Random walk reduction in dithered ring laser gyroscope.

We experimentally demonstrated that the random walk in a dithered ring laser gyroscope caused by lock-in crossing can be eliminated by lock-in error compensation. Computer simulations demonstrated the effectiveness of this method. The experimental results show that the random walk coefficient can be reduced as predicted. Furthermore, gyroscopes with different random walk performances can achieve nearly the same random walk level after compensation, illustrating that the quantum limit can be approached after removing the lock-in error.

Optical and Electrical Method Characterizing the Dynamic Behavior of the Fused Silica Cylindrical Resonator.

Fused silica cylindrical resonant gyroscope (CRG) is a novel high-precision solid-wave gyroscope, whose performance is primarily determined by the cylindrical resonator's frequency split and quality factor (Q factor). The laser Doppler vibrometer (LDV) is extensively used to measure the dynamic behavior of fused silica cylindrical resonators. An electrical method was proposed to characterize the dynamic behavior of the cylindrical resonator to enhance the measurement efficiency and decrease the equipment cost. With the data acquisition system and the designed signal analysis program based on LabVIEW software, the dynamic behavior of the fused silica cylindrical resonator can be analyzed automatically and quickly. We compared all the electrical measurement results with the optical detection by LDV, demonstrating that the fast Fourier transform (FFT) result of the resonant frequency measured by the electrical method was 0.12 Hz higher than that with the optical method. Thus, the frequency split measured by the electrical and optical methods was the same in 0.18 Hz, and the measurement of the Q factor was basically the same in 730,000. We conducted all measurements under the same operation condition, and the optical method was used as a reference, demonstrating that the electrical method could characterize the dynamic behavior of the fused silica cylindrical resonator and enhance the measurement efficiency.

Theoretical analysis on the rotation-induced frequency difference in ring lasers with coupled cavities.

We analyzed the effective scale factor of ring laser gyros with coupled cavities in a general way. The coupled cavities can be made of both an odd and even number of mirrors, or even fiber coil. Compared with the "zero-vector-area" design in previous publications, we use the propagation loss rather than transmittance and reflectivity of mirrors to characterize the coupled cavities, which are more universal and controllable. In addition, we found the area of the coupled cavities could further enhance the effective scale factor by 1+l/L, where l and L are the round-trip length of the ring lasers and the coupled cavity, respectively. Therefore, the scheme using coupled cavities to enhance the sensitivity is more practical. These findings are important to realize highly sensitive ring laser gyros.

Mirrors movement-induced equivalent rotation effect in ring laser gyros.

In this letter, the relationship between the change of the closed-loop optical path and the movement of two adjacent spherical mirrors in ring laser gyros is investigated by matrix optical approach. When one spherical mirror is pushed forward and the other is pulled backward to maintain the total length of the closed-loop optical path constant, an equivalent rotation of the closed-loop optical path is found for the first time. Both numerical simulations and experimental results show the equivalent rotation rate is proportional to the velocities of the mirrors' movement.

Instantaneous phase method for readout signal processing of body dithered ring laser gyro.

The readout signal of a body dithered ring laser gyro contains both useful information and the dither component. The dither component must be removed to get the useful information. The dither stripping method can get the useful information without latency. But the quadrature demodulator only has 1/4 pulse resolution, which means that the quantization noise will limit the short-term accuracy. The effect and the property of quantization noise are analyzed in detail. Taking advantage of high-speed analog-to-digital conversion (ADC), the analog values of the two beat frequency signals in quadrature are sampled. A novel instantaneous phase method is introduced, which can get the residual phase besides 4× resolution and the quantization noise can be removed radically. The Allan variance analysis of experimental results shows that the quantization noise coefficient using this method is only 1/7 of that using the original 4× resolution method.

[Induction of prostate cancer-specific CTLs with dendritic cells pulsed by different types of tumor antigens].

