Showing papers by "Li Li published in 2009"

EBV-induced human CD8+ NKT cells suppress tumorigenesis by EBV-associated malignancies.

Abstract: The underlying mechanism of the protective and suppressive role of NKT cells in human tumor immunosurveillance remains to be fully elucidated. We show that the frequencies of CD8(+) NKT cells in patients with EBV-associated Hodgkin's lymphoma or nasopharyngeal carcinoma are significantly lower than those in healthy EBV carriers. These CD8(+) NKT cells in tumor patients are also functionally impaired. In human-thymus-severe combined immunodeficient (hu-thym-SCID) chimeras, EBV challenge efficiently promotes the generation of IFN-gamma-biased CD8(+) NKT cells. These cells are strongly cytotoxic, drive syngeneic T cells into a Th1 bias, and enhance T-cell cytotoxicity to EBV-associated tumor cells. Interleukin-4-biased CD4(+) NKT cells are predominately generated in unchallenged chimeras. These cells are noncytotoxic, drive syngeneic T cells into a Th2 bias, and do not affect T-cell cytotoxicity. In humanized xenogeneic tumor-transplanted hu-thym-SCID chimeras, adoptive transfer with EBV-induced CD8(+) NKT cells significantly suppresses tumorigenesis by EBV-associated malignancies. EBV-induced CD8(+) NKT cells are necessary and sufficient to enhance the T-cell immunity to EBV-associated malignancies in the hu-thym-SCID chimeras. CD4(+) NKT cells are synergetic with CD8(+) NKT cells, leading to a more pronounced T-cell antitumor response in the chimeras cotransferred with CD4(+) and CD8(+) NKT cells. Thus, immune reconstitution with EBV-induced CD8(+) NKT cells could be a useful strategy in management of EBV-associated malignancies.

Single longitudinal mode and optical bistability Tm,Ho:YLF lasers at room temperature

Abstract: In this paper we report on laser diode end-pumped single longitudinal mode and optical bistability Tm,Ho:YLF lasers at room temperature. The maximal output power of single longitudinal mode can reach 106 mW by using only a 250 μm thick solid etalon. The single longitudinal mode laser can be used as a seed laser for laser lidar systems. Furthermore, for the first time, the phenomenon of low threshold optical bistability of Tm,Ho:YLF laser at room temperature is observed.

The effects of energy transfer upconversion on end-pumped Q-switched Tm, Ho?:?YLF lasers

Abstract: Based on the model of continuous wave end-pumped quasi-three-level system, the influence of energy transfer upconversion (ETU) on diode-end-pumped actively Q-switched Tm, Ho : YLF lasers is investigated by the rate equation analysis. The analytical expressions of the fractional thermal loading and the pulse energy are obtained. The influences of ETU on the fractional thermal loading and the output pulse energy are analysed. The theoretical results show that the ETU reduces not only the pulse energy but also the effective upper level lifetime of the actively Q-switched Tm, Ho : YLF laser. The practical example of the diode-end-pumped Q-switched Tm, Ho : YLF laser has been used to verify the present model.

A theoretical study of intrinsic optical bistability dynamics in Tm3+/Yb3+ codoped systems with an upconversion avalanche mechanism

Abstract: This paper presents theoretical investigations on the dynamics of intrinsic optical bistability (IOB) in Tm3+/Yb3+ codoped systems with an upconversion avalanche mechanism. Numerical simulations based on the rate equation model demonstrate distinct IOB hysteresis and critical slowing dynamics around the avalanche thresholds. Moreover, the unusual IOB characteristics are well interpreted by developing a simplified analytic model which gives the formulations of two critical thresholds and the necessary condition for IOB to occur. The simplified model shows that such IOB phenomena may occur only if the total quantum yields of the dipole–dipole energy transfer processes are much higher than that of the inherent decay losses involved in an upconversion avalanche. The analytic model developed in the paper may be useful for the prediction of new rare-earth-doped materials giving rise to IOB.

