Measurements of the gravitational constant using two independent methods.

The Newtonian gravitational constant, G, is one of the most fundamental constants of nature, but we still do not have an accurate value for it. Despite two centuries of experimental effort, the value of G remains the least precisely known of the fundamental constants. A discrepancy of up to 0.05 per cent in recent determinations of G suggests that there may be undiscovered systematic errors in the various existing methods. One way to resolve this issue is to measure G using a number of methods that are unlikely to involve the same systematic effects. Here we report two independent determinations of G using torsion pendulum experiments with the time-of-swing method and the angular-acceleration-feedback method. We obtain G values of 6.674184 × 10-11 and 6.674484 × 10-11 cubic metres per kilogram per second squared, with relative standard uncertainties of 11.64 and 11.61 parts per million, respectively. These values have the smallest uncertainties reported until now, and both agree with the latest recommended value within two standard deviations.

Combined Test of the Gravitational Inverse-Square Law at the Centimeter Range.

Experiments measuring the Newtonian gravitational constant G can offer uniquely sensitive probes of the test of the gravitational inverse-square law. An analysis of the non-Newtonian effect in two independent experiments measuring G is presented, which permits a test of the 1/r^{2} law at the centimeter range. This work establishes the strongest bound on the magnitude α of Yukawa-type deviations from Newtonian gravity in the range of 5-500 mm and improves the previous bounds by up to a factor of 7 at the length range of 60-100 mm.

Improvement for Testing the Gravitational Inverse-Square Law at the Submillimeter Range.

We improve the test of the gravitational inverse-square law at the submillimeter range by suppressing the vibration of the electrostatic shielding membrane to reduce the disturbance coupled from the residual surface potential. The result shows that, at a 95% confidence level, the gravitational inverse-square law holds (|α|≤1) down to a length scale λ=48 µm. This work establishes the strongest bound on the magnitude α of the Yukawa violation in the range of 40-350 µm, and improves the previous bounds by up to a factor of 3 at the length scale λ≈70 µm. Furthermore, the constraints on the power-law potentials are improved by about a factor of 2 for k=4 and 5.

[A clinical analysis of children with invasive pulmonary fungal infections after biliary atresia surgery].

OBJECTIVE: To investigate the clinical features of invasive pulmonary fungal infections (IPFIs) after biliary atresia (BA) surgery and related risk factors. METHODS: A retrospective analysis was performed for the clinical data of 49 children with IPFIs after BA surgery, including clinical features, lung imaging findings, and pathogenic features. The risk factors for IPFIs after BA surgery were also analyzed. RESULTS: The most common pathogens of IPFIs after BA surgery was Candida albicans (17 strains, 45%), followed by Candida tropicalis (7 strains, 18%), Aspergillus (6 strains, 16%), Candida krusei (3 strains, 8%), Candida glabrata (3 strains, 8%), and Candida parapsilosis (2 strains, 5%). Major clinical manifestations included pyrexia, cough, and shortness of breath, as well as dyspnea in severe cases; the incidence rate of shortness of breath reached 78%, and 35% of all children had no obvious rale. The multivariate logistic regression analysis showed that age at the time of surgery, time of glucocorticoid application, cumulative time of the application of broad-spectrum antibiotics, and recurrent cholangitis were major risk factors for IPFIs after BA surgery. CONCLUSIONS: The three most common pathogens of IPFIs after BA surgery are Candida albicans, Candida tropicalis, and Aspergillus. It is important to perform surgery as early as possible, avoid recurrent cholangitis, and shorten the course of the treatment with broad-spectrum antibiotics and glucocorticoids for decreasing the risk of IPFIs.

Combined Search for Lorentz Violation in Short-Range Gravity.

Short-range experiments testing the gravitational inverse-square law at the submillimeter scale offer uniquely sensitive probes of Lorentz invariance. A combined analysis of results from the short-range gravity experiments HUST-2015, HUST-2011, IU-2012, and IU-2002 permits the first independent measurements of the 14 nonrelativistic coefficients for Lorentz violation in the pure-gravity sector at the level of 10^{-9} m^{2}, improving by an order of magnitude the sensitivity to numerous types of Lorentz violation involving quadratic curvature derivatives and curvature couplings.

New Test of the Gravitational Inverse-Square Law at the Submillimeter Range with Dual Modulation and Compensation.

By using a torsion pendulum and a rotating eightfold symmetric attractor with dual modulation of both the interested signal and the gravitational calibration signal, a new test of the gravitational inverse-square law at separations down to 295 µm is presented. A dual-compensation design by adding masses on both the pendulum and the attractor was adopted to realize a null experiment. The experimental result shows that, at a 95% confidence level, the gravitational inverse-square law holds (|α|≤1) down to a length scale λ=59 µm. This work establishes the strongest bound on the magnitude α of Yukawa-type deviations from Newtonian gravity in the range of 70-300 µm, and improves the previous bounds by up to a factor of 2 at the length scale λ≈160 µm.

Investigating temperature-induced torque noise of a torsion pendulum based on temperature modulation at different frequencies.

Torsion pendulums are widely used for the measurement of small forces. In this study, we investigated the impact of temperature fluctuations on a torsion pendulum using heating devices to modulate the environmental temperature at different specific frequencies. The response coefficient between the temperature variation and the torque of the torsion pendulum was found to vary at different frequencies, with values from 4 × 10-15 N mK-1 at 0.1 mHz to 3 × 10-13 N mK-1 at 10 mHz. A passive thermal-insulation system was used to reduce the torque response within this frequency band, which is dominated by temperature noise. The results demonstrate that this modulation method provides a useful way to independently investigate the noise in a torsion pendulum resulting from environmental temperature fluctuations over a wide frequency band.

Test of the gravitational inverse square law at millimeter ranges.

We report a new test of the gravitational inverse square law at millimeter ranges by using a dual-modulation torsion pendulum. An I-shaped symmetric pendulum and I-shaped symmetric attractors were adopted to realize a null experimental design. The non-Newtonian force between two macroscopic tungsten plates is measured at separations ranging down to 0.4 mm, and the validity of the null experimental design was checked by non-null Newtonian gravity measurements. We find no deviations from the Newtonian inverse square law with 95% confidence level, and this work establishes the most stringent constraints on non-Newtonian interaction in the ranges from 0.7 to 5.0 mm, and a factor of 8 improvement is achieved at the length scale of several millimeters.

Influence of the tilt error motion of the rotation axis on the test of the equivalence principle with a rotating torsion pendulum.

Improving the precision of current tests of the equivalence principle with a rotating torsion pendulum requires a more complete analysis of systematic effects. Here, we discuss in detail one of the important systematic effects, the influence from the tilt error motion of the rotation axis of a rotary stage, namely, wandering of the instantaneous rotation axis around its average direction. Its influence on the rotating torsion pendulum is modeled phenomenologically, and the parameters in the model are calibrated. It is shown that the influence can contribute a correction of η ≈ 5 × 10-13 to the equivalence-principle violating parameter for a rotary stage whose tilt error motion of interest is about 31 nrad in magnitude. We also show that such an influence can be reduced to the level of η ≈ 1 × 10-14 by means of active compensation of the tilt error motion using a set of piezoelectric actuators placed under the stage stator.