RESUMO
The moving-base gravimeter is one of the key instruments used for Earth gravity survey. The accuracy of the survey data is closely related to the calibration precision of several key parameters, such as the damping delay time, the drift coefficient, the gravity scale factor, and the measurement accuracy. This paper will introduce the development of the CHZ-II gravimeter system in which a cylindrical sampling mass suspended vertically by a zero-length spring acts as a sensitive probe to measure specific force. Meanwhile, a GNSS (Global Navigation Satellite System) positioning system is employed to monitor the carrier motion and to remove the inertia acceleration. In order to achieve high-precision calibrations for the key parameters, a new calibration method performed along forward and reverse overlapping lines is proposed, which is used to calibrate the above parameters and to estimate the measurement accuracy of the instrument used for a normal gravity survey. The calibration principle and the shipboard calibration data processing method are introduced. The calibration was performed for three moving-base gravimeters and the corresponding results are determined, indicating that the method can significantly improve the accuracy of the parameters. For the CHZ-II gravimeter, the measurement accuracy of the survey is 0.471 mGal (1 mGal = 10-5 m/s2), which improved by 19.5% after applying the calibrated parameters. This method is also practical for use with aviation, marine and even vehicle-carried moving-base gravimeters.
RESUMO
Subclinical hypothyroidism (SCH) as mild thyroid disorder or comorbidity in patients with endocrine disorders is closely related with insulin resistance (IR) and poor glycemic control. The present study attempted to investigate the effect of SCH on IR and glycemic control in patients with type 2 diabetes mellitus (T2DM). In addition, the effects of ellagic acid (EA) on SCH C57BL/6J and db/db mice were also investigated to explore potential therapeutic drug against SCH-induced abnormal glucose metabolism. T2DM patients were recruited in our study and categorized into two groups according to thyroid stimulating hormone (TSH) value: T2DM without SCH group (TSH ≤4 µIU/ml; n = 30) and T2DM with SCH group (TSH >4µIU/ml; n = 60). Methimazole (MMI; 0.08 mg kg-1 day-1 ) was intragastrically administrated for 12 weeks to establish SCH in C57BL/6J and db/db mice. Compared with T2DM patients without SCH, poor glycemic and cholesterol control were emerged in T2DM patients with SCH and that were prominent in patients with TSH more than 10 µIU/ml. In addition, a significant positive correlation between serum TSH and fasting plasma-glucose (FPG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), or glycated hemoglobin (HbA1c) was observed in T2DM patients with SCH. Moreover, abnormal glucose metabolism in C57BL/6J and db/db mice with SCH has been attenuated by EA administration. Our findings provided data regarding the positive correlation between high TSH level with poor glycemic control in T2DM patients with SCH. EA might be a supportive strategy for preventing SCH-induced abnormal glucose metabolism. PRACTICAL APPLICATIONS: Subclinical hypothyroidism (SCH) is a potential risk factor associated with abnormal glucose metabolism in patients with type 2 diabetes mellitus (T2DM). A clinical theory of a positive correlation between high TSH level and poor glycemic control was validated in type 2 diabetes mellitus patients and mouse models. Ellagic acid (EA) might be a supportive strategy for preventing SCH-induced abnormal glucose metabolism that provided a treatment option in T2DM patients with subclinical hypothyroidism in clinical practice.
