An improved correlation method for amplitude estimation of gravitational background signal with time-varying frequency.

In the measurement of the gravitational constant G with angular acceleration method, the accurate estimation of the amplitude of the useful angular acceleration generated by source masses depends on the effective subtraction of the spurious gravitational signal caused by room fixed background masses. The gravitational background signal is of time-varying frequency, and mainly consists of the prominent fundamental frequency and second harmonic components. We propose an improved correlation method to estimate the amplitudes of the prominent components of the gravitational background signal with high precision. The improved correlation method converts a sinusoidal signal with time-varying frequency into a standard sinusoidal signal by means of the stretch processing of time. Based on Gaussian white noise model, the theoretical result shows the uncertainty of the estimated amplitude is proportional to σNT, where σ and N are the standard deviation of noise and the number of the useful signal period T, respectively.

Influence of temperature on period of torsion pendulum with a high-Q fused silica fiber.

Due to the high-Q fused silica fiber's extreme sensitivity to temperature change, the period estimation of torsion pendulum with high precision depends on the effective correction of the thermoelastic effect. In the measurement of G with the time-of-swing method, we analyze the complex relation between temperature and the pendulum's period and propose a developed method to find the shear thermoelasticity coefficient as well as isolate the influence of temperature on period alone. The result shows that the shear thermoelasticity coefficient is 101(2) × 10(-6)/°C, the resultant correction to Δ(ω(2)) is 9.16(0.18) ppm, and the relative uncertainty to G is less than 1 ppm.

[Antitumor effect of baicalin on rat brain glioma].

OBJECTIVE: To investigate the therapeutic mechanism of baicalin on rat brain glioma. METHODS: Deep brain glioma models were established by injection of glioma cell line C6 cells into the brain of Wistar rats. The rats at 7 days after modeling were randomly divided into tumor control group (0.9% NaCl solution 30 mg×kg(-1)×d(-1) gavage)and experimental groups. The experimental rats was divided into 3 groups: low dose group (50 mg×kg(-1)×d(-1)), middle dose group (100 mg×kg(-1)×d(-1)) and high dose group (200 mg×kg(-1)×d(-1)), given the baicalin by gavage. Pathological and electron microscopic changes were observed. The expressions of p53 and Bcl-2 were determined by immunohistochemistry, and the changes of MRI, the average survival time and body weight of the rats in each group after treatments were analyzed. RESULTS: Compared with the control group, the tumor diameter and volume of high dose group rats before sacrifice were significantly reduced (P < 0.01), and the survival time was significantly prolonged (P < 0.01). Immunohistochemistry revealed strong positive expression rate of mutant p53 (84.47 ± 3.74)% and moderately positive rate (47.28 ± 2.38)% in the control group, significantly higher than that in the negative group (12.91 ± 1.07)% (P < 0.01). The positive rate of mutant p53 of the high dose group was (46.42 ± 2.19)%, significantly lower than that of the control group (84.47 ± 3.74)% (P < 0.01). The expression rate of Bcl-2 in the control group was strongly positive (86.51 ± 4.17)% and moderate positive (48.19 ± 2.11)%, significantly higher than that of the negative group (10.36 ± 1.43)% (P < 0.01). Electron microscopy revealed that baicalin caused damages of the cell nuclei and organelles in the gliomas. CONCLUSIONS: Baicalin has significant inhibitory effect on glioma in vivo, and its mechanism may be related to cell apoptosis induced by down-regulated expression of mutant p53, but not related with Bcl-2 expression.

An improved correlation method for determining the period of a torsion pendulum.

Considering variation of environment temperature and unhomogeneity of background gravitational field, an improved correlation method was proposed to determine the variational period of a torsion pendulum with high precision. The result of processing experimental data shows that the uncertainty of determining the period with this method has been improved about twofolds than traditional correlation method, which is significant for the determination of gravitational constant with time-of-swing method.