End-pumped optical bistability Tm,Ho:YLF laser

Abstract: We experimentally demonstrate strong optical bistability in a 2 μm continuous wave Tm,Ho:YLF laser with a bulk crystal. The laser is end-pumped by a 792 nm fiber-coupled laser diode. The bistable region is as wide as 1.6 W and the jump power at the turning point is as high as 82.5 mW when the temperature of the laser crystal is kept at 253 K. The influences of the cavity length and the transmission of the output coupler on the characteristics of optical bistability are obtained. The theoretical analysis shows that the bistable output in the Tm,Ho:YLF lasers comes from the combined effects of the nonlinear saturation of ground state reabsorption, the energy transfer upconversion, and the excited state absorption.

Bistable Tm,Ho:YLE laser with bistable zone and adjustable width -

Abstract: The invention provides an optical bistable Tm, Ho:YLF laser, the width of pumping bistable area of a laser diode end surface of which can be adjusted; the optical bistable Tm, Ho:YLF laser comprises a laser diode pumping source, an optical fiber, a coupling lens, a resonant cavity and a thulium and holmium codoping lithium yttrium fluoride crystal; the optical bistable Tm, Ho:YLF laser is characterized in that: pumping light given off by the two laser diode pumping sources enters in the resonant cavity by respectively passing through the optical fiber and the coupling lens; the resonant cavity is an L-shaped right-angle folding cavity which is composed of a back-cavity mirror, a 45 degrees plane folding mirror and an output mirror; the front end of the resonant cavity is the back-cavity mirror, the rear end thereof is the 45 degrees plane folding mirror, and the lower end thereof is the output mirror; the thulium and holmium codoping lithium yttrium fluoride crystal is arranged in the resonant cavity. The laser has small volume, simple structure and low cost; by injecting pumping light to an absorption area, the absorption performance of the absorption area is changed, thus achieving the purpose of adjusting the width of the bistable area and leading the laser to have large adjusting magnitude and convenient usage.

Formation mechanism of optical bistability in end-pumped quasi-three-level Tm, Ho:YLF lasers

Abstract: We report on optical bistability and its formation mechanism in an end-pumped quasi-three-level 2 μm Tm,Ho:YLF laser with only a bulk laser crystal. We have experimentally observed that the characteristic output versus input curve is not linear and shows bistability when the laser crystal is singly end pumped by a 792 nm laser diode. The width of the bistable region is 1.6 W and the jump power at the turning point is 82.5 mW. However, the laser shows linear output when the laser crystal is dual end pumped. The formation mechanism of optical bistability is explained by solving coupled rate equations in which energy transfer upconversion and ground-state reabsorption are considered.

The theoretical model of 1-3-2 piezocomposites

Abstract: A theoretical model is proposed to calculate the equivalent model the electromechanical properties of (1-3-2) piezocomposite. Piezoelectric equations of state were derived in terms of equivalent parameters based on linear electromechanical response and uniform field theories. Equivalent parameters (g31, g33, beta33, d31, d33, epsiv33) of 1-3-2 piezocomposite were obtained. The computed g31 is -19.9 x 10-3 Vmiddotm/N-1, g33 is 68.4 x 10-3 Vmiddotm/N-1, d31 is -98 x 10-12 C/N, d33 is 336 x 10-12 C/N, and epsiv/T 33//epsiv0 is 555, while the volume fraction of piezoelectric phase nu1 is 0.4 and nu2 is 0.1. The variation of composite properties with volume fraction of piezoelectric phase have been modeled and experimentally verified. The computed d31, d33, and epsiv33 are within 12.5, 6.7, and 8.4% of experimental values, respectively.

