photonic crystals
- 2007
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In: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 24:6, s. 1365-1368
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Journal article (peer-reviewed)abstract
- We study the process of spontaneous parametric downconversion in a one-dimensional defective quadratic nonlinear photonic crystal. It is shown that the strong confinements of both the pump and signal waves around the defective layer result in a giant enhancement of the entangled photon-pair generation. An enhancement factor as high as 3.4 X 10(6) is obtained in our defective structure based on the dual-localized modes. Furthermore, the linewidth of the downconverted fields is only 0. 1 nm. Such a photonic crystal structure can be applied as a highly efficient source of entangled photon pairs for highly integrated all-optical circuits.
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| 16. |
- Zeng, Yong, et al.
(author)
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Optical limiting in defective quadratic nonlinear photonic crystals
- 2006
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 99:12, s. 123107-
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Journal article (peer-reviewed)abstract
- By using a nonlinear transfer matrix method and an iteration method, we investigated an optical limiting in a defective quadratic nonlinear photonic crystal under strong pump-depletion conditions. Due to a giant enhancement of the second harmonic (SH) generation induced by the strong localization of light near the defective band, the progress of the energy exchange from the forward fundamental frequency (FF) channel to the SH channels (both forward and backward) and the backward FF channel is speeded up. The structure can therefore be used as a high-efficient compact optical power limiter. We have also studied the effects of two important parameters of the defective nonlinear periodic structure, the number of the periods and the nonlinear efficiency of the composite material, on the optical limiting.
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| 17. |
- Zeng, Yong, et al.
(author)
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Optical properties of two-dimensional negative-phase-velocity-medium photonic crystals
- 2006
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In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 73:6, s. 066625-
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Journal article (peer-reviewed)abstract
- By an extended plane-wave-based transfer-matrix method, the photonic band structure and the corresponding transmission spectrum have been calculated for a two-dimensional photonic crystal composed of negative-phase-velocity-medium (NPVM) cylindrical rods. Dispersionless anticrossing bands in the two-dimensional NPVM periodic structure are generated by the couplings among surface polaritons localized in the NPVM rods. In part of the negative-phase-velocity frequency region, the photonic band structures of the NPVM photonic crystal are characterized by a topographical continuous dispersion relationship accompanied by many anticrossing bands. The effect of the filling fraction of the NPVM rods on the optical properties of photonic crystals has also been studied.
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| 18. |
- Zeng, Yong, et al.
(author)
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Selective excitation of surface-polariton Bloch waves for efficient transmission of light through a subwavelength hole array in a thin metal film
- 2007
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In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 76:3, s. 035427-
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Journal article (peer-reviewed)abstract
- Electromagnetic (EM) field was found to be able to transmit efficiently through a subwavelength hole array in a metal thin film at specific resonant frequencies. By analyzing the near-field distributions of EM fields in the array system, as well as the corresponding Fourier spectra, we show that the surface-polariton (SP) Bloch waves focus the energy of the incident plane-wave EM field to the vicinity of the hole at resonances (through SP scattering provided by the periodic hole). Furthermore, the wave vectors of the SP waves that contribute to the focusing effect are quantized as functions of the geometric shape of the holes in such a way that the focusing effect of the EM energy into the hole is maximal. The transmission efficiency and bandwidth at resonances are found to partially depend on the number of SP modes which contribute to the focusing effect.
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| 19. |
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| 20. |
- Zhang, Zhi-Yong, et al.
(author)
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Nup88 expression in normal mucosa, adenoma, primary adenocarcinoma and lymph node metastasis in the colorectum
- 2007
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In: Tumor Biology. - : Springer Science and Business Media LLC. - 1010-4283 .- 1423-0380. ; 28:2, s. 93-99
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Journal article (peer-reviewed)abstract
- Objectives: It was the aim of this study to investigate Nup88 expression in normal colorectal mucosa, adenoma, adenocarcinoma and lymph node metastasis, as well as the relationship between Nup88 expression and clinicopathological features. Methods: Nup88 expression was examined by immunohistochemistry in 84 normal mucosa samples, 32 adenomas, 181 primary adenocarcinomas, and 18 lymph node metastases from colorectal tumour patients. Results: Nup88 expression was observed in normal epithelial and tumour cells. The frequency of strong Nup88 expression was increased from normal mucosa or adenoma to primary tumour and lymph node metastasis (p < 0.0001). There was no significant difference in the expression between normal mucosa and adenoma (p = 0.41). The frequency of strong Nup88 expression was higher in ulcerated tumours (40%) than in polypoid/large fungating tumours (23%, p = 0.048). The frequency of strong Nup88 expression was significantly different among tumours with good (21%), moderate (42%) and poor differentiation (48%, p = 0.01). Nup88 expression was not related to the patients' gender, age, tumour location, size, histological type, invasive depth, lymph node status and Dukes stage (p > 0.05). Conclusion: Our results suggest that Nup88 may play a role during the development, aggressiveness and differentiation of colorectal tumours. Copyright © 2007 S. Karger AG.
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| 21. |
- Zhu, L Y, et al.
(author)
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Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1 to 5.5 GeV
- 2005
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:4
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Journal article (peer-reviewed)abstract
- The differential cross sections for the gamma n ->pi(-)p and the gamma p ->pi(+)n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50(degrees) to 110(degrees). The pi(-) and pi(+) photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi(+) data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios [d sigma/dt(gamma n ->pi(-)p)/d sigma/dt(gamma p ->pi(+)n)] at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.
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