OBJECTIVE: To study the effectiveness of freeze-thaw antigens and acid eluted peptide antigens extracted from tumor cell-pulsed dendritic cells (DC) in inducing prostate cancer-specific cytotoxic T lymphocytes (CTL) in vitro. METHODS: Tumor antigens were extracted from the prostate cancer cell line PC-3 with the repeated freeze-thaw and weak acid elution methods. Peripheral blood mononuclear cells were cultured with recombinant human GM-CSF and IL-4 for inducing DCs in vitro. Then the DCs were pulsed with the two kinds of prostate cancer tumor antigens respectively and cultured with T cells for inducing CTLs. The activity of the tumor-specific CTLs were detected by LDH release assay. RESULTS: The protein content in the tumor antigens obtained from PC-3 (2 x 10(7)) by citric acid-phosphate buffer elution and that by the repeated freeze-thaw method were (212.2 +/- 7.9) microg and (963.0 +/- 25.3) microg, respectively. The two kinds of prostate cancer antigens-pulsed DCs had a significant role in inducing the PC-3 cell-specific CTLs, and the CTLs induced by acid-eluted peptide antigen-pulsed DCs exhibited an even more significant tumor-specific cytotoxicity than those induced by repeated freeze-thaw ([60.4 +/- 5.52]% vs. [43.7 +/- 4.11]%, P < 0.01). CONCLUSION: Both the weak acid elution and repeated freeze-thaw methods for extracting prostate cancer antigens can be used for in vitro sensitization of DCs. The DCs pulsed by either of the two kinds of antigens can activate CTLs, and the antigens extracted by weak acid elution are even more effective.

Scale factor characteristics of laser gyroscopes of different sizes.

The scale factor correction characteristics of two ring laser gyroscopes of different sizes are investigated systematically in this paper. The variation in the scale factor can reach 144 or 70 ppm for square gyroscopes with arm lengths of 8.4 cm or 15.6 cm, respectively, during frequency tuning. A dip in the scale factor is observed at the line center of the gain characteristic for both gyroscope sizes. When a different longitudinal mode is excited, the scale factor behavior remains the same, but the scale factor values differ slightly from those derived from geometric prediction. The scale factor tends to decrease with increasing discharge current, but the sensitivity of the scale factor to variations in the excitation decreases with increasing discharge current.

Sensitive determination of the spin polarization of optically pumped alkali-metal atoms using near-resonant light.

A new method to measure the spin polarization of optically pumped alkali-metal atoms is demonstrated. Unlike the conventional method using far-detuned probe light, the near-resonant light with two specific frequencies was chosen. Because the Faraday rotation angle of this approach can be two orders of magnitude greater than that with the conventional method, this approach is more sensitive to the spin polarization. Based on the results of the experimental scheme, the spin polarization measurements are found to be in good agreement with the theoretical predictions, thereby demonstrating the feasibility of this approach.

Progression of Large Lymphoma Is Significantly Impeded with a Combination of Gemcitabine Chemotherapy and Dendritic Cells Intra-Tumor Vaccination.

Relapsed, refractory lymphoma remains to be a challenge and lacks efficient treatment. Some tumor cells escape from treatment, become resistant to chemotherapeutic agents, and rapidly regenerate into large tumors. Lymphoma cells induce accumulation of Gr-1(+-)CD11b(+) myeloid derived suppressor cells (MDSCs) in lymphatic organs and their vicinity. MDSCs enable tumor cells to escape from immune cells mediated surveillance and attack. Gemcitabine is a chemotherapeutic agent that eliminates both tumor cells and MDSCs, improving the immune environment favorable for subsequent treatment. We evaluated the effects of low dose gemcitabine combined with intra-tumorally delivered dendritic cells (DCs) for the treatment of A20 large-size lymphoma. We showed that MDSCs increased markedly in lymphoma-bearing mice, and that gemcitabine significantly increased the apoptosis of MDSCs. Treatment of lymphoma with either gemcitabine or intra-tumoral DCs alone could not inhibit tumor growth or rescue lymphoma-bearing mice. Treatment of lymphoma with small dose gemcitabine followed by intra-tumorally injected DCs significantly improved the efficacy of either individual treatment by reducing MDSCs, inducing onsite DCs maturation, eliminating tumor cells, inhibiting tumor growth and relapse, and extending the survival of the lymphoma-bearing mice, partly through the induction of the IFNγ secreting cells and the activation of cytotoxic lymphocytes. We showed that NK cells and CD8(+ )T cells were the major effectors to mediate the inhibition of tumor growth. Thus, the observation that gemcitabine synergizes DCs mediated immunotherapy to improve the efficacy of large size lymphoma treatment provides an experimental basis for the combination of chemotherapy and immunotherapy for the efficient treatment of relapsed or refractory lymphoma.