Intrinsic Bistability and Critical Slowing in Tm3+/Yb3+ Codoped Laser Crystal with the Photon Avalanche Mechanism

Abstract: We present theoretically a novel intrinsic optical bistability (IOB) in the Tm3+/Yb3+ codoped system with a photon avalanche mechanism. Numerical simulations based on the rate equation model demonstrate distinct IOB hysteresis and critical slowing dynamics around the avalanche thresholds. Such an IOB characteristic in Tm3+/Yb3+ codoped crystal has potential applications in solid-state bistable optical displays and luminescence switchers in visible-infrared spectra.

Theoretical and experimental investigation of optical bistability in end-pumped Tm，Ho：YLF lasers

Abstract: We demonstrate the strong optical bistability of a 2μm continuous wave Tm，Ho：YLF laser end pumped by a 792nm fiber-coupled laser diode. The quasi-three-level rate equation theoretical model is given under consideration of the energy transfer upconversion and ground state reabsorption effects. The bistable output of Tm，Ho：YLF laser is predicted theoretically by solving the coupled rate equations and the mechanism of the bistability output is analyzed. The bistable output is also studied experimentally. When the laser crystal is at 253K，the width of the bistable region is 1.6W and the jump power at the tujump point is 82.5mW. The theoretical results are in agreement with the experimental results，showing that the theoretical model is reasonable.

NiMnGaCu high temperature shape-memory alloy and manufacturing method thereof

Abstract: The invention provides a NiCoMnSn high temperature shape memory alloy and a preparation method thereof. Ni, Co and Sn are weighted according to the atomic percent of Ni43Co7Mn Sn ; wherein, X equals to 7-10; the raw materials of Ni, Co, and Sn weighted in the first step are put in a no consumable vacuum arc furnace, vacuumed to cause that the vacuum degree of the background reaches 2*10 - 5*10 Pa, and then charged with high-purity argon till 500 Pa; the raw materials are melted to NiCoMnSn button-type cast ingot by using high temperature voltaic arc; a vacuum suction mold device is used for preparing a bar-shaped cast ingot with the 10mm diameter, thus obtaining the Ni43Co7Mn Sn high temperature shape memory alloy. The martensitic phase transformation temperature of the NiCoMnSn prepared by the invention ranges from 120 DEG C-300 DEG C; the alloying elements of the raw materials are relatively cheap. The preparation method is simple and the alloy has uniform components; therefore, the follow-up heat treatment is not needed. The shape memory effect can reach up to 3.8%. The stability of the thermal circulation is high. The alloy is a new high temperature shape memory alloy with the application prospect.

Rice's non-endosperm tissue-specific expression promoter, ostsp i, and uses thereof

Abstract: Rice's non-endosperm tissue-specific expression promoter and uses thereof. The promoter has a length of 1785bp. A new plant expression construct is constructed by using the promoter instead of CaMV35S promoter in the plant expression vector pCAMBIO1305.1, and is named as pOsTSP I-GUS. Its function of driving expression is testified by transgenic methods. The result of GUS tissue dying shows that the promoter has the function of driving expression in specific tissues, i.e. driving expression in rice's non-endosperm tissues (root, stem, leaves etc), not in endosperm.

Multispectral imagery registration based on minor and noise component criterion

Abstract: For multispectral imagery, spatial registration between bands is a very important part of the overall quality of the multispectral imagery product. Due to the significant differences in scene reflectance at different wavelengths, mostly multispectral imagery registration methods are unreliable. In this paper, a robust multispectral imagery registration method is presented. As we know, the spectral information (endmembers) of some pixels will been confused when multispectral imagery is mis-registered. The change of confused endmembers can be estimated through observing minor eigenvalues. Based on this property, a minor and noise component criterion is defined. The best alignment is reached when their minor and noise component is at its minimum. Experiments were conducted using multispectral imagery from the ETM Satellite. And corresponding registration performance curve is given. Multispectral imagery is pre-registered with the method of normalized mutual information. Computer simulations show that the normalized mutual information method may have a deviation about 10 pixels between a pair of images. The method we presented can have a deviation less than 1/4 pixel. Registering curve show that this method is efficient and robust, it can be used for precise multispectral imagery registration.